[PATCH 00/20 -v5] mcount and latency tracing utility -v5

[PATCH 00/20 -v5] mcount and latency tracing utility -v5

[Steven Rostedt]

[
  version 5 of mcount / trace patches:

  changes include:

   Folded more patches together (mostly the timing stuff)

   Some minor fixes to the timing code.

   Redesigned the tracer!
   
     - Now all tracers use the same buffer. This cut down tremendously
        the code duplication).

     - consolidated the debugfs files (see below)

   This has now gone from a RFC patch series to a true PATCH series.

  New! trace-cmd.c - see below

  added printk patch to allow printk to happen with runqueue lock held.
]

All released version of these patches can be found at:

   http://people.redhat.com/srostedt/tracing/


The following patch series brings to vanilla Linux a bit of the RT kernel
trace facility. This incorporates the "-pg" profiling option of gcc
that will call the "mcount" function for all functions called in
the kernel.

Note: I did investigate using -finstrument-functions but that adds a call
to both start and end of a function. Using mcount only does the
beginning of the function. mcount alone adds ~13% overhead. The
-finstrument-functions added ~19%.  Also it caused me to do tricks with
inline, because it adds the function calls to inline functions as well.

This patch series implements the code for x86 (32 and 64 bit), but
other archs can easily be implemented as well (note: ARM and PPC are
already implemented in -rt)

Some Background:
----------------

A while back, Ingo Molnar and William Lee Irwin III created a latency tracer
to find problem latency areas in the kernel for the RT patch.  This tracer
became a very integral part of the RT kernel in solving where latency hot
spots were.  One of the features that the latency tracer added was a
function trace.  This function tracer would record all functions that
were called (implemented by the gcc "-pg" option) and would show what was
called when interrupts or preemption was turned off.

This feature is also very helpful in normal debugging. So it's been talked
about taking bits and pieces from the RT latency tracer and bring them
to LKML. But no one had the time to do it.

Arnaldo Carvalho de Melo took a crack at it. He pulled out the mcount
as well as part of the tracing code and made it generic from the point
of the tracing code.  I'm not sure why this stopped. Probably because
Arnaldo is a very busy man, and his efforts had to be utilized elsewhere.

While I still maintain my own Logdev utility:

  http://rostedt.homelinux.com/logdev

I came across a need to do the mcount with logdev too. I was successful
but found that it became very dependent on a lot of code. One thing that
I liked about my logdev utility was that it was very non-intrusive, and has
been easy to port from the Linux 2.0 days. I did not want to burden the
logdev patch with the intrusiveness of mcount (not really that intrusive,
it just needs to add a "notrace" annotation to functions in the kernel
that will cause more conflicts in applying patches for me).

Being close to the holidays, I grabbed Arnaldos old patches and started
massaging them into something that could be useful for logdev, and what
I found out (and talking this over with Arnaldo too) that this can
be much more useful for others as well.

The main thing I changed, was that I made the mcount function itself
generic, and not the dependency on the tracing code.  That is I added

register_mcount_function()
 and
clear_mcount_function()

So when ever mcount is enabled and a function is registered that function
is called for all functions in the kernel that is not labeled with the
"notrace" annotation.


The Simple Tracer:
------------------

To show the power of this I also massaged the tracer code that Arnaldo pulled
from the RT patch and made it be a nice example of what can be done
with this.

The function that is registered to mcount has the prototype:

 void func(unsigned long ip, unsigned long parent_ip);

The ip is the address of the function and parent_ip is the address of
the parent function that called it.

The x86_64 version has the assembly call the registered function directly
to save having to do a double function call.

To enable mcount, a sysctl is added:

   /proc/sys/kernel/mcount_enabled

Once mcount is enabled, when a function is registed, it will be called by
all functions. The tracer in this patch series shows how this is done.
It adds a directory in the debugfs, called mctracer. With a ctrl file that
will allow the user have the tracer register its function.  Note, the order
of enabling mcount and registering a function is not important, but both
must be done to initiate the tracing. That is, you can disable tracing
by either disabling mcount or by clearing the registered function.

Only one function may be registered at a time. If another function is
registered, it will simply override what ever was there previously.

Here's a simple example of the tracer output:

CPU 2: hackbench:11867 preempt_schedule+0xc/0x84 <-- avc_has_perm_noaudit+0x45d/0x52c
CPU 1: hackbench:12052 selinux_file_permission+0x10/0x11c <-- security_file_permission+0x16/0x18
CPU 3: hackbench:12017 update_curr+0xe/0x8b <-- put_prev_task_fair+0x24/0x4c
CPU 2: hackbench:11867 avc_audit+0x16/0x9e3 <-- avc_has_perm+0x51/0x63
CPU 0: hackbench:12019 socket_has_perm+0x16/0x7c <-- selinux_socket_sendmsg+0x27/0x3e
CPU 1: hackbench:12052 file_has_perm+0x16/0xbb <-- selinux_file_permission+0x104/0x11c

This is formated like:

 CPU <CPU#>: <task-comm>:<task-pid> <function> <-- <parent-function>


Latency Tracer Format:
----------------------

The format used by the RT patch is a bit more complex. It is designed to
record a lot of information quickly and dump out a lot too.

There's two versions of the format. Verbose and non-vebose.

verbose:

preemption latency trace v1.1.5 on 2.6.24-rc7-tst
--------------------------------------------------------------------
 latency: 89 us, #3/3, CPU#1 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
    -----------------
    | task: kjournald-600 (uid:0 nice:-5 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0x63 <c06310d2>
 => ended at:   _spin_unlock_irqrestore+0x32/0x41 <c0631245>

       kjournald   600 1 1 00000000 00000000 [397408f1] 0.003ms (+0.079ms): _spin_lock_irqsave+0x2a/0x63 <c06310d2> (scsi_dispatch_cmd+0x155/0x234 [scsi_mod] <f8867c19>)
       kjournald   600 1 1 00000000 00000001 [39740940] 0.081ms (+0.005ms): _spin_unlock_irqrestore+0x32/0x41 <c0631245> (scsi_dispatch_cmd+0x1be/0x234 [scsi_mod] <f8867c82>)
       kjournald   600 1 1 00000000 00000002 [39740945] 0.087ms (+0.000ms): trace_hardirqs_on_caller+0x74/0x86 <c0508bdc> (_spin_unlock_irqrestore+0x32/0x41 <c0631245>)


non-verbose:

preemption latency trace v1.1.5 on 2.6.24-rc7-tst
--------------------------------------------------------------------
 latency: 89 us, #3/3, CPU#2 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
    -----------------
    | task: kjournald-600 (uid:0 nice:-5 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0x63 <c06310d2>
 => ended at:   _spin_unlock_irqrestore+0x32/0x41 <c0631245>

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
kjournal-600   1d...    3us+: _spin_lock_irqsave+0x2a/0x63 <c06310d2> (scsi_dispatch_cmd+0x155/0x234 [scsi_mod] <f8867c19>)
kjournal-600   1d...   81us+: _spin_unlock_irqrestore+0x32/0x41 <c0631245> (scsi_dispatch_cmd+0x1be/0x234 [scsi_mod] <f8867c82>)
kjournal-600   1d...   87us : trace_hardirqs_on_caller+0x74/0x86 <c0508bdc> (_spin_unlock_irqrestore+0x32/0x41 <c0631245>)


Debug FS:
---------

Although enabling and disabling mcount is done through the sysctl:

/proc/sys/kernel/mcount_enabled

The rest of the tracing uses debugfs.

/debugfs/tracing

Here's the available files:

 available_tracers
  Lists the tracers that are compiled into the kernel and can be
  echoed into current_tracer

 current_tracer
   Shows the current tracer that is registered. On bootup this is
   blank. To set a new tracer, simply echo into this file the name
   found in available_tracers.

   e.g.

     echo wakeup > /debugfs/tracing/current_tracer

 trace_ctrl
   echo 1 to enable the current tracer.
   echo 0 to disable it.

    Note, the function trace also needs mcount_enabled set,
    otherwise it will not record.

 latency_trace
   Outputs the current trace in latency_trace format.

 tracing_thresh
   echo a number (in usecs) into this to record all traces that are
   greater than threshold. Only matters for those traces that use
   a max threshold (preemptoff irqsoff and wakeup)

 iter_ctrl
   echo "symonly" to not show the instruction pointers in the trace
   echo "nosymonly" to disable symonly.
   echo "verbose" for verbose output from latency format.
   echo "noverbose" to disable verbose ouput.
   cat iter_ctrl to see the current settings.

 tracing_max_latency
   Holds the current max critical latency.
   echo 0 to reset and start tracing.
   Only holds for those tracers that use a max setting.
   (preemptoff irqsoff and wakeup)

 trace
   simple output format of the current trace.

Trace tool:
-----------

 The trace_cmd.c found at
   http://people.redhat.com/srostedt/tracing/trace-cmd.c

 This tool will set up the tracer and allow you to run a program
 and trace it. (must be root)

  e.g.

   # ./trace-cmd -f echo hi
   # cat /debug/tracing/latency_trace | grep echo | head
    echo-4240  1d..1 1076us : ret_from_fork+0x6/0x1c (schedule_tail+0x9/0x5e)
    echo-4240  1d..1 1077us : schedule_tail+0x1e/0x5e (finish_task_switch+0xb/0x61)
    echo-4240  1d..1 1078us : finish_task_switch+0x24/0x61 (_spin_unlock_irq+0x8/0x40)
    echo-4240  1...1 1079us : _spin_unlock_irq+0x27/0x40 (sub_preempt_count+0xd/0x104)
    echo-4240  1...1 1080us+: sub_preempt_count+0x8d/0x104 (in_lock_functions+0x8/0x2c)
    echo-4240  1d... 1082us : error_code+0x72/0x78 (do_page_fault+0xe/0x7c0)
    echo-4240  1d... 1083us : do_page_fault+0x35b/0x7c0 (add_preempt_count+0xc/0x10f)
    echo-4240  1d..1 1085us : add_preempt_count+0x53/0x10f (in_lock_functions+0x8/0x2c)
    echo-4240  1d..1 1086us : do_page_fault+0x38f/0x7c0 (sub_preempt_count+0xd/0x104)
    echo-4240  1d..1 1087us : sub_preempt_count+0x8d/0x104 (in_lock_functions+0x8/0x2c)


  The available switches are:

    -s - context switch tracing
    -p - preemption off tracing
    -i - interrupts off tracing
    -b - both interrupts off and preemption off tracing
    -w - wakeup timings
    -f - function trace

  Only -f (function trace) may be enabled with the other tracers,
  since most the other tracers also have a function trace version
  if mcount is enabled (yes -f will enable mcount).


Overhead:
---------

Note that having mcount compiled in seems to show a little overhead.

Here's 3 runs of hackbench 50 without the patches:
Time: 2.137
Time: 2.283
Time: 2.245

 Avg: 2.221

and here's 3 runs with the patches (without tracing on):
Time: 2.738
Time: 2.469
Time: 2.388

  Avg: 2.531

So it is a 13% overhead when enabled (according to hackbench).

But full tracing can cause a bit more problems:

# hackbench 50
Time: 113.350

  113.350!!!!!

But this is tracing *every* function call!


Future:
-------
The way the mcount hook is done here, other utilities can easily add their
own functions. Just care needs to be made not to call anything that is not
marked with notrace, or you will crash the box with recursion. But
even the simple tracer adds a "disabled" feature so in case it happens
to call something that is not marked with notrace, it is a safety net
not to kill the box.

I was originally going to use the relay system to record the data, but
that had a chance of calling functions not marked with notrace. But, if
for example LTTng wanted to use this, it could disable tracing on a CPU
when doing the calls, and this will protect from recusion.

Redesign:
---------
This will be the last series that has each of the traces as a separate
buffer. The next series will be more like the RT patch implementation
of holding a single buffer for all latency traces. The only disadvantage
of this is that you can only perform one type of latency at a time.
But this has never been brought up as an issue with the RT patch.

The user will still be able to switch at runtime which type of latency
they would like to record.

SystemTap:
----------
One thing that Arnaldo and I discussed last year was using systemtap to
add hooks into the kernel to start and stop tracing.  kprobes is too
heavy to do on all funtion calls, but it would be perfect to add to
non hot paths to start the tracer and stop the tracer.

So when debugging the kernel, instead of recompiling with printks
or other markers, you could simply use systemtap to place a trace start
and stop locations and trace the problem areas to see what is happening.



These are just some of the ideas we have with this. And we are sure others
could come up with more.

These patches are for the underlining work. We'll see what happens next.

[PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Steven Rostedt]

[-- Attachment #1: printk-no-klogd-on-irqs-disabled.patch --]
[-- Type: text/plain, Size: 2873 bytes --]

[ This patch is added to the series since the wakeup timings trace
  may lockup without it. ]

I thought that one could place a printk anywhere without worrying.
But it seems that it is not wise to place a printk where the runqueue
lock is held.

I just spent two hours debugging why some of my code was locking up,
to find that the lockup was caused by some debugging printk's that
I had in the scheduler.  The printk's were only in rare paths so
they shouldn't be too much of a problem, but after I hit the printk
the system locked up.

Thinking that it was locking up on my code I went looking down the
wrong path. I finally found (after examining an NMI dump) that
the lockup happened because printk was trying to wakeup the klogd
daemon, which caused a deadlock when the try_to_wakeup code tries
to grab the runqueue lock.

Since printks are seldom called with interrupts disabled, we can
hold off the waking of klogd if they are. We don't have access to
the runqueue locks from printk, but those locks need interrupts
disabled in order to be held. 

Calling printk with interrupts disabled should only be done for
emergencies and debugging anyway.

And with this patch, my code ran fine ;-)

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/printk.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Index: linux-mcount.git/kernel/printk.c
===================================================================
--- linux-mcount.git.orig/kernel/printk.c	2008-01-18 06:29:15.000000000 -0500
+++ linux-mcount.git/kernel/printk.c	2008-01-18 06:32:38.000000000 -0500
@@ -595,9 +595,11 @@ static int have_callable_console(void)
  * @fmt: format string
  *
  * This is printk().  It can be called from any context.  We want it to work.
- * Be aware of the fact that if oops_in_progress is not set, we might try to
- * wake klogd up which could deadlock on runqueue lock if printk() is called
- * from scheduler code.
+ *
+ * Note: if printk() is called with interrupts disabled, it will not wake
+ * up the klogd. This is to avoid a deadlock from calling printk() in schedule
+ * with the runqueue lock held and having the wake_up grab the runqueue lock
+ * as well.
  *
  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
  * call the console drivers.  If we fail to get the semaphore we place the output
@@ -978,7 +980,13 @@ void release_console_sem(void)
 	console_locked = 0;
 	up(&console_sem);
 	spin_unlock_irqrestore(&logbuf_lock, flags);
-	if (wake_klogd)
+	/*
+	 * If we try to wake up klogd while printing with the runqueue lock
+	 * held, this will deadlock. We don't have access to the runqueue
+	 * lock from here, but just checking for interrupts disabled
+	 * should be enough.
+	 */
+	if (!irqs_disabled() && wake_klogd)
 		wake_up_klogd();
 }
 EXPORT_SYMBOL(release_console_sem);

-- 

[PATCH 02/20 -v5] Add basic support for gcc profiler instrumentation

[Steven Rostedt]

[-- Attachment #1: mcount-add-basic-support-for-gcc-profiler-instrum.patch --]
[-- Type: text/plain, Size: 12560 bytes --]

If CONFIG_MCOUNT is selected and /proc/sys/kernel/mcount_enabled is set to a
non-zero value the mcount routine will be called everytime we enter a kernel
function that is not marked with the "notrace" attribute.

The mcount routine will then call a registered function if a function
happens to be registered.

[This code has been highly hacked by Steven Rostedt, so don't
 blame Arnaldo for all of this ;-) ]

Update:
  It is now possible to register more than one mcount function.
  If only one mcount function is registered, that will be the
  function that mcount calls directly. If more than one function
  is registered, then mcount will call a function that will loop
  through the functions to call.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 Makefile                   |    3 
 arch/x86/Kconfig           |    1 
 arch/x86/kernel/entry_32.S |   25 +++++++
 arch/x86/kernel/entry_64.S |   36 +++++++++++
 include/linux/linkage.h    |    2 
 include/linux/mcount.h     |   38 ++++++++++++
 kernel/sysctl.c            |   11 +++
 lib/Kconfig.debug          |    2 
 lib/Makefile               |    2 
 lib/tracing/Kconfig        |   10 +++
 lib/tracing/Makefile       |    3 
 lib/tracing/mcount.c       |  141 +++++++++++++++++++++++++++++++++++++++++++++
 12 files changed, 274 insertions(+)

Index: linux-mcount.git/Makefile
===================================================================
--- linux-mcount.git.orig/Makefile	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/Makefile	2008-01-23 10:26:34.000000000 -0500
@@ -509,6 +509,9 @@ endif
 
 include $(srctree)/arch/$(SRCARCH)/Makefile
 
+ifdef CONFIG_MCOUNT
+KBUILD_CFLAGS	+= -pg
+endif
 ifdef CONFIG_FRAME_POINTER
 KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls
 else
Index: linux-mcount.git/arch/x86/Kconfig
===================================================================
--- linux-mcount.git.orig/arch/x86/Kconfig	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/Kconfig	2008-01-23 10:26:34.000000000 -0500
@@ -19,6 +19,7 @@ config X86_64
 config X86
 	bool
 	default y
+	select HAVE_MCOUNT
 
 config GENERIC_TIME
 	bool
Index: linux-mcount.git/arch/x86/kernel/entry_32.S
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/entry_32.S	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/entry_32.S	2008-01-23 10:26:34.000000000 -0500
@@ -75,6 +75,31 @@ DF_MASK		= 0x00000400 
 NT_MASK		= 0x00004000
 VM_MASK		= 0x00020000
 
+#ifdef CONFIG_MCOUNT
+.globl mcount
+mcount:
+	/* unlikely(mcount_enabled) */
+	cmpl $0, mcount_enabled
+	jnz trace
+	ret
+
+trace:
+	/* taken from glibc */
+	pushl %eax
+	pushl %ecx
+	pushl %edx
+	movl 0xc(%esp), %edx
+	movl 0x4(%ebp), %eax
+
+	call   *mcount_trace_function
+
+	popl %edx
+	popl %ecx
+	popl %eax
+
+	ret
+#endif
+
 #ifdef CONFIG_PREEMPT
 #define preempt_stop(clobbers)	DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF
 #else
Index: linux-mcount.git/arch/x86/kernel/entry_64.S
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/entry_64.S	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/entry_64.S	2008-01-23 10:26:34.000000000 -0500
@@ -53,6 +53,42 @@
 
 	.code64
 
+#ifdef CONFIG_MCOUNT
+
+ENTRY(mcount)
+	/* unlikely(mcount_enabled) */
+	cmpl $0, mcount_enabled
+	jnz trace
+	retq
+
+trace:
+	/* taken from glibc */
+	subq $0x38, %rsp
+	movq %rax, (%rsp)
+	movq %rcx, 8(%rsp)
+	movq %rdx, 16(%rsp)
+	movq %rsi, 24(%rsp)
+	movq %rdi, 32(%rsp)
+	movq %r8, 40(%rsp)
+	movq %r9, 48(%rsp)
+
+	movq 0x38(%rsp), %rsi
+	movq 8(%rbp), %rdi
+
+	call   *mcount_trace_function
+
+	movq 48(%rsp), %r9
+	movq 40(%rsp), %r8
+	movq 32(%rsp), %rdi
+	movq 24(%rsp), %rsi
+	movq 16(%rsp), %rdx
+	movq 8(%rsp), %rcx
+	movq (%rsp), %rax
+	addq $0x38, %rsp
+
+	retq
+#endif
+
 #ifndef CONFIG_PREEMPT
 #define retint_kernel retint_restore_args
 #endif	
Index: linux-mcount.git/include/linux/linkage.h
===================================================================
--- linux-mcount.git.orig/include/linux/linkage.h	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/include/linux/linkage.h	2008-01-23 10:26:34.000000000 -0500
@@ -3,6 +3,8 @@
 
 #include <asm/linkage.h>
 
+#define notrace __attribute__((no_instrument_function))
+
 #ifdef __cplusplus
 #define CPP_ASMLINKAGE extern "C"
 #else
Index: linux-mcount.git/include/linux/mcount.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/include/linux/mcount.h	2008-01-23 10:26:34.000000000 -0500
@@ -0,0 +1,38 @@
+#ifndef _LINUX_MCOUNT_H
+#define _LINUX_MCOUNT_H
+
+#ifdef CONFIG_MCOUNT
+extern int mcount_enabled;
+
+#include <linux/linkage.h>
+
+#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
+#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
+
+typedef void (*mcount_func_t)(unsigned long ip, unsigned long parent_ip);
+
+struct mcount_ops {
+	mcount_func_t func;
+	struct mcount_ops *next;
+};
+
+/*
+ * The mcount_ops must be a static and should also
+ * be read_mostly.  These functions do modify read_mostly variables
+ * so use them sparely. Never free an mcount_op or modify the
+ * next pointer after it has been registered. Even after unregistering
+ * it, the next pointer may still be used internally.
+ */
+int register_mcount_function(struct mcount_ops *ops);
+int unregister_mcount_function(struct mcount_ops *ops);
+void clear_mcount_function(void);
+
+extern void mcount(void);
+
+#else /* !CONFIG_MCOUNT */
+# define register_mcount_function(ops) do { } while (0)
+# define unregister_mcount_function(ops) do { } while (0)
+# define clear_mcount_function(ops) do { } while (0)
+#endif /* CONFIG_MCOUNT */
+#endif /* _LINUX_MCOUNT_H */
Index: linux-mcount.git/kernel/sysctl.c
===================================================================
--- linux-mcount.git.orig/kernel/sysctl.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/kernel/sysctl.c	2008-01-23 10:26:34.000000000 -0500
@@ -46,6 +46,7 @@
 #include <linux/nfs_fs.h>
 #include <linux/acpi.h>
 #include <linux/reboot.h>
+#include <linux/mcount.h>
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
@@ -470,6 +471,16 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+#ifdef CONFIG_MCOUNT
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "mcount_enabled",
+		.data		= &mcount_enabled,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+#endif
 #ifdef CONFIG_KMOD
 	{
 		.ctl_name	= KERN_MODPROBE,
Index: linux-mcount.git/lib/Kconfig.debug
===================================================================
--- linux-mcount.git.orig/lib/Kconfig.debug	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/lib/Kconfig.debug	2008-01-23 10:26:34.000000000 -0500
@@ -517,4 +517,6 @@ config FAULT_INJECTION_STACKTRACE_FILTER
 	help
 	  Provide stacktrace filter for fault-injection capabilities
 
+source lib/tracing/Kconfig
+
 source "samples/Kconfig"
Index: linux-mcount.git/lib/Makefile
===================================================================
--- linux-mcount.git.orig/lib/Makefile	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/lib/Makefile	2008-01-23 10:26:34.000000000 -0500
@@ -66,6 +66,8 @@ obj-$(CONFIG_AUDIT_GENERIC) += audit.o
 obj-$(CONFIG_SWIOTLB) += swiotlb.o
 obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
 
+obj-$(CONFIG_MCOUNT) += tracing/
+
 lib-$(CONFIG_GENERIC_BUG) += bug.o
 
 hostprogs-y	:= gen_crc32table
Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:26:34.000000000 -0500
@@ -0,0 +1,10 @@
+
+# Archs that enable MCOUNT should select HAVE_MCOUNT
+config HAVE_MCOUNT
+       bool
+
+# MCOUNT itself is useless, or will just be added overhead.
+# It needs something to register a function with it.
+config MCOUNT
+	bool
+	select FRAME_POINTER
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:26:34.000000000 -0500
@@ -0,0 +1,3 @@
+obj-$(CONFIG_MCOUNT) += libmcount.o
+
+libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/mcount.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/mcount.c	2008-01-23 10:26:34.000000000 -0500
@@ -0,0 +1,141 @@
+/*
+ * Infrastructure for profiling code inserted by 'gcc -pg'.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Originally ported from the -rt patch by:
+ *   Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
+ *
+ * Based on code in the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+
+#include <linux/module.h>
+#include <linux/mcount.h>
+
+/*
+ * Since we have nothing protecting between the test of
+ * mcount_trace_function and the call to it, we can't
+ * set it to NULL without risking a race that will have
+ * the kernel call the NULL pointer. Instead, we just
+ * set the function pointer to a dummy function.
+ */
+notrace void dummy_mcount_tracer(unsigned long ip,
+				 unsigned long parent_ip)
+{
+	/* do nothing */
+}
+
+static DEFINE_SPINLOCK(mcount_func_lock);
+static struct mcount_ops mcount_list_end __read_mostly =
+{
+	.func = dummy_mcount_tracer,
+};
+
+static struct mcount_ops *mcount_list __read_mostly = &mcount_list_end;
+mcount_func_t mcount_trace_function __read_mostly = dummy_mcount_tracer;
+int mcount_enabled __read_mostly;
+
+/* mcount is defined per arch in assembly */
+EXPORT_SYMBOL_GPL(mcount);
+
+notrace void mcount_list_func(unsigned long ip, unsigned long parent_ip)
+{
+	struct mcount_ops *op = mcount_list;
+
+	while (op != &mcount_list_end) {
+		op->func(ip, parent_ip);
+		op = op->next;
+	};
+}
+
+/**
+ * register_mcount_function - register a function for profiling
+ * @ops - ops structure that holds the function for profiling.
+ *
+ * Register a function to be called by all functions in the
+ * kernel.
+ *
+ * Note: @ops->func and all the functions it calls must be labeled
+ *       with "notrace", otherwise it will go into a
+ *       recursive loop.
+ */
+int register_mcount_function(struct mcount_ops *ops)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&mcount_func_lock, flags);
+	ops->next = mcount_list;
+	/* must have next seen before we update the list pointer */
+	smp_wmb();
+	mcount_list = ops;
+	/*
+	 * For one func, simply call it directly.
+	 * For more than one func, call the chain.
+	 */
+	if (ops->next == &mcount_list_end)
+		mcount_trace_function = ops->func;
+	else
+		mcount_trace_function = mcount_list_func;
+	spin_unlock_irqrestore(&mcount_func_lock, flags);
+
+	return 0;
+}
+
+/**
+ * unregister_mcount_function - unresgister a function for profiling.
+ * @ops - ops structure that holds the function to unregister
+ *
+ * Unregister a function that was added to be called by mcount profiling.
+ */
+int unregister_mcount_function(struct mcount_ops *ops)
+{
+	unsigned long flags;
+	struct mcount_ops **p;
+	int ret = 0;
+
+	spin_lock_irqsave(&mcount_func_lock, flags);
+
+	/*
+	 * If we are the only function, then the mcount pointer is
+	 * pointing directly to that function.
+	 */
+	if (mcount_list == ops && ops->next == &mcount_list_end) {
+		mcount_trace_function = dummy_mcount_tracer;
+		mcount_list = &mcount_list_end;
+		goto out;
+	}
+
+	for (p = &mcount_list; *p != &mcount_list_end; p = &(*p)->next)
+		if (*p == ops)
+			break;
+
+	if (*p != ops) {
+		ret = -1;
+		goto out;
+	}
+
+	*p = (*p)->next;
+
+	/* If we only have one func left, then call that directly */
+	if (mcount_list->next == &mcount_list_end)
+		mcount_trace_function = mcount_list->func;
+
+ out:
+	spin_unlock_irqrestore(&mcount_func_lock, flags);
+
+	return 0;
+}
+
+/**
+ * clear_mcount_function - reset the mcount function
+ *
+ * This NULLs the mcount function and in essence stops
+ * tracing.  There may be lag
+ */
+void clear_mcount_function(void)
+{
+	mcount_trace_function = dummy_mcount_tracer;
+}

-- 

[PATCH 03/20 -v5] Annotate core code that should not be traced

[Steven Rostedt]

[-- Attachment #1: mcount-annotate-generic-code.patch --]
[-- Type: text/plain, Size: 919 bytes --]

Mark with "notrace" functions in core code that should not be
traced.  The "notrace" attribute will prevent gcc from adding
a call to mcount on the annotated funtions.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

---
 lib/smp_processor_id.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-mcount.git/lib/smp_processor_id.c
===================================================================
--- linux-mcount.git.orig/lib/smp_processor_id.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/lib/smp_processor_id.c	2008-01-23 10:26:39.000000000 -0500
@@ -7,7 +7,7 @@
 #include <linux/kallsyms.h>
 #include <linux/sched.h>
 
-unsigned int debug_smp_processor_id(void)
+notrace unsigned int debug_smp_processor_id(void)
 {
 	unsigned long preempt_count = preempt_count();
 	int this_cpu = raw_smp_processor_id();

-- 

[PATCH 04/20 -v5] x86_64: notrace annotations

[Steven Rostedt]

[-- Attachment #1: mcount-add-x86_64-notrace-annotations.patch --]
[-- Type: text/plain, Size: 2212 bytes --]

Add "notrace" annotation to x86_64 specific files.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/head64.c     |    2 +-
 arch/x86/kernel/setup64.c    |    4 ++--
 arch/x86/kernel/smpboot_64.c |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/head64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/head64.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/head64.c	2008-01-23 10:26:44.000000000 -0500
@@ -46,7 +46,7 @@ static void __init copy_bootdata(char *r
 	}
 }
 
-void __init x86_64_start_kernel(char * real_mode_data)
+notrace void __init x86_64_start_kernel(char *real_mode_data)
 {
 	int i;
 
Index: linux-mcount.git/arch/x86/kernel/setup64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/setup64.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/setup64.c	2008-01-23 10:26:44.000000000 -0500
@@ -114,7 +114,7 @@ void __init setup_per_cpu_areas(void)
 	}
 } 
 
-void pda_init(int cpu)
+notrace void pda_init(int cpu)
 { 
 	struct x8664_pda *pda = cpu_pda(cpu);
 
@@ -197,7 +197,7 @@ DEFINE_PER_CPU(struct orig_ist, orig_ist
  * 'CPU state barrier', nothing should get across.
  * A lot of state is already set up in PDA init.
  */
-void __cpuinit cpu_init (void)
+notrace void __cpuinit cpu_init(void)
 {
 	int cpu = stack_smp_processor_id();
 	struct tss_struct *t = &per_cpu(init_tss, cpu);
Index: linux-mcount.git/arch/x86/kernel/smpboot_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/smpboot_64.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/smpboot_64.c	2008-01-23 10:26:44.000000000 -0500
@@ -317,7 +317,7 @@ static inline void set_cpu_sibling_map(i
 /*
  * Setup code on secondary processor (after comming out of the trampoline)
  */
-void __cpuinit start_secondary(void)
+notrace __cpuinit void start_secondary(void)
 {
 	/*
 	 * Dont put anything before smp_callin(), SMP

-- 

[PATCH 05/20 -v5] add notrace annotations to vsyscall.

[Steven Rostedt]

[-- Attachment #1: mcount-add-x86-vdso-notrace-annotations.patch --]
[-- Type: text/plain, Size: 4566 bytes --]

Add the notrace annotations to some of the vsyscall functions.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/vsyscall_64.c  |    3 ++-
 arch/x86/vdso/vclock_gettime.c |   15 ++++++++-------
 arch/x86/vdso/vgetcpu.c        |    3 ++-
 include/asm-x86/vsyscall.h     |    3 ++-
 4 files changed, 14 insertions(+), 10 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/vsyscall_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/vsyscall_64.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/vsyscall_64.c	2008-01-23 10:26:49.000000000 -0500
@@ -42,7 +42,8 @@
 #include <asm/topology.h>
 #include <asm/vgtod.h>
 
-#define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
+#define __vsyscall(nr) \
+		__attribute__ ((unused, __section__(".vsyscall_" #nr))) notrace
 #define __syscall_clobber "r11","rcx","memory"
 #define __pa_vsymbol(x)			\
 	({unsigned long v;  		\
Index: linux-mcount.git/arch/x86/vdso/vclock_gettime.c
===================================================================
--- linux-mcount.git.orig/arch/x86/vdso/vclock_gettime.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/vdso/vclock_gettime.c	2008-01-23 10:26:49.000000000 -0500
@@ -24,7 +24,7 @@
 
 #define gtod vdso_vsyscall_gtod_data
 
-static long vdso_fallback_gettime(long clock, struct timespec *ts)
+notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 {
 	long ret;
 	asm("syscall" : "=a" (ret) :
@@ -32,7 +32,7 @@ static long vdso_fallback_gettime(long c
 	return ret;
 }
 
-static inline long vgetns(void)
+notrace static inline long vgetns(void)
 {
 	long v;
 	cycles_t (*vread)(void);
@@ -41,7 +41,7 @@ static inline long vgetns(void)
 	return (v * gtod->clock.mult) >> gtod->clock.shift;
 }
 
-static noinline int do_realtime(struct timespec *ts)
+notrace static noinline int do_realtime(struct timespec *ts)
 {
 	unsigned long seq, ns;
 	do {
@@ -55,7 +55,8 @@ static noinline int do_realtime(struct t
 }
 
 /* Copy of the version in kernel/time.c which we cannot directly access */
-static void vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
+notrace static void
+vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
 {
 	while (nsec >= NSEC_PER_SEC) {
 		nsec -= NSEC_PER_SEC;
@@ -69,7 +70,7 @@ static void vset_normalized_timespec(str
 	ts->tv_nsec = nsec;
 }
 
-static noinline int do_monotonic(struct timespec *ts)
+notrace static noinline int do_monotonic(struct timespec *ts)
 {
 	unsigned long seq, ns, secs;
 	do {
@@ -83,7 +84,7 @@ static noinline int do_monotonic(struct 
 	return 0;
 }
 
-int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
 	if (likely(gtod->sysctl_enabled && gtod->clock.vread))
 		switch (clock) {
@@ -97,7 +98,7 @@ int __vdso_clock_gettime(clockid_t clock
 int clock_gettime(clockid_t, struct timespec *)
 	__attribute__((weak, alias("__vdso_clock_gettime")));
 
-int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
 	long ret;
 	if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
Index: linux-mcount.git/arch/x86/vdso/vgetcpu.c
===================================================================
--- linux-mcount.git.orig/arch/x86/vdso/vgetcpu.c	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/arch/x86/vdso/vgetcpu.c	2008-01-23 10:26:49.000000000 -0500
@@ -13,7 +13,8 @@
 #include <asm/vgtod.h>
 #include "vextern.h"
 
-long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
+notrace long
+__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
 {
 	unsigned int dummy, p;
 
Index: linux-mcount.git/include/asm-x86/vsyscall.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/vsyscall.h	2008-01-23 10:26:31.000000000 -0500
+++ linux-mcount.git/include/asm-x86/vsyscall.h	2008-01-23 10:26:49.000000000 -0500
@@ -24,7 +24,8 @@ enum vsyscall_num {
 	((unused, __section__ (".vsyscall_gtod_data"),aligned(16)))
 #define __section_vsyscall_clock __attribute__ \
 	((unused, __section__ (".vsyscall_clock"),aligned(16)))
-#define __vsyscall_fn __attribute__ ((unused,__section__(".vsyscall_fn")))
+#define __vsyscall_fn \
+	__attribute__ ((unused, __section__(".vsyscall_fn"))) notrace
 
 #define VGETCPU_RDTSCP	1
 #define VGETCPU_LSL	2

-- 

[PATCH 06/20 -v5] add notrace annotations for NMI routines

[Steven Rostedt]

[-- Attachment #1: mcount-nmi-notrace-annotations.patch --]
[-- Type: text/plain, Size: 2466 bytes --]

This annotates NMI functions with notrace. Some tracers may be able
to live with this, but some cannot. So we turn off NMI tracing.

