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* [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
@ 2020-01-14 12:49 Marco Elver
  2020-01-14 17:24 ` Alexander Potapenko
  0 siblings, 1 reply; 15+ messages in thread
From: Marco Elver @ 2020-01-14 12:49 UTC (permalink / raw)
  To: elver
  Cc: paulmck, andreyknvl, glider, dvyukov, kasan-dev, linux-kernel,
	peterz, mingo, will, Qian Cai

To avoid unexpected reentry into lockdep's IRQ tracing code via KCSAN
(if TRACE_IRQFLAGS is enabled), (1) use raw versions of
local_irq_{save,restore} in kcsan_setup_watchpoint(), and (2) disable
lockdep in kcsan_report() to avoid IRQ flags tracing upon generating the
report.

Tested with:

  CONFIG_LOCKDEP=y
  CONFIG_DEBUG_LOCKDEP=y

Where previously, the following warning (and variants with different
stack traces) was consistently generated, with the fix introduced in
this patch, the warning cannot be reproduced.

    WARNING: CPU: 0 PID: 2 at kernel/locking/lockdep.c:4406 check_flags.part.0+0x101/0x220
    Modules linked in:
    CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.5.0-rc1+ #11
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
    RIP: 0010:check_flags.part.0+0x101/0x220
    <snip>
    Call Trace:
     lock_is_held_type+0x69/0x150
     freezer_fork+0x20b/0x370
     cgroup_post_fork+0x2c9/0x5c0
     copy_process+0x2675/0x3b40
     _do_fork+0xbe/0xa30
     ? _raw_spin_unlock_irqrestore+0x40/0x50
     ? match_held_lock+0x56/0x250
     ? kthread_park+0xf0/0xf0
     kernel_thread+0xa6/0xd0
     ? kthread_park+0xf0/0xf0
     kthreadd+0x321/0x3d0
     ? kthread_create_on_cpu+0x130/0x130
     ret_from_fork+0x3a/0x50
    irq event stamp: 64
    hardirqs last  enabled at (63): [<ffffffff9a7995d0>] _raw_spin_unlock_irqrestore+0x40/0x50
    hardirqs last disabled at (64): [<ffffffff992a96d2>] kcsan_setup_watchpoint+0x92/0x460
    softirqs last  enabled at (32): [<ffffffff990489b8>] fpu__copy+0xe8/0x470
    softirqs last disabled at (30): [<ffffffff99048939>] fpu__copy+0x69/0x470

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Marco Elver <elver@google.com>
---
 kernel/kcsan/core.c     |  4 ++--
 kernel/kcsan/report.c   | 11 +++++++++++
 kernel/locking/Makefile |  3 +++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 87bf857c8893..e75f3dbf627e 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 	 *      detection point of view) to simply disable preemptions to ensure
 	 *      as many tasks as possible run on other CPUs.
 	 */
-	local_irq_save(irq_flags);
+	raw_local_irq_save(irq_flags);
 
 	watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
 	if (watchpoint == NULL) {
@@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 
 	kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
 out_unlock:
-	local_irq_restore(irq_flags);
+	raw_local_irq_restore(irq_flags);
 out:
 	user_access_restore(ua_flags);
 }
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index b5b4feea49de..57ab7ef9786c 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -2,6 +2,7 @@
 
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/lockdep.h>
 #include <linux/preempt.h>
 #include <linux/printk.h>
 #include <linux/sched.h>
@@ -410,6 +411,14 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type,
 {
 	unsigned long flags = 0;
 
+	/*
+	 * With TRACE_IRQFLAGS, lockdep's internal IRQ flags state becomes
+	 * corrupted if we do not turn off lockdep. The likely cause is
+	 * unexpected reentry into IRQ tracing code via KCSAN if we detect a
+	 * data race.
+	 */
+	lockdep_off();
+
 	kcsan_disable_current();
 	if (prepare_report(&flags, ptr, size, access_type, cpu_id, type)) {
 		if (print_report(ptr, size, access_type, value_change, cpu_id, type) && panic_on_warn)
@@ -418,4 +427,6 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type,
 		release_report(&flags, type);
 	}
 	kcsan_enable_current();
+
+	lockdep_on();
 }
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 45452facff3b..6d11cfb9b41f 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -5,6 +5,9 @@ KCOV_INSTRUMENT		:= n
 
 obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
 
+# Avoid recursion lockdep -> KCSAN -> ... -> lockdep.
+KCSAN_SANITIZE_lockdep.o := n
+
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_lockdep.o = $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_lockdep_proc.o = $(CC_FLAGS_FTRACE)
-- 
2.25.0.rc1.283.g88dfdc4193-goog


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-14 12:49 [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep Marco Elver
@ 2020-01-14 17:24 ` Alexander Potapenko
  2020-01-15 16:26   ` Marco Elver
  0 siblings, 1 reply; 15+ messages in thread
From: Alexander Potapenko @ 2020-01-14 17:24 UTC (permalink / raw)
  To: Marco Elver
  Cc: paulmck, Andrey Konovalov, Dmitriy Vyukov, kasan-dev, LKML,
	Peter Zijlstra, Ingo Molnar, will, Qian Cai

> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>          *      detection point of view) to simply disable preemptions to ensure
>          *      as many tasks as possible run on other CPUs.
>          */
> -       local_irq_save(irq_flags);
> +       raw_local_irq_save(irq_flags);

Please reflect the need to use raw_local_irq_save() in the comment.

>
>         watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
>         if (watchpoint == NULL) {
> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>
>         kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
>  out_unlock:
> -       local_irq_restore(irq_flags);
> +       raw_local_irq_restore(irq_flags);

Ditto

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-14 17:24 ` Alexander Potapenko
@ 2020-01-15 16:26   ` Marco Elver
  2020-01-15 16:37     ` Paul E. McKenney
  0 siblings, 1 reply; 15+ messages in thread
From: Marco Elver @ 2020-01-15 16:26 UTC (permalink / raw)
  To: Alexander Potapenko
  Cc: Paul E. McKenney, Andrey Konovalov, Dmitriy Vyukov, kasan-dev,
	LKML, Peter Zijlstra, Ingo Molnar, Will Deacon, Qian Cai

On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
>
> > --- a/kernel/kcsan/core.c
> > +++ b/kernel/kcsan/core.c
> > @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >          *      detection point of view) to simply disable preemptions to ensure
> >          *      as many tasks as possible run on other CPUs.
> >          */
> > -       local_irq_save(irq_flags);
> > +       raw_local_irq_save(irq_flags);
>
> Please reflect the need to use raw_local_irq_save() in the comment.
>
> >
> >         watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> >         if (watchpoint == NULL) {
> > @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >
> >         kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> >  out_unlock:
> > -       local_irq_restore(irq_flags);
> > +       raw_local_irq_restore(irq_flags);
>
> Ditto

Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com

Thanks,
-- Marco

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-15 16:26   ` Marco Elver
@ 2020-01-15 16:37     ` Paul E. McKenney
  2020-01-16  3:39       ` Qian Cai
  0 siblings, 1 reply; 15+ messages in thread
From: Paul E. McKenney @ 2020-01-15 16:37 UTC (permalink / raw)
  To: Marco Elver
  Cc: Alexander Potapenko, Andrey Konovalov, Dmitriy Vyukov, kasan-dev,
	LKML, Peter Zijlstra, Ingo Molnar, Will Deacon, Qian Cai

On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> >
> > > --- a/kernel/kcsan/core.c
> > > +++ b/kernel/kcsan/core.c
> > > @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > >          *      detection point of view) to simply disable preemptions to ensure
> > >          *      as many tasks as possible run on other CPUs.
> > >          */
> > > -       local_irq_save(irq_flags);
> > > +       raw_local_irq_save(irq_flags);
> >
> > Please reflect the need to use raw_local_irq_save() in the comment.
> >
> > >
> > >         watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> > >         if (watchpoint == NULL) {
> > > @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > >
> > >         kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> > >  out_unlock:
> > > -       local_irq_restore(irq_flags);
> > > +       raw_local_irq_restore(irq_flags);
> >
> > Ditto
> 
> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com

Alexander and Qian, could you please let me know if this fixes things
up for you?

							Thanx, Paul

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-15 16:37     ` Paul E. McKenney
@ 2020-01-16  3:39       ` Qian Cai
  2020-01-16  4:37         ` Qian Cai
  2020-01-16 18:57         ` Marco Elver
  0 siblings, 2 replies; 15+ messages in thread
From: Qian Cai @ 2020-01-16  3:39 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon



> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> 
> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
>>> 
>>>> --- a/kernel/kcsan/core.c
>>>> +++ b/kernel/kcsan/core.c
>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>         *      detection point of view) to simply disable preemptions to ensure
>>>>         *      as many tasks as possible run on other CPUs.
>>>>         */
>>>> -       local_irq_save(irq_flags);
>>>> +       raw_local_irq_save(irq_flags);
>>> 
>>> Please reflect the need to use raw_local_irq_save() in the comment.
>>> 
>>>> 
>>>>        watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
>>>>        if (watchpoint == NULL) {
>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>> 
>>>>        kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
>>>> out_unlock:
>>>> -       local_irq_restore(irq_flags);
>>>> +       raw_local_irq_restore(irq_flags);
>>> 
>>> Ditto
>> 
>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> 
> Alexander and Qian, could you please let me know if this fixes things
> up for you?

The lockdep warning is gone, so feel free to add,

Tested-by: Qian Cai <cai@lca.pw>

for that patch, but the system is still unable to boot due to spam of
warnings due to incompatible with debug_pagealloc, debugobjects, so
the warning rate limit does not help.

[   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
[   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
[   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
[   28.992752][  T394] =============================================================== 
[   28.992752][  T394] ================================================================== 
[   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
[   28.992752][  T394]  
[   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
[   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
[   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
[   28.992752][  T394]  __set_pages_np+0xcc/0x100 
[   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
[   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
[   28.992752][  T394]  __free_pages+0x51/0x90 
[   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
[   28.992752][  T394]  deferred_free_range+0x59/0x8f 
[   28.992752][  T394]  deferred_init_max21d 
[   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
[   28.992752][  T394]  kthread+0x1e0/0x200 
[   28.992752][  T394]  ret_from_fork+0x3a/0x50 
[   28.992752][  T394]  
[   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
[   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
[   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
[   28.992752][  T394]  __set_pages_np+0xcc/0x100 
[   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
[   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
[   28.992752][  T394]  __free_pages+0x51/0x90 
[   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
[   28.992752][  T394]  deferred_free_range+0x59/0x8f 
[   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
[   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
[   28.992752][  T394]  kthread+0x1e0/0x200 
[   28.992752][  T394]  ret_from_fork+0x3a/0x50 


[   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
[   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
[   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
[   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
[   93.378715][  T349] ================================================================== 
[   93.416183][  T616] ================================================================== 
[   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
[   93.486775][  T616]  
[   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
[   93.534139][  T616]  fill_pool+0x38/0x700 
[   93.554913][  T616]  __debug_object_init+0x3f/0x900 
[   93.579459][  T616]  debug_object_init+0x39/0x50 
[   93.601952][  T616]  __init_work+0x3e/0x50 
[   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
[   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
[   93.665134][  T616]  __kmalloc_node+0x60/0x300 
[   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
[   93.704235][  T616]  seq_read+0x57c/0x7a0 
[   93.722460][  T616]  proc_reg_read+0x11a/0x160 
[   93.743570][  T616]  __vfs_read+0x59/0xa0 
[   93.761660][  T616]  vfs_read+0xcf/0x1c0 
[   93.779269][  T616]  ksys_read+0x9d/0x130 
[   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
[   93.817205][  T616]  do_syscall_64+0x91/0xb47 
[   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
[   93.864425][  T616]  
[   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
[   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
[   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
[   93.954131][  T616]  call_rcu+0x4c/0x4e0 
[   93.971959][  T616]  put_object+0x6a/0x90 
[   93.989955][  T616]  __delete_object+0xb9/0xf0 
[   94.009996][  T616]  delete_object_full+0x2d/0x40 
[   94.031812][  T616]  kmemleak_free+0x5f/0x90 
[   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
[   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
[   94.103806][  T616]  vm_area_free+0x31/0x40 
[   94.124587][  T616]  remove_vma+0xb0/0xc0 
[   94.143484][  T616]  exit_mmap+0x14c/0x220 
[   94.163826][  T616]  mmput+0x10e/0x270 
[   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
[   94.202760][  T616]  load_elf_binary+0x467/0x2180 
[   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
[   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
[   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
[   94.292254][  T616]  do_syscall_64+0x91/0xb47 
[   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 

[  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
[  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
[  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
[  103.561771][   C22] ================================================================== 
[  103.598005][   C41] ================================================================== 
[  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
[  103.673408][   C41]  
[  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
[  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
[  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
[  103.762611][   C41]  update_blocked_averages+0x585/0x630 
[  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
[  103.812821][   C41]  __do_softirq+0xd9/0x57c 
[  103.834438][   C41]  irq_exit+0xa2/0xc0 
[  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
[  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
[  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
[  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
[  103.938405][   C41]  call_cpuidle+0x23/0x40 
[  103.957152][   C41]  do_idle+0x248/0x280 
[  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
[  103.995059][   C41]  start_secondary+0x1ad/0x230 
[  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
[  104.037376][   C41]  
[  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
[  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
[  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
[  104.127759][   C41]  update_load_avg+0x70e/0x800 
[  104.148400][   C41]  task_tick_fair+0x5c/0x680 
[  104.168325][   C41]  scheduler_tick+0xab/0x120 
[  104.188881][   C41]  update_process_times+0x44/0x60 
[  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
[  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
[  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
[  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
[  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
[  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
[  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
[  104.370100][   C41]  __read_once_size+0x1f/0xe0 
[  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
[  104.413591][   C41]  on_each_cpu+0x46/0x90 
[  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
[  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
[  104.476699][   C41]  remove_vm_area+0xf4/0x100 
[  104.496763][   C41]  __vunmap+0x10a/0x460 
[  104.514807][   C41]  __vfree+0x33/0x90 
[  104.531597][   C41]  vfree+0x47/0x80 
[  104.547600][   C41]  n_tty_close+0x56/0x80 
[  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
[  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
[  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
[  104.627098][   C41]  tty_release_struct+0x23/0x60 
[  104.648268][   C41]  tty_release+0x673/0x9c0 
[  104.667517][   C41]  __fput+0x187/0x410 
[  104.684357][   C41]  ____fput+0x1e/0x30 
[  104.701542][   C41]  task_work_run+0xed/0x140 
[  104.721358][   C41]  do_syscall_64+0x803/0xb47 
[  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe

[  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
[  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
[  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
[  136.861974][   C34] ================================================================== 
[  136.911354][    T1] ================================================================== 
[  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
[  136.981645][    T1]  
[  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
[  137.026513][    T1]  fill_pool+0x38/0x700 
[  137.045575][    T1]  __debug_object_init+0x3f/0x900 
[  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
[  137.093102][    T1]  call_rcu+0x4c/0x4e0 
[  137.111520][    T1]  __fput+0x23a/0x410 
[  137.129618][    T1]  ____fput+0x1e/0x30 
[  137.147627][    T1]  task_work_run+0xed/0x140 
[  137.168322][    T1]  do_syscall_64+0x803/0xb47 
[  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
[  137.215309][    T1]  
[  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
[  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
[  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
[  137.306988][    T1]  call_rcu+0x4c/0x4e0 
[  137.326804][    T1]  dentry_free+0x70/0xe0 
[  137.347208][    T1]  __dentry_kill+0x1db/0x300 
[  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
[  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
[  137.417174][    T1]  d_invalidate+0x80/0x130 
[  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
[  137.459263][    T1]  release_task.part.21+0x156/0xb50 
[  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
[  137.507550][    T1]  do_wait+0x25b/0x560 
[  137.526175][    T1]  kernel_waitid+0x194/0x270 
[  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
[  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
[  137.590291][    T1]  do_syscall_64+0x91/0xb47 
[  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16  3:39       ` Qian Cai
@ 2020-01-16  4:37         ` Qian Cai
  2020-01-16 17:40           ` Paul E. McKenney
  2020-01-16 18:57         ` Marco Elver
  1 sibling, 1 reply; 15+ messages in thread
From: Qian Cai @ 2020-01-16  4:37 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon



> On Jan 15, 2020, at 10:39 PM, Qian Cai <cai@lca.pw> wrote:
> 
> 
> 
>> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
>> 
>> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
>>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
>>>> 
>>>>> --- a/kernel/kcsan/core.c
>>>>> +++ b/kernel/kcsan/core.c
>>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>>        *      detection point of view) to simply disable preemptions to ensure
>>>>>        *      as many tasks as possible run on other CPUs.
>>>>>        */
>>>>> -       local_irq_save(irq_flags);
>>>>> +       raw_local_irq_save(irq_flags);
>>>> 
>>>> Please reflect the need to use raw_local_irq_save() in the comment.
>>>> 
>>>>> 
>>>>>       watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
>>>>>       if (watchpoint == NULL) {
>>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>> 
>>>>>       kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
>>>>> out_unlock:
>>>>> -       local_irq_restore(irq_flags);
>>>>> +       raw_local_irq_restore(irq_flags);
>>>> 
>>>> Ditto
>>> 
>>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
>> 
>> Alexander and Qian, could you please let me know if this fixes things
>> up for you?
> 
> The lockdep warning is gone, so feel free to add,
> 
> Tested-by: Qian Cai <cai@lca.pw>
> 
> for that patch, but the system is still unable to boot due to spam of
> warnings due to incompatible with debug_pagealloc, debugobjects, so
> the warning rate limit does not help.

I set CONFIG_DEBUG_OBJECTS=n to see how further it could go, but
the kernel is dead after those lines. Unable to boot any further.