One solution might be to make a notrace_nmi which would only turn
off NMI tracing if a trace utility needed it off.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

---
 arch/x86/kernel/nmi_32.c   |    2 +-
 arch/x86/kernel/nmi_64.c   |    2 +-
 arch/x86/kernel/traps_32.c |    4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/nmi_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/nmi_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/nmi_32.c	2008-01-23 10:26:53.000000000 -0500
@@ -323,7 +323,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
 
 extern void die_nmi(struct pt_regs *, const char *msg);
 
-__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
+notrace __kprobes int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 {
 
 	/*
Index: linux-mcount.git/arch/x86/kernel/nmi_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/nmi_64.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/nmi_64.c	2008-01-23 10:26:53.000000000 -0500
@@ -314,7 +314,7 @@ void touch_nmi_watchdog(void)
  	touch_softlockup_watchdog();
 }
 
-int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
+notrace __kprobes int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 {
 	int sum;
 	int touched = 0;
Index: linux-mcount.git/arch/x86/kernel/traps_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/traps_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/traps_32.c	2008-01-23 10:26:53.000000000 -0500
@@ -723,7 +723,7 @@ void __kprobes die_nmi(struct pt_regs *r
 	do_exit(SIGSEGV);
 }
 
-static __kprobes void default_do_nmi(struct pt_regs * regs)
+static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 {
 	unsigned char reason = 0;
 
@@ -763,7 +763,7 @@ static __kprobes void default_do_nmi(str
 
 static int ignore_nmis;
 
-fastcall __kprobes void do_nmi(struct pt_regs * regs, long error_code)
+notrace fastcall __kprobes void do_nmi(struct pt_regs *regs, long error_code)
 {
 	int cpu;
 

-- 

[PATCH 07/20 -v5] handle accurate time keeping over long delays

[Steven Rostedt]

[-- Attachment #1: rt-time-starvation-fix.patch --]
[-- Type: text/plain, Size: 10266 bytes --]

Handle accurate time even if there's a long delay between
accumulated clock cycles.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/powerpc/kernel/time.c    |    3 +-
 arch/x86/kernel/vsyscall_64.c |    5 ++-
 include/asm-x86/vgtod.h       |    2 -
 include/linux/clocksource.h   |   58 ++++++++++++++++++++++++++++++++++++++++--
 kernel/time/timekeeping.c     |   36 +++++++++++++-------------
 5 files changed, 82 insertions(+), 22 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/vsyscall_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/vsyscall_64.c	2008-01-23 10:26:49.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/vsyscall_64.c	2008-01-23 10:26:57.000000000 -0500
@@ -86,6 +86,7 @@ void update_vsyscall(struct timespec *wa
 	vsyscall_gtod_data.clock.mask = clock->mask;
 	vsyscall_gtod_data.clock.mult = clock->mult;
 	vsyscall_gtod_data.clock.shift = clock->shift;
+	vsyscall_gtod_data.clock.cycle_accumulated = clock->cycle_accumulated;
 	vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
 	vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
 	vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
@@ -121,7 +122,7 @@ static __always_inline long time_syscall
 
 static __always_inline void do_vgettimeofday(struct timeval * tv)
 {
-	cycle_t now, base, mask, cycle_delta;
+	cycle_t now, base, accumulated, mask, cycle_delta;
 	unsigned seq;
 	unsigned long mult, shift, nsec;
 	cycle_t (*vread)(void);
@@ -135,6 +136,7 @@ static __always_inline void do_vgettimeo
 		}
 		now = vread();
 		base = __vsyscall_gtod_data.clock.cycle_last;
+		accumulated  = __vsyscall_gtod_data.clock.cycle_accumulated;
 		mask = __vsyscall_gtod_data.clock.mask;
 		mult = __vsyscall_gtod_data.clock.mult;
 		shift = __vsyscall_gtod_data.clock.shift;
@@ -145,6 +147,7 @@ static __always_inline void do_vgettimeo
 
 	/* calculate interval: */
 	cycle_delta = (now - base) & mask;
+	cycle_delta += accumulated;
 	/* convert to nsecs: */
 	nsec += (cycle_delta * mult) >> shift;
 
Index: linux-mcount.git/include/asm-x86/vgtod.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/vgtod.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/asm-x86/vgtod.h	2008-01-23 10:26:57.000000000 -0500
@@ -15,7 +15,7 @@ struct vsyscall_gtod_data {
 	struct timezone sys_tz;
 	struct { /* extract of a clocksource struct */
 		cycle_t (*vread)(void);
-		cycle_t	cycle_last;
+		cycle_t	cycle_last, cycle_accumulated;
 		cycle_t	mask;
 		u32	mult;
 		u32	shift;
Index: linux-mcount.git/include/linux/clocksource.h
===================================================================
--- linux-mcount.git.orig/include/linux/clocksource.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/linux/clocksource.h	2008-01-23 10:26:57.000000000 -0500
@@ -50,8 +50,12 @@ struct clocksource;
  * @flags:		flags describing special properties
  * @vread:		vsyscall based read
  * @resume:		resume function for the clocksource, if necessary
+ * @cycle_last:		Used internally by timekeeping core, please ignore.
+ * @cycle_accumulated:	Used internally by timekeeping core, please ignore.
  * @cycle_interval:	Used internally by timekeeping core, please ignore.
  * @xtime_interval:	Used internally by timekeeping core, please ignore.
+ * @xtime_nsec:		Used internally by timekeeping core, please ignore.
+ * @error:		Used internally by timekeeping core, please ignore.
  */
 struct clocksource {
 	/*
@@ -82,7 +86,10 @@ struct clocksource {
 	 * Keep it in a different cache line to dirty no
 	 * more than one cache line.
 	 */
-	cycle_t cycle_last ____cacheline_aligned_in_smp;
+	struct {
+		cycle_t cycle_last, cycle_accumulated;
+	} ____cacheline_aligned_in_smp;
+
 	u64 xtime_nsec;
 	s64 error;
 
@@ -168,11 +175,44 @@ static inline cycle_t clocksource_read(s
 }
 
 /**
+ * clocksource_get_cycles: - Access the clocksource's accumulated cycle value
+ * @cs:		pointer to clocksource being read
+ * @now:	current cycle value
+ *
+ * Uses the clocksource to return the current cycle_t value.
+ * NOTE!!!: This is different from clocksource_read, because it
+ * returns the accumulated cycle value! Must hold xtime lock!
+ */
+static inline cycle_t
+clocksource_get_cycles(struct clocksource *cs, cycle_t now)
+{
+	cycle_t offset = (now - cs->cycle_last) & cs->mask;
+	offset += cs->cycle_accumulated;
+	return offset;
+}
+
+/**
+ * clocksource_accumulate: - Accumulates clocksource cycles
+ * @cs:		pointer to clocksource being read
+ * @now:	current cycle value
+ *
+ * Used to avoids clocksource hardware overflow by periodically
+ * accumulating the current cycle delta. Must hold xtime write lock!
+ */
+static inline void clocksource_accumulate(struct clocksource *cs, cycle_t now)
+{
+	cycle_t offset = (now - cs->cycle_last) & cs->mask;
+	cs->cycle_last = now;
+	cs->cycle_accumulated += offset;
+}
+
+/**
  * cyc2ns - converts clocksource cycles to nanoseconds
  * @cs:		Pointer to clocksource
  * @cycles:	Cycles
  *
  * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
+ * Must hold xtime lock!
  *
  * XXX - This could use some mult_lxl_ll() asm optimization
  */
@@ -184,13 +224,27 @@ static inline s64 cyc2ns(struct clocksou
 }
 
 /**
+ * ns2cyc - converts nanoseconds to clocksource cycles
+ * @cs:		Pointer to clocksource
+ * @nsecs:	Nanoseconds
+ */
+static inline cycle_t ns2cyc(struct clocksource *cs, u64 nsecs)
+{
+	cycle_t ret = nsecs << cs->shift;
+
+	do_div(ret, cs->mult + 1);
+
+	return ret;
+}
+
+/**
  * clocksource_calculate_interval - Calculates a clocksource interval struct
  *
  * @c:		Pointer to clocksource.
  * @length_nsec: Desired interval length in nanoseconds.
  *
  * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
- * pair and interval request.
+ * pair and interval request. Must hold xtime_lock!
  *
  * Unless you're the timekeeping code, you should not be using this!
  */
Index: linux-mcount.git/kernel/time/timekeeping.c
===================================================================
--- linux-mcount.git.orig/kernel/time/timekeeping.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/kernel/time/timekeeping.c	2008-01-23 10:26:57.000000000 -0500
@@ -66,16 +66,10 @@ static struct clocksource *clock; /* poi
  */
 static inline s64 __get_nsec_offset(void)
 {
-	cycle_t cycle_now, cycle_delta;
+	cycle_t cycle_delta;
 	s64 ns_offset;
 
-	/* read clocksource: */
-	cycle_now = clocksource_read(clock);
-
-	/* calculate the delta since the last update_wall_time: */
-	cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
-
-	/* convert to nanoseconds: */
+	cycle_delta = clocksource_get_cycles(clock, clocksource_read(clock));
 	ns_offset = cyc2ns(clock, cycle_delta);
 
 	return ns_offset;
@@ -195,7 +189,7 @@ static void change_clocksource(void)
 
 	clock = new;
 	clock->cycle_last = now;
-
+	clock->cycle_accumulated = 0;
 	clock->error = 0;
 	clock->xtime_nsec = 0;
 	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -205,9 +199,15 @@ static void change_clocksource(void)
 	printk(KERN_INFO "Time: %s clocksource has been installed.\n",
 	       clock->name);
 }
+
+void timekeeping_accumulate(void)
+{
+	clocksource_accumulate(clock, clocksource_read(clock));
+}
 #else
 static inline void change_clocksource(void) { }
 static inline s64 __get_nsec_offset(void) { return 0; }
+void timekeeping_accumulate(void) { }
 #endif
 
 /**
@@ -302,6 +302,7 @@ static int timekeeping_resume(struct sys
 	timespec_add_ns(&xtime, timekeeping_suspend_nsecs);
 	/* re-base the last cycle value */
 	clock->cycle_last = clocksource_read(clock);
+	clock->cycle_accumulated = 0;
 	clock->error = 0;
 	timekeeping_suspended = 0;
 	write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -448,27 +449,28 @@ static void clocksource_adjust(s64 offse
  */
 void update_wall_time(void)
 {
-	cycle_t offset;
+	cycle_t cycle_now;
 
 	/* Make sure we're fully resumed: */
 	if (unlikely(timekeeping_suspended))
 		return;
 
 #ifdef CONFIG_GENERIC_TIME
-	offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask;
+	cycle_now = clocksource_read(clock);
 #else
-	offset = clock->cycle_interval;
+	cycle_now = clock->cycle_last + clock->cycle_interval;
 #endif
+	clocksource_accumulate(clock, cycle_now);
+
 	clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift;
 
 	/* normally this loop will run just once, however in the
 	 * case of lost or late ticks, it will accumulate correctly.
 	 */
-	while (offset >= clock->cycle_interval) {
+	while (clock->cycle_accumulated >= clock->cycle_interval) {
 		/* accumulate one interval */
 		clock->xtime_nsec += clock->xtime_interval;
-		clock->cycle_last += clock->cycle_interval;
-		offset -= clock->cycle_interval;
+		clock->cycle_accumulated -= clock->cycle_interval;
 
 		if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
 			clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
@@ -482,13 +484,13 @@ void update_wall_time(void)
 	}
 
 	/* correct the clock when NTP error is too big */
-	clocksource_adjust(offset);
+	clocksource_adjust(clock->cycle_accumulated);
 
 	/* store full nanoseconds into xtime */
 	xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
 	clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
 
-	update_xtime_cache(cyc2ns(clock, offset));
+	update_xtime_cache(cyc2ns(clock, clock->cycle_accumulated));
 
 	/* check to see if there is a new clocksource to use */
 	change_clocksource();
Index: linux-mcount.git/arch/powerpc/kernel/time.c
===================================================================
--- linux-mcount.git.orig/arch/powerpc/kernel/time.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/powerpc/kernel/time.c	2008-01-23 10:26:57.000000000 -0500
@@ -773,7 +773,8 @@ void update_vsyscall(struct timespec *wa
 	stamp_xsec = (u64) xtime.tv_nsec * XSEC_PER_SEC;
 	do_div(stamp_xsec, 1000000000);
 	stamp_xsec += (u64) xtime.tv_sec * XSEC_PER_SEC;
-	update_gtod(clock->cycle_last, stamp_xsec, t2x);
+	update_gtod(clock->cycle_last-clock->cycle_accumulated,
+		    stamp_xsec, t2x);
 }
 
 void update_vsyscall_tz(void)

-- 

[PATCH 08/20 -v5] initialize the clock source to jiffies clock.

[Steven Rostedt]

[-- Attachment #1: initialize-clocksource-to-jiffies.patch --]
[-- Type: text/plain, Size: 2086 bytes --]

The latency tracer can call clocksource_read very early in bootup and
before the clock source variable has been initialized. This results in a
crash at boot up (even before earlyprintk is initialized). Since the
clock->read variable points to NULL.

This patch simply initializes the clock to use clocksource_jiffies, so
that any early user of clocksource_read will not crash.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: John Stultz <johnstul@us.ibm.com>
---
 include/linux/clocksource.h |    3 +++
 kernel/time/timekeeping.c   |    9 +++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

Index: linux-mcount.git/include/linux/clocksource.h
===================================================================
--- linux-mcount.git.orig/include/linux/clocksource.h	2008-01-23 10:26:57.000000000 -0500
+++ linux-mcount.git/include/linux/clocksource.h	2008-01-23 10:27:04.000000000 -0500
@@ -273,6 +273,9 @@ extern struct clocksource* clocksource_g
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 extern void clocksource_resume(void);
 
+/* used to initialize clock */
+extern struct clocksource clocksource_jiffies;
+
 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
 extern void update_vsyscall_tz(void);
Index: linux-mcount.git/kernel/time/timekeeping.c
===================================================================
--- linux-mcount.git.orig/kernel/time/timekeeping.c	2008-01-23 10:26:57.000000000 -0500
+++ linux-mcount.git/kernel/time/timekeeping.c	2008-01-23 10:27:04.000000000 -0500
@@ -53,8 +53,13 @@ static inline void update_xtime_cache(u6
 	timespec_add_ns(&xtime_cache, nsec);
 }
 
-static struct clocksource *clock; /* pointer to current clocksource */
-
+/*
+ * pointer to current clocksource
+ *  Just in case we use clocksource_read before we initialize
+ *  the actual clock source. Instead of calling a NULL read pointer
+ *  we return jiffies.
+ */
+static struct clocksource *clock = &clocksource_jiffies;
 
 #ifdef CONFIG_GENERIC_TIME
 /**

-- 

[PATCH 09/20 -v5] add get_monotonic_cycles

[Steven Rostedt]

[-- Attachment #1: get-monotonic-cycles.patch --]
[-- Type: text/plain, Size: 5342 bytes --]

The latency tracer needs a way to get an accurate time
without grabbing any locks. Locks themselves might call
the latency tracer and cause at best a slow down.

This patch adds get_monotonic_cycles that returns cycles
from a reliable clock source in a monotonic fashion.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 include/linux/clocksource.h |   54 +++++++++++++++++++++++++++++++++++++-------
 kernel/time/timekeeping.c   |   26 +++++++++++++++++++--
 2 files changed, 70 insertions(+), 10 deletions(-)

Index: linux-mcount.git/include/linux/clocksource.h
===================================================================
--- linux-mcount.git.orig/include/linux/clocksource.h	2008-01-23 10:27:04.000000000 -0500
+++ linux-mcount.git/include/linux/clocksource.h	2008-01-23 10:27:10.000000000 -0500
@@ -88,8 +88,16 @@ struct clocksource {
 	 */
 	struct {
 		cycle_t cycle_last, cycle_accumulated;
-	} ____cacheline_aligned_in_smp;
 
+		/* base structure provides lock-free read
+		 * access to a virtualized 64bit counter
+		 * Uses RCU-like update.
+		 */
+		struct {
+			cycle_t cycle_base_last, cycle_base;
+		} base[2];
+		int base_num;
+	} ____cacheline_aligned_in_smp;
 	u64 xtime_nsec;
 	s64 error;
 
@@ -175,19 +183,30 @@ static inline cycle_t clocksource_read(s
 }
 
 /**
- * clocksource_get_cycles: - Access the clocksource's accumulated cycle value
+ * clocksource_get_basecycles: - get the clocksource's accumulated cycle value
  * @cs:		pointer to clocksource being read
  * @now:	current cycle value
  *
  * Uses the clocksource to return the current cycle_t value.
  * NOTE!!!: This is different from clocksource_read, because it
- * returns the accumulated cycle value! Must hold xtime lock!
+ * returns a 64bit wide accumulated value.
  */
 static inline cycle_t
-clocksource_get_cycles(struct clocksource *cs, cycle_t now)
+clocksource_get_basecycles(struct clocksource *cs)
 {
-	cycle_t offset = (now - cs->cycle_last) & cs->mask;
-	offset += cs->cycle_accumulated;
+	int num;
+	cycle_t now, offset;
+
+	preempt_disable();
+	num = cs->base_num;
+	/* base_num is shared, and some archs are wacky */
+	smp_read_barrier_depends();
+	now = clocksource_read(cs);
+	offset = (now - cs->base[num].cycle_base_last);
+	offset &= cs->mask;
+	offset += cs->base[num].cycle_base;
+	preempt_enable();
+
 	return offset;
 }
 
@@ -197,11 +216,27 @@ clocksource_get_cycles(struct clocksourc
  * @now:	current cycle value
  *
  * Used to avoids clocksource hardware overflow by periodically
- * accumulating the current cycle delta. Must hold xtime write lock!
+ * accumulating the current cycle delta. Uses RCU-like update, but
+ * ***still requires the xtime_lock is held for writing!***
  */
 static inline void clocksource_accumulate(struct clocksource *cs, cycle_t now)
 {
-	cycle_t offset = (now - cs->cycle_last) & cs->mask;
+	/*
+	 * First update the monotonic base portion.
+	 * The dual array update method allows for lock-free reading.
+	 * 'num' is always 1 or 0.
+	 */
+	int num = 1 - cs->base_num;
+	cycle_t offset = (now - cs->base[1-num].cycle_base_last);
+	offset &= cs->mask;
+	cs->base[num].cycle_base = cs->base[1-num].cycle_base + offset;
+	cs->base[num].cycle_base_last = now;
+	/* make sure this array is visible to the world first */
+	smp_wmb();
+	cs->base_num = num;
+
+	/* Now update the cycle_accumulated portion */
+	offset = (now - cs->cycle_last) & cs->mask;
 	cs->cycle_last = now;
 	cs->cycle_accumulated += offset;
 }
@@ -272,6 +307,9 @@ extern int clocksource_register(struct c
 extern struct clocksource* clocksource_get_next(void);
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 extern void clocksource_resume(void);
+extern cycle_t get_monotonic_cycles(void);
+extern unsigned long cycles_to_usecs(cycle_t cycles);
+extern cycle_t usecs_to_cycles(unsigned long usecs);
 
 /* used to initialize clock */
 extern struct clocksource clocksource_jiffies;
Index: linux-mcount.git/kernel/time/timekeeping.c
===================================================================
--- linux-mcount.git.orig/kernel/time/timekeeping.c	2008-01-23 10:27:04.000000000 -0500
+++ linux-mcount.git/kernel/time/timekeeping.c	2008-01-23 10:27:10.000000000 -0500
@@ -71,10 +71,12 @@ static struct clocksource *clock = &cloc
  */
 static inline s64 __get_nsec_offset(void)
 {
-	cycle_t cycle_delta;
+	cycle_t now, cycle_delta;
 	s64 ns_offset;
 
-	cycle_delta = clocksource_get_cycles(clock, clocksource_read(clock));
+	now = clocksource_read(clock);
+	cycle_delta = (now - clock->cycle_last) & clock->mask;
+	cycle_delta += clock->cycle_accumulated;
 	ns_offset = cyc2ns(clock, cycle_delta);
 
 	return ns_offset;
@@ -103,6 +105,26 @@ static inline void __get_realtime_clock_
 	timespec_add_ns(ts, nsecs);
 }
 
+cycle_t notrace get_monotonic_cycles(void)
+{
+	return clocksource_get_basecycles(clock);
+}
+
+unsigned long notrace cycles_to_usecs(cycle_t cycles)
+{
+	u64 ret = cyc2ns(clock, cycles);
+
+	ret += NSEC_PER_USEC/2; /* For rounding in do_div() */
+	do_div(ret, NSEC_PER_USEC);
+
+	return ret;
+}
+
+cycle_t notrace usecs_to_cycles(unsigned long usecs)
+{
+	return ns2cyc(clock, (u64)usecs * 1000);
+}
+
 /**
  * getnstimeofday - Returns the time of day in a timespec
  * @ts:		pointer to the timespec to be set

-- 

[PATCH 10/20 -v5] add notrace annotations to timing events

[Steven Rostedt]

[-- Attachment #1: mcount-add-time-notrace-annotations.patch --]
[-- Type: text/plain, Size: 5179 bytes --]

This patch adds notrace annotations to timer functions
that will be used by tracing. This helps speed things up and
also keeps the ugliness of printing these functions down.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/apic_32.c     |    2 +-
 arch/x86/kernel/hpet.c        |    2 +-
 arch/x86/kernel/time_32.c     |    2 +-
 arch/x86/kernel/tsc_32.c      |    2 +-
 arch/x86/kernel/tsc_64.c      |    4 ++--
 arch/x86/lib/delay_32.c       |    6 +++---
 drivers/clocksource/acpi_pm.c |    8 ++++----
 7 files changed, 13 insertions(+), 13 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/apic_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/apic_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/apic_32.c	2008-01-23 10:27:14.000000000 -0500
@@ -577,7 +577,7 @@ static void local_apic_timer_interrupt(v
  *   interrupt as well. Thus we cannot inline the local irq ... ]
  */
 
-void fastcall smp_apic_timer_interrupt(struct pt_regs *regs)
+notrace fastcall void smp_apic_timer_interrupt(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
Index: linux-mcount.git/arch/x86/kernel/hpet.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/hpet.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/hpet.c	2008-01-23 10:27:14.000000000 -0500
@@ -295,7 +295,7 @@ static int hpet_legacy_next_event(unsign
 /*
  * Clock source related code
  */
-static cycle_t read_hpet(void)
+static notrace cycle_t read_hpet(void)
 {
 	return (cycle_t)hpet_readl(HPET_COUNTER);
 }
Index: linux-mcount.git/arch/x86/kernel/time_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/time_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/time_32.c	2008-01-23 10:27:14.000000000 -0500
@@ -122,7 +122,7 @@ static int set_rtc_mmss(unsigned long no
 
 int timer_ack;
 
-unsigned long profile_pc(struct pt_regs *regs)
+notrace unsigned long profile_pc(struct pt_regs *regs)
 {
 	unsigned long pc = instruction_pointer(regs);
 
Index: linux-mcount.git/arch/x86/kernel/tsc_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/tsc_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/tsc_32.c	2008-01-23 10:27:14.000000000 -0500
@@ -269,7 +269,7 @@ core_initcall(cpufreq_tsc);
 
 static unsigned long current_tsc_khz = 0;
 
-static cycle_t read_tsc(void)
+static notrace cycle_t read_tsc(void)
 {
 	cycle_t ret;
 
Index: linux-mcount.git/arch/x86/kernel/tsc_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/tsc_64.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/tsc_64.c	2008-01-23 10:27:14.000000000 -0500
@@ -248,13 +248,13 @@ __setup("notsc", notsc_setup);
 
 
 /* clock source code: */
-static cycle_t read_tsc(void)
+static notrace cycle_t read_tsc(void)
 {
 	cycle_t ret = (cycle_t)get_cycles_sync();
 	return ret;
 }
 
-static cycle_t __vsyscall_fn vread_tsc(void)
+static notrace cycle_t __vsyscall_fn vread_tsc(void)
 {
 	cycle_t ret = (cycle_t)get_cycles_sync();
 	return ret;
Index: linux-mcount.git/arch/x86/lib/delay_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/lib/delay_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/lib/delay_32.c	2008-01-23 10:27:14.000000000 -0500
@@ -24,7 +24,7 @@
 #endif
 
 /* simple loop based delay: */
-static void delay_loop(unsigned long loops)
+static notrace void delay_loop(unsigned long loops)
 {
 	int d0;
 
@@ -39,7 +39,7 @@ static void delay_loop(unsigned long loo
 }
 
 /* TSC based delay: */
-static void delay_tsc(unsigned long loops)
+static notrace void delay_tsc(unsigned long loops)
 {
 	unsigned long bclock, now;
 
@@ -72,7 +72,7 @@ int read_current_timer(unsigned long *ti
 	return -1;
 }
 
-void __delay(unsigned long loops)
+notrace void __delay(unsigned long loops)
 {
 	delay_fn(loops);
 }
Index: linux-mcount.git/drivers/clocksource/acpi_pm.c
===================================================================
--- linux-mcount.git.orig/drivers/clocksource/acpi_pm.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/drivers/clocksource/acpi_pm.c	2008-01-23 10:27:14.000000000 -0500
@@ -30,13 +30,13 @@
  */
 u32 pmtmr_ioport __read_mostly;
 
-static inline u32 read_pmtmr(void)
+static inline notrace u32 read_pmtmr(void)
 {
 	/* mask the output to 24 bits */
 	return inl(pmtmr_ioport) & ACPI_PM_MASK;
 }
 
-u32 acpi_pm_read_verified(void)
+notrace u32 acpi_pm_read_verified(void)
 {
 	u32 v1 = 0, v2 = 0, v3 = 0;
 
@@ -56,12 +56,12 @@ u32 acpi_pm_read_verified(void)
 	return v2;
 }
 
-static cycle_t acpi_pm_read_slow(void)
+static notrace cycle_t acpi_pm_read_slow(void)
 {
 	return (cycle_t)acpi_pm_read_verified();
 }
 
-static cycle_t acpi_pm_read(void)
+static notrace cycle_t acpi_pm_read(void)
 {
 	return (cycle_t)read_pmtmr();
 }

-- 

[PATCH 11/20 -v5] mcount based trace in the form of a header file library

[Steven Rostedt]

[-- Attachment #1: mcount-function-tracer.patch --]
[-- Type: text/plain, Size: 37970 bytes --]

This is a simple trace that uses the mcount infrastructure. It is
designed to be fast and small, and easy to use. It is useful to
record things that happen over a very short period of time, and
not to analyze the system in general.

An interface is added to the debugfs

  /debugfs/tracing/

This patch adds the following files:

  available_tracers
     list of available tracers. Currently only "function" is
     available.

  current_tracer
     The trace that is currently active. Empty on start up.
     To switch to a tracer simply echo one of the tracers that
     are listed in available_tracers:

      echo function > /debugfs/tracing/current_tracer


  trace_ctrl
     echoing "1" into this file starts the mcount function tracing
      (if sysctl kernel.mcount_enabled=1)
     echoing "0" turns it off.

  latency_trace
      This file is readonly and holds the result of the trace.

  trace
      This file outputs a easier to read version of the trace.

  iter_ctrl
      Controls the way the output of traces look.
      So far there's two controls:
        echoing in "symonly" will only show the kallsyms variables
            without the addresses (if kallsyms was configured)
        echoing in "verbose" will change the output to show
            a lot more data, but not very easy to understand by
            humans.
        echoing in "nosymonly" turns off symonly.
        echoing in "noverbose" turns off verbose.