…
[  111.345991][  T789] Reported by Kernel Concurrency Sanitizer on:
[  111.373039][  T789] CPU: 44 PID: 789 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
[  111.414596][  T789] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
[  111.459984][  T789] ==================================================================
[  111.554563][  T777] ==================================================================
[  111.590304][  T777] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
[  111.626392][  T777] 
[  111.636881][  T777] write to 0xffffffff9a19cde0 of 8 bytes by task 796 on cpu 1:
[  111.671544][  T777]  __change_page_attr+0xe9c/0x1620
[  111.695067][  T777]  __change_page_attr_set_clr+0xde/0x4c0
[  111.722124][  T777]  __set_pages_p+0xcc/0x100
[  111.742644][  T777]  __kernel_map_pages+0x2e/0xdb
[  111.765379][  T777]  prep_new_page+0x87/0x1f0
[  111.785804][  T777]  get_page_from_freelist+0x1583/0x22b0
[  111.810633][  T777]  __alloc_pages_nodemask+0x1b1/0x450
[  111.835196][  T777]  alloc_pages_current+0xa6/0x120
[  111.858619][  T777]  __vmalloc_node_range+0x338/0x480
[  111.882253][  T777]  __vmalloc_node.constprop.29+0x70/0xb0
[  111.908550][  T777]  vmalloc+0x69/0x80
[  111.927150][  T777]  kernel_read_file+0x241/0x2b0
[  111.950372][  T777]  kernel_read_file_from_fd+0x56/0x90
[  111.976025][  T777]  __do_sys_finit_module+0xc7/0x190
[  111.999847][  T777]  __x64_sys_finit_module+0x4c/0x60
[  112.023326][  T777]  do_syscall_64+0x91/0xb47
[  112.043903][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  112.070954][  T777] 
[  112.081261][  T777] read to 0xffffffff9a19cde0 of 8 bytes by task 777 on cpu 16:
[  112.115510][  T777]  __change_page_attr+0xe81/0x1620
[  112.138564][  T777]  __change_page_attr_set_clr+0xde/0x4c0
[  112.164452][  T777]  __set_pages_p+0xcc/0x100
[  112.185228][  T777]  __kernel_map_pages+0x2e/0xdb
[  112.207122][  T777]  prep_new_page+0x87/0x1f0
[  112.227507][  T777]  get_page_from_freelist+0x1583/0x22b0
[  112.252947][  T777]  __alloc_pages_nodemask+0x1b1/0x450
[  112.277504][  T777]  alloc_pages_current+0xa6/0x120
[  112.300450][  T777]  alloc_slab_page+0x3b1/0x540
[  112.322039][  T777]  allocate_slab+0x70/0x660
[  112.342387][  T777]  new_slab+0x46/0x70
[  112.360102][  T777]  ___slab_alloc+0x4ad/0x7d0
[  112.380944][  T777]  __slab_alloc+0x43/0x70
[  112.400596][  T777]  kmem_cache_alloc+0x2c3/0x420
[  112.423674][  T777]  create_object+0x69/0x690
[  112.447347][  T777]  kmemleak_alloc+0x7d/0xb0
[  112.469100][  T777]  __kmalloc_track_caller+0x157/0x3c0
[  112.493548][  T777]  kstrdup+0x3d/0x70
[  112.510959][  T777]  mod_sysfs_setup+0x5e5/0xb10
[  112.532234][  T777]  load_module+0x2510/0x2b60
[  112.552985][  T777]  __do_sys_finit_module+0x14d/0x190
[  112.577212][  T777]  __x64_sys_finit_module+0x4c/0x60
[  112.601135][  T777]  do_syscall_64+0x91/0xb47
[  112.621690][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  112.648566][  T777] 
[  112.659018][  T777] Reported by Kernel Concurrency Sanitizer on:
[  112.687603][  T777] CPU: 16 PID: 777 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
[  112.729082][  T777] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
[  112.772563][  T777] ==================================================================
[  112.810304][  T364] ==================================================================
[  112.848145][  T364] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
[  112.884579][  T364] 
[  112.884586][  T364] read to 0xffffffff9a19cde0 of 8 bytes by task 789 on cpu 12:
[  112.884595][  T364]  __change_page_attr+0xe81/0x1620
[  112.884602][  T364]  __change_page_attr_set_clr+0xde/0x4c0
[  112.884607][  T364]  __set_pages_p+0xcc/0x100
[  112.884612][  T364]  __kernel_map_pages+0x2e/0xdb
         [  112.884619][  T364]  prep_new_page+0x87/0x1f0
[  112.884627][  T364]  get_page_from_freelist+0x1583/0x22b0
[  112.884633][  T364]  __alloc_pages_nodemask+0x1b1/0x450
[  112.884640][  T364]  alloc_pages_vma+0x8a/0x2c0
[  112.884646][  T364]  wp_page_copy+0x100/0x930
Starting Show Pl[  112.884653][  T364]  do_wp_page+0x107/0x7b0
[  112.884660][  T364]  __handle_mm_fault+0xce6/0xd40
[  112.884667][  T364]  handle_mm_fault+0xfc/0x2f0
[  112.884677][  T364]  do_page_fault+0x263/0x6f9
ymouth Boot Screen...
perf: interrupt took too long (7468 > 7338), lowering kernel.perf_event_max_sample_rate to 26700
perf: interrupt took too long (9463 > 9335), lowering kernel.perf_event_max_sample_rate to 21100

> 
> [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
> [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
> [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> [   28.992752][  T394] =============================================================== 
> [   28.992752][  T394] ================================================================== 
> [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
> [   28.992752][  T394]  
> [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
> [   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> [   28.992752][  T394]  __free_pages+0x51/0x90 
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> [   28.992752][  T394]  deferred_init_max21d 
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> [   28.992752][  T394]  kthread+0x1e0/0x200 
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> [   28.992752][  T394]  
> [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
> [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> [   28.992752][  T394]  __free_pages+0x51/0x90 
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> [   28.992752][  T394]  kthread+0x1e0/0x200 
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> 
> 
> [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
> [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
> [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
> [   93.378715][  T349] ================================================================== 
> [   93.416183][  T616] ================================================================== 
> [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> [   93.486775][  T616]  
> [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
> [   93.534139][  T616]  fill_pool+0x38/0x700 
> [   93.554913][  T616]  __debug_object_init+0x3f/0x900 
> [   93.579459][  T616]  debug_object_init+0x39/0x50 
> [   93.601952][  T616]  __init_work+0x3e/0x50 
> [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
> [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
> [   93.665134][  T616]  __kmalloc_node+0x60/0x300 
> [   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
> [   93.704235][  T616]  seq_read+0x57c/0x7a0 
> [   93.722460][  T616]  proc_reg_read+0x11a/0x160 
> [   93.743570][  T616]  __vfs_read+0x59/0xa0 
> [   93.761660][  T616]  vfs_read+0xcf/0x1c0 
> [   93.779269][  T616]  ksys_read+0x9d/0x130 
> [   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
> [   93.817205][  T616]  do_syscall_64+0x91/0xb47 
> [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> [   93.864425][  T616]  
> [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
> [   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
> [   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
> [   93.954131][  T616]  call_rcu+0x4c/0x4e0 
> [   93.971959][  T616]  put_object+0x6a/0x90 
> [   93.989955][  T616]  __delete_object+0xb9/0xf0 
> [   94.009996][  T616]  delete_object_full+0x2d/0x40 
> [   94.031812][  T616]  kmemleak_free+0x5f/0x90 
> [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
> [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
> [   94.103806][  T616]  vm_area_free+0x31/0x40 
> [   94.124587][  T616]  remove_vma+0xb0/0xc0 
> [   94.143484][  T616]  exit_mmap+0x14c/0x220 
> [   94.163826][  T616]  mmput+0x10e/0x270 
> [   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
> [   94.202760][  T616]  load_elf_binary+0x467/0x2180 
> [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
> [   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
> [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
> [   94.292254][  T616]  do_syscall_64+0x91/0xb47 
> [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> 
> [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
> [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
> [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> [  103.561771][   C22] ================================================================== 
> [  103.598005][   C41] ================================================================== 
> [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
> [  103.673408][   C41]  
> [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
> [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
> [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
> [  103.762611][   C41]  update_blocked_averages+0x585/0x630 
> [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
> [  103.812821][   C41]  __do_softirq+0xd9/0x57c 
> [  103.834438][   C41]  irq_exit+0xa2/0xc0 
> [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
> [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
> [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
> [  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
> [  103.938405][   C41]  call_cpuidle+0x23/0x40 
> [  103.957152][   C41]  do_idle+0x248/0x280 
> [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
> [  103.995059][   C41]  start_secondary+0x1ad/0x230 
> [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
> [  104.037376][   C41]  
> [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
> [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
> [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
> [  104.127759][   C41]  update_load_avg+0x70e/0x800 
> [  104.148400][   C41]  task_tick_fair+0x5c/0x680 
> [  104.168325][   C41]  scheduler_tick+0xab/0x120 
> [  104.188881][   C41]  update_process_times+0x44/0x60 
> [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
> [  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
> [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
> [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
> [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
> [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
> [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
> [  104.370100][   C41]  __read_once_size+0x1f/0xe0 
> [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
> [  104.413591][   C41]  on_each_cpu+0x46/0x90 
> [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
> [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
> [  104.476699][   C41]  remove_vm_area+0xf4/0x100 
> [  104.496763][   C41]  __vunmap+0x10a/0x460 
> [  104.514807][   C41]  __vfree+0x33/0x90 
> [  104.531597][   C41]  vfree+0x47/0x80 
> [  104.547600][   C41]  n_tty_close+0x56/0x80 
> [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
> [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
> [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
> [  104.627098][   C41]  tty_release_struct+0x23/0x60 
> [  104.648268][   C41]  tty_release+0x673/0x9c0 
> [  104.667517][   C41]  __fput+0x187/0x410 
> [  104.684357][   C41]  ____fput+0x1e/0x30 
> [  104.701542][   C41]  task_work_run+0xed/0x140 
> [  104.721358][   C41]  do_syscall_64+0x803/0xb47 
> [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
> [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
> [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> [  136.861974][   C34] ================================================================== 
> [  136.911354][    T1] ================================================================== 
> [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> [  136.981645][    T1]  
> [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
> [  137.026513][    T1]  fill_pool+0x38/0x700 
> [  137.045575][    T1]  __debug_object_init+0x3f/0x900 
> [  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
> [  137.093102][    T1]  call_rcu+0x4c/0x4e0 
> [  137.111520][    T1]  __fput+0x23a/0x410 
> [  137.129618][    T1]  ____fput+0x1e/0x30 
> [  137.147627][    T1]  task_work_run+0xed/0x140 
> [  137.168322][    T1]  do_syscall_64+0x803/0xb47 
> [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> [  137.215309][    T1]  
> [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
> [  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
> [  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
> [  137.306988][    T1]  call_rcu+0x4c/0x4e0 
> [  137.326804][    T1]  dentry_free+0x70/0xe0 
> [  137.347208][    T1]  __dentry_kill+0x1db/0x300 
> [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
> [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
> [  137.417174][    T1]  d_invalidate+0x80/0x130 
> [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
> [  137.459263][    T1]  release_task.part.21+0x156/0xb50 
> [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
> [  137.507550][    T1]  do_wait+0x25b/0x560 
> [  137.526175][    T1]  kernel_waitid+0x194/0x270 
> [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
> [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
> [  137.590291][    T1]  do_syscall_64+0x91/0xb47 
> [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16  4:37         ` Qian Cai
@ 2020-01-16 17:40           ` Paul E. McKenney
  2020-01-16 17:50             ` Qian Cai
  0 siblings, 1 reply; 15+ messages in thread
From: Paul E. McKenney @ 2020-01-16 17:40 UTC (permalink / raw)
  To: Qian Cai
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon

On Wed, Jan 15, 2020 at 11:37:47PM -0500, Qian Cai wrote:
> 
> > On Jan 15, 2020, at 10:39 PM, Qian Cai <cai@lca.pw> wrote:
> >> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> >> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> >>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> >>>> 
> >>>>> --- a/kernel/kcsan/core.c
> >>>>> +++ b/kernel/kcsan/core.c
> >>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>>        *      detection point of view) to simply disable preemptions to ensure
> >>>>>        *      as many tasks as possible run on other CPUs.
> >>>>>        */
> >>>>> -       local_irq_save(irq_flags);
> >>>>> +       raw_local_irq_save(irq_flags);
> >>>> 
> >>>> Please reflect the need to use raw_local_irq_save() in the comment.
> >>>> 
> >>>>> 
> >>>>>       watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> >>>>>       if (watchpoint == NULL) {
> >>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>> 
> >>>>>       kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> >>>>> out_unlock:
> >>>>> -       local_irq_restore(irq_flags);
> >>>>> +       raw_local_irq_restore(irq_flags);
> >>>> 
> >>>> Ditto
> >>> 
> >>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> >> 
> >> Alexander and Qian, could you please let me know if this fixes things
> >> up for you?
> > 
> > The lockdep warning is gone, so feel free to add,
> > 
> > Tested-by: Qian Cai <cai@lca.pw>
> > 
> > for that patch, but the system is still unable to boot due to spam of
> > warnings due to incompatible with debug_pagealloc, debugobjects, so
> > the warning rate limit does not help.
> 
> I set CONFIG_DEBUG_OBJECTS=n to see how further it could go, but
> the kernel is dead after those lines. Unable to boot any further.

How large a system are you running on?  The reason that I ask is that I
have been running it on a 12-CPU system with and without lockdep for some
time.  So perhaps you are running this on a large system (thus indicating
a need for better scalability) or are using an additional Kconfig option?