The output of the function_trace file is as follows

  "echo noverbose > /debugfs/tracing/iter_ctrl"

preemption latency trace v1.1.5 on 2.6.24-rc7-tst
--------------------------------------------------------------------
 latency: 0 us, #419428/4361791, CPU#1 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
    -----------------
    | task: -0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     0d.h. 1595128us+: set_normalized_timespec+0x8/0x2d <c043841d> (ktime_get_ts+0x4a/0x4e <c04499d4>)
 swapper-0     0d.h. 1595131us+: _spin_lock+0x8/0x18 <c0630690> (hrtimer_interrupt+0x6e/0x1b0 <c0449c56>)

Or with verbose turned on:

  "echo verbose > /debugfs/tracing/iter_ctrl"

preemption latency trace v1.1.5 on 2.6.24-rc7-tst
--------------------------------------------------------------------
 latency: 0 us, #419428/4361791, CPU#1 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
    -----------------
    | task: -0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------

         swapper     0 0 9 00000000 00000000 [f3675f41] 1595.128ms (+0.003ms): set_normalized_timespec+0x8/0x2d <c043841d> (ktime_get_ts+0x4a/0x4e <c04499d4>)
         swapper     0 0 9 00000000 00000001 [f3675f45] 1595.131ms (+0.003ms): _spin_lock+0x8/0x18 <c0630690> (hrtimer_interrupt+0x6e/0x1b0 <c0449c56>)
         swapper     0 0 9 00000000 00000002 [f3675f48] 1595.135ms (+0.003ms): _spin_lock+0x8/0x18 <c0630690> (hrtimer_interrupt+0x6e/0x1b0 <c0449c56>)


The "trace" file is not affected by the verbose mode, but is by the symonly.

 echo "nosymonly" > /debugfs/tracing/iter_ctrl

tracer:
[   81.479967] CPU 0: bash:3154 register_mcount_function+0x5f/0x66 <ffffffff80337a4d> <-- _spin_unlock_irqrestore+0xe/0x5a <ffffffff8048cc8f>
[   81.479967] CPU 0: bash:3154 _spin_unlock_irqrestore+0x3e/0x5a <ffffffff8048ccbf> <-- sub_preempt_count+0xc/0x7a <ffffffff80233d7b>
[   81.479968] CPU 0: bash:3154 sub_preempt_count+0x30/0x7a <ffffffff80233d9f> <-- in_lock_functions+0x9/0x24 <ffffffff8025a75d>
[   81.479968] CPU 0: bash:3154 vfs_write+0x11d/0x155 <ffffffff8029a043> <-- dnotify_parent+0x12/0x78 <ffffffff802d54fb>
[   81.479968] CPU 0: bash:3154 dnotify_parent+0x2d/0x78 <ffffffff802d5516> <-- _spin_lock+0xe/0x70 <ffffffff8048c910>
[   81.479969] CPU 0: bash:3154 _spin_lock+0x1b/0x70 <ffffffff8048c91d> <-- add_preempt_count+0xe/0x77 <ffffffff80233df7>
[   81.479969] CPU 0: bash:3154 add_preempt_count+0x3e/0x77 <ffffffff80233e27> <-- in_lock_functions+0x9/0x24 <ffffffff8025a75d>


 echo "symonly" > /debugfs/tracing/iter_ctrl

tracer:
[   81.479913] CPU 0: bash:3154 register_mcount_function+0x5f/0x66 <-- _spin_unlock_irqrestore+0xe/0x5a
[   81.479913] CPU 0: bash:3154 _spin_unlock_irqrestore+0x3e/0x5a <-- sub_preempt_count+0xc/0x7a
[   81.479913] CPU 0: bash:3154 sub_preempt_count+0x30/0x7a <-- in_lock_functions+0x9/0x24
[   81.479914] CPU 0: bash:3154 vfs_write+0x11d/0x155 <-- dnotify_parent+0x12/0x78
[   81.479914] CPU 0: bash:3154 dnotify_parent+0x2d/0x78 <-- _spin_lock+0xe/0x70
[   81.479914] CPU 0: bash:3154 _spin_lock+0x1b/0x70 <-- add_preempt_count+0xe/0x77
[   81.479914] CPU 0: bash:3154 add_preempt_count+0x3e/0x77 <-- in_lock_functions+0x9/0x24


Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
---
 lib/Makefile                 |    1 
 lib/tracing/Kconfig          |   15 
 lib/tracing/Makefile         |    3 
 lib/tracing/trace_function.c |   72 ++
 lib/tracing/tracer.c         | 1149 +++++++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.h         |   96 +++
 6 files changed, 1336 insertions(+)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:26:34.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:19.000000000 -0500
@@ -8,3 +8,18 @@ config HAVE_MCOUNT
 config MCOUNT
 	bool
 	select FRAME_POINTER
+
+config TRACING
+        bool
+	select DEBUG_FS
+
+config FUNCTION_TRACER
+	bool "Profiler instrumentation based tracer"
+	depends on DEBUG_KERNEL && HAVE_MCOUNT
+	select MCOUNT
+	select TRACING
+	help
+	  Use profiler instrumentation, adding -pg to CFLAGS. This will
+	  insert a call to an architecture specific __mcount routine,
+	  that the debugging mechanism using this facility will hook by
+	  providing a set of inline routines.
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:26:34.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:27:19.000000000 -0500
@@ -1,3 +1,6 @@
 obj-$(CONFIG_MCOUNT) += libmcount.o
 
+obj-$(CONFIG_TRACING) += tracer.o
+obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:19.000000000 -0500
@@ -0,0 +1,1149 @@
+/*
+ * ring buffer based mcount tracer
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Originally taken from the RT patch by:
+ *    Arnaldo Carvalho de Melo <acme@redhat.com>
+ *
+ * Based on code from the latency_tracer, that is:
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/linkage.h>
+#include <linux/seq_file.h>
+#include <linux/percpu.h>
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/utsrelease.h>
+#include <linux/uaccess.h>
+#include <linux/hardirq.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace tracer_trace __read_mostly;
+static DEFINE_PER_CPU(struct tracing_trace_cpu, tracer_trace_cpu);
+static int trace_enabled __read_mostly;
+static unsigned long trace_nr_entries = (65536UL);
+
+static struct trace_types_struct *trace_types __read_mostly;
+static struct trace_types_struct *current_trace __read_mostly;
+static int max_tracer_type_len;
+
+static DEFINE_MUTEX(trace_types_lock);
+
+static int __init set_nr_entries(char *str)
+{
+	if (!str)
+		return 0;
+	trace_nr_entries = simple_strtoul(str, &str, 0);
+	return 1;
+}
+__setup("trace_entries=", set_nr_entries);
+
+enum trace_type {
+	__TRACE_FIRST_TYPE = 0,
+
+	TRACE_FN,
+
+	__TRACE_LAST_TYPE
+};
+
+enum trace_flag_type {
+	TRACE_FLAG_IRQS_OFF		= 0x01,
+	TRACE_FLAG_NEED_RESCHED		= 0x02,
+	TRACE_FLAG_HARDIRQ		= 0x04,
+	TRACE_FLAG_SOFTIRQ		= 0x08,
+};
+
+int register_trace(struct trace_types_struct *type)
+{
+	struct trace_types_struct *t;
+	int len;
+	int ret = 0;
+
+	if (!type->name) {
+		pr_info("Tracer must have a name\n");
+		return -1;
+	}
+
+	mutex_lock(&trace_types_lock);
+	for (t = trace_types; t; t = t->next) {
+		if (strcmp(type->name, t->name) == 0) {
+			/* already found */
+			pr_info("Trace %s already registered\n",
+				type->name);
+			ret = -1;
+			goto out;
+		}
+	}
+
+	type->next = trace_types;
+	trace_types = type;
+	len = strlen(type->name);
+	if (len > max_tracer_type_len)
+		max_tracer_type_len = len;
+ out:
+	mutex_unlock(&trace_types_lock);
+
+	return ret;
+}
+
+void unregister_trace(struct trace_types_struct *type)
+{
+	struct trace_types_struct **t;
+	int len;
+
+	mutex_lock(&trace_types_lock);
+	for (t = &trace_types; *t; t = &(*t)->next) {
+		if (*t == type)
+			goto found;
+	}
+	pr_info("Trace %s not registered\n", type->name);
+	goto out;
+
+ found:
+	*t = (*t)->next;
+	if (strlen(type->name) != max_tracer_type_len)
+		goto out;
+
+	max_tracer_type_len = 0;
+	for (t = &trace_types; *t; t = &(*t)->next) {
+		len = strlen((*t)->name);
+		if (len > max_tracer_type_len)
+			max_tracer_type_len = len;
+	}
+ out:
+	mutex_unlock(&trace_types_lock);
+}
+
+void notrace tracing_reset(struct tracing_trace_cpu *data)
+{
+	data->trace_idx = 0;
+	atomic_set(&data->underrun, 0);
+}
+
+static void notrace function_trace_call(unsigned long ip,
+					unsigned long parent_ip)
+{
+	struct tracing_trace *tr = &tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+	int cpu;
+
+	if (unlikely(!trace_enabled))
+		return;
+
+	raw_local_irq_save(flags);
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+	atomic_inc(&data->disabled);
+
+	if (likely(atomic_read(&data->disabled) == 1))
+		tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+	atomic_dec(&data->disabled);
+	raw_local_irq_restore(flags);
+}
+
+static struct mcount_ops trace_ops __read_mostly =
+{
+	.func = function_trace_call,
+};
+
+void tracing_start_function_trace(void)
+{
+	register_mcount_function(&trace_ops);
+}
+
+void tracing_stop_function_trace(void)
+{
+	unregister_mcount_function(&trace_ops);
+}
+
+static inline notrace struct tracing_entry *
+tracing_get_trace_entry(struct tracing_trace *tr,
+			struct tracing_trace_cpu *data)
+{
+	unsigned long idx, idx_next;
+	struct tracing_entry *entry;
+
+	idx = data->trace_idx;
+	idx_next = idx + 1;
+
+	if (unlikely(idx_next >= tr->entries)) {
+		atomic_inc(&data->underrun);
+		idx_next = 0;
+	}
+
+	data->trace_idx = idx_next;
+
+	if (unlikely(idx_next != 0 && atomic_read(&data->underrun)))
+		atomic_inc(&data->underrun);
+
+	entry = data->trace + idx * TRACING_ENTRY_SIZE;
+
+	return entry;
+}
+
+static inline notrace void
+tracing_generic_entry_update(struct tracing_entry *entry,
+			     unsigned long flags)
+{
+	struct task_struct *tsk = current;
+	unsigned long pc;
+
+	pc = preempt_count();
+
+	entry->preempt_count = pc & 0xff;
+	entry->pid	 = tsk->pid;
+	entry->t	 = now();
+	entry->flags = (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
+		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
+		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
+		(need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
+	memcpy(entry->comm, tsk->comm, TASK_COMM_LEN);
+}
+
+notrace void tracing_function_trace(struct tracing_trace *tr,
+				    struct tracing_trace_cpu *data,
+				    unsigned long ip,
+				    unsigned long parent_ip,
+				    unsigned long flags)
+{
+	struct tracing_entry *entry;
+
+	entry = tracing_get_trace_entry(tr, data);
+	tracing_generic_entry_update(entry, flags);
+	entry->type	    = TRACE_FN;
+	entry->fn.ip	    = ip;
+	entry->fn.parent_ip = parent_ip;
+}
+
+enum trace_iterator {
+	TRACE_ITER_SYM_ONLY	= 1,
+	TRACE_ITER_VERBOSE	= 2,
+};
+
+/* These must match the bit postions above */
+static const char *trace_options[] = {
+	"symonly",
+	"verbose",
+	NULL
+};
+
+static unsigned trace_flags;
+
+enum trace_file_type {
+	TRACE_FILE_LAT_FMT	= 1,
+};
+
+static struct tracing_entry *tracing_entry_idx(struct tracing_trace *tr,
+					       unsigned long idx,
+					       int cpu)
+{
+	struct tracing_entry *array = tr->data[cpu]->trace;
+	unsigned long underrun;
+
+	if (idx >= tr->entries)
+		return NULL;
+
+	underrun = atomic_read(&tr->data[cpu]->underrun);
+	if (underrun)
+		idx = ((underrun - 1) + idx) % tr->entries;
+	else if (idx >= tr->data[cpu]->trace_idx)
+		return NULL;
+
+	return &array[idx];
+}
+
+static struct notrace tracing_entry *
+find_next_entry(struct tracing_iterator *iter, int *ent_cpu)
+{
+	struct tracing_trace *tr = iter->tr;
+	struct tracing_entry *ent, *next = NULL;
+	int next_cpu = -1;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		if (!tr->data[cpu]->trace)
+			continue;
+		ent = tracing_entry_idx(tr, iter->next_idx[cpu], cpu);
+		if (ent && (!next || next->t > ent->t)) {
+			next = ent;
+			next_cpu = cpu;
+		}
+	}
+
+	if (ent_cpu)
+		*ent_cpu = next_cpu;
+
+	return next;
+}
+
+static void *find_next_entry_inc(struct tracing_iterator *iter)
+{
+	struct tracing_entry *next;
+	int next_cpu = -1;
+
+	next = find_next_entry(iter, &next_cpu);
+
+	if (next) {
+		iter->next_idx[next_cpu]++;
+		iter->idx++;
+	}
+	iter->ent = next;
+	iter->cpu = next_cpu;
+
+	return next ? iter : NULL;
+}
+
+static void notrace *
+s_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct tracing_iterator *iter = m->private;
+	void *ent;
+	void *last_ent = iter->ent;
+	int i = (int)*pos;
+
+	(*pos)++;
+
+	/* can't go backwards */
+	if (iter->idx > i)
+		return NULL;
+
+	if (iter->idx < 0)
+		ent = find_next_entry_inc(iter);
+	else
+		ent = iter;
+
+	while (ent && iter->idx < i)
+		ent = find_next_entry_inc(iter);
+
+	iter->pos = *pos;
+
+	if (last_ent && !ent)
+		seq_puts(m, "\n\nvim:ft=help\n");
+
+	return ent;
+}
+
+static void *s_start(struct seq_file *m, loff_t *pos)
+{
+	struct tracing_iterator *iter = m->private;
+	void *p = NULL;
+	loff_t l = 0;
+	int i;
+
+	mutex_lock(&trace_types_lock);
+
+	if (!current_trace || current_trace != iter->trace)
+		return NULL;
+
+	/* let the tracer grab locks here if needed */
+	if (current_trace->start)
+		current_trace->start(iter);
+
+	if (*pos != iter->pos) {
+		iter->ent = NULL;
+		iter->cpu = 0;
+		iter->idx = -1;
+
+		for (i = 0; i < NR_CPUS; i++)
+			iter->next_idx[i] = 0;
+
+		for (p = iter; p && l < *pos; p = s_next(m, p, &l))
+			;
+
+	} else {
+		l = *pos;
+		p = s_next(m, p, &l);
+	}
+
+	return p;
+}
+
+static void s_stop(struct seq_file *m, void *p)
+{
+	struct tracing_iterator *iter = m->private;
+
+	/* let the tracer release locks here if needed */
+	if (current_trace && current_trace == iter->trace && iter->trace->stop)
+		iter->trace->stop(iter);
+
+	mutex_unlock(&trace_types_lock);
+}
+
+#ifdef CONFIG_KALLSYMS
+static void seq_print_symbol(struct seq_file *m,
+			     const char *fmt, unsigned long address)
+{
+	char buffer[KSYM_SYMBOL_LEN];
+
+	sprint_symbol(buffer, address);
+	seq_printf(m, fmt, buffer);
+}
+#else
+# define seq_print_symbol(m, fmt, address) do { } while (0)
+#endif
+
+#ifndef CONFIG_64BIT
+# define IP_FMT "%08lx"
+#else
+# define IP_FMT "%016lx"
+#endif
+
+static void notrace seq_print_ip_sym(struct seq_file *m,
+				     unsigned long ip, int sym_only)
+{
+	if (!ip) {
+		seq_printf(m, "0");
+		return;
+	}
+
+	seq_print_symbol(m, "%s", ip);
+	if (!sym_only)
+		seq_printf(m, " <" IP_FMT ">", ip);
+}
+
+static void notrace print_help_header(struct seq_file *m)
+{
+	seq_puts(m, "                 _------=> CPU#            \n");
+	seq_puts(m, "                / _-----=> irqs-off        \n");
+	seq_puts(m, "               | / _----=> need-resched    \n");
+	seq_puts(m, "               || / _---=> hardirq/softirq \n");
+	seq_puts(m, "               ||| / _--=> preempt-depth   \n");
+	seq_puts(m, "               |||| /                      \n");
+	seq_puts(m, "               |||||     delay             \n");
+	seq_puts(m, "   cmd     pid ||||| time  |   caller      \n");
+	seq_puts(m, "      \\   /    |||||   \\   |   /           \n");
+}
+
+static void notrace print_trace_header(struct seq_file *m,
+				       struct tracing_iterator *iter)
+{
+	struct tracing_trace *tr = iter->tr;
+	struct tracing_trace_cpu *data = tr->data[tr->cpu];
+	struct trace_types_struct *type = current_trace;
+	unsigned long underruns = 0;
+	unsigned long underrun;
+	unsigned long entries   = 0;
+	int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
+	int cpu;
+	const char *name = "preemption";
+
+	if (type)
+		name = type->name;
+
+	for_each_possible_cpu(cpu) {
+		if (tr->data[cpu]->trace) {
+			underrun = atomic_read(&tr->data[cpu]->underrun);
+			if (underrun) {
+				underruns += underrun;
+				entries += tr->entries;
+			} else
+				entries += tr->data[cpu]->trace_idx;
+		}
+	}
+
+	seq_printf(m, "%s latency trace v1.1.5 on %s\n",
+		   name, UTS_RELEASE);
+	seq_puts(m, "-----------------------------------"
+		 "---------------------------------\n");
+	seq_printf(m, " latency: %lu us, #%lu/%lu, CPU#%d |"
+		   " (M:%s VP:%d, KP:%d, SP:%d HP:%d",
+		   cycles_to_usecs(data->saved_latency),
+		   entries,
+		   (entries + underruns),
+		   tr->cpu,
+#if defined(CONFIG_PREEMPT_NONE)
+		   "server",
+#elif defined(CONFIG_PREEMPT_VOLUNTARY)
+		   "desktop",
+#elif defined(CONFIG_PREEMPT_DESKTOP)
+		   "preempt",
+#else
+		   "unknown",
+#endif
+		   /* These are reserved for later use */
+		   0, 0, 0, 0);
+#ifdef CONFIG_SMP
+	seq_printf(m, " #P:%d)\n", num_online_cpus());
+#else
+	seq_puts(m, ")\n");
+#endif
+	seq_puts(m, "    -----------------\n");
+	seq_printf(m, "    | task: %.16s-%d "
+		   "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
+		   data->comm, data->pid, data->uid, data->nice,
+		   data->policy, data->rt_priority);
+	seq_puts(m, "    -----------------\n");
+
+	if (data->critical_start) {
+		seq_puts(m, " => started at: ");
+		seq_print_ip_sym(m, data->critical_start, sym_only);
+		seq_puts(m, "\n => ended at:   ");
+		seq_print_ip_sym(m, data->critical_end, sym_only);
+		seq_puts(m, "\n");
+	}
+
+	seq_puts(m, "\n");
+}
+
+
+static void notrace
+lat_print_generic(struct seq_file *m, struct tracing_entry *entry, int cpu)
+{
+	int hardirq, softirq;
+
+	seq_printf(m, "%8.8s-%-5d ", entry->comm, entry->pid);
+	seq_printf(m, "%d", cpu);
+	seq_printf(m, "%c%c",
+		   (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
+		   ((entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'));
+
+	hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
+	softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
+	if (hardirq && softirq)
+		seq_putc(m, 'H');
+	else {
+		if (hardirq)
+			seq_putc(m, 'h');
+		else {
+			if (softirq)
+				seq_putc(m, 's');
+			else
+				seq_putc(m, '.');
+		}
+	}
+
+	if (entry->preempt_count)
+		seq_printf(m, "%x", entry->preempt_count);
+	else
+		seq_puts(m, ".");
+}
+
+unsigned long preempt_mark_thresh = 100;
+
+static void notrace
+lat_print_timestamp(struct seq_file *m, unsigned long long abs_usecs,
+		    unsigned long rel_usecs)
+{
+	seq_printf(m, " %4lldus", abs_usecs);
+	if (rel_usecs > preempt_mark_thresh)
+		seq_puts(m, "!: ");
+	else if (rel_usecs > 1)
+		seq_puts(m, "+: ");
+	else
+		seq_puts(m, " : ");
+}
+
+static void notrace
+print_lat_fmt(struct seq_file *m, struct tracing_iterator *iter,
+	      unsigned int trace_idx, int cpu)
+{
+	struct tracing_entry *entry = iter->ent;
+	struct tracing_entry *next_entry = find_next_entry(iter, NULL);
+	unsigned long abs_usecs;
+	unsigned long rel_usecs;
+	int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
+	int verbose = !!(trace_flags & TRACE_ITER_VERBOSE);
+
+	if (!next_entry)
+		next_entry = entry;
+	rel_usecs = cycles_to_usecs(next_entry->t - entry->t);
+	abs_usecs = cycles_to_usecs(entry->t - iter->tr->time_start);
+
+	if (verbose) {
+		seq_printf(m, "%16s %5d %d %d %08x %08x [%08lx]"
+			   " %ld.%03ldms (+%ld.%03ldms): ",
+			   entry->comm,
+			   entry->pid, cpu, entry->flags,
+			   entry->preempt_count, trace_idx,
+			   cycles_to_usecs(entry->t),
+			   abs_usecs/1000,
+			   abs_usecs % 1000, rel_usecs/1000, rel_usecs % 1000);
+	} else {
+		lat_print_generic(m, entry, cpu);
+		lat_print_timestamp(m, abs_usecs, rel_usecs);
+	}
+	switch (entry->type) {
+	case TRACE_FN:
+		seq_print_ip_sym(m, entry->fn.ip, sym_only);
+		seq_puts(m, " (");
+		seq_print_ip_sym(m, entry->fn.parent_ip, sym_only);
+		seq_puts(m, ")\n");
+		break;
+	}
+}
+
+static void notrace print_trace_fmt(struct seq_file *m,
+				    struct tracing_iterator *iter)
+{
+	unsigned long usec_rem;
+	unsigned long secs;
+	int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
+	unsigned long long t;
+
+	t = cycles_to_usecs(iter->ent->t);
+	usec_rem = do_div(t, 1000000ULL);
+	secs = (unsigned long)t;
+
+	seq_printf(m, "[%5lu.%06lu] ", secs, usec_rem);
+	seq_printf(m, "CPU %d: ", iter->cpu);
+	seq_printf(m, "%s:%d ", iter->ent->comm,
+		   iter->ent->pid);
+	switch (iter->ent->type) {
+	case TRACE_FN:
+		seq_print_ip_sym(m, iter->ent->fn.ip, sym_only);
+		if (iter->ent->fn.parent_ip) {
+			seq_printf(m, " <-- ");
+			seq_print_ip_sym(m, iter->ent->fn.parent_ip,
+					 sym_only);
+		}
+		break;
+	}
+	seq_printf(m, "\n");
+}
+
+static int trace_empty(struct tracing_iterator *iter)
+{
+	struct tracing_trace_cpu *data;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		data = iter->tr->data[cpu];
+
+		if (data->trace &&
+		    (data->trace_idx ||
+		     atomic_read(&data->underrun)))
+			return 0;
+	}
+	return 1;
+}
+
+static int s_show(struct seq_file *m, void *v)
+{
+	struct tracing_iterator *iter = v;
+
+	if (iter->ent == NULL) {
+		if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
+			/* print nothing if the buffers are empty */
+			if (trace_empty(iter))
+				return 0;
+			print_trace_header(m, iter);
+			if (!(trace_flags & TRACE_ITER_VERBOSE))
+				print_help_header(m);
+		} else
+			seq_printf(m, "tracer:\n");
+	} else {
+		if (iter->iter_flags & TRACE_FILE_LAT_FMT)
+			print_lat_fmt(m, iter, iter->idx, iter->cpu);
+		else
+			print_trace_fmt(m, iter);
+	}
+
+	return 0;
+}
+
+static struct seq_operations tracer_seq_ops = {
+	.start = s_start,
+	.next = s_next,
+	.stop = s_stop,
+	.show = s_show,
+};
+
+static struct tracing_iterator notrace *
+__tracing_open(struct inode *inode, struct file *file, int *ret)
+{
+	struct tracing_iterator *iter;
+
+	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
+	if (!iter) {
+		*ret = -ENOMEM;
+		goto out;
+	}
+
+	iter->tr = inode->i_private;
+	iter->trace = current_trace;
+	iter->pos = -1;
+
+	/* TODO stop tracer */
+	*ret = seq_open(file, &tracer_seq_ops);
+	if (!*ret) {
+		struct seq_file *m = file->private_data;
+		m->private = iter;
+
+		/* stop the trace while dumping */
+		if (iter->tr->ctrl)
+			trace_enabled = 0;
+
+		if (iter->trace && iter->trace->open)
+			iter->trace->open(iter);
+	} else {
+		kfree(iter);
+		iter = NULL;
+	}
+
+ out:
+	return iter;
+}
+
+int tracing_open_generic(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+	return 0;
+}
+
+int tracing_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *m = (struct seq_file *)file->private_data;
+	struct tracing_iterator *iter = m->private;
+
+	if (iter->trace && iter->trace->close)
+		iter->trace->close(iter);
+
+	/* reenable tracing if it was previously enabled */
+	if (iter->tr->ctrl)
+		trace_enabled = 1;
+
+	seq_release(inode, file);
+	kfree(iter);
+	return 0;
+}
+
+static int tracing_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	__tracing_open(inode, file, &ret);
+
+	return ret;
+}
+
+static int tracing_lt_open(struct inode *inode, struct file *file)
+{
+	struct tracing_iterator *iter;
+	int ret;
+
+	iter = __tracing_open(inode, file, &ret);
+
+	if (!ret)
+		iter->iter_flags |= TRACE_FILE_LAT_FMT;
+
+	return ret;
+}
+
+
+static void notrace *
+t_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct trace_types_struct *t = m->private;
+
+	(*pos)++;
+
+	if (t)
+		t = t->next;
+
+	m->private = t;
+
+	return t;
+}
+
+static void *t_start(struct seq_file *m, loff_t *pos)
+{
+	struct trace_types_struct *t = m->private;
+	loff_t l = 0;
+
+	mutex_lock(&trace_types_lock);
+	for (; t && l < *pos; t = t_next(m, t, &l))
+		;
+
+	return t;
+}
+
+static void t_stop(struct seq_file *m, void *p)
+{
+	mutex_unlock(&trace_types_lock);
+}
+
+static int t_show(struct seq_file *m, void *v)
+{
+	struct trace_types_struct *t = v;
+
+	if (!t)
+		return 0;
+
+	seq_printf(m, "%s", t->name);
+	if (t->next)
+		seq_putc(m, ' ');
+	else
+		seq_putc(m, '\n');
+
+	return 0;
+}
+
+static struct seq_operations show_traces_seq_ops = {
+	.start = t_start,
+	.next = t_next,
+	.stop = t_stop,
+	.show = t_show,
+};
+
+static int show_traces_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open(file, &show_traces_seq_ops);
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+		m->private = trace_types;
+	}
+
+	return ret;
+}
+
+static struct file_operations tracing_fops = {
+	.open = tracing_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = tracing_release,
+};
+
+static struct file_operations tracing_lt_fops = {
+	.open = tracing_lt_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = tracing_release,
+};
+
+static struct file_operations show_traces_fops = {
+	.open = show_traces_open,
+	.read = seq_read,
+	.release = seq_release,
+};
+
+static ssize_t tracing_iter_ctrl_read(struct file *filp, char __user *ubuf,
+				      size_t cnt, loff_t *ppos)
+{
+	char *buf;
+	int r = 0;
+	int len = 0;
+	int i;
+
+	/* calulate max size */
+	for (i = 0; trace_options[i]; i++) {
+		len += strlen(trace_options[i]);
+		len += 3; /* "no" and space */
+	}
+
+	/* +2 for \n and \0 */
+	buf = kmalloc(len + 2, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	for (i = 0; trace_options[i]; i++) {
+		if (trace_flags & (1 << i))
+			r += sprintf(buf + r, "%s ", trace_options[i]);
+		else
+			r += sprintf(buf + r, "no%s ", trace_options[i]);
+	}
+
+	r += sprintf(buf + r, "\n");
+	WARN_ON(r >= len + 2);
+
+	r = simple_read_from_buffer(ubuf, cnt, ppos,
+				    buf, r);
+
+	kfree(buf);
+
+	return r;
+}
+
+static ssize_t tracing_iter_ctrl_write(struct file *filp,
+				       const char __user *ubuf,
+				       size_t cnt, loff_t *ppos)
+{
+	char buf[64];
+	char *cmp = buf;
+	int neg = 0;
+	int i;
+
+	if (cnt > 63)
+		cnt = 63;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	if (strncmp(buf, "no", 2) == 0) {
+		neg = 1;
+		cmp += 2;
+	}
+
+	for (i = 0; trace_options[i]; i++) {
+		int len = strlen(trace_options[i]);
+
+		if (strncmp(cmp, trace_options[i], len) == 0) {
+			if (neg)
+				trace_flags &= ~(1 << i);
+			else
+				trace_flags |= (1 << i);
+			break;
+		}
+	}
+
+	filp->f_pos += cnt;
+
+	return cnt;
+}
+
+static struct file_operations tracing_iter_fops = {
+	.open = tracing_open_generic,
+	.read = tracing_iter_ctrl_read,
+	.write = tracing_iter_ctrl_write,
+};
+
+static ssize_t tracing_ctrl_read(struct file *filp, char __user *ubuf,
+				 size_t cnt, loff_t *ppos)
+{
+	struct tracing_trace *tr = filp->private_data;
+	char buf[64];
+	int r;
+
+	r = sprintf(buf, "%ld\n", tr->ctrl);
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+				       buf, r);
+}
+
+static ssize_t tracing_ctrl_write(struct file *filp,
+				  const char __user *ubuf,
+				  size_t cnt, loff_t *ppos)
+{
+	struct tracing_trace *tr = filp->private_data;
+	long val;
+	char buf[64];
+
+	if (cnt > 63)
+		cnt = 63;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	val = simple_strtoul(buf, NULL, 10);
+
+	val = !!val;
+
+	if (tr->ctrl ^ val) {
+		if (val)
+			trace_enabled = 1;
+		else
+			trace_enabled = 0;
+
+		tr->ctrl = val;
+
+		mutex_lock(&trace_types_lock);
+		if (current_trace->ctrl_update)
+			current_trace->ctrl_update(tr);
+		mutex_unlock(&trace_types_lock);
+	}
+
+	filp->f_pos += cnt;
+
+	return cnt;
+}
+
+static ssize_t tracing_set_trace_read(struct file *filp, char __user *ubuf,
+				      size_t cnt, loff_t *ppos)
+{
+	char buf[max_tracer_type_len+2];
+	int r;
+
+	mutex_lock(&trace_types_lock);
+	if (current_trace)
+		r = sprintf(buf, "%s\n", current_trace->name);
+	else
+		r = sprintf(buf, "\n");
+	mutex_unlock(&trace_types_lock);
+
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+				       buf, r);
+}
+
+static ssize_t tracing_set_trace_write(struct file *filp,
+				       const char __user *ubuf,
+				       size_t cnt, loff_t *ppos)
+{
+	struct tracing_trace *tr = &tracer_trace;
+	struct trace_types_struct *t;
+	char buf[max_tracer_type_len+1];
+	int i;
+
+	if (cnt > max_tracer_type_len)
+		cnt = max_tracer_type_len;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	/* strip ending whitespace. */
+	for (i = cnt - 1; i > 0 && isspace(buf[i]); i--)
+		buf[i] = 0;
+
+	mutex_lock(&trace_types_lock);
+	for (t = trace_types; t; t = t->next) {
+		if (strcmp(t->name, buf) == 0)
+			break;
+	}
+	if (!t || t == current_trace)
+		goto out;
+
+	if (current_trace && current_trace->reset)
+		current_trace->reset(tr);
+
+	current_trace = t;
+	if (t->init)
+		t->init(tr);
+
+ out:
+	mutex_unlock(&trace_types_lock);
+
+	filp->f_pos += cnt;
+
+	return cnt;
+}
+
+static struct file_operations tracing_ctrl_fops = {
+	.open = tracing_open_generic,
+	.read = tracing_ctrl_read,
+	.write = tracing_ctrl_write,
+};
+
+static struct file_operations set_tracer_fops = {
+	.open = tracing_open_generic,
+	.read = tracing_set_trace_read,
+	.write = tracing_set_trace_write,
+};
+
+static struct dentry *d_tracer;
+
+struct dentry *tracing_init_dentry(void)
+{
+	static int once;
+
+	if (d_tracer)
+		return d_tracer;
+
+	d_tracer = debugfs_create_dir("tracing", NULL);
+
+	if (!d_tracer && !once) {
+		once = 1;
+		pr_warning("Could not create debugfs directory 'tracing'\n");
+		return NULL;
+	}
+
+	return d_tracer;
+}
+
+static __init void tracer_init_debugfs(void)
+{
+	struct dentry *d_tracer;
+	struct dentry *entry;
+
+	d_tracer = tracing_init_dentry();
+
+	entry = debugfs_create_file("trace_ctrl", 0644, d_tracer,
+				    &tracer_trace, &tracing_ctrl_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'trace_ctrl' entry\n");
+
+	entry = debugfs_create_file("iter_ctrl", 0644, d_tracer,
+				    NULL, &tracing_iter_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'iter_ctrl' entry\n");
+
+	entry = debugfs_create_file("latency_trace", 0444, d_tracer,
+				    &tracer_trace, &tracing_lt_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'latency_trace' entry\n");
+
+	entry = debugfs_create_file("trace", 0444, d_tracer,
+				    &tracer_trace, &tracing_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'trace' entry\n");
+
+	entry = debugfs_create_file("available_tracers", 0444, d_tracer,
+				    &tracer_trace, &show_traces_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'trace' entry\n");
+
+	entry = debugfs_create_file("current_tracer", 0444, d_tracer,
+				    &tracer_trace, &set_tracer_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs 'trace' entry\n");
+}
+
+static inline notrace int page_order(const unsigned long size)
+{
+	const unsigned long nr_pages = DIV_ROUND_UP(size, PAGE_SIZE);
+	return ilog2(roundup_pow_of_two(nr_pages));
+}
+
+__init static int tracer_alloc_buffers(void)
+{
+	const int order = page_order(trace_nr_entries * TRACING_ENTRY_SIZE);
+	const unsigned long size = (1UL << order) << PAGE_SHIFT;
+	struct tracing_entry *array;
+	int i;
+
+	for_each_possible_cpu(i) {
+		tracer_trace.data[i] = &per_cpu(tracer_trace_cpu, i);
+		array = (struct tracing_entry *)
+			  __get_free_pages(GFP_KERNEL, order);
+		if (array == NULL) {
+			printk(KERN_ERR "tracer: failed to allocate"
+			       " %ld bytes for trace buffer!\n", size);
+			goto free_buffers;
+		}
+		tracer_trace.data[i]->trace = array;
+	}
+
+	/*
+	 * Since we allocate by orders of pages, we may be able to
+	 * round up a bit.
+	 */
+	tracer_trace.entries = size / TRACING_ENTRY_SIZE;
+
+	pr_info("tracer: %ld bytes allocated for %ld",
+		size, trace_nr_entries);
+	pr_info(" entries of %ld bytes\n", (long)TRACING_ENTRY_SIZE);
+	pr_info("   actual entries %ld\n", tracer_trace.entries);
+
+	tracer_init_debugfs();
+
+	return 0;
+
+ free_buffers:
+	for (i-- ; i >= 0; i--) {
+		struct tracing_trace_cpu *data = tracer_trace.data[i];
+
+		if (data && data->trace) {
+			free_pages((unsigned long)data->trace, order);
+			data->trace = NULL;
+		}
+	}
+	return -ENOMEM;
+}
+
+device_initcall(tracer_alloc_buffers);
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:19.000000000 -0500
@@ -0,0 +1,96 @@
+#ifndef _LINUX_MCOUNT_TRACER_H
+#define _LINUX_MCOUNT_TRACER_H
+
+#include <asm/atomic.h>
+#include <linux/sched.h>
+#include <linux/clocksource.h>
+
+struct tracing_function {
+	unsigned long ip;
+	unsigned long parent_ip;
+};
+
+struct tracing_entry {
+	char type;
+	char cpu;  /* who will want to trace more than 256 CPUS? */
+	char flags;
+	char preempt_count; /* assumes PREEMPT_MASK is 8 bits or less */
+	int pid;
+	cycle_t t;
+	char comm[TASK_COMM_LEN];
+	struct tracing_function fn;
+};
+
+struct tracing_trace_cpu {
+	void *trace;
+	unsigned long trace_idx;
+	atomic_t      disabled;
+	atomic_t      underrun;
+	unsigned long saved_latency;
+	unsigned long critical_start;
+	unsigned long critical_end;
+	unsigned long critical_sequence;
+	unsigned long nice;
+	unsigned long policy;
+	unsigned long rt_priority;
+	cycle_t preempt_timestamp;
+	pid_t	      pid;
+	uid_t	      uid;
+	char comm[TASK_COMM_LEN];
+};
+
+struct tracing_iterator;
+
+struct tracing_trace {
+	unsigned long entries;
+	long	      ctrl;
+	int	      cpu;
+	cycle_t	      time_start;
+	struct tracing_trace_cpu *data[NR_CPUS];
+};
+
+struct trace_types_struct {
+	const char *name;
+	void (*init)(struct tracing_trace *tr);
+	void (*reset)(struct tracing_trace *tr);
+	void (*open)(struct tracing_iterator *iter);
+	void (*close)(struct tracing_iterator *iter);
+	void (*start)(struct tracing_iterator *iter);
+	void (*stop)(struct tracing_iterator *iter);
+	void (*ctrl_update)(struct tracing_trace *tr);
+	struct trace_types_struct *next;
+};
+
+struct tracing_iterator {
+	struct tracing_trace *tr;
+	struct trace_types_struct *trace;
+	struct tracing_entry *ent;
+	unsigned long iter_flags;
+	loff_t pos;
+	unsigned long next_idx[NR_CPUS];
+	int cpu;
+	int idx;
+};
+
+#define TRACING_ENTRY_SIZE sizeof(struct tracing_entry)
+
+void notrace tracing_reset(struct tracing_trace_cpu *data);
+int tracing_open_generic(struct inode *inode, struct file *filp);
+struct dentry *tracing_init_dentry(void);
+void tracing_function_trace(struct tracing_trace *tr,
+			    struct tracing_trace_cpu *data,
+			    unsigned long ip,
+			    unsigned long parent_ip,
+			    unsigned long flags);
+
+void tracing_start_function_trace(void);
+void tracing_stop_function_trace(void);
+int register_trace(struct trace_types_struct *type);
+void unregister_trace(struct trace_types_struct *type);
+
+static inline notrace cycle_t now(void)
+{
+	return get_monotonic_cycles();
+}
+
+#endif /* _LINUX_MCOUNT_TRACER_H */
Index: linux-mcount.git/lib/Makefile
===================================================================
--- linux-mcount.git.orig/lib/Makefile	2008-01-23 10:26:34.000000000 -0500
+++ linux-mcount.git/lib/Makefile	2008-01-23 10:27:19.000000000 -0500
@@ -67,6 +67,7 @@ obj-$(CONFIG_SWIOTLB) += swiotlb.o
 obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
 
 obj-$(CONFIG_MCOUNT) += tracing/
+obj-$(CONFIG_TRACING) += tracing/
 
 lib-$(CONFIG_GENERIC_BUG) += bug.o
 
Index: linux-mcount.git/lib/tracing/trace_function.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_function.c	2008-01-23 10:27:19.000000000 -0500
@@ -0,0 +1,72 @@
+/*
+ * ring buffer based mcount tracer
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Based on code from the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static notrace void function_reset(struct tracing_trace *tr)
+{
+	int cpu;
+
+	tr->time_start = now();
+
+	for_each_online_cpu(cpu)
+		tracing_reset(tr->data[cpu]);
+}
+
+static notrace void start_function_trace(struct tracing_trace *tr)
+{
+	function_reset(tr);
+	tracing_start_function_trace();
+}
+
+static notrace void stop_function_trace(struct tracing_trace *tr)
+{
+	tracing_stop_function_trace();
+}
+
+static notrace void function_trace_init(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_function_trace(tr);
+}
+
+static notrace void function_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		stop_function_trace(tr);
+}
+
+static notrace void function_trace_ctrl_update(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_function_trace(tr);
+	else
+		stop_function_trace(tr);
+}
+
+static struct trace_types_struct function_trace __read_mostly =
+{
+	.name = "function",
+	.init = function_trace_init,
+	.reset = function_trace_reset,
+	.ctrl_update = function_trace_ctrl_update,
+};
+
+static __init int init_function_trace(void)
+{
+	return register_trace(&function_trace);
+}
+
+device_initcall(init_function_trace);

-- 

[PATCH 12/20 -v5] Add context switch marker to sched.c

[Steven Rostedt]

[-- Attachment #1: add-trace-hooks-to-sched.patch --]
[-- Type: text/plain, Size: 703 bytes --]

Add marker into context_switch to record the prev and next tasks.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/sched.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-mcount.git/kernel/sched.c
===================================================================
--- linux-mcount.git.orig/kernel/sched.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/kernel/sched.c	2008-01-23 10:27:25.000000000 -0500
@@ -1933,6 +1933,8 @@ context_switch(struct rq *rq, struct tas
 	struct mm_struct *mm, *oldmm;
 
 	prepare_task_switch(rq, prev, next);
+	trace_mark(kernel_sched_schedule,
+		   "prev %p next %p", prev, next);
 	mm = next->mm;
 	oldmm = prev->active_mm;
 	/*

-- 

[PATCH 13/20 -v5] Make the task State char-string visible to all

[Steven Rostedt]

[-- Attachment #1: parse-out-task-state-to-char-string.patch --]
[-- Type: text/plain, Size: 1306 bytes --]

The tracer wants to be able to convert the state number
into a user visible character. This patch pulls that conversion
string out the scheduler into the header. This way if it were to
ever change, other parts of the kernel will know.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 include/linux/sched.h |    2 ++
 kernel/sched.c        |    2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

Index: linux-mcount.git/include/linux/sched.h
===================================================================
--- linux-mcount.git.orig/include/linux/sched.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/linux/sched.h	2008-01-23 10:27:28.000000000 -0500
@@ -1987,6 +1987,8 @@ static inline void migration_init(void)
 }
 #endif
 
+#define TASK_STATE_TO_CHAR_STR "RSDTtZX"
+
 #endif /* __KERNEL__ */
 
 #endif
Index: linux-mcount.git/kernel/sched.c
===================================================================
--- linux-mcount.git.orig/kernel/sched.c	2008-01-23 10:27:25.000000000 -0500
+++ linux-mcount.git/kernel/sched.c	2008-01-23 10:27:28.000000000 -0500
@@ -4890,7 +4890,7 @@ out_unlock:
 	return retval;
 }
 
-static const char stat_nam[] = "RSDTtZX";
+static const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
 
 static void show_task(struct task_struct *p)
 {

-- 

[PATCH 14/20 -v5] Add tracing of context switches

[Steven Rostedt]

[-- Attachment #1: trace-add-cmdline-switch.patch --]
[-- Type: text/plain, Size: 9266 bytes --]

This patch adds context switch tracing, of the format of:

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
 swapper-0     1d..3  137us+:  0:140:R --> 2912:120
    sshd-2912  1d..3  216us+:  2912:120:S --> 0:140
 swapper-0     1d..3  261us+:  0:140:R --> 2912:120
    bash-2920  0d..3  267us+:  2920:120:S --> 0:140
    sshd-2912  1d..3  330us!:  2912:120:S --> 0:140
 swapper-0     1d..3 2389us+:  0:140:R --> 2847:120
yum-upda-2847  1d..3 2411us!:  2847:120:S --> 0:140
 swapper-0     0d..3 11089us+:  0:140:R --> 3139:120
gdm-bina-3139  0d..3 11113us!:  3139:120:S --> 0:140
 swapper-0     1d..3 102328us+:  0:140:R --> 2847:120
yum-upda-2847  1d..3 102348us!:  2847:120:S --> 0:140


 "sched_switch" is added to /debugfs/tracing/available_tracers

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
 lib/tracing/Kconfig              |    9 ++
 lib/tracing/Makefile             |    1 
 lib/tracing/trace_sched_switch.c |  134 +++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.c             |   32 +++++++++
 lib/tracing/tracer.h             |   19 +++++
 5 files changed, 194 insertions(+), 1 deletion(-)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:19.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:31.000000000 -0500
@@ -23,3 +23,12 @@ config FUNCTION_TRACER
 	  insert a call to an architecture specific __mcount routine,
 	  that the debugging mechanism using this facility will hook by
 	  providing a set of inline routines.
+
+config CONTEXT_SWITCH_TRACER
+	bool "Trace process context switches"
+	depends on DEBUG_KERNEL
+	select TRACING
+	help
+	  This tracer hooks into the context switch and records
+	  all switching of tasks.
+
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:27:19.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:27:31.000000000 -0500
@@ -1,6 +1,7 @@
 obj-$(CONFIG_MCOUNT) += libmcount.o
 
 obj-$(CONFIG_TRACING) += tracer.o
+obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_sched_switch.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_sched_switch.c	2008-01-23 10:27:31.000000000 -0500
@@ -0,0 +1,134 @@
+/*
+ * trace context switch
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/marker.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace *tracer_trace;
+static int trace_enabled __read_mostly;
+
+static notrace void sched_switch_callback(const struct marker *mdata,
+					  void *private_data,
+					  const char *format, ...)
+{
+	struct tracing_trace **p = mdata->private;
+	struct tracing_trace *tr = *p;
+	struct tracing_trace_cpu *data;
+	struct task_struct *prev;
+	struct task_struct *next;
+	unsigned long flags;
+	va_list ap;
+	int cpu;
+
+	if (likely(!trace_enabled))
+		return;
+
+	va_start(ap, format);
+	prev = va_arg(ap, typeof(prev));
+	next = va_arg(ap, typeof(next));
+	va_end(ap);
+
+	raw_local_irq_save(flags);
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+	atomic_inc(&data->disabled);
+
+	if (likely(atomic_read(&data->disabled) == 1))
+		tracing_sched_switch_trace(tr, data, prev, next, flags);
+
+	atomic_dec(&data->disabled);
+	raw_local_irq_restore(flags);
+}
+
+static notrace void sched_switch_reset(struct tracing_trace *tr)
+{
+	int cpu;
+
+	tr->time_start = now();
+
+	for_each_online_cpu(cpu)
+		tracing_reset(tr->data[cpu]);
+}
+
+static notrace void start_sched_trace(struct tracing_trace *tr)
+{
+	sched_switch_reset(tr);
+	trace_enabled = 1;
+}
+
+static notrace void stop_sched_trace(struct tracing_trace *tr)
+{
+	trace_enabled = 0;
+}
+
+static notrace void sched_switch_trace_init(struct tracing_trace *tr)
+{
+	tracer_trace = tr;
+
+	if (tr->ctrl)
+		start_sched_trace(tr);
+}
+
+static notrace void sched_switch_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		stop_sched_trace(tr);
+}
+
+static void sched_switch_trace_ctrl_update(struct tracing_trace *tr)
+{
+	/* When starting a new trace, reset the buffers */
+	if (tr->ctrl)
+		start_sched_trace(tr);
+	else
+		stop_sched_trace(tr);
+}
+
+static struct trace_types_struct sched_switch_trace __read_mostly =
+{
+	.name = "sched_switch",
+	.init = sched_switch_trace_init,
+	.reset = sched_switch_trace_reset,
+	.ctrl_update = sched_switch_trace_ctrl_update,
+};
+
+
+__init static int init_sched_switch_trace(void)
+{
+	int ret;
+
+	ret = register_trace(&sched_switch_trace);
+	if (ret)
+		return ret;
+
+	ret = marker_probe_register("kernel_sched_schedule",
+				    "prev %p next %p",
+				    sched_switch_callback,
+				    &tracer_trace);
+	if (ret) {
+		pr_info("sched trace: Couldn't add marker"
+			" probe to switch_to\n");
+		goto out;
+	}
+
+	ret = marker_arm("kernel_sched_schedule");
+	if (ret) {
+		pr_info("sched trace: Couldn't arm probe switch_to\n");
+		goto out;
+	}
+
+ out:
+	return ret;
+}
+
+device_initcall(init_sched_switch_trace);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:27:19.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:31.000000000 -0500
@@ -52,6 +52,7 @@ enum trace_type {
 	__TRACE_FIRST_TYPE = 0,
 
 	TRACE_FN,
+	TRACE_CTX,
 
 	__TRACE_LAST_TYPE
 };
@@ -227,6 +228,24 @@ notrace void tracing_function_trace(stru
 	entry->fn.parent_ip = parent_ip;
 }
 
+notrace void tracing_sched_switch_trace(struct tracing_trace *tr,
+					struct tracing_trace_cpu *data,
+					struct task_struct *prev,
+					struct task_struct *next,
+					unsigned long flags)
+{
+	struct tracing_entry *entry;
+
+	entry = tracing_get_trace_entry(tr, data);
+	tracing_generic_entry_update(entry, flags);
+	entry->type		= TRACE_CTX;
+	entry->ctx.prev_pid	= prev->pid;
+	entry->ctx.prev_prio	= prev->prio;
+	entry->ctx.prev_state	= prev->state;
+	entry->ctx.next_pid	= next->pid;
+	entry->ctx.next_prio	= next->prio;
+}
+
 enum trace_iterator {
 	TRACE_ITER_SYM_ONLY	= 1,
 	TRACE_ITER_VERBOSE	= 2,
@@ -545,6 +564,8 @@ lat_print_timestamp(struct seq_file *m, 
 		seq_puts(m, " : ");
 }
 
+static const char state_to_char[] = TASK_STATE_TO_CHAR_STR;
+
 static void notrace
 print_lat_fmt(struct seq_file *m, struct tracing_iterator *iter,
 	      unsigned int trace_idx, int cpu)
@@ -555,6 +576,7 @@ print_lat_fmt(struct seq_file *m, struct
 	unsigned long rel_usecs;
 	int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
 	int verbose = !!(trace_flags & TRACE_ITER_VERBOSE);
+	int S;
 
 	if (!next_entry)
 		next_entry = entry;
@@ -581,6 +603,16 @@ print_lat_fmt(struct seq_file *m, struct
 		seq_print_ip_sym(m, entry->fn.parent_ip, sym_only);
 		seq_puts(m, ")\n");
 		break;
+	case TRACE_CTX:
+		S = entry->ctx.prev_state < sizeof(state_to_char) ?
+			state_to_char[entry->ctx.prev_state] : 'X';
+		seq_printf(m, " %d:%d:%c --> %d:%d\n",
+			   entry->ctx.prev_pid,
+			   entry->ctx.prev_prio,
+			   S,
+			   entry->ctx.next_pid,
+			   entry->ctx.next_prio);
+		break;
 	}
 }
 
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:19.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:31.000000000 -0500
@@ -10,6 +10,14 @@ struct tracing_function {
 	unsigned long parent_ip;
 };
 
+struct tracing_sched_switch {
+	unsigned int prev_pid;
+	unsigned char prev_prio;
+	unsigned char prev_state;
+	unsigned int next_pid;
+	unsigned char next_prio;
+};
+
 struct tracing_entry {
 	char type;
 	char cpu;  /* who will want to trace more than 256 CPUS? */
@@ -18,7 +26,10 @@ struct tracing_entry {
 	int pid;
 	cycle_t t;
 	char comm[TASK_COMM_LEN];
-	struct tracing_function fn;
+	union {
+		struct tracing_function fn;
+		struct tracing_sched_switch ctx;
+	};
 };
 
 struct tracing_trace_cpu {
@@ -82,6 +93,12 @@ void tracing_function_trace(struct traci
 			    unsigned long ip,
 			    unsigned long parent_ip,
 			    unsigned long flags);
+void tracing_sched_switch_trace(struct tracing_trace *tr,
+				struct tracing_trace_cpu *data,
+				struct task_struct *prev,
+				struct task_struct *next,
+				unsigned long flags);
+
 
 void tracing_start_function_trace(void);
 void tracing_stop_function_trace(void);

-- 

[PATCH 15/20 -v5] Generic command line storage

[Steven Rostedt]

[-- Attachment #1: trace-generic-cmdline.patch --]
[-- Type: text/plain, Size: 8986 bytes --]

Saving the comm of tasks for each trace is very expensive.
This patch includes in the context switch hook, a way to
store the last 100 command lines of tasks. This table is
examined when a trace is to be printed.

Note: The comm may be destroyed if other traces are performed.
Later (TBD) patches may simply store this information in the trace
itself.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 lib/tracing/Kconfig              |    1 
 lib/tracing/trace_function.c     |    2 
 lib/tracing/trace_sched_switch.c |    7 ++
 lib/tracing/tracer.c             |  104 +++++++++++++++++++++++++++++++++++++--
 lib/tracing/tracer.h             |    6 +-
 5 files changed, 114 insertions(+), 6 deletions(-)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:39.000000000 -0500
@@ -18,6 +18,7 @@ config FUNCTION_TRACER
 	depends on DEBUG_KERNEL && HAVE_MCOUNT
 	select MCOUNT
 	select TRACING
+	select CONTEXT_SWITCH_TRACER
 	help
 	  Use profiler instrumentation, adding -pg to CFLAGS. This will
 	  insert a call to an architecture specific __mcount routine,
Index: linux-mcount.git/lib/tracing/trace_function.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/trace_function.c	2008-01-23 10:27:19.000000000 -0500
+++ linux-mcount.git/lib/tracing/trace_function.c	2008-01-23 10:27:39.000000000 -0500
@@ -28,11 +28,13 @@ static notrace void function_reset(struc
 static notrace void start_function_trace(struct tracing_trace *tr)
 {
 	function_reset(tr);
+	atomic_inc(&trace_record_cmdline);
 	tracing_start_function_trace();
 }
 
 static notrace void stop_function_trace(struct tracing_trace *tr)
 {
+	atomic_dec(&trace_record_cmdline);
 	tracing_stop_function_trace();
 }
 
Index: linux-mcount.git/lib/tracing/trace_sched_switch.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/trace_sched_switch.c	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/trace_sched_switch.c	2008-01-23 10:27:39.000000000 -0500
@@ -30,6 +30,11 @@ static notrace void sched_switch_callbac
 	va_list ap;
 	int cpu;
 
+	if (likely(!atomic_read(&trace_record_cmdline)))
+		return;
+
+	tracing_record_cmdline(current);
+
 	if (likely(!trace_enabled))
 		return;
 
@@ -62,6 +67,7 @@ static notrace void sched_switch_reset(s
 
 static notrace void start_sched_trace(struct tracing_trace *tr)
 {
+	atomic_inc(&trace_record_cmdline);
 	sched_switch_reset(tr);
 	trace_enabled = 1;
 }
@@ -69,6 +75,7 @@ static notrace void start_sched_trace(st
 static notrace void stop_sched_trace(struct tracing_trace *tr)
 {
 	trace_enabled = 0;
+	atomic_dec(&trace_record_cmdline);
 }
 
 static notrace void sched_switch_trace_init(struct tracing_trace *tr)
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:39.000000000 -0500
@@ -169,6 +169,88 @@ void tracing_stop_function_trace(void)
 	unregister_mcount_function(&trace_ops);
 }
 
+#define SAVED_CMDLINES 128
+static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
+static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
+static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
+static int cmdline_idx;
+static DEFINE_SPINLOCK(trace_cmdline_lock);
+atomic_t trace_record_cmdline;
+atomic_t trace_record_cmdline_disabled;
+
+static void trace_init_cmdlines(void)
+{
+	memset(&map_pid_to_cmdline, -1, sizeof(map_pid_to_cmdline));
+	memset(&map_cmdline_to_pid, -1, sizeof(map_cmdline_to_pid));
+	cmdline_idx = 0;
+}
+
+notrace void trace_stop_cmdline_recording(void);
+
+static void notrace trace_save_cmdline(struct task_struct *tsk)
+{
+	unsigned map;
+	unsigned idx;
+
+	if (!tsk->pid || unlikely(tsk->pid > PID_MAX_DEFAULT))
+		return;
+
+	/*
+	 * It's not the end of the world if we don't get
+	 * the lock, but we also don't want to spin
+	 * nor do we want to disable interrupts,
+	 * so if we miss here, then better luck next time.
+	 */
+	if (!spin_trylock(&trace_cmdline_lock))
+		return;
+
+	idx = map_pid_to_cmdline[tsk->pid];
+	if (idx >= SAVED_CMDLINES) {
+		idx = (cmdline_idx + 1) % SAVED_CMDLINES;
+
+		map = map_cmdline_to_pid[idx];
+		if (map <= PID_MAX_DEFAULT)
+			map_pid_to_cmdline[map] = (unsigned)-1;
+
+		map_pid_to_cmdline[tsk->pid] = idx;
+
+		cmdline_idx = idx;
+	}
+
+	memcpy(&saved_cmdlines[idx], tsk->comm, TASK_COMM_LEN);
+
+	spin_unlock(&trace_cmdline_lock);
+}
+
+static notrace char *trace_find_cmdline(int pid)
+{
+	char *cmdline = "<...>";
+	unsigned map;
+
+	if (!pid)
+		return "<idle>";
+
+	if (pid > PID_MAX_DEFAULT)
+		goto out;
+
+	map = map_pid_to_cmdline[pid];
+	if (map >= SAVED_CMDLINES)
+		goto out;
+
+	cmdline = saved_cmdlines[map];
+
+ out:
+	return cmdline;
+}
+
+void tracing_record_cmdline(struct task_struct *tsk)
+{
+	if (atomic_read(&trace_record_cmdline_disabled))
+		return;
+
+	trace_save_cmdline(tsk);
+}
+
 static inline notrace struct tracing_entry *
 tracing_get_trace_entry(struct tracing_trace *tr,
 			struct tracing_trace_cpu *data)
@@ -210,7 +292,6 @@ tracing_generic_entry_update(struct trac
 		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
 		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
 		(need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
-	memcpy(entry->comm, tsk->comm, TASK_COMM_LEN);
 }
 
 notrace void tracing_function_trace(struct tracing_trace *tr,
@@ -366,6 +447,8 @@ static void *s_start(struct seq_file *m,
 	if (!current_trace || current_trace != iter->trace)
 		return NULL;
 
+	atomic_inc(&trace_record_cmdline_disabled);
+
 	/* let the tracer grab locks here if needed */
 	if (current_trace->start)
 		current_trace->start(iter);
@@ -393,6 +476,8 @@ static void s_stop(struct seq_file *m, v
 {
 	struct tracing_iterator *iter = m->private;
 
+	atomic_dec(&trace_record_cmdline_disabled);
+
 	/* let the tracer release locks here if needed */
 	if (current_trace && current_trace == iter->trace && iter->trace->stop)
 		iter->trace->stop(iter);
@@ -521,8 +606,11 @@ static void notrace
 lat_print_generic(struct seq_file *m, struct tracing_entry *entry, int cpu)
 {
 	int hardirq, softirq;
+	char *comm;
+
+	comm = trace_find_cmdline(entry->pid);
 
-	seq_printf(m, "%8.8s-%-5d ", entry->comm, entry->pid);
+	seq_printf(m, "%8.8s-%-5d ", comm, entry->pid);
 	seq_printf(m, "%d", cpu);
 	seq_printf(m, "%c%c",
 		   (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
@@ -584,9 +672,12 @@ print_lat_fmt(struct seq_file *m, struct
 	abs_usecs = cycles_to_usecs(entry->t - iter->tr->time_start);
 
 	if (verbose) {
+		char *comm;
+
+		comm = trace_find_cmdline(entry->pid);
 		seq_printf(m, "%16s %5d %d %d %08x %08x [%08lx]"
 			   " %ld.%03ldms (+%ld.%03ldms): ",
-			   entry->comm,
+			   comm,
 			   entry->pid, cpu, entry->flags,
 			   entry->preempt_count, trace_idx,
 			   cycles_to_usecs(entry->t),
@@ -623,6 +714,9 @@ static void notrace print_trace_fmt(stru
 	unsigned long secs;
 	int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
 	unsigned long long t;
+	char *comm;
+
+	comm = trace_find_cmdline(iter->ent->pid);
 
 	t = cycles_to_usecs(iter->ent->t);
 	usec_rem = do_div(t, 1000000ULL);
@@ -630,7 +724,7 @@ static void notrace print_trace_fmt(stru
 
 	seq_printf(m, "[%5lu.%06lu] ", secs, usec_rem);
 	seq_printf(m, "CPU %d: ", iter->cpu);
-	seq_printf(m, "%s:%d ", iter->ent->comm,
+	seq_printf(m, "%s:%d ", comm,
 		   iter->ent->pid);
 	switch (iter->ent->type) {
 	case TRACE_FN:
@@ -1164,6 +1258,8 @@ __init static int tracer_alloc_buffers(v
 
 	tracer_init_debugfs();
 
+	trace_init_cmdlines();
+
 	return 0;
 
  free_buffers:
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:39.000000000 -0500
@@ -25,7 +25,6 @@ struct tracing_entry {
 	char preempt_count; /* assumes PREEMPT_MASK is 8 bits or less */
 	int pid;
 	cycle_t t;
-	char comm[TASK_COMM_LEN];
 	union {
 		struct tracing_function fn;
 		struct tracing_sched_switch ctx;
@@ -98,13 +97,16 @@ void tracing_sched_switch_trace(struct t
 				struct task_struct *prev,
 				struct task_struct *next,
 				unsigned long flags);
-
+void tracing_record_cmdline(struct task_struct *tsk);
 
 void tracing_start_function_trace(void);
 void tracing_stop_function_trace(void);
 int register_trace(struct trace_types_struct *type);
 void unregister_trace(struct trace_types_struct *type);
 
+extern atomic_t trace_record_cmdline;
+extern atomic_t trace_record_cmdline_disabled;
+
 static inline notrace cycle_t now(void)
 {
 	return get_monotonic_cycles();

-- 

[PATCH 16/20 -v5] trace generic call to schedule switch

[Steven Rostedt]

[-- Attachment #1: trace-sched-hooks.patch --]
[-- Type: text/plain, Size: 5068 bytes --]

This patch adds hooks into the schedule switch tracing to
allow other latency traces to hook into the schedule switches.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 lib/tracing/trace_sched_switch.c |  123 +++++++++++++++++++++++++++++++++------
 lib/tracing/tracer.h             |   14 ++++
 2 files changed, 119 insertions(+), 18 deletions(-)

Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:42.000000000 -0500
@@ -112,4 +112,18 @@ static inline notrace cycle_t now(void)
 	return get_monotonic_cycles();
 }
 
+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+typedef void (*tracer_switch_func_t)(void *private,
+				     struct task_struct *prev,
+				     struct task_struct *next);
+struct tracer_switch_ops {
+	tracer_switch_func_t func;
+	void *private;
+	struct tracer_switch_ops *next;
+};
+
+extern int register_tracer_switch(struct tracer_switch_ops *ops);
+extern int unregister_tracer_switch(struct tracer_switch_ops *ops);
+#endif /* CONFIG_CONTEXT_SWITCH_TRACER */
+
 #endif /* _LINUX_MCOUNT_TRACER_H */
Index: linux-mcount.git/lib/tracing/trace_sched_switch.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/trace_sched_switch.c	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/trace_sched_switch.c	2008-01-23 10:27:42.000000000 -0500
@@ -16,33 +16,21 @@
 
 static struct tracing_trace *tracer_trace;
 static int trace_enabled __read_mostly;
+static DEFINE_SPINLOCK(sched_switch_func_lock);
 
-static notrace void sched_switch_callback(const struct marker *mdata,
-					  void *private_data,
-					  const char *format, ...)
+static void notrace sched_switch_func(void *private,
+				      struct task_struct *prev,
+				      struct task_struct *next)
 {
-	struct tracing_trace **p = mdata->private;
-	struct tracing_trace *tr = *p;
+	struct tracing_trace **ptr = private;
+	struct tracing_trace *tr = *ptr;
 	struct tracing_trace_cpu *data;
-	struct task_struct *prev;
-	struct task_struct *next;
 	unsigned long flags;
-	va_list ap;
 	int cpu;
 
-	if (likely(!atomic_read(&trace_record_cmdline)))
-		return;
-
-	tracing_record_cmdline(current);
-
 	if (likely(!trace_enabled))
 		return;
 
-	va_start(ap, format);
-	prev = va_arg(ap, typeof(prev));
-	next = va_arg(ap, typeof(next));
-	va_end(ap);
-
 	raw_local_irq_save(flags);
 	cpu = raw_smp_processor_id();
 	data = tr->data[cpu];
@@ -55,6 +43,105 @@ static notrace void sched_switch_callbac
 	raw_local_irq_restore(flags);
 }
 
+static struct tracer_switch_ops sched_switch_ops __read_mostly =
+{
+	.func = sched_switch_func,
+	.private = &tracer_trace,
+};
+
+static tracer_switch_func_t tracer_switch_func __read_mostly =
+	sched_switch_func;
+
+static struct tracer_switch_ops *tracer_switch_func_ops __read_mostly =
+	&sched_switch_ops;
+
+static void notrace sched_switch_func_loop(void *private,
+					   struct task_struct *prev,
+					   struct task_struct *next)
+{
+	struct tracer_switch_ops *ops = tracer_switch_func_ops;
+
+	for (; ops != NULL; ops = ops->next)
+		ops->func(ops->private, prev, next);
+}
+
+notrace int register_tracer_switch(struct tracer_switch_ops *ops)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sched_switch_func_lock, flags);
+	ops->next = tracer_switch_func_ops;
+	smp_wmb();
+	tracer_switch_func_ops = ops;
+
+	if (ops->next == &sched_switch_ops)
+		tracer_switch_func = sched_switch_func_loop;
+
+	spin_unlock_irqrestore(&sched_switch_func_lock, flags);
+
+	return 0;
+}
+
+notrace int unregister_tracer_switch(struct tracer_switch_ops *ops)
+{
+	unsigned long flags;
+	struct tracer_switch_ops **p = &tracer_switch_func_ops;
+	int ret;
+
+	spin_lock_irqsave(&sched_switch_func_lock, flags);
+
+	/*
+	 * If the sched_switch is the only one left, then
+	 *  only call that function.
+	 */
+	if (*p == ops && ops->next == &sched_switch_ops) {
+		tracer_switch_func = sched_switch_func;
+		tracer_switch_func_ops = &sched_switch_ops;
+		goto out;
+	}
+
+	for (; *p != &sched_switch_ops; p = &(*p)->next)
+		if (*p == ops)
+			break;
+
+	if (*p != ops) {
+		ret = -1;
+		goto out;
+	}
+
+	*p = (*p)->next;
+
+ out:
+	spin_unlock_irqrestore(&sched_switch_func_lock, flags);
+
+	return 0;
+}
+
+static notrace void sched_switch_callback(const struct marker *mdata,
+					  void *private_data,
+					  const char *format, ...)
+{
+	struct task_struct *prev;
+	struct task_struct *next;
+	va_list ap;
+
+	if (likely(!atomic_read(&trace_record_cmdline)))
+		return;
+
+	tracing_record_cmdline(current);
+
+	va_start(ap, format);
+	prev = va_arg(ap, typeof(prev));
+	next = va_arg(ap, typeof(next));
+	va_end(ap);
+
+	/*
+	 * If tracer_switch_func only points to the local
+	 * switch func, it still needs the ptr passed to it.
+	 */
+	tracer_switch_func(mdata->private, prev, next);
+}
+
 static notrace void sched_switch_reset(struct tracing_trace *tr)
 {
 	int cpu;

-- 

[PATCH 17/20 -v5] Add marker in try_to_wake_up

[Steven Rostedt]

[-- Attachment #1: add-markers-to-wakeup.patch --]
[-- Type: text/plain, Size: 708 bytes --]

Add markers into the wakeup code, to allow the tracer to
record wakeup timings.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/sched.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-mcount.git/kernel/sched.c
===================================================================
--- linux-mcount.git.orig/kernel/sched.c	2008-01-23 10:27:28.000000000 -0500
+++ linux-mcount.git/kernel/sched.c	2008-01-23 10:27:45.000000000 -0500
@@ -1633,6 +1633,10 @@ out_set_cpu:
 
 out_activate:
 #endif /* CONFIG_SMP */
+	trace_mark(kernel_sched_wakeup,
+		   "p %p rq->curr %p",
+		   p, rq->curr);
+
 	schedstat_inc(p, se.nr_wakeups);
 	if (sync)
 		schedstat_inc(p, se.nr_wakeups_sync);

-- 

[PATCH 18/20 -v5] mcount tracer for wakeup latency timings.

[Steven Rostedt]

[-- Attachment #1: mcount-trace-wakeup-latency.patch --]
[-- Type: text/plain, Size: 20668 bytes --]

This patch adds hooks to trace the wake up latency of the highest
priority waking task.

  "wakeup" is added to /debugfs/tracing/available_tracers

Also added to /debugfs/tracing

  tracing_max_latency
     holds the current max latency for the wakeup

  wakeup_thresh
     if set to other than zero, a log will be recorded
     for every wakeup that takes longer than the number
     entered in here (usecs for all counters)
     (deletes previous trace)

Examples:

  (with mcount_enabled = 0)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
--------------------------------------------------------------------
 latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
   quilt-8551  0d..3    0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
   quilt-8551  0d..4   26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)


vim:ft=help
============

    
  (with mcount_enabled = 1)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
--------------------------------------------------------------------
 latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
    bash-10653 1d..3    0us : wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
    bash-10653 1d..3    1us : try_to_wake_up+0x271/0x2e7 <ffffffff80233dcf> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..2    2us : try_to_wake_up+0x296/0x2e7 <ffffffff80233df4> (update_rq_clock+0x9/0x20 <ffffffff802303f3>)
    bash-10653 1d..2    2us : update_rq_clock+0x1e/0x20 <ffffffff80230408> (__update_rq_clock+0xc/0x90 <ffffffff80230366>)
    bash-10653 1d..2    3us : __update_rq_clock+0x1b/0x90 <ffffffff80230375> (sched_clock+0x9/0x29 <ffffffff80214529>)
    bash-10653 1d..2    4us : try_to_wake_up+0x2a6/0x2e7 <ffffffff80233e04> (activate_task+0xc/0x3f <ffffffff8022ffca>)
    bash-10653 1d..2    4us : activate_task+0x2d/0x3f <ffffffff8022ffeb> (enqueue_task+0xe/0x66 <ffffffff8022ff66>)
    bash-10653 1d..2    5us : enqueue_task+0x5b/0x66 <ffffffff8022ffb3> (enqueue_task_rt+0x9/0x3c <ffffffff80233351>)
    bash-10653 1d..2    6us : try_to_wake_up+0x2ba/0x2e7 <ffffffff80233e18> (check_preempt_wakeup+0x12/0x99 <ffffffff80234f84>)
[...]
    bash-10653 1d..5   33us : tracing_record_cmdline+0xcf/0xd4 <ffffffff80338aad> (_spin_unlock+0x9/0x33 <ffffffff8048d3ec>)
    bash-10653 1d..5   34us : _spin_unlock+0x19/0x33 <ffffffff8048d3fc> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..4   35us : wakeup_sched_switch+0x65/0x2ff <ffffffff80339f66> (_spin_lock_irqsave+0xc/0xa9 <ffffffff8048d08b>)
    bash-10653 1d..4   35us : _spin_lock_irqsave+0x19/0xa9 <ffffffff8048d098> (add_preempt_count+0xe/0x77 <ffffffff8023311a>)
    bash-10653 1d..4   36us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)


vim:ft=help
============

The [...] was added here to not waste your email box space.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 lib/tracing/Kconfig        |   14 +
 lib/tracing/Makefile       |    1 
 lib/tracing/trace_wakeup.c |  333 +++++++++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.c       |  131 +++++++++++++++++
 lib/tracing/tracer.h       |    6 
 5 files changed, 483 insertions(+), 2 deletions(-)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:49.000000000 -0500
@@ -9,6 +9,9 @@ config MCOUNT
 	bool
 	select FRAME_POINTER
 
+config TRACER_MAX_TRACE
+	bool
+
 config TRACING
         bool
 	select DEBUG_FS
@@ -25,6 +28,17 @@ config FUNCTION_TRACER
 	  that the debugging mechanism using this facility will hook by
 	  providing a set of inline routines.
 