						Thanx, Paul

> …
> [  111.345991][  T789] Reported by Kernel Concurrency Sanitizer on:
> [  111.373039][  T789] CPU: 44 PID: 789 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
> [  111.414596][  T789] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  111.459984][  T789] ==================================================================
> [  111.554563][  T777] ==================================================================
> [  111.590304][  T777] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [  111.626392][  T777] 
> [  111.636881][  T777] write to 0xffffffff9a19cde0 of 8 bytes by task 796 on cpu 1:
> [  111.671544][  T777]  __change_page_attr+0xe9c/0x1620
> [  111.695067][  T777]  __change_page_attr_set_clr+0xde/0x4c0
> [  111.722124][  T777]  __set_pages_p+0xcc/0x100
> [  111.742644][  T777]  __kernel_map_pages+0x2e/0xdb
> [  111.765379][  T777]  prep_new_page+0x87/0x1f0
> [  111.785804][  T777]  get_page_from_freelist+0x1583/0x22b0
> [  111.810633][  T777]  __alloc_pages_nodemask+0x1b1/0x450
> [  111.835196][  T777]  alloc_pages_current+0xa6/0x120
> [  111.858619][  T777]  __vmalloc_node_range+0x338/0x480
> [  111.882253][  T777]  __vmalloc_node.constprop.29+0x70/0xb0
> [  111.908550][  T777]  vmalloc+0x69/0x80
> [  111.927150][  T777]  kernel_read_file+0x241/0x2b0
> [  111.950372][  T777]  kernel_read_file_from_fd+0x56/0x90
> [  111.976025][  T777]  __do_sys_finit_module+0xc7/0x190
> [  111.999847][  T777]  __x64_sys_finit_module+0x4c/0x60
> [  112.023326][  T777]  do_syscall_64+0x91/0xb47
> [  112.043903][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  112.070954][  T777] 
> [  112.081261][  T777] read to 0xffffffff9a19cde0 of 8 bytes by task 777 on cpu 16:
> [  112.115510][  T777]  __change_page_attr+0xe81/0x1620
> [  112.138564][  T777]  __change_page_attr_set_clr+0xde/0x4c0
> [  112.164452][  T777]  __set_pages_p+0xcc/0x100
> [  112.185228][  T777]  __kernel_map_pages+0x2e/0xdb
> [  112.207122][  T777]  prep_new_page+0x87/0x1f0
> [  112.227507][  T777]  get_page_from_freelist+0x1583/0x22b0
> [  112.252947][  T777]  __alloc_pages_nodemask+0x1b1/0x450
> [  112.277504][  T777]  alloc_pages_current+0xa6/0x120
> [  112.300450][  T777]  alloc_slab_page+0x3b1/0x540
> [  112.322039][  T777]  allocate_slab+0x70/0x660
> [  112.342387][  T777]  new_slab+0x46/0x70
> [  112.360102][  T777]  ___slab_alloc+0x4ad/0x7d0
> [  112.380944][  T777]  __slab_alloc+0x43/0x70
> [  112.400596][  T777]  kmem_cache_alloc+0x2c3/0x420
> [  112.423674][  T777]  create_object+0x69/0x690
> [  112.447347][  T777]  kmemleak_alloc+0x7d/0xb0
> [  112.469100][  T777]  __kmalloc_track_caller+0x157/0x3c0
> [  112.493548][  T777]  kstrdup+0x3d/0x70
> [  112.510959][  T777]  mod_sysfs_setup+0x5e5/0xb10
> [  112.532234][  T777]  load_module+0x2510/0x2b60
> [  112.552985][  T777]  __do_sys_finit_module+0x14d/0x190
> [  112.577212][  T777]  __x64_sys_finit_module+0x4c/0x60
> [  112.601135][  T777]  do_syscall_64+0x91/0xb47
> [  112.621690][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  112.648566][  T777] 
> [  112.659018][  T777] Reported by Kernel Concurrency Sanitizer on:
> [  112.687603][  T777] CPU: 16 PID: 777 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
> [  112.729082][  T777] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  112.772563][  T777] ==================================================================
> [  112.810304][  T364] ==================================================================
> [  112.848145][  T364] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [  112.884579][  T364] 
> [  112.884586][  T364] read to 0xffffffff9a19cde0 of 8 bytes by task 789 on cpu 12:
> [  112.884595][  T364]  __change_page_attr+0xe81/0x1620
> [  112.884602][  T364]  __change_page_attr_set_clr+0xde/0x4c0
> [  112.884607][  T364]  __set_pages_p+0xcc/0x100
> [  112.884612][  T364]  __kernel_map_pages+0x2e/0xdb
>          [  112.884619][  T364]  prep_new_page+0x87/0x1f0
> [  112.884627][  T364]  get_page_from_freelist+0x1583/0x22b0
> [  112.884633][  T364]  __alloc_pages_nodemask+0x1b1/0x450
> [  112.884640][  T364]  alloc_pages_vma+0x8a/0x2c0
> [  112.884646][  T364]  wp_page_copy+0x100/0x930
> Starting Show Pl[  112.884653][  T364]  do_wp_page+0x107/0x7b0
> [  112.884660][  T364]  __handle_mm_fault+0xce6/0xd40
> [  112.884667][  T364]  handle_mm_fault+0xfc/0x2f0
> [  112.884677][  T364]  do_page_fault+0x263/0x6f9
> ymouth Boot Screen...
> perf: interrupt took too long (7468 > 7338), lowering kernel.perf_event_max_sample_rate to 26700
> perf: interrupt took too long (9463 > 9335), lowering kernel.perf_event_max_sample_rate to 21100
> 
> > 
> > [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
> > [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [   28.992752][  T394] =============================================================== 
> > [   28.992752][  T394] ================================================================== 
> > [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
> > [   28.992752][  T394]  
> > [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
> > [   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> > [   28.992752][  T394]  __free_pages+0x51/0x90 
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> > [   28.992752][  T394]  deferred_init_max21d 
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> > [   28.992752][  T394]  kthread+0x1e0/0x200 
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> > [   28.992752][  T394]  
> > [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
> > [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> > [   28.992752][  T394]  __free_pages+0x51/0x90 
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> > [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> > [   28.992752][  T394]  kthread+0x1e0/0x200 
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> > 
> > 
> > [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
> > [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
> > [   93.378715][  T349] ================================================================== 
> > [   93.416183][  T616] ================================================================== 
> > [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> > [   93.486775][  T616]  
> > [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
> > [   93.534139][  T616]  fill_pool+0x38/0x700 
> > [   93.554913][  T616]  __debug_object_init+0x3f/0x900 
> > [   93.579459][  T616]  debug_object_init+0x39/0x50 
> > [   93.601952][  T616]  __init_work+0x3e/0x50 
> > [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
> > [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
> > [   93.665134][  T616]  __kmalloc_node+0x60/0x300 
> > [   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
> > [   93.704235][  T616]  seq_read+0x57c/0x7a0 
> > [   93.722460][  T616]  proc_reg_read+0x11a/0x160 
> > [   93.743570][  T616]  __vfs_read+0x59/0xa0 
> > [   93.761660][  T616]  vfs_read+0xcf/0x1c0 
> > [   93.779269][  T616]  ksys_read+0x9d/0x130 
> > [   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
> > [   93.817205][  T616]  do_syscall_64+0x91/0xb47 
> > [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > [   93.864425][  T616]  
> > [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
> > [   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
> > [   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
> > [   93.954131][  T616]  call_rcu+0x4c/0x4e0 
> > [   93.971959][  T616]  put_object+0x6a/0x90 
> > [   93.989955][  T616]  __delete_object+0xb9/0xf0 
> > [   94.009996][  T616]  delete_object_full+0x2d/0x40 
> > [   94.031812][  T616]  kmemleak_free+0x5f/0x90 
> > [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
> > [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
> > [   94.103806][  T616]  vm_area_free+0x31/0x40 
> > [   94.124587][  T616]  remove_vma+0xb0/0xc0 
> > [   94.143484][  T616]  exit_mmap+0x14c/0x220 
> > [   94.163826][  T616]  mmput+0x10e/0x270 
> > [   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
> > [   94.202760][  T616]  load_elf_binary+0x467/0x2180 
> > [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
> > [   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
> > [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
> > [   94.292254][  T616]  do_syscall_64+0x91/0xb47 
> > [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > 
> > [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
> > [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [  103.561771][   C22] ================================================================== 
> > [  103.598005][   C41] ================================================================== 
> > [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
> > [  103.673408][   C41]  
> > [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
> > [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
> > [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
> > [  103.762611][   C41]  update_blocked_averages+0x585/0x630 
> > [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
> > [  103.812821][   C41]  __do_softirq+0xd9/0x57c 
> > [  103.834438][   C41]  irq_exit+0xa2/0xc0 
> > [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
> > [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
> > [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
> > [  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
> > [  103.938405][   C41]  call_cpuidle+0x23/0x40 
> > [  103.957152][   C41]  do_idle+0x248/0x280 
> > [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
> > [  103.995059][   C41]  start_secondary+0x1ad/0x230 
> > [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
> > [  104.037376][   C41]  
> > [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
> > [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
> > [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
> > [  104.127759][   C41]  update_load_avg+0x70e/0x800 
> > [  104.148400][   C41]  task_tick_fair+0x5c/0x680 
> > [  104.168325][   C41]  scheduler_tick+0xab/0x120 
> > [  104.188881][   C41]  update_process_times+0x44/0x60 
> > [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
> > [  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
> > [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
> > [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
> > [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
> > [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
> > [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
> > [  104.370100][   C41]  __read_once_size+0x1f/0xe0 
> > [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
> > [  104.413591][   C41]  on_each_cpu+0x46/0x90 
> > [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
> > [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
> > [  104.476699][   C41]  remove_vm_area+0xf4/0x100 
> > [  104.496763][   C41]  __vunmap+0x10a/0x460 
> > [  104.514807][   C41]  __vfree+0x33/0x90 
> > [  104.531597][   C41]  vfree+0x47/0x80 
> > [  104.547600][   C41]  n_tty_close+0x56/0x80 
> > [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
> > [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
> > [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
> > [  104.627098][   C41]  tty_release_struct+0x23/0x60 
> > [  104.648268][   C41]  tty_release+0x673/0x9c0 
> > [  104.667517][   C41]  __fput+0x187/0x410 
> > [  104.684357][   C41]  ____fput+0x1e/0x30 
> > [  104.701542][   C41]  task_work_run+0xed/0x140 
> > [  104.721358][   C41]  do_syscall_64+0x803/0xb47 
> > [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > 
> > [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
> > [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [  136.861974][   C34] ================================================================== 
> > [  136.911354][    T1] ================================================================== 
> > [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> > [  136.981645][    T1]  
> > [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
> > [  137.026513][    T1]  fill_pool+0x38/0x700 
> > [  137.045575][    T1]  __debug_object_init+0x3f/0x900 
> > [  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
> > [  137.093102][    T1]  call_rcu+0x4c/0x4e0 
> > [  137.111520][    T1]  __fput+0x23a/0x410 
> > [  137.129618][    T1]  ____fput+0x1e/0x30 
> > [  137.147627][    T1]  task_work_run+0xed/0x140 
> > [  137.168322][    T1]  do_syscall_64+0x803/0xb47 
> > [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > [  137.215309][    T1]  
> > [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
> > [  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
> > [  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
> > [  137.306988][    T1]  call_rcu+0x4c/0x4e0 
> > [  137.326804][    T1]  dentry_free+0x70/0xe0 
> > [  137.347208][    T1]  __dentry_kill+0x1db/0x300 
> > [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
> > [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
> > [  137.417174][    T1]  d_invalidate+0x80/0x130 
> > [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
> > [  137.459263][    T1]  release_task.part.21+0x156/0xb50 
> > [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
> > [  137.507550][    T1]  do_wait+0x25b/0x560 
> > [  137.526175][    T1]  kernel_waitid+0x194/0x270 
> > [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
> > [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
> > [  137.590291][    T1]  do_syscall_64+0x91/0xb47 
> > [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> 