+config WAKEUP_TRACER
+	bool "Trace wakeup latencies"
+	depends on DEBUG_KERNEL
+	select TRACING
+	select CONTEXT_SWITCH_TRACER
+	select TRACER_MAX_TRACE
+	help
+	  This tracer adds hooks into scheduling to time the latency
+	  of the highest priority task tasks to be scheduled in
+	  after it has worken up.
+
 config CONTEXT_SWITCH_TRACER
 	bool "Trace process context switches"
 	depends on DEBUG_KERNEL
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:27:49.000000000 -0500
@@ -3,5 +3,6 @@ obj-$(CONFIG_MCOUNT) += libmcount.o
 obj-$(CONFIG_TRACING) += tracer.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+obj-$(CONFIG_WAKEUP_TRACER) += trace_wakeup.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_wakeup.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_wakeup.c	2008-01-23 10:27:49.000000000 -0500
@@ -0,0 +1,333 @@
+/*
+ * trace task wakeup timings
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Based on code from the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace *tracer_trace __read_mostly;
+static int trace_enabled __read_mostly;
+
+static struct task_struct *wakeup_task;
+static int wakeup_cpu;
+static unsigned wakeup_prio = -1;
+
+static DEFINE_SPINLOCK(wakeup_lock);
+
+static void notrace __wakeup_reset(struct tracing_trace *tr);
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+	if (tracing_thresh) {
+		if (delta < tracing_thresh)
+			return 0;
+	} else {
+		if (delta <= tracing_max_latency)
+			return 0;
+	}
+	return 1;
+}
+
+static void notrace wakeup_sched_switch(void *private,
+					struct task_struct *prev,
+					struct task_struct *next)
+{
+	struct tracing_trace **ptr = private;
+	struct tracing_trace *tr = *ptr;
+	struct tracing_trace_cpu *data;
+	unsigned long latency = 0, t0 = 0, t1 = 0;
+	cycle_t T0, T1, delta;
+	unsigned long flags;
+	int cpu;
+
+	if (unlikely(!trace_enabled) || next != wakeup_task)
+		return;
+
+	/* The task we are waitng for is waking up */
+	data = tr->data[wakeup_cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    unlikely(atomic_read(&data->disabled)))
+		return;
+
+	spin_lock_irqsave(&wakeup_lock, flags);
+
+	/* disable local data, not wakeup_cpu data */
+	cpu = raw_smp_processor_id();
+	atomic_inc(&tr->data[cpu]->disabled);
+
+	/* We could race with grabbing wakeup_lock */
+	if (unlikely(!trace_enabled || next != wakeup_task))
+		goto out;
+
+	tracing_function_trace(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
+
+	/*
+	 * usecs conversion is slow so we try to delay the conversion
+	 * as long as possible:
+	 */
+	T0 = data->preempt_timestamp;
+	T1 = now();
+	delta = T1-T0;
+
+	if (!report_latency(delta))
+		goto out;
+
+	latency = cycles_to_usecs(delta);
+
+	tracing_max_latency = delta;
+	t0 = cycles_to_usecs(T0);
+	t1 = cycles_to_usecs(T1);
+
+	update_max_tr(tr, wakeup_task, wakeup_cpu);
+
+	if (tracing_thresh)
+		printk(KERN_WARNING "(%16s-%-5d|#%d): %lu us wakeup latency "
+		       "violates %lu us threshold.\n"
+		       " => started at timestamp %lu: ",
+				wakeup_task->comm, wakeup_task->pid,
+				raw_smp_processor_id(),
+				latency, cycles_to_usecs(tracing_thresh), t0);
+	else
+		printk(KERN_WARNING "(%16s-%-5d|#%d): new %lu us maximum "
+		       "wakeup latency.\n => started at timestamp %lu: ",
+				wakeup_task->comm, wakeup_task->pid,
+				cpu, latency, t0);
+
+	printk(KERN_CONT "   ended at timestamp %lu: ", t1);
+	dump_stack();
+	t1 = cycles_to_usecs(now());
+	printk(KERN_CONT "   dump-end timestamp %lu\n\n", t1);
+
+out:
+	__wakeup_reset(tr);
+	atomic_dec(&tr->data[cpu]->disabled);
+	spin_unlock_irqrestore(&wakeup_lock, flags);
+
+}
+
+static struct tracer_switch_ops switch_ops __read_mostly = {
+	.func = wakeup_sched_switch,
+	.private = &tracer_trace,
+};
+
+static void notrace __wakeup_reset(struct tracing_trace *tr)
+{
+	struct tracing_trace_cpu *data;
+	int cpu;
+
+	assert_spin_locked(&wakeup_lock);
+
+	for_each_possible_cpu(cpu) {
+		data = tr->data[cpu];
+		tracing_reset(data);
+	}
+
+	wakeup_cpu = -1;
+	wakeup_prio = -1;
+	if (wakeup_task) {
+		put_task_struct(wakeup_task);
+		atomic_dec(&trace_record_cmdline);
+		tracing_stop_function_trace();
+		unregister_tracer_switch(&switch_ops);
+	}
+
+	wakeup_task = NULL;
+
+	/*
+	 * Don't let the trace_enabled = 1 show up before
+	 * the wakeup_task is reset.
+	 */
+	smp_wmb();
+}
+
+static void notrace wakeup_reset(struct tracing_trace *tr)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&wakeup_lock, flags);
+	__wakeup_reset(tr);
+	spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+static notrace void wakeup_check_start(struct tracing_trace *tr,
+				       struct task_struct *p,
+				       struct task_struct *curr)
+{
+	unsigned long flags;
+	int cpu = smp_processor_id();
+
+	if (likely(!rt_task(p)) ||
+	    p->prio >= wakeup_prio ||
+	    p->prio >= curr->prio)
+		return;
+
+	atomic_inc(&tr->data[cpu]->disabled);
+	if (unlikely(atomic_read(&tr->data[cpu]->disabled) != 1))
+		goto out;
+
+	/* interrupts should be off from try_to_wake_up */
+	spin_lock(&wakeup_lock);
+
+	/* check for races. */
+	if (!trace_enabled || p->prio >= wakeup_prio)
+		goto out_locked;
+
+	/* reset the trace */
+	__wakeup_reset(tr);
+
+	wakeup_cpu = task_cpu(p);
+	wakeup_prio = p->prio;
+
+	wakeup_task = p;
+	get_task_struct(wakeup_task);
+	register_tracer_switch(&switch_ops);
+	tracing_start_function_trace();
+	atomic_inc(&trace_record_cmdline);
+
+	tr->data[wakeup_cpu]->preempt_timestamp = now();
+
+	local_save_flags(flags);
+	tracing_function_trace(tr, tr->data[wakeup_cpu],
+			       CALLER_ADDR1, CALLER_ADDR2, flags);
+
+
+ out_locked:
+	spin_unlock(&wakeup_lock);
+ out:
+	atomic_dec(&tr->data[cpu]->disabled);
+}
+
+static notrace void wake_up_callback(const struct marker *mdata,
+				     void *private_data,
+				     const char *format, ...)
+{
+	struct tracing_trace **ptr = mdata->private;
+	struct tracing_trace *tr = *ptr;
+	struct task_struct *curr;
+	struct task_struct *p;
+	va_list ap;
+
+	if (likely(!trace_enabled))
+		return;
+
+	va_start(ap, format);
+
+	/* now get the meat: "p %p rq->curr %p" */
+	p = va_arg(ap, typeof(p));
+	curr = va_arg(ap, typeof(curr));
+
+	va_end(ap);
+
+	wakeup_check_start(tr, p, curr);
+}
+
+static notrace void start_wakeup_trace(struct tracing_trace *tr)
+{
+	wakeup_reset(tr);
+	trace_enabled = 1;
+}
+
+static notrace void stop_wakeup_trace(struct tracing_trace *tr)
+{
+	trace_enabled = 0;
+}
+
+static notrace void wakeup_trace_init(struct tracing_trace *tr)
+{
+	tracer_trace = tr;
+
+	if (tr->ctrl)
+		start_wakeup_trace(tr);
+}
+
+static notrace void wakeup_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl) {
+		stop_wakeup_trace(tr);
+		/* make sure we put back any tasks we are tracing */
+		wakeup_reset(tr);
+	}
+}
+
+static void wakeup_trace_ctrl_update(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_wakeup_trace(tr);
+	else
+		stop_wakeup_trace(tr);
+}
+
+static void notrace wakeup_trace_open(struct tracing_iterator *iter)
+{
+	/* stop the trace while dumping */
+	if (iter->tr->ctrl)
+		stop_wakeup_trace(iter->tr);
+}
+
+static void notrace wakeup_trace_close(struct tracing_iterator *iter)
+{
+	/* forget about any processes we were recording */
+	if (iter->tr->ctrl)
+		start_wakeup_trace(iter->tr);
+}
+
+static struct trace_types_struct wakeup_trace __read_mostly =
+{
+	.name = "wakeup",
+	.init = wakeup_trace_init,
+	.reset = wakeup_trace_reset,
+	.open = wakeup_trace_open,
+	.close = wakeup_trace_close,
+	.ctrl_update = wakeup_trace_ctrl_update,
+	.print_max = 1,
+};
+
+__init static int init_wakeup_trace(void)
+{
+	int ret;
+
+	ret = register_trace(&wakeup_trace);
+	if (ret)
+		return ret;
+
+	ret = marker_probe_register("kernel_sched_wakeup",
+				    "p %p rq->curr %p",
+				    wake_up_callback,
+				    &tracer_trace);
+	if (ret) {
+		pr_info("wakeup trace: Couldn't add marker"
+			" probe to kernel_sched_wakeup\n");
+		goto fail;
+	}
+
+	ret = marker_arm("kernel_sched_wakeup");
+	if (ret) {
+		pr_info("wakeup trace: Couldn't arm probe"
+			" kernel_sched_wakeup\n");
+		goto fail_deprobe;
+	}
+
+	return 0;
+ fail_deprobe:
+	marker_probe_unregister("kernel_sched_wakeup");
+ fail:
+	unregister_trace(&wakeup_trace);
+	return 0;
+}
+
+device_initcall(init_wakeup_trace);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:49.000000000 -0500
@@ -28,8 +28,13 @@
 
 #include "tracer.h"
 
+unsigned long tracing_max_latency __read_mostly = (cycle_t)ULONG_MAX;
+unsigned long tracing_thresh __read_mostly;
+
 static struct tracing_trace tracer_trace __read_mostly;
 static DEFINE_PER_CPU(struct tracing_trace_cpu, tracer_trace_cpu);
+static struct tracing_trace max_tr __read_mostly;
+static DEFINE_PER_CPU(struct tracing_trace_cpu, max_data);
 static int trace_enabled __read_mostly;
 static unsigned long trace_nr_entries = (65536UL);
 
@@ -64,6 +69,43 @@ enum trace_flag_type {
 	TRACE_FLAG_SOFTIRQ		= 0x08,
 };
 
+/*
+ * Copy the new maximum trace into the separate maximum-trace
+ * structure. (this way the maximum trace is permanently saved,
+ * for later retrieval via /debugfs/tracing/latency_trace)
+ */
+void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data = tr->data[cpu];
+	void *save_trace;
+	int i;
+
+	max_tr.cpu = cpu;
+	max_tr.time_start = data->preempt_timestamp;
+
+
+	/* clear out all the previous traces */
+	for_each_possible_cpu(i) {
+		data = tr->data[i];
+		save_trace = max_tr.data[i]->trace;
+		memcpy(max_tr.data[i], data, sizeof(*data));
+		data->trace = save_trace;
+	}
+
+	data = max_tr.data[cpu];
+	data->saved_latency = tracing_max_latency;
+
+	memcpy(data->comm, tsk->comm, TASK_COMM_LEN);
+	data->pid = tsk->pid;
+	data->uid = tsk->uid;
+	data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
+	data->policy = tsk->policy;
+	data->rt_priority = tsk->rt_priority;
+
+	/* record this tasks comm */
+	tracing_record_cmdline(current);
+}
+
 int register_trace(struct trace_types_struct *type)
 {
 	struct trace_types_struct *t;
@@ -797,9 +839,14 @@ __tracing_open(struct inode *inode, stru
 		goto out;
 	}
 
-	iter->tr = inode->i_private;
+	mutex_lock(&trace_types_lock);
+	if (current_trace && current_trace->print_max)
+		iter->tr = &max_tr;
+	else
+		iter->tr = inode->i_private;
 	iter->trace = current_trace;
 	iter->pos = -1;
+	mutex_unlock(&trace_types_lock);
 
 	/* TODO stop tracer */
 	*ret = seq_open(file, &tracer_seq_ops);
@@ -1079,7 +1126,7 @@ static ssize_t tracing_ctrl_write(struct
 		tr->ctrl = val;
 
 		mutex_lock(&trace_types_lock);
-		if (current_trace->ctrl_update)
+		if (current_trace && current_trace->ctrl_update)
 			current_trace->ctrl_update(tr);
 		mutex_unlock(&trace_types_lock);
 	}
@@ -1150,6 +1197,50 @@ static ssize_t tracing_set_trace_write(s
 	return cnt;
 }
 
+static ssize_t tracing_max_lat_read(struct file *filp, char __user *ubuf,
+				    size_t cnt, loff_t *ppos)
+{
+	unsigned long *ptr = filp->private_data;
+	char buf[64];
+	int r;
+
+	r = snprintf(buf, 64, "%ld\n",
+		     *ptr == (unsigned long)-1 ? -1 : cycles_to_usecs(*ptr));
+	if (r > 64)
+		r = 64;
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+				       buf, r);
+}
+
+static ssize_t tracing_max_lat_write(struct file *filp,
+				     const char __user *ubuf,
+				     size_t cnt, loff_t *ppos)
+{
+	long *ptr = filp->private_data;
+	long val;
+	char buf[64];
+
+	if (cnt > 63)
+		cnt = 63;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	val = simple_strtoul(buf, NULL, 10);
+
+	*ptr = usecs_to_cycles(val);
+
+	return cnt;
+}
+
+static struct file_operations tracing_max_lat_fops = {
+	.open = tracing_open_generic,
+	.read = tracing_max_lat_read,
+	.write = tracing_max_lat_write,
+};
+
 static struct file_operations tracing_ctrl_fops = {
 	.open = tracing_open_generic,
 	.read = tracing_ctrl_read,
@@ -1218,6 +1309,19 @@ static __init void tracer_init_debugfs(v
 				    &tracer_trace, &set_tracer_fops);
 	if (!entry)
 		pr_warning("Could not create debugfs 'trace' entry\n");
+
+	entry = debugfs_create_file("tracing_max_latency", 0644, d_tracer,
+				    &tracing_max_latency,
+				    &tracing_max_lat_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'tracing_max_latency' entry\n");
+
+	entry = debugfs_create_file("tracing_thresh", 0644, d_tracer,
+				    &tracing_thresh, &tracing_max_lat_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'tracing_threash' entry\n");
 }
 
 static inline notrace int page_order(const unsigned long size)
@@ -1235,6 +1339,8 @@ __init static int tracer_alloc_buffers(v
 
 	for_each_possible_cpu(i) {
 		tracer_trace.data[i] = &per_cpu(tracer_trace_cpu, i);
+		max_tr.data[i] = &per_cpu(max_data, i);
+
 		array = (struct tracing_entry *)
 			  __get_free_pages(GFP_KERNEL, order);
 		if (array == NULL) {
@@ -1243,6 +1349,18 @@ __init static int tracer_alloc_buffers(v
 			goto free_buffers;
 		}
 		tracer_trace.data[i]->trace = array;
+
+/* Only allocate if we are actually using the max trace */
+#ifdef CONFIG_TRACER_MAX_TRACE
+		array = (struct tracing_entry *)
+			  __get_free_pages(GFP_KERNEL, order);
+		if (array == NULL) {
+			printk(KERN_ERR "wakeup tracer: failed to allocate"
+			       " %ld bytes for trace buffer!\n", size);
+			goto free_buffers;
+		}
+		max_tr.data[i]->trace = array;
+#endif
 	}
 
 	/*
@@ -1250,6 +1368,7 @@ __init static int tracer_alloc_buffers(v
 	 * round up a bit.
 	 */
 	tracer_trace.entries = size / TRACING_ENTRY_SIZE;
+	max_tr.entries = tracer_trace.entries;
 
 	pr_info("tracer: %ld bytes allocated for %ld",
 		size, trace_nr_entries);
@@ -1270,6 +1389,14 @@ __init static int tracer_alloc_buffers(v
 			free_pages((unsigned long)data->trace, order);
 			data->trace = NULL;
 		}
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+		data = max_tr.data[i];
+		if (data && data->trace) {
+			free_pages((unsigned long)data->trace, order);
+			data->trace = NULL;
+		}
+#endif
 	}
 	return -ENOMEM;
 }
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:42.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:49.000000000 -0500
@@ -69,6 +69,7 @@ struct trace_types_struct {
 	void (*stop)(struct tracing_iterator *iter);
 	void (*ctrl_update)(struct tracing_trace *tr);
 	struct trace_types_struct *next;
+	int print_max;
 };
 
 struct tracing_iterator {
@@ -107,6 +108,11 @@ void unregister_trace(struct trace_types
 extern atomic_t trace_record_cmdline;
 extern atomic_t trace_record_cmdline_disabled;
 
+extern unsigned long tracing_max_latency;
+extern unsigned long tracing_thresh;
+
+void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu);
+
 static inline notrace cycle_t now(void)
 {
 	return get_monotonic_cycles();

-- 

[PATCH 19/20 -v5] Trace irq disabled critical timings

[Steven Rostedt]

[-- Attachment #1: mcount-tracer-latency-trace-irqs-off.patch --]
[-- Type: text/plain, Size: 28919 bytes --]

This patch adds latency tracing for critical timings
(how long interrupts are disabled for).

 "irqsoff" is added to /debugfs/tracing/available_tracers

Note:
  tracing_max_latency
    also holds the max latency for irqsoff (in usecs).
   (default to large number so one must start latency tracing)

  tracing_thresh
    threshold (in usecs) to always print out if irqs off
    is detected to be longer than stated here.
    If irq_thresh is non-zero, then max_irq_latency
    is ignored.

Here's an example of a trace with mcount_enabled = 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
 swapper-0     1d.s3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1d.s3  100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1d.s3  100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


And this is a trace with mcount_enabled == 1


=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
 swapper-0     1dNs3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
 swapper-0     1dNs3   46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
 swapper-0     1dNs3   47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
 swapper-0     1dNs3   47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
 swapper-0     1dNs3   97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
 swapper-0     1dNs3   98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
 swapper-0     1dNs3   99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
 swapper-0     1dNs3  101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/process_64.c  |    3 
 arch/x86/lib/thunk_64.S       |   18 +
 include/asm-x86/irqflags_32.h |    4 
 include/asm-x86/irqflags_64.h |    4 
 include/linux/irqflags.h      |   37 ++-
 include/linux/mcount.h        |   31 ++-
 kernel/fork.c                 |    2 
 kernel/lockdep.c              |   20 +-
 lib/tracing/Kconfig           |   18 +
 lib/tracing/Makefile          |    1 
 lib/tracing/trace_irqsoff.c   |  415 ++++++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.c          |   59 ++++-
 lib/tracing/tracer.h          |    2 
 13 files changed, 579 insertions(+), 35 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/process_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/process_64.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/process_64.c	2008-01-23 10:27:53.000000000 -0500
@@ -233,7 +233,10 @@ void cpu_idle (void)
 			 */
 			local_irq_disable();
 			enter_idle();
+			/* Don't trace irqs off for idle */
+			stop_critical_timings();
 			idle();
+			start_critical_timings();
 			/* In many cases the interrupt that ended idle
 			   has already called exit_idle. But some idle
 			   loops can be woken up without interrupt. */
Index: linux-mcount.git/arch/x86/lib/thunk_64.S
===================================================================
--- linux-mcount.git.orig/arch/x86/lib/thunk_64.S	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/lib/thunk_64.S	2008-01-23 10:27:53.000000000 -0500
@@ -47,8 +47,22 @@
 	thunk __up_wakeup,__up
 
 #ifdef CONFIG_TRACE_IRQFLAGS
-	thunk trace_hardirqs_on_thunk,trace_hardirqs_on
-	thunk trace_hardirqs_off_thunk,trace_hardirqs_off
+	/* put return address in rdi (arg1) */
+	.macro thunk_ra name,func
+	.globl \name
+\name:
+	CFI_STARTPROC
+	SAVE_ARGS
+	/* SAVE_ARGS pushs 9 elements */
+	/* the next element would be the rip */
+	movq 9*8(%rsp), %rdi
+	call \func
+	jmp  restore
+	CFI_ENDPROC
+	.endm
+
+	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller
+	thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller
 #endif
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
Index: linux-mcount.git/include/asm-x86/irqflags_32.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/irqflags_32.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/asm-x86/irqflags_32.h	2008-01-23 10:27:53.000000000 -0500
@@ -139,9 +139,9 @@ static inline int raw_irqs_disabled(void
 static inline void trace_hardirqs_fixup_flags(unsigned long flags)
 {
 	if (raw_irqs_disabled_flags(flags))
-		trace_hardirqs_off();
+		__trace_hardirqs_off();
 	else
-		trace_hardirqs_on();
+		__trace_hardirqs_on();
 }
 
 static inline void trace_hardirqs_fixup(void)
Index: linux-mcount.git/include/asm-x86/irqflags_64.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/irqflags_64.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/asm-x86/irqflags_64.h	2008-01-23 10:27:53.000000000 -0500
@@ -120,9 +120,9 @@ static inline int raw_irqs_disabled(void
 static inline void trace_hardirqs_fixup_flags(unsigned long flags)
 {
 	if (raw_irqs_disabled_flags(flags))
-		trace_hardirqs_off();
+		__trace_hardirqs_off();
 	else
-		trace_hardirqs_on();
+		__trace_hardirqs_on();
 }
 
 static inline void trace_hardirqs_fixup(void)
Index: linux-mcount.git/include/linux/irqflags.h
===================================================================
--- linux-mcount.git.orig/include/linux/irqflags.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/linux/irqflags.h	2008-01-23 10:27:53.000000000 -0500
@@ -12,10 +12,21 @@
 #define _LINUX_TRACE_IRQFLAGS_H
 
 #ifdef CONFIG_TRACE_IRQFLAGS
-  extern void trace_hardirqs_on(void);
-  extern void trace_hardirqs_off(void);
+# include <linux/mcount.h>
+  extern void trace_hardirqs_on_caller(unsigned long ip);
+  extern void trace_hardirqs_off_caller(unsigned long ip);
   extern void trace_softirqs_on(unsigned long ip);
   extern void trace_softirqs_off(unsigned long ip);
+  extern void trace_hardirqs_on(void);
+  extern void trace_hardirqs_off(void);
+  static inline void notrace __trace_hardirqs_on(void)
+  {
+	trace_hardirqs_on_caller(CALLER_ADDR0);
+  }
+  static inline void notrace __trace_hardirqs_off(void)
+  {
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+  }
 # define trace_hardirq_context(p)	((p)->hardirq_context)
 # define trace_softirq_context(p)	((p)->softirq_context)
 # define trace_hardirqs_enabled(p)	((p)->hardirqs_enabled)
@@ -28,6 +39,8 @@
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
+# define __trace_hardirqs_on()		do { } while (0)
+# define __trace_hardirqs_off()		do { } while (0)
 # define trace_softirqs_on(ip)		do { } while (0)
 # define trace_softirqs_off(ip)		do { } while (0)
 # define trace_hardirq_context(p)	0
@@ -41,24 +54,32 @@
 # define INIT_TRACE_IRQFLAGS
 #endif
 
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ extern void stop_critical_timings(void);
+ extern void start_critical_timings(void);
+#else
+# define stop_critical_timings() do { } while (0)
+# define start_critical_timings() do { } while (0)
+#endif
+
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 
 #include <asm/irqflags.h>
 
 #define local_irq_enable() \
-	do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
+	do { __trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
 #define local_irq_disable() \
-	do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)
+	do { raw_local_irq_disable(); __trace_hardirqs_off(); } while (0)
 #define local_irq_save(flags) \
-	do { raw_local_irq_save(flags); trace_hardirqs_off(); } while (0)
+	do { raw_local_irq_save(flags); __trace_hardirqs_off(); } while (0)
 
 #define local_irq_restore(flags)				\
 	do {							\
 		if (raw_irqs_disabled_flags(flags)) {		\
 			raw_local_irq_restore(flags);		\
-			trace_hardirqs_off();			\
+			__trace_hardirqs_off();			\
 		} else {					\
-			trace_hardirqs_on();			\
+			__trace_hardirqs_on();			\
 			raw_local_irq_restore(flags);		\
 		}						\
 	} while (0)
@@ -76,7 +97,7 @@
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 #define safe_halt()						\
 	do {							\
-		trace_hardirqs_on();				\
+		__trace_hardirqs_on();				\
 		raw_safe_halt();				\
 	} while (0)
 
Index: linux-mcount.git/include/linux/mcount.h
===================================================================
--- linux-mcount.git.orig/include/linux/mcount.h	2008-01-23 10:26:34.000000000 -0500
+++ linux-mcount.git/include/linux/mcount.h	2008-01-23 10:27:53.000000000 -0500
@@ -6,10 +6,6 @@ extern int mcount_enabled;
 
 #include <linux/linkage.h>
 
-#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
-#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
-#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
-
 typedef void (*mcount_func_t)(unsigned long ip, unsigned long parent_ip);
 
 struct mcount_ops {
@@ -35,4 +31,31 @@ extern void mcount(void);
 # define unregister_mcount_function(ops) do { } while (0)
 # define clear_mcount_function(ops) do { } while (0)
 #endif /* CONFIG_MCOUNT */
+
+
+#ifdef CONFIG_FRAME_POINTER
+/* TODO: need to fix this for ARM */
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
+# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
+# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
+# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
+# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
+#else
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 0UL
+# define CALLER_ADDR2 0UL
+# define CALLER_ADDR3 0UL
+# define CALLER_ADDR4 0UL
+# define CALLER_ADDR5 0UL
+#endif
+
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+  extern void notrace time_hardirqs_on(unsigned long a0, unsigned long a1);
+  extern void notrace time_hardirqs_off(unsigned long a0, unsigned long a1);
+#else
+# define time_hardirqs_on(a0, a1)		do { } while (0)
+# define time_hardirqs_off(a0, a1)		do { } while (0)
+#endif
+
 #endif /* _LINUX_MCOUNT_H */
Index: linux-mcount.git/kernel/fork.c
===================================================================
--- linux-mcount.git.orig/kernel/fork.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/kernel/fork.c	2008-01-23 10:27:53.000000000 -0500
@@ -1010,7 +1010,7 @@ static struct task_struct *copy_process(
 
 	rt_mutex_init_task(p);
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_LOCKDEP)
 	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 #endif
Index: linux-mcount.git/kernel/lockdep.c
===================================================================
--- linux-mcount.git.orig/kernel/lockdep.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/kernel/lockdep.c	2008-01-23 10:27:53.000000000 -0500
@@ -39,6 +39,7 @@
 #include <linux/irqflags.h>
 #include <linux/utsname.h>
 #include <linux/hash.h>
+#include <linux/mcount.h>
 
 #include <asm/sections.h>
 
@@ -2009,7 +2010,7 @@ void early_boot_irqs_on(void)
 /*
  * Hardirqs will be enabled:
  */
-void trace_hardirqs_on(void)
+void notrace trace_hardirqs_on_caller(unsigned long a0)
 {
 	struct task_struct *curr = current;
 	unsigned long ip;
@@ -2050,14 +2051,24 @@ void trace_hardirqs_on(void)
 	curr->hardirq_enable_ip = ip;
 	curr->hardirq_enable_event = ++curr->irq_events;
 	debug_atomic_inc(&hardirqs_on_events);
+	time_hardirqs_on(CALLER_ADDR0, a0);
 }
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
+void notrace trace_hardirqs_on(void) {
+	trace_hardirqs_on_caller(CALLER_ADDR0);
+}
 EXPORT_SYMBOL(trace_hardirqs_on);
 
+void notrace trace_hardirqs_off(void) {
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
 /*
  * Hardirqs were disabled:
  */
-void trace_hardirqs_off(void)
+void notrace trace_hardirqs_off_caller(unsigned long a0)
 {
 	struct task_struct *curr = current;
 
@@ -2075,10 +2086,15 @@ void trace_hardirqs_off(void)
 		curr->hardirq_disable_ip = _RET_IP_;
 		curr->hardirq_disable_event = ++curr->irq_events;
 		debug_atomic_inc(&hardirqs_off_events);
+		time_hardirqs_off(CALLER_ADDR0, a0);
 	} else
 		debug_atomic_inc(&redundant_hardirqs_off);
 }
 
+void notrace trace_hardirqs_off(void) {
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+}
+
 EXPORT_SYMBOL(trace_hardirqs_off);
 
 /*
Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:49.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:53.000000000 -0500
@@ -28,6 +28,24 @@ config FUNCTION_TRACER
 	  that the debugging mechanism using this facility will hook by
 	  providing a set of inline routines.
 
+config CRITICAL_IRQSOFF_TIMING
+	bool "Interrupts-off critical section latency timing"
+	default n
+	depends on TRACE_IRQFLAGS_SUPPORT
+	depends on GENERIC_TIME
+	select TRACE_IRQFLAGS
+	select TRACING
+	select TRACER_MAX_TRACE
+	help
+	  This option measures the time spent in irqs-off critical
+	  sections, with microsecond accuracy.
+
+	  The default measurement method is a maximum search, which is
+	  disabled by default and can be runtime (re-)started
+	  via:
+
+	      echo 0 > /debugfs/tracing/tracing_max_latency
+
 config WAKEUP_TRACER
 	bool "Trace wakeup latencies"
 	depends on DEBUG_KERNEL
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:27:49.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:27:53.000000000 -0500
@@ -3,6 +3,7 @@ obj-$(CONFIG_MCOUNT) += libmcount.o
 obj-$(CONFIG_TRACING) += tracer.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+obj-$(CONFIG_CRITICAL_IRQSOFF_TIMING) += trace_irqsoff.o
 obj-$(CONFIG_WAKEUP_TRACER) += trace_wakeup.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_irqsoff.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_irqsoff.c	2008-01-23 10:28:35.000000000 -0500
@@ -0,0 +1,415 @@
+/*
+ * trace irqs off criticall timings
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * From code in the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace *tracer_trace __read_mostly;
+static __cacheline_aligned_in_smp DEFINE_MUTEX(max_mutex);
+static int trace_enabled __read_mostly;
+
+/*
+ * Sequence count - we record it when starting a measurement and
+ * skip the latency if the sequence has changed - some other section
+ * did a maximum and could disturb our measurement with serial console
+ * printouts, etc. Truly coinciding maximum latencies should be rare
+ * and what happens together happens separately as well, so this doesnt
+ * decrease the validity of the maximum found:
+ */
+static __cacheline_aligned_in_smp unsigned long max_sequence;
+
+#ifdef CONFIG_MCOUNT
+/* irqsoff uses its own function trace to keep the overhead down */
+static void notrace irqsoff_trace_call(unsigned long ip,
+				       unsigned long parent_ip)
+{
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+	int cpu;
+
+	if (likely(!trace_enabled))
+		return;
+
+	local_save_flags(flags);
+
+	if (!irqs_disabled_flags(flags))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+	atomic_inc(&data->disabled);
+
+	if (likely(atomic_read(&data->disabled) == 1))
+		tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+	atomic_dec(&data->disabled);
+}
+
+static struct mcount_ops trace_ops __read_mostly =
+{
+	.func = irqsoff_trace_call,
+};
+#endif /* CONFIG_MCOUNT */
+
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+	if (tracing_thresh) {
+		if (delta < tracing_thresh)
+			return 0;
+	} else {
+		if (delta <= tracing_max_latency)
+			return 0;
+	}
+	return 1;
+}
+
+static void notrace
+check_critical_timing(struct tracing_trace *tr,
+		      struct tracing_trace_cpu *data,
+		      unsigned long parent_ip,
+		      int cpu)
+{
+	unsigned long latency, t0, t1;
+	cycle_t T0, T1, T2, delta;
+	unsigned long flags;
+
+	/*
+	 * usecs conversion is slow so we try to delay the conversion
+	 * as long as possible:
+	 */
+	T0 = data->preempt_timestamp;
+	T1 = now();
+	delta = T1-T0;
+
+	local_save_flags(flags);
+
+	if (!report_latency(delta))
+		goto out;
+
+	tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+	/*
+	 * Update the timestamp, because the trace entry above
+	 * might change it (it can only get larger so the latency
+	 * is fair to be reported):
+	 */
+	T2 = now();
+
+	delta = T2-T0;
+
+	latency = cycles_to_usecs(delta);
+
+	if (data->critical_sequence != max_sequence ||
+	    !mutex_trylock(&max_mutex))
+		goto out;
+
+	tracing_max_latency = delta;
+	t0 = cycles_to_usecs(T0);
+	t1 = cycles_to_usecs(T1);
+
+	data->critical_end = parent_ip;
+
+	update_max_tr_single(tr, current, cpu);
+
+	if (tracing_thresh)
+		printk(KERN_WARNING "(%16s-%-5d|#%d): %lu us critical section "
+		       "violates %lu us threshold.\n"
+		       " => started at timestamp %lu: ",
+				current->comm, current->pid,
+				raw_smp_processor_id(),
+				latency, cycles_to_usecs(tracing_thresh), t0);
+	else
+		printk(KERN_WARNING "(%16s-%-5d|#%d):"
+		       " new %lu us maximum-latency "
+		       "critical section.\n => started at timestamp %lu: ",
+				current->comm, current->pid,
+				raw_smp_processor_id(),
+				latency, t0);
+
+	print_symbol(KERN_CONT "<%s>\n", data->critical_start);
+	printk(KERN_CONT " =>   ended at timestamp %lu: ", t1);
+	print_symbol(KERN_CONT "<%s>\n", data->critical_end);
+	dump_stack();
+	t1 = cycles_to_usecs(now());
+	printk(KERN_CONT " =>   dump-end timestamp %lu\n\n", t1);
+
+	max_sequence++;
+
+	mutex_unlock(&max_mutex);
+
+out:
+	data->critical_sequence = max_sequence;
+	data->preempt_timestamp = now();
+	tracing_reset(data);
+	tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+}
+
+static inline void notrace
+start_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+	int cpu;
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+
+	if (likely(!trace_enabled))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    data->critical_start || atomic_read(&data->disabled))
+		return;
+
+	atomic_inc(&data->disabled);
+
+	data->critical_sequence = max_sequence;
+	data->preempt_timestamp = now();
+	data->critical_start = parent_ip;
+	tracing_reset(data);
+
+	local_save_flags(flags);
+	tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+	atomic_dec(&data->disabled);
+}
+
+static inline void notrace
+stop_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+	int cpu;
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+
+	if (likely(!trace_enabled))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    !data->critical_start || atomic_read(&data->disabled))
+		return;
+
+	atomic_inc(&data->disabled);
+	local_save_flags(flags);
+	tracing_function_trace(tr, data, ip, parent_ip, flags);
+	check_critical_timing(tr, data, parent_ip, cpu);
+	data->critical_start = 0;
+	atomic_dec(&data->disabled);
+}
+
+void notrace start_critical_timings(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, 0);
+}
+
+void notrace stop_critical_timings(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, 0);
+}
+
+#ifdef CONFIG_LOCKDEP
+void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(a0, a1);
+}
+
+void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(a0, a1);
+}
+
+#else /* !CONFIG_LOCKDEP */
+
+/*
+ * Stubs:
+ */
+
+void early_boot_irqs_off(void)
+{
+}
+
+void early_boot_irqs_on(void)
+{
+}
+
+void trace_softirqs_on(unsigned long ip)
+{
+}
+
+void trace_softirqs_off(unsigned long ip)
+{
+}
+
+inline void print_irqtrace_events(struct task_struct *curr)
+{
+}
+
+/*
+ * We are only interested in hardirq on/off events:
+ */
+void notrace trace_hardirqs_on(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void notrace trace_hardirqs_off(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+
+#endif /* CONFIG_LOCKDEP */
+
+static void start_irqsoff_trace(struct tracing_trace *tr)
+{
+	trace_enabled = 1;
+	register_mcount_function(&trace_ops);
+}
+
+static void stop_irqsoff_trace(struct tracing_trace *tr)
+{
+	unregister_mcount_function(&trace_ops);
+	trace_enabled = 0;
+}
+
+static void irqsoff_trace_init(struct tracing_trace *tr)
+{
+	tracer_trace = tr;
+	/* make sure that the tracer is visibel */
+	smp_wmb();
+
+	if (tr->ctrl)
+		start_irqsoff_trace(tr);
+}
+
+static void irqsoff_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		stop_irqsoff_trace(tr);
+}
+
+static void irqsoff_trace_ctrl_update(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_irqsoff_trace(tr);
+	else
+		stop_irqsoff_trace(tr);
+}
+
+static void notrace irqsoff_trace_open(struct tracing_iterator *iter)
+{
+	/* stop the trace while dumping */
+	if (iter->tr->ctrl)
+		stop_irqsoff_trace(iter->tr);
+}
+
+static void notrace irqsoff_trace_close(struct tracing_iterator *iter)
+{
+	if (iter->tr->ctrl)
+		start_irqsoff_trace(iter->tr);
+}
+
+static void irqsoff_trace_start(struct tracing_iterator *iter)
+{
+	mutex_lock(&max_mutex);
+}
+
+static void irqsoff_trace_stop(struct tracing_iterator *iter)
+{
+	mutex_unlock(&max_mutex);
+}
+
+static struct trace_types_struct irqsoff_trace __read_mostly =
+{
+	.name = "irqsoff",
+	.init = irqsoff_trace_init,
+	.reset = irqsoff_trace_reset,
+	.open = irqsoff_trace_open,
+	.close = irqsoff_trace_close,
+	.start = irqsoff_trace_start,
+	.stop = irqsoff_trace_stop,
+	.ctrl_update = irqsoff_trace_ctrl_update,
+	.print_max = 1,
+};
+
+__init static int init_irqsoff_trace(void)
+{
+	register_trace(&irqsoff_trace);
+
+	return 0;
+}
+
+device_initcall(init_irqsoff_trace);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:27:49.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:53.000000000 -0500
@@ -74,24 +74,14 @@ enum trace_flag_type {
  * structure. (this way the maximum trace is permanently saved,
  * for later retrieval via /debugfs/tracing/latency_trace)
  */
-void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu)
+static void notrace __update_max_tr(struct tracing_trace *tr,
+				    struct task_struct *tsk, int cpu)
 {
 	struct tracing_trace_cpu *data = tr->data[cpu];
-	void *save_trace;
-	int i;
 
 	max_tr.cpu = cpu;
 	max_tr.time_start = data->preempt_timestamp;
 
-
-	/* clear out all the previous traces */
-	for_each_possible_cpu(i) {
-		data = tr->data[i];
-		save_trace = max_tr.data[i]->trace;
-		memcpy(max_tr.data[i], data, sizeof(*data));
-		data->trace = save_trace;
-	}
-
 	data = max_tr.data[cpu];
 	data->saved_latency = tracing_max_latency;
 
@@ -106,6 +96,47 @@ void update_max_tr(struct tracing_trace 
 	tracing_record_cmdline(current);
 }
 
+notrace void update_max_tr(struct tracing_trace *tr,
+			   struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data;
+	void *save_trace;
+	int i;
+
+	/* clear out all the previous traces */
+	for_each_possible_cpu(i) {
+		data = tr->data[i];
+		save_trace = max_tr.data[i]->trace;
+		memcpy(max_tr.data[i], data, sizeof(*data));
+		data->trace = save_trace;
+	}
+
+	__update_max_tr(tr, tsk, cpu);
+}
+
+/**
+ * update_max_tr_single - only copy one trace over, and reset the rest
+ * @tr - tracer
+ * @tsk - task with the latency
+ * @cpu - the cpu of the buffer to copy.
+ */
+notrace void update_max_tr_single(struct tracing_trace *tr,
+				  struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data = tr->data[cpu];
+	void *save_trace;
+	int i;
+
+	for_each_possible_cpu(i)
+		tracing_reset(max_tr.data[i]);
+
+	save_trace = max_tr.data[cpu]->trace;
+	memcpy(max_tr.data[cpu], data, sizeof(*data));
+	data->trace = save_trace;
+
+	__update_max_tr(tr, tsk, cpu);
+}
+
 int register_trace(struct trace_types_struct *type)
 {
 	struct trace_types_struct *t;
@@ -201,12 +232,12 @@ static struct mcount_ops trace_ops __rea
 	.func = function_trace_call,
 };
 
-void tracing_start_function_trace(void)
+notrace void tracing_start_function_trace(void)
 {
 	register_mcount_function(&trace_ops);
 }
 
-void tracing_stop_function_trace(void)
+notrace void tracing_stop_function_trace(void)
 {
 	unregister_mcount_function(&trace_ops);
 }
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:49.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:53.000000000 -0500
@@ -112,6 +112,8 @@ extern unsigned long tracing_max_latency
 extern unsigned long tracing_thresh;
 
 void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu);
+void update_max_tr_single(struct tracing_trace *tr,
+			  struct task_struct *tsk, int cpu);
 
 static inline notrace cycle_t now(void)
 {

-- 

[PATCH 20/20 -v5] trace preempt off critical timings

[Steven Rostedt]

[-- Attachment #1: mcount-trace-latency-trace-preempt-off.patch --]
[-- Type: text/plain, Size: 15610 bytes --]

Add preempt off timings. A lot of kernel core code is taken from the RT patch
latency trace that was written by Ingo Molnar.

This adds "preemptoff" and "preemptirqsoff" to /debugfs/tracing/available_tracers

Now instead of just tracing irqs off, preemption off can be selected
to be recorded.

When this is selected, it shares the same files as irqs off timings.
One can either trace preemption off, irqs off, or one or the other off.

By echoing "preemptoff" into /debugfs/tracing/current_tracer, recording
of preempt off only is performed. "irqsoff" will only record the time
irqs are disabled, but "preemptirqsoff" will take the total time irqs
or preemption are disabled. Runtime switching of these options is now
supported by simpling echoing in the appropriate trace name into
/debugfs/tracing/current_tracer.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/process_32.c |    3 
 include/linux/irqflags.h     |    3 
 include/linux/mcount.h       |    8 +
 include/linux/preempt.h      |    2 
 kernel/sched.c               |   24 +++++
 lib/tracing/Kconfig          |   25 +++++
 lib/tracing/Makefile         |    1 
 lib/tracing/trace_irqsoff.c  |  181 +++++++++++++++++++++++++++++++------------
 8 files changed, 195 insertions(+), 52 deletions(-)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:53.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:28:54.000000000 -0500
@@ -46,6 +46,31 @@ config CRITICAL_IRQSOFF_TIMING
 
 	      echo 0 > /debugfs/tracing/tracing_max_latency
 
+	  (Note that kernel size and overhead increases with this option
+	  enabled. This option and the preempt-off timing option can be
+	  used together or separately.)
+
+config CRITICAL_PREEMPT_TIMING
+	bool "Preemption-off critical section latency timing"
+	default n
+	depends on GENERIC_TIME
+	depends on PREEMPT
+	select TRACING
+	select TRACER_MAX_TRACE
+	help
+	  This option measures the time spent in preemption off critical
+	  sections, with microsecond accuracy.
+
+	  The default measurement method is a maximum search, which is
+	  disabled by default and can be runtime (re-)started
+	  via:
+
+	      echo 0 > /debugfs/tracing/tracing_max_latency
+
+	  (Note that kernel size and overhead increases with this option
+	  enabled. This option and the irqs-off timing option can be
+	  used together or separately.)
+
 config WAKEUP_TRACER
 	bool "Trace wakeup latencies"
 	depends on DEBUG_KERNEL
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:27:53.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:28:54.000000000 -0500
@@ -4,6 +4,7 @@ obj-$(CONFIG_TRACING) += tracer.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
 obj-$(CONFIG_CRITICAL_IRQSOFF_TIMING) += trace_irqsoff.o
+obj-$(CONFIG_CRITICAL_PREEMPT_TIMING) += trace_irqsoff.o
 obj-$(CONFIG_WAKEUP_TRACER) += trace_wakeup.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_irqsoff.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/trace_irqsoff.c	2008-01-23 10:28:35.000000000 -0500
+++ linux-mcount.git/lib/tracing/trace_irqsoff.c	2008-01-23 10:28:54.000000000 -0500
@@ -21,6 +21,34 @@ static struct tracing_trace *tracer_trac
 static __cacheline_aligned_in_smp DEFINE_MUTEX(max_mutex);
 static int trace_enabled __read_mostly;
 
+static DEFINE_PER_CPU(int, tracing_cpu);
+
+enum {
+	TRACER_IRQS_OFF		= (1 << 1),
+	TRACER_PREEMPT_OFF	= (1 << 2),
+};
+
+static int trace_type __read_mostly;
+
+#ifdef CONFIG_CRITICAL_PREEMPT_TIMING
+# define preempt_trace() \
+	((trace_type & TRACER_PREEMPT_OFF) && preempt_count())
+#else
+# define preempt_trace() (0)
+#endif
+
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+# define irq_trace()				\
+	((trace_type & TRACER_IRQS_OFF) &&	\
+	 ({					\
+		 unsigned long __flags;		\
+		 local_save_flags(__flags);	\
+		 irqs_disabled_flags(__flags);	\
+	 }))
+#else
+# define irq_trace() (0)
+#endif
+
 /*
  * Sequence count - we record it when starting a measurement and
  * skip the latency if the sequence has changed - some other section
@@ -41,14 +69,11 @@ static void notrace irqsoff_trace_call(u
 	unsigned long flags;
 	int cpu;
 
-	if (likely(!trace_enabled))
+	if (likely(!__get_cpu_var(tracing_cpu)))
 		return;
 
 	local_save_flags(flags);
 
-	if (!irqs_disabled_flags(flags))
-		return;
-
 	cpu = raw_smp_processor_id();
 	data = tr->data[cpu];
 	atomic_inc(&data->disabled);
@@ -171,23 +196,29 @@ start_critical_timing(unsigned long ip, 
 	if (likely(!trace_enabled))
 		return;
 
+	if (__get_cpu_var(tracing_cpu))
+		return;
+
 	cpu = raw_smp_processor_id();
 	data = tr->data[cpu];
 
 	if (unlikely(!data) || unlikely(!data->trace) ||
-	    data->critical_start || atomic_read(&data->disabled))
+	    atomic_read(&data->disabled))
 		return;
 
 	atomic_inc(&data->disabled);
 
 	data->critical_sequence = max_sequence;
 	data->preempt_timestamp = now();
-	data->critical_start = parent_ip;
+	data->critical_start = parent_ip ? : ip;
 	tracing_reset(data);
 
 	local_save_flags(flags);
+
 	tracing_function_trace(tr, data, ip, parent_ip, flags);
 
+	__get_cpu_var(tracing_cpu) = 1;
+
 	atomic_dec(&data->disabled);
 }
 
@@ -199,6 +230,12 @@ stop_critical_timing(unsigned long ip, u
 	struct tracing_trace_cpu *data;
 	unsigned long flags;
 
+	/* Always clear the tracing cpu on stopping the trace */
+	if (unlikely(__get_cpu_var(tracing_cpu)))
+		__get_cpu_var(tracing_cpu) = 0;
+	else
+		return;
+
 	if (likely(!trace_enabled))
 		return;
 
@@ -212,49 +249,35 @@ stop_critical_timing(unsigned long ip, u
 	atomic_inc(&data->disabled);
 	local_save_flags(flags);
 	tracing_function_trace(tr, data, ip, parent_ip, flags);
-	check_critical_timing(tr, data, parent_ip, cpu);
+	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
 	data->critical_start = 0;
 	atomic_dec(&data->disabled);
 }
 
+/* start and stop critical timings used to for stoppage (in idle) */
 void notrace start_critical_timings(void)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (preempt_trace() || irq_trace())
 		start_critical_timing(CALLER_ADDR0, 0);
 }
 
 void notrace stop_critical_timings(void)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (preempt_trace() || irq_trace())
 		stop_critical_timing(CALLER_ADDR0, 0);
 }
 
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
 #ifdef CONFIG_LOCKDEP
 void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(a0, a1);
 }
 
 void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		start_critical_timing(a0, a1);
 }
 
@@ -289,49 +312,46 @@ inline void print_irqtrace_events(struct
  */
 void notrace trace_hardirqs_on(void)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, 0);
 }
 EXPORT_SYMBOL(trace_hardirqs_on);
 
 void notrace trace_hardirqs_off(void)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		start_critical_timing(CALLER_ADDR0, 0);
 }
 EXPORT_SYMBOL(trace_hardirqs_off);
 
 void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, caller_addr);
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
 void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
 {
-	unsigned long flags;
-
-	local_save_flags(flags);
-
-	if (irqs_disabled_flags(flags))
+	if (!preempt_trace() && irq_trace())
 		start_critical_timing(CALLER_ADDR0, caller_addr);
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
 #endif /* CONFIG_LOCKDEP */
+#endif /*  CONFIG_CRITICAL_IRQSOFF_TIMING */
+
+#ifdef CONFIG_CRITICAL_PREEMPT_TIMING
+void notrace trace_preempt_on(unsigned long a0, unsigned long a1)
+{
+	stop_critical_timing(a0, a1);
+}
+
+void notrace trace_preempt_off(unsigned long a0, unsigned long a1)
+{
+	start_critical_timing(a0, a1);
+}
+#endif /* CONFIG_CRITICAL_PREEMPT_TIMING */
 
 static void start_irqsoff_trace(struct tracing_trace *tr)
 {
@@ -345,7 +365,7 @@ static void stop_irqsoff_trace(struct tr
 	trace_enabled = 0;
 }
 
-static void irqsoff_trace_init(struct tracing_trace *tr)
+static void __irqsoff_trace_init(struct tracing_trace *tr)
 {
 	tracer_trace = tr;
 	/* make sure that the tracer is visibel */
@@ -392,6 +412,13 @@ static void irqsoff_trace_stop(struct tr
 	mutex_unlock(&max_mutex);
 }
 
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+static void irqsoff_trace_init(struct tracing_trace *tr)
+{
+	trace_type = TRACER_IRQS_OFF;
+
+	__irqsoff_trace_init(tr);
+}
 static struct trace_types_struct irqsoff_trace __read_mostly =
 {
 	.name = "irqsoff",
@@ -404,10 +431,66 @@ static struct trace_types_struct irqsoff
 	.ctrl_update = irqsoff_trace_ctrl_update,
 	.print_max = 1,
 };
+# define register_irqsoff(trace) register_trace(&trace)
+#else
+# define register_irqsoff(trace) do { } while (0)
+#endif
+
+#ifdef CONFIG_CRITICAL_PREEMPT_TIMING
+static void preemptoff_trace_init(struct tracing_trace *tr)
+{
+	trace_type = TRACER_PREEMPT_OFF;
+
+	__irqsoff_trace_init(tr);
+}
+static struct trace_types_struct preemptoff_trace __read_mostly =
+{
+	.name = "preemptoff",
+	.init = preemptoff_trace_init,
+	.reset = irqsoff_trace_reset,
+	.open = irqsoff_trace_open,
+	.close = irqsoff_trace_close,
+	.start = irqsoff_trace_start,
+	.stop = irqsoff_trace_stop,
+	.ctrl_update = irqsoff_trace_ctrl_update,
+	.print_max = 1,
+};
+# define register_preemptoff(trace) register_trace(&trace)
+#else
+# define register_preemptoff(trace) do { } while (0)
+#endif
+
+
+#if defined(CONFIG_CRITICAL_IRQSOFF_TIMING) && \
+	defined(CONFIG_CRITICAL_PREEMPT_TIMING)
+static void preemptirqsoff_trace_init(struct tracing_trace *tr)
+{
+	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
+
+	__irqsoff_trace_init(tr);
+}
+static struct trace_types_struct preemptirqsoff_trace __read_mostly =
+{
+	.name = "preemptirqsoff",
+	.init = preemptirqsoff_trace_init,
+	.reset = irqsoff_trace_reset,
+	.open = irqsoff_trace_open,
+	.close = irqsoff_trace_close,
+	.start = irqsoff_trace_start,
+	.stop = irqsoff_trace_stop,
+	.ctrl_update = irqsoff_trace_ctrl_update,
+	.print_max = 1,
+};
+# define register_preemptirqsoff(trace) register_trace(&trace)
+#else
+# define register_preemptirqsoff(trace) do { } while (0)
+#endif
 
 __init static int init_irqsoff_trace(void)
 {
-	register_trace(&irqsoff_trace);
+	register_irqsoff(irqsoff_trace);
+	register_preemptoff(preemptoff_trace);
+	register_preemptirqsoff(preemptirqsoff_trace);
 
 	return 0;
 }
Index: linux-mcount.git/include/linux/preempt.h
===================================================================
--- linux-mcount.git.orig/include/linux/preempt.h	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/include/linux/preempt.h	2008-01-23 10:28:54.000000000 -0500
@@ -10,7 +10,7 @@
 #include <linux/linkage.h>
 #include <linux/list.h>
 
-#ifdef CONFIG_DEBUG_PREEMPT
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_CRITICAL_PREEMPT_TIMING)
   extern void fastcall add_preempt_count(int val);
   extern void fastcall sub_preempt_count(int val);
 #else
Index: linux-mcount.git/kernel/sched.c
===================================================================
--- linux-mcount.git.orig/kernel/sched.c	2008-01-23 10:27:45.000000000 -0500
+++ linux-mcount.git/kernel/sched.c	2008-01-23 10:28:54.000000000 -0500
@@ -63,6 +63,7 @@
 #include <linux/reciprocal_div.h>
 #include <linux/unistd.h>
 #include <linux/pagemap.h>
+#include <linux/mcount.h>
 
 #include <asm/tlb.h>
 #include <asm/irq_regs.h>
@@ -3505,26 +3506,44 @@ void scheduler_tick(void)
 #endif
 }
 
-#if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
+#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
+				defined(CONFIG_CRITICAL_PREEMPT_TIMING))
+
+static inline unsigned long get_parent_ip(unsigned long addr)
+{
+	if (in_lock_functions(addr)) {
+		addr = CALLER_ADDR2;
+		if (in_lock_functions(addr))
+			addr = CALLER_ADDR3;
+	}
+	return addr;
+}
 
 void fastcall add_preempt_count(int val)
 {
+#ifdef CONFIG_DEBUG_PREEMPT
 	/*
 	 * Underflow?
 	 */
 	if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
 		return;
+#endif
 	preempt_count() += val;
+#ifdef CONFIG_DEBUG_PREEMPT
 	/*
 	 * Spinlock count overflowing soon?
 	 */
 	DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
 				PREEMPT_MASK - 10);
+#endif
+	if (preempt_count() == val)
+		trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
 }
 EXPORT_SYMBOL(add_preempt_count);
 
 void fastcall sub_preempt_count(int val)
 {
+#ifdef CONFIG_DEBUG_PREEMPT
 	/*
 	 * Underflow?
 	 */
@@ -3536,7 +3555,10 @@ void fastcall sub_preempt_count(int val)
 	if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
 			!(preempt_count() & PREEMPT_MASK)))
 		return;
+#endif
 
+	if (preempt_count() == val)
+		trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
 	preempt_count() -= val;
 }
 EXPORT_SYMBOL(sub_preempt_count);
Index: linux-mcount.git/arch/x86/kernel/process_32.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/process_32.c	2008-01-23 10:26:11.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/process_32.c	2008-01-23 10:28:54.000000000 -0500
@@ -195,7 +195,10 @@ void cpu_idle(void)
 				play_dead();
 
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
+			/* Don't trace irqs off for idle */
+			stop_critical_timings();
 			idle();
+			start_critical_timings();
 		}
 		tick_nohz_restart_sched_tick();
 		preempt_enable_no_resched();
Index: linux-mcount.git/include/linux/mcount.h
===================================================================
--- linux-mcount.git.orig/include/linux/mcount.h	2008-01-23 10:27:53.000000000 -0500
+++ linux-mcount.git/include/linux/mcount.h	2008-01-23 10:28:54.000000000 -0500
@@ -58,4 +58,12 @@ extern void mcount(void);
 # define time_hardirqs_off(a0, a1)		do { } while (0)
 #endif
 
+#ifdef CONFIG_CRITICAL_PREEMPT_TIMING
+  extern void notrace trace_preempt_on(unsigned long a0, unsigned long a1);
+  extern void notrace trace_preempt_off(unsigned long a0, unsigned long a1);
+#else
+# define trace_preempt_on(a0, a1)		do { } while (0)
+# define trace_preempt_off(a0, a1)		do { } while (0)
+#endif
+
 #endif /* _LINUX_MCOUNT_H */
Index: linux-mcount.git/include/linux/irqflags.h
===================================================================
--- linux-mcount.git.orig/include/linux/irqflags.h	2008-01-23 10:27:53.000000000 -0500
+++ linux-mcount.git/include/linux/irqflags.h	2008-01-23 10:28:54.000000000 -0500
@@ -54,7 +54,8 @@
 # define INIT_TRACE_IRQFLAGS
 #endif
 
-#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+#if defined(CONFIG_CRITICAL_IRQSOFF_TIMING) || \
+	defined(CONFIG_CRITICAL_PREEMPT_TIMING)
  extern void stop_critical_timings(void);
  extern void start_critical_timings(void);
 #else

-- 

Re: [PATCH 08/20 -v5] initialize the clock source to jiffies clock.

[Tim Bird]

Steven Rostedt wrote:
> The latency tracer can call clocksource_read very early in bootup and
> before the clock source variable has been initialized. This results in a
> crash at boot up (even before earlyprintk is initialized). Since the
> clock->read variable points to NULL.
> 
> This patch simply initializes the clock to use clocksource_jiffies, so
> that any early user of clocksource_read will not crash.

There's a similar problem with reads of sched_clock() too early
on some architectures.  This problem reminds me of a fix I need
to re-send to the ARM mailing list.  That aside, I heartily recommend
applying this patch, whether the rest of this system gets mainlined
or not.

FWIW:
Acked-by: Tim Bird <tim.bird@am.sony.com>

 -- Tim


=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Steven Rostedt]

On Wed, Jan 23, 2008 at 11:02:55AM -0500, Steven Rostedt wrote:
> This patch adds latency tracing for critical timings
> (how long interrupts are disabled for).
> 
>  "irqsoff" is added to /debugfs/tracing/available_tracers
> 

> Index: linux-mcount.git/kernel/lockdep.c
> ===================================================================
> --- linux-mcount.git.orig/kernel/lockdep.c	2008-01-23 10:26:11.000000000 -0500
> +++ linux-mcount.git/kernel/lockdep.c	2008-01-23 10:27:53.000000000 -0500
> @@ -39,6 +39,7 @@
>  #include <linux/irqflags.h>
>  #include <linux/utsname.h>
>  #include <linux/hash.h>
> +#include <linux/mcount.h>
>  
>  #include <asm/sections.h>
>  
> @@ -2009,7 +2010,7 @@ void early_boot_irqs_on(void)
>  /*
>   * Hardirqs will be enabled:
>   */
> -void trace_hardirqs_on(void)
> +void notrace trace_hardirqs_on_caller(unsigned long a0)
>  {
>  	struct task_struct *curr = current;
>  	unsigned long ip;
> @@ -2050,14 +2051,24 @@ void trace_hardirqs_on(void)
>  	curr->hardirq_enable_ip = ip;
>  	curr->hardirq_enable_event = ++curr->irq_events;
>  	debug_atomic_inc(&hardirqs_on_events);
> +	time_hardirqs_on(CALLER_ADDR0, a0);
>  }
> +EXPORT_SYMBOL(trace_hardirqs_on_caller);
>  
> +void notrace trace_hardirqs_on(void) {
> +	trace_hardirqs_on_caller(CALLER_ADDR0);
> +}
>  EXPORT_SYMBOL(trace_hardirqs_on);
>  

vvvvvvvvvvvvvvvv

> +void notrace trace_hardirqs_off(void) {
> +	trace_hardirqs_off_caller(CALLER_ADDR0);
> +}
> +EXPORT_SYMBOL(trace_hardirqs_off);
> +

^^^^^^^^^^^^^^^^

>  /*
>   * Hardirqs were disabled:
>   */
> -void trace_hardirqs_off(void)
> +void notrace trace_hardirqs_off_caller(unsigned long a0)
>  {
>  	struct task_struct *curr = current;
>  
> @@ -2075,10 +2086,15 @@ void trace_hardirqs_off(void)
>  		curr->hardirq_disable_ip = _RET_IP_;
>  		curr->hardirq_disable_event = ++curr->irq_events;
>  		debug_atomic_inc(&hardirqs_off_events);
> +		time_hardirqs_off(CALLER_ADDR0, a0);
>  	} else
>  		debug_atomic_inc(&redundant_hardirqs_off);
>  }
>  


> +void notrace trace_hardirqs_off(void) {
> +	trace_hardirqs_off_caller(CALLER_ADDR0);
> +}
> +
>  EXPORT_SYMBOL(trace_hardirqs_off);
> 


Bah, I didn't refresh quilt! I'll update the website with a -v5a with
this fix.

-- Steve

>  /*

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Daniel Walker]

On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:

> +	if (!irqs_disabled() && wake_klogd)
>  		wake_up_klogd();

This causes a regression .. When printk is called during an OOPS in
kernels without this change then the OOPS will get logged, since the
logging process (klogd) is woken to handle the messages.. If you apply
this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
you remove the wakeup here you have to add it someplace else to maintain
the logging ..

(I'm not theorizing here, I have defects logged against this specific
piece of code..)

Daniel

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Steven Rostedt]

[ Here's the updated patch anyway ]


This patch adds latency tracing for critical timings
(how long interrupts are disabled for).

 "irqsoff" is added to /debugfs/tracing/available_tracers

Note:
  tracing_max_latency
    also holds the max latency for irqsoff (in usecs).
   (default to large number so one must start latency tracing)

  tracing_thresh
    threshold (in usecs) to always print out if irqs off
    is detected to be longer than stated here.
    If irq_thresh is non-zero, then max_irq_latency
    is ignored.

Here's an example of a trace with mcount_enabled = 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
 swapper-0     1d.s3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1d.s3  100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1d.s3  100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


And this is a trace with mcount_enabled == 1


=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
 swapper-0     1dNs3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
 swapper-0     1dNs3   46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
 swapper-0     1dNs3   47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
 swapper-0     1dNs3   47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
 swapper-0     1dNs3   97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
 swapper-0     1dNs3   98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
 swapper-0     1dNs3   99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
 swapper-0     1dNs3  101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)


vim:ft=help
=======


Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86/kernel/process_64.c  |    3 
 arch/x86/lib/thunk_64.S       |   18 +
 include/asm-x86/irqflags_32.h |    4 
 include/asm-x86/irqflags_64.h |    4 
 include/linux/irqflags.h      |   37 ++-
 include/linux/mcount.h        |   31 ++-
 kernel/fork.c                 |    2 
 kernel/lockdep.c              |   16 +
 lib/tracing/Kconfig           |   18 +
 lib/tracing/Makefile          |    1 
 lib/tracing/trace_irqsoff.c   |  415 ++++++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.c          |   59 ++++-
 lib/tracing/tracer.h          |    2 
 13 files changed, 575 insertions(+), 35 deletions(-)

Index: linux-mcount.git/arch/x86/kernel/process_64.c
===================================================================
--- linux-mcount.git.orig/arch/x86/kernel/process_64.c	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/arch/x86/kernel/process_64.c	2008-01-23 10:29:09.000000000 -0500
@@ -233,7 +233,10 @@ void cpu_idle (void)
 			 */
 			local_irq_disable();
 			enter_idle();
+			/* Don't trace irqs off for idle */
+			stop_critical_timings();
 			idle();
+			start_critical_timings();
 			/* In many cases the interrupt that ended idle
 			   has already called exit_idle. But some idle
 			   loops can be woken up without interrupt. */
Index: linux-mcount.git/arch/x86/lib/thunk_64.S
===================================================================
--- linux-mcount.git.orig/arch/x86/lib/thunk_64.S	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/arch/x86/lib/thunk_64.S	2008-01-23 10:29:09.000000000 -0500
@@ -47,8 +47,22 @@
 	thunk __up_wakeup,__up
 
 #ifdef CONFIG_TRACE_IRQFLAGS
-	thunk trace_hardirqs_on_thunk,trace_hardirqs_on
-	thunk trace_hardirqs_off_thunk,trace_hardirqs_off
+	/* put return address in rdi (arg1) */
+	.macro thunk_ra name,func
+	.globl \name
+\name:
+	CFI_STARTPROC
+	SAVE_ARGS
+	/* SAVE_ARGS pushs 9 elements */
+	/* the next element would be the rip */
+	movq 9*8(%rsp), %rdi
+	call \func
+	jmp  restore
+	CFI_ENDPROC
+	.endm
+
+	thunk_ra trace_hardirqs_on_thunk,trace_hardirqs_on_caller
+	thunk_ra trace_hardirqs_off_thunk,trace_hardirqs_off_caller
 #endif
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
Index: linux-mcount.git/include/asm-x86/irqflags_32.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/irqflags_32.h	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/include/asm-x86/irqflags_32.h	2008-01-23 10:29:09.000000000 -0500
@@ -139,9 +139,9 @@ static inline int raw_irqs_disabled(void
 static inline void trace_hardirqs_fixup_flags(unsigned long flags)
 {
 	if (raw_irqs_disabled_flags(flags))
-		trace_hardirqs_off();
+		__trace_hardirqs_off();
 	else
-		trace_hardirqs_on();
+		__trace_hardirqs_on();
 }
 
 static inline void trace_hardirqs_fixup(void)
Index: linux-mcount.git/include/asm-x86/irqflags_64.h
===================================================================
--- linux-mcount.git.orig/include/asm-x86/irqflags_64.h	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/include/asm-x86/irqflags_64.h	2008-01-23 10:29:09.000000000 -0500
@@ -120,9 +120,9 @@ static inline int raw_irqs_disabled(void
 static inline void trace_hardirqs_fixup_flags(unsigned long flags)
 {
 	if (raw_irqs_disabled_flags(flags))
-		trace_hardirqs_off();
+		__trace_hardirqs_off();
 	else
-		trace_hardirqs_on();
+		__trace_hardirqs_on();
 }
 
 static inline void trace_hardirqs_fixup(void)
Index: linux-mcount.git/include/linux/irqflags.h
===================================================================
--- linux-mcount.git.orig/include/linux/irqflags.h	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/include/linux/irqflags.h	2008-01-23 11:11:48.000000000 -0500
@@ -12,10 +12,21 @@
 #define _LINUX_TRACE_IRQFLAGS_H
 
 #ifdef CONFIG_TRACE_IRQFLAGS
-  extern void trace_hardirqs_on(void);
-  extern void trace_hardirqs_off(void);
+# include <linux/mcount.h>
+  extern void trace_hardirqs_on_caller(unsigned long ip);
+  extern void trace_hardirqs_off_caller(unsigned long ip);
   extern void trace_softirqs_on(unsigned long ip);
   extern void trace_softirqs_off(unsigned long ip);
+  extern void trace_hardirqs_on(void);
+  extern void trace_hardirqs_off(void);
+  static inline void notrace __trace_hardirqs_on(void)
+  {
+	trace_hardirqs_on_caller(CALLER_ADDR0);
+  }
+  static inline void notrace __trace_hardirqs_off(void)
+  {
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+  }
 # define trace_hardirq_context(p)	((p)->hardirq_context)
 # define trace_softirq_context(p)	((p)->softirq_context)
 # define trace_hardirqs_enabled(p)	((p)->hardirqs_enabled)
@@ -28,6 +39,8 @@
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
+# define __trace_hardirqs_on()		do { } while (0)
+# define __trace_hardirqs_off()		do { } while (0)
 # define trace_softirqs_on(ip)		do { } while (0)
 # define trace_softirqs_off(ip)		do { } while (0)
 # define trace_hardirq_context(p)	0
@@ -41,24 +54,32 @@
 # define INIT_TRACE_IRQFLAGS
 #endif
 