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16 17:40           ` Paul E. McKenney
@ 2020-01-16 17:50             ` Qian Cai
  2020-01-16 17:55               ` Qian Cai
  0 siblings, 1 reply; 15+ messages in thread
From: Qian Cai @ 2020-01-16 17:50 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon



> On Jan 16, 2020, at 12:40 PM, Paul E. McKenney <paulmck@kernel.org> wrote:
> 
> On Wed, Jan 15, 2020 at 11:37:47PM -0500, Qian Cai wrote:
>> 
>>> On Jan 15, 2020, at 10:39 PM, Qian Cai <cai@lca.pw> wrote:
>>>> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
>>>> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
>>>>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
>>>>>> 
>>>>>>> --- a/kernel/kcsan/core.c
>>>>>>> +++ b/kernel/kcsan/core.c
>>>>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>>>>       *      detection point of view) to simply disable preemptions to ensure
>>>>>>>       *      as many tasks as possible run on other CPUs.
>>>>>>>       */
>>>>>>> -       local_irq_save(irq_flags);
>>>>>>> +       raw_local_irq_save(irq_flags);
>>>>>> 
>>>>>> Please reflect the need to use raw_local_irq_save() in the comment.
>>>>>> 
>>>>>>> 
>>>>>>>      watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
>>>>>>>      if (watchpoint == NULL) {
>>>>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>>>> 
>>>>>>>      kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
>>>>>>> out_unlock:
>>>>>>> -       local_irq_restore(irq_flags);
>>>>>>> +       raw_local_irq_restore(irq_flags);
>>>>>> 
>>>>>> Ditto
>>>>> 
>>>>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
>>>> 
>>>> Alexander and Qian, could you please let me know if this fixes things
>>>> up for you?
>>> 
>>> The lockdep warning is gone, so feel free to add,
>>> 
>>> Tested-by: Qian Cai <cai@lca.pw>
>>> 
>>> for that patch, but the system is still unable to boot due to spam of
>>> warnings due to incompatible with debug_pagealloc, debugobjects, so
>>> the warning rate limit does not help.
>> 
>> I set CONFIG_DEBUG_OBJECTS=n to see how further it could go, but
>> the kernel is dead after those lines. Unable to boot any further.
> 
> How large a system are you running on?  The reason that I ask is that I
> have been running it on a 12-CPU system with and without lockdep for some
> time.  So perhaps you are running this on a large system (thus indicating
> a need for better scalability) or are using an additional Kconfig option?