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+ extern void stop_critical_timings(void);
+ extern void start_critical_timings(void);
+#else
+# define stop_critical_timings() do { } while (0)
+# define start_critical_timings() do { } while (0)
+#endif
+
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 
 #include <asm/irqflags.h>
 
 #define local_irq_enable() \
-	do { trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
+	do { __trace_hardirqs_on(); raw_local_irq_enable(); } while (0)
 #define local_irq_disable() \
-	do { raw_local_irq_disable(); trace_hardirqs_off(); } while (0)
+	do { raw_local_irq_disable(); __trace_hardirqs_off(); } while (0)
 #define local_irq_save(flags) \
-	do { raw_local_irq_save(flags); trace_hardirqs_off(); } while (0)
+	do { raw_local_irq_save(flags); __trace_hardirqs_off(); } while (0)
 
 #define local_irq_restore(flags)				\
 	do {							\
 		if (raw_irqs_disabled_flags(flags)) {		\
 			raw_local_irq_restore(flags);		\
-			trace_hardirqs_off();			\
+			__trace_hardirqs_off();			\
 		} else {					\
-			trace_hardirqs_on();			\
+			__trace_hardirqs_on();			\
 			raw_local_irq_restore(flags);		\
 		}						\
 	} while (0)
@@ -76,7 +97,7 @@
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 #define safe_halt()						\
 	do {							\
-		trace_hardirqs_on();				\
+		__trace_hardirqs_on();				\
 		raw_safe_halt();				\
 	} while (0)
 
Index: linux-mcount.git/include/linux/mcount.h
===================================================================
--- linux-mcount.git.orig/include/linux/mcount.h	2008-01-23 10:29:08.000000000 -0500
+++ linux-mcount.git/include/linux/mcount.h	2008-01-23 11:11:48.000000000 -0500
@@ -6,10 +6,6 @@ extern int mcount_enabled;
 
 #include <linux/linkage.h>
 
-#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
-#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
-#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
-
 typedef void (*mcount_func_t)(unsigned long ip, unsigned long parent_ip);
 
 struct mcount_ops {
@@ -35,4 +31,31 @@ extern void mcount(void);
 # define unregister_mcount_function(ops) do { } while (0)
 # define clear_mcount_function(ops) do { } while (0)
 #endif /* CONFIG_MCOUNT */
+
+
+#ifdef CONFIG_FRAME_POINTER
+/* TODO: need to fix this for ARM */
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
+# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
+# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
+# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
+# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
+#else
+# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+# define CALLER_ADDR1 0UL
+# define CALLER_ADDR2 0UL
+# define CALLER_ADDR3 0UL
+# define CALLER_ADDR4 0UL
+# define CALLER_ADDR5 0UL
+#endif
+
+#ifdef CONFIG_CRITICAL_IRQSOFF_TIMING
+  extern void notrace time_hardirqs_on(unsigned long a0, unsigned long a1);
+  extern void notrace time_hardirqs_off(unsigned long a0, unsigned long a1);
+#else
+# define time_hardirqs_on(a0, a1)		do { } while (0)
+# define time_hardirqs_off(a0, a1)		do { } while (0)
+#endif
+
 #endif /* _LINUX_MCOUNT_H */
Index: linux-mcount.git/kernel/fork.c
===================================================================
--- linux-mcount.git.orig/kernel/fork.c	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/kernel/fork.c	2008-01-23 10:29:09.000000000 -0500
@@ -1010,7 +1010,7 @@ static struct task_struct *copy_process(
 
 	rt_mutex_init_task(p);
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_LOCKDEP)
 	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 #endif
Index: linux-mcount.git/kernel/lockdep.c
===================================================================
--- linux-mcount.git.orig/kernel/lockdep.c	2008-01-23 10:29:05.000000000 -0500
+++ linux-mcount.git/kernel/lockdep.c	2008-01-23 11:50:55.000000000 -0500
@@ -39,6 +39,7 @@
 #include <linux/irqflags.h>
 #include <linux/utsname.h>
 #include <linux/hash.h>
+#include <linux/mcount.h>
 
 #include <asm/sections.h>
 
@@ -2009,7 +2010,7 @@ void early_boot_irqs_on(void)
 /*
  * Hardirqs will be enabled:
  */
-void trace_hardirqs_on(void)
+void notrace trace_hardirqs_on_caller(unsigned long a0)
 {
 	struct task_struct *curr = current;
 	unsigned long ip;
@@ -2050,14 +2051,19 @@ void trace_hardirqs_on(void)
 	curr->hardirq_enable_ip = ip;
 	curr->hardirq_enable_event = ++curr->irq_events;
 	debug_atomic_inc(&hardirqs_on_events);
+	time_hardirqs_on(CALLER_ADDR0, a0);
 }
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
+void notrace trace_hardirqs_on(void) {
+	trace_hardirqs_on_caller(CALLER_ADDR0);
+}
 EXPORT_SYMBOL(trace_hardirqs_on);
 
 /*
  * Hardirqs were disabled:
  */
-void trace_hardirqs_off(void)
+void notrace trace_hardirqs_off_caller(unsigned long a0)
 {
 	struct task_struct *curr = current;
 
@@ -2075,9 +2081,15 @@ void trace_hardirqs_off(void)
 		curr->hardirq_disable_ip = _RET_IP_;
 		curr->hardirq_disable_event = ++curr->irq_events;
 		debug_atomic_inc(&hardirqs_off_events);
+		time_hardirqs_off(CALLER_ADDR0, a0);
 	} else
 		debug_atomic_inc(&redundant_hardirqs_off);
 }
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+
+void notrace trace_hardirqs_off(void) {
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+}
 
 EXPORT_SYMBOL(trace_hardirqs_off);
 
Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:29:09.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 11:11:48.000000000 -0500
@@ -28,6 +28,24 @@ config FUNCTION_TRACER
 	  that the debugging mechanism using this facility will hook by
 	  providing a set of inline routines.
 
+config CRITICAL_IRQSOFF_TIMING
+	bool "Interrupts-off critical section latency timing"
+	default n
+	depends on TRACE_IRQFLAGS_SUPPORT
+	depends on GENERIC_TIME
+	select TRACE_IRQFLAGS
+	select TRACING
+	select TRACER_MAX_TRACE
+	help
+	  This option measures the time spent in irqs-off critical
+	  sections, with microsecond accuracy.
+
+	  The default measurement method is a maximum search, which is
+	  disabled by default and can be runtime (re-)started
+	  via:
+
+	      echo 0 > /debugfs/tracing/tracing_max_latency
+
 config WAKEUP_TRACER
 	bool "Trace wakeup latencies"
 	depends on DEBUG_KERNEL
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:29:09.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 11:11:48.000000000 -0500
@@ -3,6 +3,7 @@ obj-$(CONFIG_MCOUNT) += libmcount.o
 obj-$(CONFIG_TRACING) += tracer.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+obj-$(CONFIG_CRITICAL_IRQSOFF_TIMING) += trace_irqsoff.o
 obj-$(CONFIG_WAKEUP_TRACER) += trace_wakeup.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_irqsoff.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_irqsoff.c	2008-01-23 11:11:48.000000000 -0500
@@ -0,0 +1,415 @@
+/*
+ * trace irqs off criticall timings
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * From code in the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace *tracer_trace __read_mostly;
+static __cacheline_aligned_in_smp DEFINE_MUTEX(max_mutex);
+static int trace_enabled __read_mostly;
+
+/*
+ * Sequence count - we record it when starting a measurement and
+ * skip the latency if the sequence has changed - some other section
+ * did a maximum and could disturb our measurement with serial console
+ * printouts, etc. Truly coinciding maximum latencies should be rare
+ * and what happens together happens separately as well, so this doesnt
+ * decrease the validity of the maximum found:
+ */
+static __cacheline_aligned_in_smp unsigned long max_sequence;
+
+#ifdef CONFIG_MCOUNT
+/* irqsoff uses its own function trace to keep the overhead down */
+static void notrace irqsoff_trace_call(unsigned long ip,
+				       unsigned long parent_ip)
+{
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+	int cpu;
+
+	if (likely(!trace_enabled))
+		return;
+
+	local_save_flags(flags);
+
+	if (!irqs_disabled_flags(flags))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+	atomic_inc(&data->disabled);
+
+	if (likely(atomic_read(&data->disabled) == 1))
+		tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+	atomic_dec(&data->disabled);
+}
+
+static struct mcount_ops trace_ops __read_mostly =
+{
+	.func = irqsoff_trace_call,
+};
+#endif /* CONFIG_MCOUNT */
+
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+	if (tracing_thresh) {
+		if (delta < tracing_thresh)
+			return 0;
+	} else {
+		if (delta <= tracing_max_latency)
+			return 0;
+	}
+	return 1;
+}
+
+static void notrace
+check_critical_timing(struct tracing_trace *tr,
+		      struct tracing_trace_cpu *data,
+		      unsigned long parent_ip,
+		      int cpu)
+{
+	unsigned long latency, t0, t1;
+	cycle_t T0, T1, T2, delta;
+	unsigned long flags;
+
+	/*
+	 * usecs conversion is slow so we try to delay the conversion
+	 * as long as possible:
+	 */
+	T0 = data->preempt_timestamp;
+	T1 = now();
+	delta = T1-T0;
+
+	local_save_flags(flags);
+
+	if (!report_latency(delta))
+		goto out;
+
+	tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+	/*
+	 * Update the timestamp, because the trace entry above
+	 * might change it (it can only get larger so the latency
+	 * is fair to be reported):
+	 */
+	T2 = now();
+
+	delta = T2-T0;
+
+	latency = cycles_to_usecs(delta);
+
+	if (data->critical_sequence != max_sequence ||
+	    !mutex_trylock(&max_mutex))
+		goto out;
+
+	tracing_max_latency = delta;
+	t0 = cycles_to_usecs(T0);
+	t1 = cycles_to_usecs(T1);
+
+	data->critical_end = parent_ip;
+
+	update_max_tr_single(tr, current, cpu);
+
+	if (tracing_thresh)
+		printk(KERN_WARNING "(%16s-%-5d|#%d): %lu us critical section "
+		       "violates %lu us threshold.\n"
+		       " => started at timestamp %lu: ",
+				current->comm, current->pid,
+				raw_smp_processor_id(),
+				latency, cycles_to_usecs(tracing_thresh), t0);
+	else
+		printk(KERN_WARNING "(%16s-%-5d|#%d):"
+		       " new %lu us maximum-latency "
+		       "critical section.\n => started at timestamp %lu: ",
+				current->comm, current->pid,
+				raw_smp_processor_id(),
+				latency, t0);
+
+	print_symbol(KERN_CONT "<%s>\n", data->critical_start);
+	printk(KERN_CONT " =>   ended at timestamp %lu: ", t1);
+	print_symbol(KERN_CONT "<%s>\n", data->critical_end);
+	dump_stack();
+	t1 = cycles_to_usecs(now());
+	printk(KERN_CONT " =>   dump-end timestamp %lu\n\n", t1);
+
+	max_sequence++;
+
+	mutex_unlock(&max_mutex);
+
+out:
+	data->critical_sequence = max_sequence;
+	data->preempt_timestamp = now();
+	tracing_reset(data);
+	tracing_function_trace(tr, data, CALLER_ADDR0, parent_ip, flags);
+}
+
+static inline void notrace
+start_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+	int cpu;
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+
+	if (likely(!trace_enabled))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    data->critical_start || atomic_read(&data->disabled))
+		return;
+
+	atomic_inc(&data->disabled);
+
+	data->critical_sequence = max_sequence;
+	data->preempt_timestamp = now();
+	data->critical_start = parent_ip;
+	tracing_reset(data);
+
+	local_save_flags(flags);
+	tracing_function_trace(tr, data, ip, parent_ip, flags);
+
+	atomic_dec(&data->disabled);
+}
+
+static inline void notrace
+stop_critical_timing(unsigned long ip, unsigned long parent_ip)
+{
+	int cpu;
+	struct tracing_trace *tr = tracer_trace;
+	struct tracing_trace_cpu *data;
+	unsigned long flags;
+
+	if (likely(!trace_enabled))
+		return;
+
+	cpu = raw_smp_processor_id();
+	data = tr->data[cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    !data->critical_start || atomic_read(&data->disabled))
+		return;
+
+	atomic_inc(&data->disabled);
+	local_save_flags(flags);
+	tracing_function_trace(tr, data, ip, parent_ip, flags);
+	check_critical_timing(tr, data, parent_ip, cpu);
+	data->critical_start = 0;
+	atomic_dec(&data->disabled);
+}
+
+void notrace start_critical_timings(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, 0);
+}
+
+void notrace stop_critical_timings(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, 0);
+}
+
+#ifdef CONFIG_LOCKDEP
+void notrace time_hardirqs_on(unsigned long a0, unsigned long a1)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(a0, a1);
+}
+
+void notrace time_hardirqs_off(unsigned long a0, unsigned long a1)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(a0, a1);
+}
+
+#else /* !CONFIG_LOCKDEP */
+
+/*
+ * Stubs:
+ */
+
+void early_boot_irqs_off(void)
+{
+}
+
+void early_boot_irqs_on(void)
+{
+}
+
+void trace_softirqs_on(unsigned long ip)
+{
+}
+
+void trace_softirqs_off(unsigned long ip)
+{
+}
+
+inline void print_irqtrace_events(struct task_struct *curr)
+{
+}
+
+/*
+ * We are only interested in hardirq on/off events:
+ */
+void notrace trace_hardirqs_on(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void notrace trace_hardirqs_off(void)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+void notrace trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		stop_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+void notrace trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+	unsigned long flags;
+
+	local_save_flags(flags);
+
+	if (irqs_disabled_flags(flags))
+		start_critical_timing(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+
+#endif /* CONFIG_LOCKDEP */
+
+static void start_irqsoff_trace(struct tracing_trace *tr)
+{
+	trace_enabled = 1;
+	register_mcount_function(&trace_ops);
+}
+
+static void stop_irqsoff_trace(struct tracing_trace *tr)
+{
+	unregister_mcount_function(&trace_ops);
+	trace_enabled = 0;
+}
+
+static void irqsoff_trace_init(struct tracing_trace *tr)
+{
+	tracer_trace = tr;
+	/* make sure that the tracer is visibel */
+	smp_wmb();
+
+	if (tr->ctrl)
+		start_irqsoff_trace(tr);
+}
+
+static void irqsoff_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		stop_irqsoff_trace(tr);
+}
+
+static void irqsoff_trace_ctrl_update(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_irqsoff_trace(tr);
+	else
+		stop_irqsoff_trace(tr);
+}
+
+static void notrace irqsoff_trace_open(struct tracing_iterator *iter)
+{
+	/* stop the trace while dumping */
+	if (iter->tr->ctrl)
+		stop_irqsoff_trace(iter->tr);
+}
+
+static void notrace irqsoff_trace_close(struct tracing_iterator *iter)
+{
+	if (iter->tr->ctrl)
+		start_irqsoff_trace(iter->tr);
+}
+
+static void irqsoff_trace_start(struct tracing_iterator *iter)
+{
+	mutex_lock(&max_mutex);
+}
+
+static void irqsoff_trace_stop(struct tracing_iterator *iter)
+{
+	mutex_unlock(&max_mutex);
+}
+
+static struct trace_types_struct irqsoff_trace __read_mostly =
+{
+	.name = "irqsoff",
+	.init = irqsoff_trace_init,
+	.reset = irqsoff_trace_reset,
+	.open = irqsoff_trace_open,
+	.close = irqsoff_trace_close,
+	.start = irqsoff_trace_start,
+	.stop = irqsoff_trace_stop,
+	.ctrl_update = irqsoff_trace_ctrl_update,
+	.print_max = 1,
+};
+
+__init static int init_irqsoff_trace(void)
+{
+	register_trace(&irqsoff_trace);
+
+	return 0;
+}
+
+device_initcall(init_irqsoff_trace);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:29:09.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:29:09.000000000 -0500
@@ -74,24 +74,14 @@ enum trace_flag_type {
  * structure. (this way the maximum trace is permanently saved,
  * for later retrieval via /debugfs/tracing/latency_trace)
  */
-void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu)
+static void notrace __update_max_tr(struct tracing_trace *tr,
+				    struct task_struct *tsk, int cpu)
 {
 	struct tracing_trace_cpu *data = tr->data[cpu];
-	void *save_trace;
-	int i;
 
 	max_tr.cpu = cpu;
 	max_tr.time_start = data->preempt_timestamp;
 
-
-	/* clear out all the previous traces */
-	for_each_possible_cpu(i) {
-		data = tr->data[i];
-		save_trace = max_tr.data[i]->trace;
-		memcpy(max_tr.data[i], data, sizeof(*data));
-		data->trace = save_trace;
-	}
-
 	data = max_tr.data[cpu];
 	data->saved_latency = tracing_max_latency;
 
@@ -106,6 +96,47 @@ void update_max_tr(struct tracing_trace 
 	tracing_record_cmdline(current);
 }
 
+notrace void update_max_tr(struct tracing_trace *tr,
+			   struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data;
+	void *save_trace;
+	int i;
+
+	/* clear out all the previous traces */
+	for_each_possible_cpu(i) {
+		data = tr->data[i];
+		save_trace = max_tr.data[i]->trace;
+		memcpy(max_tr.data[i], data, sizeof(*data));
+		data->trace = save_trace;
+	}
+
+	__update_max_tr(tr, tsk, cpu);
+}
+
+/**
+ * update_max_tr_single - only copy one trace over, and reset the rest
+ * @tr - tracer
+ * @tsk - task with the latency
+ * @cpu - the cpu of the buffer to copy.
+ */
+notrace void update_max_tr_single(struct tracing_trace *tr,
+				  struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data = tr->data[cpu];
+	void *save_trace;
+	int i;
+
+	for_each_possible_cpu(i)
+		tracing_reset(max_tr.data[i]);
+
+	save_trace = max_tr.data[cpu]->trace;
+	memcpy(max_tr.data[cpu], data, sizeof(*data));
+	data->trace = save_trace;
+
+	__update_max_tr(tr, tsk, cpu);
+}
+
 int register_trace(struct trace_types_struct *type)
 {
 	struct trace_types_struct *t;
@@ -201,12 +232,12 @@ static struct mcount_ops trace_ops __rea
 	.func = function_trace_call,
 };
 
-void tracing_start_function_trace(void)
+notrace void tracing_start_function_trace(void)
 {
 	register_mcount_function(&trace_ops);
 }
 
-void tracing_stop_function_trace(void)
+notrace void tracing_stop_function_trace(void)
 {
 	unregister_mcount_function(&trace_ops);
 }
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:29:09.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:29:09.000000000 -0500
@@ -112,6 +112,8 @@ extern unsigned long tracing_max_latency
 extern unsigned long tracing_thresh;
 
 void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu);
+void update_max_tr_single(struct tracing_trace *tr,
+			  struct task_struct *tsk, int cpu);
 
 static inline notrace cycle_t now(void)
 {

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Mathieu Desnoyers]

* Daniel Walker (dwalker@mvista.com) wrote:
> 
> On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:
> 
> > +	if (!irqs_disabled() && wake_klogd)
> >  		wake_up_klogd();
> 
> This causes a regression .. When printk is called during an OOPS in
> kernels without this change then the OOPS will get logged, since the
> logging process (klogd) is woken to handle the messages.. If you apply
> this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
> you remove the wakeup here you have to add it someplace else to maintain
> the logging ..
> 
> (I'm not theorizing here, I have defects logged against this specific
> piece of code..)
> 

Can we change this for :
if (!(irqs_disabled() && !oops_in_progress) && wake_klogd)
  wake_up_klogd();

?

(totally untested)

> Daniel
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Steven Rostedt]

On Wed, 23 Jan 2008, Daniel Walker wrote:

>
> On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:
>
> > +	if (!irqs_disabled() && wake_klogd)
> >  		wake_up_klogd();
>
> This causes a regression .. When printk is called during an OOPS in
> kernels without this change then the OOPS will get logged, since the
> logging process (klogd) is woken to handle the messages.. If you apply
> this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
> you remove the wakeup here you have to add it someplace else to maintain
> the logging ..
>
> (I'm not theorizing here, I have defects logged against this specific
> piece of code..)

It wont get woken up anyway. Did you look at wake_up_klogd?

void wake_up_klogd(void)
{
	if (!oops_in_progress && waitqueue_active(&log_wait))
		wake_up_interruptible(&log_wait);
}


So if oops_in_progress is set, then it still wont get woken. Perhaps it
got woken some other way? Or is oops_in_progress not set in these oops?

One other solution is to make the runqueue locks visible externally. Like:

in sched.c:

int runqueue_is_locked(void)
{
	int cpu = get_cpu();
	struct rq *rq = cpu_rq(cpu);
	int ret;

	ret = spin_is_locked(&rq->lock);
	put_cpu();
	return ret;
}

And in printk we could do:

	if (wake_klogd && !runqueue_is_locked())
		wake_up_klogd();

This probably is the cleanest solution since it simply prevents the
deadlock from occurring.

-- Steve

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Frank Ch. Eigler]

Hi -

On Wed, Jan 23, 2008 at 12:11:07PM -0500, Steven Rostedt wrote:
> This patch adds latency tracing for critical timings
> (how long interrupts are disabled for).
> [...]

Is there an opportunity here to share effort with latencytop, and
ideally to use markers as much as possible for these event hooks?

- FChE

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Mathieu Desnoyers]

* Steven Rostedt (rostedt@goodmis.org) wrote:
> 
> On Wed, 23 Jan 2008, Daniel Walker wrote:
> 
> >
> > On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:
> >
> > > +	if (!irqs_disabled() && wake_klogd)
> > >  		wake_up_klogd();
> >
> > This causes a regression .. When printk is called during an OOPS in
> > kernels without this change then the OOPS will get logged, since the
> > logging process (klogd) is woken to handle the messages.. If you apply
> > this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
> > you remove the wakeup here you have to add it someplace else to maintain
> > the logging ..
> >
> > (I'm not theorizing here, I have defects logged against this specific
> > piece of code..)
> 
> It wont get woken up anyway. Did you look at wake_up_klogd?
> 
> void wake_up_klogd(void)
> {
> 	if (!oops_in_progress && waitqueue_active(&log_wait))
> 		wake_up_interruptible(&log_wait);
> }
> 
> 
> So if oops_in_progress is set, then it still wont get woken. Perhaps it
> got woken some other way? Or is oops_in_progress not set in these oops?
> 
> One other solution is to make the runqueue locks visible externally. Like:
> 
> in sched.c:
> 
> int runqueue_is_locked(void)
> {
> 	int cpu = get_cpu();
> 	struct rq *rq = cpu_rq(cpu);
> 	int ret;
> 
> 	ret = spin_is_locked(&rq->lock);
> 	put_cpu();
> 	return ret;
> }
> 
> And in printk we could do:
> 
> 	if (wake_klogd && !runqueue_is_locked())
> 		wake_up_klogd();
> 
> This probably is the cleanest solution since it simply prevents the
> deadlock from occurring.
> 


FYI :

kernel/panic.c

NORET_TYPE void panic(const char * fmt, ...)
{
....
bust_spinlocks(1);
...
bust_spinlocks(0);
...

In bust_spinlocks :


void __attribute__((weak)) bust_spinlocks(int yes)
{
        if (yes) {
                ++oops_in_progress;
        } else {
#ifdef CONFIG_VT
                unblank_screen();
#endif
                if (--oops_in_progress == 0)
                        wake_up_klogd();
        }
}

Where the final wake_up happens while oops_in_progress is 0, but
interrupts are still disabled.

So about my previous email, proposing testing oops_in_progress, it just
won't work.

Mathieu

> -- Steve
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Daniel Walker]

> 	if (wake_klogd && !runqueue_is_locked())
> 		wake_up_klogd();
> 
> This probably is the cleanest solution since it simply prevents the
> deadlock from occurring.

Do you really need to call it with the runqueue lock held .. There are
other issue with the calls at that level.. For instance in -rt these
call can actually hang the system in the console laying from inside
printk (something I reported more than 6 months ago) .. It would be
better to move them around the scheduler rather than inside it..

Daniel

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Steven Rostedt]

On Wed, 23 Jan 2008, Frank Ch. Eigler wrote:
> On Wed, Jan 23, 2008 at 12:11:07PM -0500, Steven Rostedt wrote:
> > This patch adds latency tracing for critical timings
> > (how long interrupts are disabled for).
> > [...]
>
> Is there an opportunity here to share effort with latencytop, and
> ideally to use markers as much as possible for these event hooks?

Well, I just found out about latencytop a couple of days ago when Arjan
announced it. I took a quick look and it seems to be more of a general
collection of information. This tracer pinpoints out specific maxes.
Although I may be wrong (I have to admit, I haven't had the time to really
look at what LatencyTop does, but I have been using this tracer in -rt for
a number of years).

As for using markers, I just piggied back on top of lockdep, since it has
the same hooks that I needed. If we were to replace them with markers,
then I would say lockdep should use the markers too.

One thing about markers, only one probe may be allowed at a time. Perhaps
we should fix this by using something like I did with the mcount hook.

-- Steve

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Tim Bird]

Mathieu Desnoyers wrote:
> Can we change this for :
> if (!(irqs_disabled() && !oops_in_progress) && wake_klogd)
>   wake_up_klogd();

!oops_in_progress is already inside wake_up_klogd().

Also, I think you'd want that first '!' inside the parens.

I've been working on a system to handle deferred displaying
of printk messages, when printk is called in interrupt context.
Currently on a serial console if printk is called with
ints disabled, it can hold interrupts off for up to 20
milliseconds.

My solution was to set up a worker thread to handle deferred
printk activity.  I don't think this works for the oops case,
because you don't want to defer the output.  However, I can
post this code if you think it would help with this problem.

I hesitate to just drop the call to wake_up_klogd() without
some kind of mechanism call it later.  Waiting until the
next printk will work to drain the buffer, but could lead
to indefinite intervals with printks waiting to be logged.
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Mathieu Desnoyers]

* Steven Rostedt (rostedt@goodmis.org) wrote:
> 
> On Wed, 23 Jan 2008, Frank Ch. Eigler wrote:
> > On Wed, Jan 23, 2008 at 12:11:07PM -0500, Steven Rostedt wrote:
> > > This patch adds latency tracing for critical timings
> > > (how long interrupts are disabled for).
> > > [...]
> >
> > Is there an opportunity here to share effort with latencytop, and
> > ideally to use markers as much as possible for these event hooks?
> 
> Well, I just found out about latencytop a couple of days ago when Arjan
> announced it. I took a quick look and it seems to be more of a general
> collection of information. This tracer pinpoints out specific maxes.
> Although I may be wrong (I have to admit, I haven't had the time to really
> look at what LatencyTop does, but I have been using this tracer in -rt for
> a number of years).
> 
> As for using markers, I just piggied back on top of lockdep, since it has
> the same hooks that I needed. If we were to replace them with markers,
> then I would say lockdep should use the markers too.
> 
> One thing about markers, only one probe may be allowed at a time. Perhaps
> we should fix this by using something like I did with the mcount hook.
> 

It's already in my -mm patches (multiple probes support). It's also in
my current LTTng patchset.

Mathieu

> -- Steve
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Peter Zijlstra]

On Wed, 2008-01-23 at 12:27 -0500, Frank Ch. Eigler wrote:
> Hi -
> 
> On Wed, Jan 23, 2008 at 12:11:07PM -0500, Steven Rostedt wrote:
> > This patch adds latency tracing for critical timings
> > (how long interrupts are disabled for).
> > [...]
> 
> Is there an opportunity here to share effort with latencytop, and
> ideally to use markers as much as possible for these event hooks?

I'm still thinking latencytop should only record stack traces and do the
rest in user-space. 

Also, the things the latency tracer and latecytop measure are quite
different. the latency tracer measures how long a non-schedulable
section is, latencytop measures how a task was scheduled away.

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Steven Rostedt]

On Wed, 23 Jan 2008, Daniel Walker wrote:

>
> > 	if (wake_klogd && !runqueue_is_locked())
> > 		wake_up_klogd();
> >
> > This probably is the cleanest solution since it simply prevents the
> > deadlock from occurring.
>
> Do you really need to call it with the runqueue lock held .. There are
> other issue with the calls at that level.. For instance in -rt these
> call can actually hang the system in the console laying from inside
> printk (something I reported more than 6 months ago) .. It would be
> better to move them around the scheduler rather than inside it..

The wakeup hook in schedule is when we find out that we hit our max. I
could postpone that somehow, but that would require more glue code than I
would like to add.

As for -rt, we've disabled printk for consoles not ATOMIC safe. So the
only consoles that will print in atomic sections so far are, earlyprintk
and the VGA.

Tim, could you send me your "postponed print" patches. That sounds like
something the -rt patch could use.

Thanks,

-- Steve

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Frank Ch. Eigler]

Hi -

On Wed, Jan 23, 2008 at 06:58:23PM +0100, Peter Zijlstra wrote:
> [...]
> > Is there an opportunity here to share effort with latencytop, and
> > ideally to use markers as much as possible for these event hooks?
> 
> I'm still thinking latencytop should only record stack traces and do the
> rest in user-space. 
> 
> Also, the things the latency tracer and latecytop measure are quite
> different. the latency tracer measures how long a non-schedulable
> section is, latencytop measures how a task was scheduled away.

The commonality I imagine is not in what sorts of reports they create,
or where they complete the formatting for and end-user.  It is solely
whether the kernel-side instrumentation sites can be represented by
individual markers, so that these particular tools as well as future
ones don't need to keep inserting custom code in similar or even the
same places.

- FChE

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Daniel Walker]

On Wed, 2008-01-23 at 13:18 -0500, Steven Rostedt wrote:

> The wakeup hook in schedule is when we find out that we hit our max. I
> could postpone that somehow, but that would require more glue code than I
> would like to add.

Which hook specifically ?

> As for -rt, we've disabled printk for consoles not ATOMIC safe. So the
> only consoles that will print in atomic sections so far are, earlyprintk
> and the VGA.

Is this code you added recently for tracing?

Daniel

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Steven Rostedt]

On Wed, 23 Jan 2008, Daniel Walker wrote:

>
> On Wed, 2008-01-23 at 13:18 -0500, Steven Rostedt wrote:
>
> > The wakeup hook in schedule is when we find out that we hit our max. I
> > could postpone that somehow, but that would require more glue code than I
> > would like to add.
>
> Which hook specifically ?

The wakeup tracer does a print on max when the new task is about to be
switched to (in context_switch).

>
> > As for -rt, we've disabled printk for consoles not ATOMIC safe. So the
> > only consoles that will print in atomic sections so far are, earlyprintk
> > and the VGA.
>
> Is this code you added recently for tracing?

Nope, it's been there for a few releases and had nothing to do with the
latency tracer.

<looks at code>

Hmm, seems that only the "hack" fix is in upstream. The Red Hat version
has the better fix, but mainline didn't get it. OK, I'll add that to the
next -rt release.

-- Steve

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Steven Rostedt]

On Wed, 23 Jan 2008, Frank Ch. Eigler wrote:
> >
> > Also, the things the latency tracer and latecytop measure are quite
> > different. the latency tracer measures how long a non-schedulable
> > section is, latencytop measures how a task was scheduled away.
>
> The commonality I imagine is not in what sorts of reports they create,
> or where they complete the formatting for and end-user.  It is solely
> whether the kernel-side instrumentation sites can be represented by
> individual markers, so that these particular tools as well as future
> ones don't need to keep inserting custom code in similar or even the
> same places.

So basically just having the marker implementation there to let all
tracers access to irqs enabled/disabled.

One problem is that the hooks are alse in entry.S, so the tracing ends up
being architecture dependent. One solution is to have a "generic" hook for
trace_hardirqs_on/off (kind of like what I did here) and add a marker
inside that. The hooks in entry.S can call the generic function and have
the marker call the registered probes, be that lockdep, latencytap or
latency-trace.

Have the generic hook only be compiled in when one of the tracers or
lockdep is configured on and they select it.

-- Steve

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Daniel Walker]

On Wed, 2008-01-23 at 13:43 -0500, Steven Rostedt wrote:
> On Wed, 23 Jan 2008, Daniel Walker wrote:
> 
> >
> > On Wed, 2008-01-23 at 13:18 -0500, Steven Rostedt wrote:
> >
> > > The wakeup hook in schedule is when we find out that we hit our max. I
> > > could postpone that somehow, but that would require more glue code than I
> > > would like to add.
> >
> > Which hook specifically ?
> 
> The wakeup tracer does a print on max when the new task is about to be
> switched to (in context_switch).

You can't move that hook to when the task actually starts running (i.e.
at the end of schedule() )..

> >
> > > As for -rt, we've disabled printk for consoles not ATOMIC safe. So the
> > > only consoles that will print in atomic sections so far are, earlyprintk
> > > and the VGA.
> >
> > Is this code you added recently for tracing?
> 
> Nope, it's been there for a few releases and had nothing to do with the
> latency tracer.
> 
> <looks at code>
> 
> Hmm, seems that only the "hack" fix is in upstream. The Red Hat version
> has the better fix, but mainline didn't get it. OK, I'll add that to the
> next -rt release.

mainline ? The problem I'm thinking of was directly tracing related..

Daniel

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Daniel Walker]

On Wed, 2008-01-23 at 10:50 -0800, Daniel Walker wrote:
> On Wed, 2008-01-23 at 13:43 -0500, Steven Rostedt wrote:
> > On Wed, 23 Jan 2008, Daniel Walker wrote:
> > 
> > >
> > > On Wed, 2008-01-23 at 13:18 -0500, Steven Rostedt wrote:
> > >
> > > > The wakeup hook in schedule is when we find out that we hit our max. I
> > > > could postpone that somehow, but that would require more glue code than I
> > > > would like to add.
> > >
> > > Which hook specifically ?
> > 
> > The wakeup tracer does a print on max when the new task is about to be
> > switched to (in context_switch).
> 
> You can't move that hook to when the task actually starts running (i.e.
> at the end of schedule() )..

I mean , why can't you?

Daniel

Re: [PATCH 19/20 -v5] Trace irq disabled critical timings

[Mathieu Desnoyers]

* Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:
> 
> On Wed, 2008-01-23 at 12:27 -0500, Frank Ch. Eigler wrote:
> > Hi -
> > 
> > On Wed, Jan 23, 2008 at 12:11:07PM -0500, Steven Rostedt wrote:
> > > This patch adds latency tracing for critical timings
> > > (how long interrupts are disabled for).
> > > [...]
> > 
> > Is there an opportunity here to share effort with latencytop, and
> > ideally to use markers as much as possible for these event hooks?
> 
> I'm still thinking latencytop should only record stack traces and do the
> rest in user-space. 
> 
> Also, the things the latency tracer and latecytop measure are quite
> different. the latency tracer measures how long a non-schedulable
> section is, latencytop measures how a task was scheduled away.

Hrm, if it's really the only thing latencytop is doing.. ever thought
about trying LTTng ? ;) A simple plugin could be written in lttv to
perform this kind of analysis.

Mathieu

> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

[Mathieu Desnoyers]

* Steven Rostedt (rostedt@goodmis.org) wrote:
> This annotates NMI functions with notrace. Some tracers may be able
> to live with this, but some cannot. So we turn off NMI tracing.
> 
> One solution might be to make a notrace_nmi which would only turn
> off NMI tracing if a trace utility needed it off.
> 
Is this still needed with the atomic clocksource read ?

> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
> 
> ---
>  arch/x86/kernel/nmi_32.c   |    2 +-
>  arch/x86/kernel/nmi_64.c   |    2 +-
>  arch/x86/kernel/traps_32.c |    4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> Index: linux-mcount.git/arch/x86/kernel/nmi_32.c
> ===================================================================
> --- linux-mcount.git.orig/arch/x86/kernel/nmi_32.c	2008-01-23 10:26:11.000000000 -0500
> +++ linux-mcount.git/arch/x86/kernel/nmi_32.c	2008-01-23 10:26:53.000000000 -0500
> @@ -323,7 +323,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
>  
>  extern void die_nmi(struct pt_regs *, const char *msg);
>  
> -__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
> +notrace __kprobes int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
>  {
>  
>  	/*
> Index: linux-mcount.git/arch/x86/kernel/nmi_64.c
> ===================================================================
> --- linux-mcount.git.orig/arch/x86/kernel/nmi_64.c	2008-01-23 10:26:11.000000000 -0500
> +++ linux-mcount.git/arch/x86/kernel/nmi_64.c	2008-01-23 10:26:53.000000000 -0500
> @@ -314,7 +314,7 @@ void touch_nmi_watchdog(void)
>   	touch_softlockup_watchdog();
>  }
>  
> -int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
> +notrace __kprobes int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
>  {
>  	int sum;
>  	int touched = 0;
> Index: linux-mcount.git/arch/x86/kernel/traps_32.c
> ===================================================================
> --- linux-mcount.git.orig/arch/x86/kernel/traps_32.c	2008-01-23 10:26:11.000000000 -0500
> +++ linux-mcount.git/arch/x86/kernel/traps_32.c	2008-01-23 10:26:53.000000000 -0500
> @@ -723,7 +723,7 @@ void __kprobes die_nmi(struct pt_regs *r
>  	do_exit(SIGSEGV);
>  }
>  
> -static __kprobes void default_do_nmi(struct pt_regs * regs)
> +static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
>  {
>  	unsigned char reason = 0;
>  
> @@ -763,7 +763,7 @@ static __kprobes void default_do_nmi(str
>  
>  static int ignore_nmis;
>  
> -fastcall __kprobes void do_nmi(struct pt_regs * regs, long error_code)
> +notrace fastcall __kprobes void do_nmi(struct pt_regs *regs, long error_code)
>  {
>  	int cpu;
>  
> 
> -- 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

[Steven Rostedt]

On Wed, 23 Jan 2008, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > This annotates NMI functions with notrace. Some tracers may be able
> > to live with this, but some cannot. So we turn off NMI tracing.
> >
> > One solution might be to make a notrace_nmi which would only turn
> > off NMI tracing if a trace utility needed it off.
> >
> Is this still needed with the atomic clocksource read ?

This never had to do with the clocksource. The tracer itself isn't atomic
against NMIs. hmm, it may actually be. It does a tracer disable for the
CPU by an atomic_inc and this would prevent the NMI from causing harm.

I'll test without this patch and see what happens when I turn on a high
rate of NMIS.

I still want to add a bit more notraces around for the simple
reason of cleaning up the output and prehaps speeding up the code a bit.

-- Steve

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Pavel Machek]

On Wed 2008-01-23 12:25:09, Mathieu Desnoyers wrote:
> * Daniel Walker (dwalker@mvista.com) wrote:
> > 
> > On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:
> > 
> > > +	if (!irqs_disabled() && wake_klogd)
> > >  		wake_up_klogd();
> > 
> > This causes a regression .. When printk is called during an OOPS in
> > kernels without this change then the OOPS will get logged, since the
> > logging process (klogd) is woken to handle the messages.. If you apply
> > this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
> > you remove the wakeup here you have to add it someplace else to maintain
> > the logging ..
> > 
> > (I'm not theorizing here, I have defects logged against this specific
> > piece of code..)
> > 
> 
> Can we change this for :
> if (!(irqs_disabled() && !oops_in_progress) && wake_klogd)
>   wake_up_klogd();
> 
> ?

That's wrong, too.

Just make wake_up_klogd do trylock, if it finds that it can't get
neccessary locks, printk(KERN_ALERT) so at least console gets the
message, but proceed without the lock.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 01/20 -v5] printk - dont wakeup klogd with interrupts disabled

[Pavel Machek]

On Wed 2008-01-23 12:27:12, Steven Rostedt wrote:
> 
> On Wed, 23 Jan 2008, Daniel Walker wrote:
> 
> >
> > On Wed, 2008-01-23 at 11:02 -0500, Steven Rostedt wrote:
> >
> > > +	if (!irqs_disabled() && wake_klogd)
> > >  		wake_up_klogd();
> >
> > This causes a regression .. When printk is called during an OOPS in
> > kernels without this change then the OOPS will get logged, since the
> > logging process (klogd) is woken to handle the messages.. If you apply
> > this change klogd doesn't wakeup, and hence doesn't log the oops.. So if
> > you remove the wakeup here you have to add it someplace else to maintain
> > the logging ..
> >
> > (I'm not theorizing here, I have defects logged against this specific
> > piece of code..)
> 
> It wont get woken up anyway. Did you look at wake_up_klogd?
> 
> void wake_up_klogd(void)
> {
> 	if (!oops_in_progress && waitqueue_active(&log_wait))
> 		wake_up_interruptible(&log_wait);
> }
> 
> 
> So if oops_in_progress is set, then it still wont get woken. Perhaps it
> got woken some other way? Or is oops_in_progress not set in these oops?
> 
> One other solution is to make the runqueue locks visible externally. Like:
> 
> in sched.c:
> 
> int runqueue_is_locked(void)
> {
> 	int cpu = get_cpu();
> 	struct rq *rq = cpu_rq(cpu);
> 	int ret;
> 
> 	ret = spin_is_locked(&rq->lock);
> 	put_cpu();
> 	return ret;
> }
> 
> And in printk we could do:
> 
> 	if (wake_klogd && !runqueue_is_locked())
> 		wake_up_klogd();
> 
> This probably is the cleanest solution since it simply prevents the
> deadlock from occurring.

Yes please... this looks like a solution to me.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[PATCH] defer printks in irqs

[Tim Bird]

Steven Rostedt wrote:
> Tim, could you send me your "postponed print" patches. That sounds like
> something the -rt patch could use.

Sure.  See below.

This patch changes the way the printk code processes output to the
console buffer.  On some platforms, especially those with a serial
console, the way printk output the messages to console caused significant
interrupt-off periods.  This code introduces two config options to
improve that handling.

Without this change, test code run on a 178 MHZ ARM platform
showed an interrupt off period for a particularly long printk message
of 24 milliseconds.  With this patch applied, and the options set
to 'Y', the same message only had an interrupt-off period of
482 microseconds.

Portions of this (some parts that reorder locking and irq management
primitives) were taken from the RT-preempt patch.

The patch does several things:

   1. It moves the location of the irqrestore operations in the
   printk code, so that the console writing can occur with interrupts enabled

   2. It changes the code so that characters are written to the console
   one-at-a-time. The serial console code holds interrupts disabled for the
   duration of its output to the serial port. To decrease the interrupt-off
   time, only a small amount of data is written at a time. (This could be tuned
   by writing chunks larger than 1 character at a time, but the current solution
   was easiest, and gives the lowest interrupt-off times.)

   3. The printk code was changed so that if it is entered with interrupts
   disabled, it does not output to console immediately. Rather, a workqueue
   routine is scheduled to process the console output later (when interrupts
   are enabled).

   4. An init-time routine was created, to prevent trying to schedule the
   workqueue routine too early in the system boot sequence.

Here's the patch:

Signed-off-by: Tim Bird tim.bird@am.sony.com
---
 kernel/printk.c   |   92 	85 +	7 -	0 !
 lib/Kconfig.debug |   42 	42 +	0 -	0 !
 2 files changed, 127 insertions(+), 7 deletions(-)

Index: linux-2.6.24-rc8/kernel/printk.c
===================================================================
--- linux-2.6.24-rc8.orig/kernel/printk.c
+++ linux-2.6.24-rc8/kernel/printk.c
@@ -33,11 +33,14 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
+#include <linux/workqueue.h>

 #include <asm/uaccess.h>

 #define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)

+#define PRINTK_BUF_SIZE		1024
+
 /* printk's without a loglevel use this.. */
 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */

@@ -47,6 +50,10 @@

 DECLARE_WAIT_QUEUE_HEAD(log_wait);

+static void printk_console_flush(struct work_struct *ignored);
+static int have_callable_console(void);
+static DECLARE_WORK(printk_console_work, printk_console_flush);
+
 int console_printk[4] = {
 	DEFAULT_CONSOLE_LOGLEVEL,	/* console_loglevel */
 	DEFAULT_MESSAGE_LOGLEVEL,	/* default_message_loglevel */
@@ -220,6 +227,43 @@ static inline void boot_delay_msec(void)
 #endif

 /*
+ * We can't schedule printk console flushing during early boot.
+ * This flag holds it off until after we've initialized some
+ * important stuff.
+ */
+static int pcf_ok = 0;
+
+static int __init init_printk_console_flush(void)
+{
+	pcf_ok = 1;
+	return 0;
+}
+__initcall(init_printk_console_flush);
+
+void printk_console_flush(struct work_struct *ignored)
+{
+	unsigned long flags;
+	int chars_to_flush;
+
+	spin_lock_irqsave(&logbuf_lock, flags);
+	chars_to_flush = log_end - con_start;
+	spin_unlock_irqrestore(&logbuf_lock, flags);
+
+	if (chars_to_flush) {
+		acquire_console_sem();
+
+		if ((cpu_online(smp_processor_id()) ||
+		   have_callable_console())) {
+			console_may_schedule = 0;
+			release_console_sem();
+		} else {
+			console_locked = 0;
+			up(&console_sem);
+		}
+	}
+}
+
+/*
  * Return the number of unread characters in the log buffer.
  */
 int log_buf_get_len(void)
@@ -436,8 +480,16 @@ static void __call_console_drivers(unsig
 	for (con = console_drivers; con; con = con->next) {
 		if ((con->flags & CON_ENABLED) && con->write &&
 				(cpu_online(smp_processor_id()) ||
-				(con->flags & CON_ANYTIME)))
+				(con->flags & CON_ANYTIME))) {
+#ifdef CONFIG_PRINTK_SHORT_IRQ_DISABLE
+			int i;
+			for(i=0; i<end-start; i++) {
+				con->write(con, &LOG_BUF(start+i), 1);
+			}
+#else
 			con->write(con, &LOG_BUF(start), end - start);
+#endif
+		}
 	}
 }

@@ -633,8 +685,9 @@ asmlinkage int vprintk(const char *fmt,
 	unsigned long flags;
 	int printed_len;
 	char *p;
-	static char printk_buf[1024];
+	static char printk_buf[PRINTK_BUF_SIZE];
 	static int log_level_unknown = 1;
+	int defer;

 	boot_delay_msec();

@@ -649,6 +702,7 @@ asmlinkage int vprintk(const char *fmt,
 	lockdep_off();
 	spin_lock(&logbuf_lock);
 	printk_cpu = smp_processor_id();
+	preempt_enable();

 	/* Emit the output into the temporary buffer */
 	printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
@@ -718,6 +772,19 @@ asmlinkage int vprintk(const char *fmt,
 		console_locked = 1;
 		printk_cpu = UINT_MAX;
 		spin_unlock(&logbuf_lock);
+		lockdep_on();
+		local_irq_restore(flags);
+
+		defer = 0;
+#ifdef CONFIG_PRINTK_DEFER_IN_IRQ
+		/*
+		 * If we're in an interrupt and it's not an emergency,
+		 * don't emit to console just yet.
+	         */
+		if ((irqs_disabled() || in_interrupt()) && !oops_in_progress) {
+			defer = 1;
+		}
+#endif

 		/*
 		 * Console drivers may assume that per-cpu resources have
@@ -725,7 +792,8 @@ asmlinkage int vprintk(const char *fmt,
 		 * being able to cope (CON_ANYTIME) don't call them until
 		 * this CPU is officially up.
 		 */
-		if (cpu_online(smp_processor_id()) || have_callable_console()) {
+		if (!defer && (cpu_online(smp_processor_id()) ||
+		   have_callable_console())) {
 			console_may_schedule = 0;
 			release_console_sem();
 		} else {
@@ -733,8 +801,6 @@ asmlinkage int vprintk(const char *fmt,
 			console_locked = 0;
 			up(&console_sem);
 		}
-		lockdep_on();
-		raw_local_irq_restore(flags);
 	} else {
 		/*
 		 * Someone else owns the drivers.  We drop the spinlock, which
@@ -747,7 +813,11 @@ asmlinkage int vprintk(const char *fmt,
 		raw_local_irq_restore(flags);
 	}

-	preempt_enable();
+	/* didn't flush console all the way yet? - schedule for later */
+	if ((log_end - con_start) && pcf_ok) {
+		schedule_work(&printk_console_work);
+	}
+
 	return printed_len;
 }
 EXPORT_SYMBOL(printk);
@@ -971,13 +1041,21 @@ void release_console_sem(void)
 		_con_start = con_start;
 		_log_end = log_end;
 		con_start = log_end;		/* Flush */
+
+#ifdef CONFIG_PRINTK_SHORT_IRQ_DISABLE
+		/* allow irqs during console out */
+		spin_unlock_irqrestore(&logbuf_lock, flags);
+		call_console_drivers(_con_start, _log_end);
+#else
 		spin_unlock(&logbuf_lock);
 		call_console_drivers(_con_start, _log_end);
 		local_irq_restore(flags);
+#endif
 	}
 	console_locked = 0;
-	up(&console_sem);
 	spin_unlock_irqrestore(&logbuf_lock, flags);
+	up(&console_sem);
+
 	if (wake_klogd)
 		wake_up_klogd();
 }
Index: linux-2.6.24-rc8/lib/Kconfig.debug
===================================================================
--- linux-2.6.24-rc8.orig/lib/Kconfig.debug
+++ linux-2.6.24-rc8/lib/Kconfig.debug
@@ -17,6 +17,48 @@ config ENABLE_WARN_DEPRECATED
 	  Disable this to suppress the "warning: 'foo' is deprecated
 	  (declared at kernel/power/somefile.c:1234)" messages.

+config PRINTK_SHORT_IRQ_DISABLE
+	bool "Enable interrupts for shorter times during printk output"
+	default n
+	depends on PRINTK
+	help
+	  Selecting this option will cause the kernel to write the
+	  contents of the printk buffer to the console with interrupts
+	  enabled, and in small increments.
+
+	  With the default setting of 'n', the kernel attempts to
+	  send printk messages to the console with interrupts disabled,
+	  and it sends the entire contents of the printk buffer in one go.
+
+	  For some consoles (notably the serial console, which is commonly
+	  used in embedded products), this results in long interrupt-off
+	  periods.
+
+	  Users interested in good real-time scheduling should set this
+	  to 'y'.
+
+config PRINTK_DEFER_IN_IRQ
+	bool "Defer writing printk output to console during interrupts"
+	default n
+	depends on PRINTK && PRINTK_SHORT_IRQ_DISABLE
+	help
+	  Selecting this option will cause the kernel to hold off writing
+	  printk messages to the console until interrupts are enabled.
+	  On some systems, printk buffer and console handling can take
+	  a long time.  If done with interrupts off for the entire duration
+	  of the operation, this results in long interrupt-off periods.
+
+	  With the default setting of 'n', the kernel attempts to
+	  send printk messages to the console whether it is in interrupt
+	  context or not.
+
+	  With a setting of 'y', when printk is called with interrupts
+	  disabled, the messages are buffered in the kernel's
+	  log buffer until later.  If you are debugging the kernel
+	  with printks in interrupt routines, you should set this
+	  to 'n'.  Users interested in good real-time scheduling
+	  should set this to 'y'.
+
 config ENABLE_MUST_CHECK
 	bool "Enable __must_check logic"
 	default y

Re: [PATCH] defer printks in irqs

[Peter Zijlstra]

On Thu, 2008-01-24 at 14:42 -0800, Tim Bird wrote:
> Steven Rostedt wrote:
> > Tim, could you send me your "postponed print" patches. That sounds like
> > something the -rt patch could use.
> 
> Sure.  See below.
> 
> This patch changes the way the printk code processes output to the
> console buffer.  On some platforms, especially those with a serial
> console, the way printk output the messages to console caused significant
> interrupt-off periods.  This code introduces two config options to
> improve that handling.
> 
> Without this change, test code run on a 178 MHZ ARM platform
> showed an interrupt off period for a particularly long printk message
> of 24 milliseconds.  With this patch applied, and the options set
> to 'Y', the same message only had an interrupt-off period of
> 482 microseconds.
> 
> Portions of this (some parts that reorder locking and irq management
> primitives) were taken from the RT-preempt patch.
> 
> The patch does several things:
> 
>    1. It moves the location of the irqrestore operations in the
>    printk code, so that the console writing can occur with interrupts enabled
> 
>    2. It changes the code so that characters are written to the console
>    one-at-a-time. The serial console code holds interrupts disabled for the
>    duration of its output to the serial port. To decrease the interrupt-off
>    time, only a small amount of data is written at a time. (This could be tuned
>    by writing chunks larger than 1 character at a time, but the current solution
>    was easiest, and gives the lowest interrupt-off times.)
> 
>    3. The printk code was changed so that if it is entered with interrupts
>    disabled, it does not output to console immediately. Rather, a workqueue
>    routine is scheduled to process the console output later (when interrupts
>    are enabled).
> 
>    4. An init-time routine was created, to prevent trying to schedule the
>    workqueue routine too early in the system boot sequence.
> 
> Here's the patch:

I suspect these features reduce the change a crash messages makes it out
onto the console, but fail to spot any of the copious text mention this
critical issue.

> Signed-off-by: Tim Bird tim.bird@am.sony.com
> ---
>  kernel/printk.c   |   92 	85 +	7 -	0 !
>  lib/Kconfig.debug |   42 	42 +	0 -	0 !
>  2 files changed, 127 insertions(+), 7 deletions(-)
> 
> Index: linux-2.6.24-rc8/kernel/printk.c
> ===================================================================
> --- linux-2.6.24-rc8.orig/kernel/printk.c
> +++ linux-2.6.24-rc8/kernel/printk.c
> @@ -33,11 +33,14 @@
>  #include <linux/bootmem.h>
>  #include <linux/syscalls.h>
>  #include <linux/jiffies.h>
> +#include <linux/workqueue.h>
> 
>  #include <asm/uaccess.h>
> 
>  #define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)
> 
> +#define PRINTK_BUF_SIZE		1024
> +
>  /* printk's without a loglevel use this.. */
>  #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
> 
> @@ -47,6 +50,10 @@
> 
>  DECLARE_WAIT_QUEUE_HEAD(log_wait);
> 
> +static void printk_console_flush(struct work_struct *ignored);
> +static int have_callable_console(void);
> +static DECLARE_WORK(printk_console_work, printk_console_flush);
> +
>  int console_printk[4] = {
>  	DEFAULT_CONSOLE_LOGLEVEL,	/* console_loglevel */
>  	DEFAULT_MESSAGE_LOGLEVEL,	/* default_message_loglevel */
> @@ -220,6 +227,43 @@ static inline void boot_delay_msec(void)
>  #endif
> 
>  /*
> + * We can't schedule printk console flushing during early boot.
> + * This flag holds it off until after we've initialized some
> + * important stuff.
> + */
> +static int pcf_ok = 0;
> +
> +static int __init init_printk_console_flush(void)
> +{
> +	pcf_ok = 1;
> +	return 0;
> +}
> +__initcall(init_printk_console_flush);
> +
> +void printk_console_flush(struct work_struct *ignored)
> +{
> +	unsigned long flags;
> +	int chars_to_flush;
> +
> +	spin_lock_irqsave(&logbuf_lock, flags);
> +	chars_to_flush = log_end - con_start;
> +	spin_unlock_irqrestore(&logbuf_lock, flags);
> +
> +	if (chars_to_flush) {
> +		acquire_console_sem();
> +
> +		if ((cpu_online(smp_processor_id()) ||
> +		   have_callable_console())) {
> +			console_may_schedule = 0;
> +			release_console_sem();
> +		} else {
> +			console_locked = 0;
> +			up(&console_sem);
> +		}
> +	}
> +}
> +
> +/*
>   * Return the number of unread characters in the log buffer.
>   */
>  int log_buf_get_len(void)
> @@ -436,8 +480,16 @@ static void __call_console_drivers(unsig
>  	for (con = console_drivers; con; con = con->next) {
>  		if ((con->flags & CON_ENABLED) && con->write &&
>  				(cpu_online(smp_processor_id()) ||
> -				(con->flags & CON_ANYTIME)))
> +				(con->flags & CON_ANYTIME))) {
> +#ifdef CONFIG_PRINTK_SHORT_IRQ_DISABLE
> +			int i;
> +			for(i=0; i<end-start; i++) {
> +				con->write(con, &LOG_BUF(start+i), 1);
> +			}
> +#else
>  			con->write(con, &LOG_BUF(start), end - start);
> +#endif
> +		}
>  	}
>  }
> 
> @@ -633,8 +685,9 @@ asmlinkage int vprintk(const char *fmt,
>  	unsigned long flags;
>  	int printed_len;
>  	char *p;
> -	static char printk_buf[1024];
> +	static char printk_buf[PRINTK_BUF_SIZE];
>  	static int log_level_unknown = 1;
> +	int defer;
> 
>  	boot_delay_msec();
> 
> @@ -649,6 +702,7 @@ asmlinkage int vprintk(const char *fmt,
>  	lockdep_off();
>  	spin_lock(&logbuf_lock);
>  	printk_cpu = smp_processor_id();
> +	preempt_enable();
> 
>  	/* Emit the output into the temporary buffer */
>  	printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
> @@ -718,6 +772,19 @@ asmlinkage int vprintk(const char *fmt,
>  		console_locked = 1;
>  		printk_cpu = UINT_MAX;
>  		spin_unlock(&logbuf_lock);
> +		lockdep_on();
> +		local_irq_restore(flags);
> +
> +		defer = 0;
> +#ifdef CONFIG_PRINTK_DEFER_IN_IRQ
> +		/*
> +		 * If we're in an interrupt and it's not an emergency,
> +		 * don't emit to console just yet.
> +	         */
> +		if ((irqs_disabled() || in_interrupt()) && !oops_in_progress) {
> +			defer = 1;
> +		}
> +#endif
> 
>  		/*
>  		 * Console drivers may assume that per-cpu resources have
> @@ -725,7 +792,8 @@ asmlinkage int vprintk(const char *fmt,
>  		 * being able to cope (CON_ANYTIME) don't call them until
>  		 * this CPU is officially up.
>  		 */
> -		if (cpu_online(smp_processor_id()) || have_callable_console()) {
> +		if (!defer && (cpu_online(smp_processor_id()) ||
> +		   have_callable_console())) {
>  			console_may_schedule = 0;
>  			release_console_sem();
>  		} else {
> @@ -733,8 +801,6 @@ asmlinkage int vprintk(const char *fmt,
>  			console_locked = 0;
>  			up(&console_sem);
>  		}
> -		lockdep_on();
> -		raw_local_irq_restore(flags);
>  	} else {
>  		/*
>  		 * Someone else owns the drivers.  We drop the spinlock, which
> @@ -747,7 +813,11 @@ asmlinkage int vprintk(const char *fmt,
>  		raw_local_irq_restore(flags);
>  	}
> 
> -	preempt_enable();
> +	/* didn't flush console all the way yet? - schedule for later */
> +	if ((log_end - con_start) && pcf_ok) {
> +		schedule_work(&printk_console_work);
> +	}
> +
>  	return printed_len;
>  }
>  EXPORT_SYMBOL(printk);
> @@ -971,13 +1041,21 @@ void release_console_sem(void)
>  		_con_start = con_start;
>  		_log_end = log_end;
>  		con_start = log_end;		/* Flush */
> +
> +#ifdef CONFIG_PRINTK_SHORT_IRQ_DISABLE
> +		/* allow irqs during console out */
> +		spin_unlock_irqrestore(&logbuf_lock, flags);
> +		call_console_drivers(_con_start, _log_end);
> +#else
>  		spin_unlock(&logbuf_lock);
>  		call_console_drivers(_con_start, _log_end);
>  		local_irq_restore(flags);
> +#endif
>  	}
>  	console_locked = 0;
> -	up(&console_sem);
>  	spin_unlock_irqrestore(&logbuf_lock, flags);
> +	up(&console_sem);
> +
>  	if (wake_klogd)
>  		wake_up_klogd();
>  }
> Index: linux-2.6.24-rc8/lib/Kconfig.debug
> ===================================================================
> --- linux-2.6.24-rc8.orig/lib/Kconfig.debug
> +++ linux-2.6.24-rc8/lib/Kconfig.debug
> @@ -17,6 +17,48 @@ config ENABLE_WARN_DEPRECATED
>  	  Disable this to suppress the "warning: 'foo' is deprecated
>  	  (declared at kernel/power/somefile.c:1234)" messages.
> 
> +config PRINTK_SHORT_IRQ_DISABLE
> +	bool "Enable interrupts for shorter times during printk output"
> +	default n
> +	depends on PRINTK
> +	help
> +	  Selecting this option will cause the kernel to write the
> +	  contents of the printk buffer to the console with interrupts
> +	  enabled, and in small increments.
> +
> +	  With the default setting of 'n', the kernel attempts to
> +	  send printk messages to the console with interrupts disabled,
> +	  and it sends the entire contents of the printk buffer in one go.
> +
> +	  For some consoles (notably the serial console, which is commonly
> +	  used in embedded products), this results in long interrupt-off
> +	  periods.
> +
> +	  Users interested in good real-time scheduling should set this
> +	  to 'y'.
> +
> +config PRINTK_DEFER_IN_IRQ
> +	bool "Defer writing printk output to console during interrupts"
> +	default n
> +	depends on PRINTK && PRINTK_SHORT_IRQ_DISABLE
> +	help
> +	  Selecting this option will cause the kernel to hold off writing
> +	  printk messages to the console until interrupts are enabled.
> +	  On some systems, printk buffer and console handling can take
> +	  a long time.  If done with interrupts off for the entire duration
> +	  of the operation, this results in long interrupt-off periods.
> +
> +	  With the default setting of 'n', the kernel attempts to
> +	  send printk messages to the console whether it is in interrupt
> +	  context or not.
> +
> +	  With a setting of 'y', when printk is called with interrupts
> +	  disabled, the messages are buffered in the kernel's
> +	  log buffer until later.  If you are debugging the kernel
> +	  with printks in interrupt routines, you should set this
> +	  to 'n'.  Users interested in good real-time scheduling
> +	  should set this to 'y'.
> +
>  config ENABLE_MUST_CHECK
>  	bool "Enable __must_check logic"
>  	default y
> 
> 

Re: [PATCH] defer printks in irqs

[Tim Bird]

Peter Zijlstra wrote:
> I suspect these features reduce the chance a crash messages makes it out
> onto the console, but fail to spot any of the copious text mention this
> critical issue.

Anything not in interrupts would not be deferred.
The following code is meant to avoid deferring in oops as well.
I'm not sure if that covers all crash cases or not.
If you know of other cases, and ways to detect them, please advise.

>> +#ifdef CONFIG_PRINTK_DEFER_IN_IRQ
>> +		/*
>> +		 * If we're in an interrupt and it's not an emergency,
>> +		 * don't emit to console just yet.
>> +	         */
>> +		if ((irqs_disabled() || in_interrupt()) && !oops_in_progress) {
>> +			defer = 1;
>> +		}
>> +#endif

I made the code conditional because printk messages are pretty
critical for debugging, and I wanted someone to be aware if they
altered the behavior in any way.  I suspect that only in embedded,
when people are having realtime performance problems, would this
change be of interest.

Please recognize that I'm not submitting this for kernel inclusion
at this time.  Please see the larger thread for context.  That said,
I appreciate the feedback on the code.
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================

Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

[Steven Rostedt]

On Wed, 23 Jan 2008, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@goodmis.org) wrote:
> > This annotates NMI functions with notrace. Some tracers may be able
> > to live with this, but some cannot. So we turn off NMI tracing.
> >
> > One solution might be to make a notrace_nmi which would only turn
> > off NMI tracing if a trace utility needed it off.
> >
> Is this still needed with the atomic clocksource read ?
>

Before you ask again, I've still included this in -v6, simply because I
didn't get a chance to test it without this patch. I'll try to remember to
do that on Monday.

-- Steve

Re: [PATCH] defer printks in irqs

[Andrew Morton]

> On Thu, 24 Jan 2008 15:23:03 -0800 Tim Bird <tim.bird@am.sony.com> wrote:
> Peter Zijlstra wrote:
> > I suspect these features reduce the chance a crash messages makes it out
> > onto the console, but fail to spot any of the copious text mention this
> > critical issue.
> 
> Anything not in interrupts would not be deferred.
> The following code is meant to avoid deferring in oops as well.
> I'm not sure if that covers all crash cases or not.
> If you know of other cases, and ways to detect them, please advise.
> 

Yes, using oops_in_progress seems an appropriate fix for that.

I assume that another downside is that printk-from-interrupt will now get
jumbled up with an interrupted pritk-from-non-interrupt.

Please use checkpatch.

Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

[Jan Kiszka]

Steven Rostedt wrote:
> On Wed, 23 Jan 2008, Mathieu Desnoyers wrote:
> 
>> * Steven Rostedt (rostedt@goodmis.org) wrote:
>>> This annotates NMI functions with notrace. Some tracers may be able
>>> to live with this, but some cannot. So we turn off NMI tracing.
>>>
>>> One solution might be to make a notrace_nmi which would only turn
>>> off NMI tracing if a trace utility needed it off.
>>>
>> Is this still needed with the atomic clocksource read ?
>>
> 
> Before you ask again, I've still included this in -v6, simply because I
> didn't get a chance to test it without this patch. I'll try to remember to
> do that on Monday.

Only in case you finally have to keep the annotations for the posted
tracer: Then please make it a Kconfig selectable restriction, because
there are use cases of the mcount hook where you are interested in NMI
invocations.

TiA,
Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

Re: [PATCH 06/20 -v5] add notrace annotations for NMI routines

[Steven Rostedt]

On Mon, 28 Jan 2008, Jan Kiszka wrote:
> Steven Rostedt wrote:
> > On Wed, 23 Jan 2008, Mathieu Desnoyers wrote:
> >
> >> * Steven Rostedt (rostedt@goodmis.org) wrote:
> >>> This annotates NMI functions with notrace. Some tracers may be able
> >>> to live with this, but some cannot. So we turn off NMI tracing.
> >>>
> >>> One solution might be to make a notrace_nmi which would only turn
> >>> off NMI tracing if a trace utility needed it off.
> >>>
> >> Is this still needed with the atomic clocksource read ?
> >>
> >
> > Before you ask again, I've still included this in -v6, simply because I
> > didn't get a chance to test it without this patch. I'll try to remember to
> > do that on Monday.
>
> Only in case you finally have to keep the annotations for the posted
> tracer: Then please make it a Kconfig selectable restriction, because
> there are use cases of the mcount hook where you are interested in NMI
> invocations.

I've thought about adding a notrace_nmi which would do precisely that.
This week I'll take this patch out and turn on a bunch of nmi profiling
and see how it holds up.

Thanks,

-- Steve

Re: [PATCH] defer printks in irqs

[Tim Bird]

Andrew Morton wrote:
>> On Thu, 24 Jan 2008 15:23:03 -0800 Tim Bird <tim.bird@am.sony.com> wrote:
>> Peter Zijlstra wrote:
>>> I suspect these features reduce the chance a crash messages makes it out
>>> onto the console, but fail to spot any of the copious text mention this
>>> critical issue.
>> Anything not in interrupts would not be deferred.
>> The following code is meant to avoid deferring in oops as well.
>> I'm not sure if that covers all crash cases or not.
>> If you know of other cases, and ways to detect them, please advise.
>>
> 
> Yes, using oops_in_progress seems an appropriate fix for that.
> 
> I assume that another downside is that printk-from-interrupt will now get
> jumbled up with an interrupted pritk-from-non-interrupt.

No.  The order of printk messages (whether printk'ed
from interrupt context or not) should not be affected.
This patch should only affect the timing of when the
messages are output to console.

Note that an oops will flush any buffered messages
ahead of the oops messages themselves.

Some messages, not in oops, that were printk'ed in
interrupt context, may still be in the log buffer
but not have made it to console if the machine hangs
hard.  Because of this (IMO slight) downgrade in
debugging utility, I chose to make the changes
configurable.

> Please use checkpatch.

Will do from now on!  Thanks!
  -- Tim


=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================