The system has 64 CPUs with additional debug options enabled,

https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config

> 
>> …
>> [  111.345991][  T789] Reported by Kernel Concurrency Sanitizer on:
>> [  111.373039][  T789] CPU: 44 PID: 789 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
>> [  111.414596][  T789] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
>> [  111.459984][  T789] ==================================================================
>> [  111.554563][  T777] ==================================================================
>> [  111.590304][  T777] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
>> [  111.626392][  T777] 
>> [  111.636881][  T777] write to 0xffffffff9a19cde0 of 8 bytes by task 796 on cpu 1:
>> [  111.671544][  T777]  __change_page_attr+0xe9c/0x1620
>> [  111.695067][  T777]  __change_page_attr_set_clr+0xde/0x4c0
>> [  111.722124][  T777]  __set_pages_p+0xcc/0x100
>> [  111.742644][  T777]  __kernel_map_pages+0x2e/0xdb
>> [  111.765379][  T777]  prep_new_page+0x87/0x1f0
>> [  111.785804][  T777]  get_page_from_freelist+0x1583/0x22b0
>> [  111.810633][  T777]  __alloc_pages_nodemask+0x1b1/0x450
>> [  111.835196][  T777]  alloc_pages_current+0xa6/0x120
>> [  111.858619][  T777]  __vmalloc_node_range+0x338/0x480
>> [  111.882253][  T777]  __vmalloc_node.constprop.29+0x70/0xb0
>> [  111.908550][  T777]  vmalloc+0x69/0x80
>> [  111.927150][  T777]  kernel_read_file+0x241/0x2b0
>> [  111.950372][  T777]  kernel_read_file_from_fd+0x56/0x90
>> [  111.976025][  T777]  __do_sys_finit_module+0xc7/0x190
>> [  111.999847][  T777]  __x64_sys_finit_module+0x4c/0x60
>> [  112.023326][  T777]  do_syscall_64+0x91/0xb47
>> [  112.043903][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> [  112.070954][  T777] 
>> [  112.081261][  T777] read to 0xffffffff9a19cde0 of 8 bytes by task 777 on cpu 16:
>> [  112.115510][  T777]  __change_page_attr+0xe81/0x1620
>> [  112.138564][  T777]  __change_page_attr_set_clr+0xde/0x4c0
>> [  112.164452][  T777]  __set_pages_p+0xcc/0x100
>> [  112.185228][  T777]  __kernel_map_pages+0x2e/0xdb
>> [  112.207122][  T777]  prep_new_page+0x87/0x1f0
>> [  112.227507][  T777]  get_page_from_freelist+0x1583/0x22b0
>> [  112.252947][  T777]  __alloc_pages_nodemask+0x1b1/0x450
>> [  112.277504][  T777]  alloc_pages_current+0xa6/0x120
>> [  112.300450][  T777]  alloc_slab_page+0x3b1/0x540
>> [  112.322039][  T777]  allocate_slab+0x70/0x660
>> [  112.342387][  T777]  new_slab+0x46/0x70
>> [  112.360102][  T777]  ___slab_alloc+0x4ad/0x7d0
>> [  112.380944][  T777]  __slab_alloc+0x43/0x70
>> [  112.400596][  T777]  kmem_cache_alloc+0x2c3/0x420
>> [  112.423674][  T777]  create_object+0x69/0x690
>> [  112.447347][  T777]  kmemleak_alloc+0x7d/0xb0
>> [  112.469100][  T777]  __kmalloc_track_caller+0x157/0x3c0
>> [  112.493548][  T777]  kstrdup+0x3d/0x70
>> [  112.510959][  T777]  mod_sysfs_setup+0x5e5/0xb10
>> [  112.532234][  T777]  load_module+0x2510/0x2b60
>> [  112.552985][  T777]  __do_sys_finit_module+0x14d/0x190
>> [  112.577212][  T777]  __x64_sys_finit_module+0x4c/0x60
>> [  112.601135][  T777]  do_syscall_64+0x91/0xb47
>> [  112.621690][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> [  112.648566][  T777] 
>> [  112.659018][  T777] Reported by Kernel Concurrency Sanitizer on:
>> [  112.687603][  T777] CPU: 16 PID: 777 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
>> [  112.729082][  T777] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
>> [  112.772563][  T777] ==================================================================
>> [  112.810304][  T364] ==================================================================
>> [  112.848145][  T364] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
>> [  112.884579][  T364] 
>> [  112.884586][  T364] read to 0xffffffff9a19cde0 of 8 bytes by task 789 on cpu 12:
>> [  112.884595][  T364]  __change_page_attr+0xe81/0x1620
>> [  112.884602][  T364]  __change_page_attr_set_clr+0xde/0x4c0
>> [  112.884607][  T364]  __set_pages_p+0xcc/0x100
>> [  112.884612][  T364]  __kernel_map_pages+0x2e/0xdb
>>         [  112.884619][  T364]  prep_new_page+0x87/0x1f0
>> [  112.884627][  T364]  get_page_from_freelist+0x1583/0x22b0
>> [  112.884633][  T364]  __alloc_pages_nodemask+0x1b1/0x450
>> [  112.884640][  T364]  alloc_pages_vma+0x8a/0x2c0
>> [  112.884646][  T364]  wp_page_copy+0x100/0x930
>> Starting Show Pl[  112.884653][  T364]  do_wp_page+0x107/0x7b0
>> [  112.884660][  T364]  __handle_mm_fault+0xce6/0xd40
>> [  112.884667][  T364]  handle_mm_fault+0xfc/0x2f0
>> [  112.884677][  T364]  do_page_fault+0x263/0x6f9
>> ymouth Boot Screen...
>> perf: interrupt took too long (7468 > 7338), lowering kernel.perf_event_max_sample_rate to 26700
>> perf: interrupt took too long (9463 > 9335), lowering kernel.perf_event_max_sample_rate to 21100
>> 
>>> 
>>> [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
>>> [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>> [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>> [   28.992752][  T394] =============================================================== 
>>> [   28.992752][  T394] ================================================================== 
>>> [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
>>> [   28.992752][  T394]  
>>> [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
>>> [   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
>>> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
>>> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
>>> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
>>> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
>>> [   28.992752][  T394]  __free_pages+0x51/0x90 
>>> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
>>> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
>>> [   28.992752][  T394]  deferred_init_max21d 
>>> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
>>> [   28.992752][  T394]  kthread+0x1e0/0x200 
>>> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
>>> [   28.992752][  T394]  
>>> [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
>>> [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
>>> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
>>> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
>>> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
>>> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
>>> [   28.992752][  T394]  __free_pages+0x51/0x90 
>>> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
>>> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
>>> [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
>>> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
>>> [   28.992752][  T394]  kthread+0x1e0/0x200 
>>> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
>>> 
>>> 
>>> [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
>>> [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>> [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>> [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
>>> [   93.378715][  T349] ================================================================== 
>>> [   93.416183][  T616] ================================================================== 
>>> [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
>>> [   93.486775][  T616]  
>>> [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
>>> [   93.534139][  T616]  fill_pool+0x38/0x700 
>>> [   93.554913][  T616]  __debug_object_init+0x3f/0x900 
>>> [   93.579459][  T616]  debug_object_init+0x39/0x50 
>>> [   93.601952][  T616]  __init_work+0x3e/0x50 
>>> [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
>>> [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
>>> [   93.665134][  T616]  __kmalloc_node+0x60/0x300 
>>> [   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
>>> [   93.704235][  T616]  seq_read+0x57c/0x7a0 
>>> [   93.722460][  T616]  proc_reg_read+0x11a/0x160 
>>> [   93.743570][  T616]  __vfs_read+0x59/0xa0 
>>> [   93.761660][  T616]  vfs_read+0xcf/0x1c0 
>>> [   93.779269][  T616]  ksys_read+0x9d/0x130 
>>> [   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
>>> [   93.817205][  T616]  do_syscall_64+0x91/0xb47 
>>> [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>> [   93.864425][  T616]  
>>> [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
>>> [   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
>>> [   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
>>> [   93.954131][  T616]  call_rcu+0x4c/0x4e0 
>>> [   93.971959][  T616]  put_object+0x6a/0x90 
>>> [   93.989955][  T616]  __delete_object+0xb9/0xf0 
>>> [   94.009996][  T616]  delete_object_full+0x2d/0x40 
>>> [   94.031812][  T616]  kmemleak_free+0x5f/0x90 
>>> [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
>>> [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
>>> [   94.103806][  T616]  vm_area_free+0x31/0x40 
>>> [   94.124587][  T616]  remove_vma+0xb0/0xc0 
>>> [   94.143484][  T616]  exit_mmap+0x14c/0x220 
>>> [   94.163826][  T616]  mmput+0x10e/0x270 
>>> [   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
>>> [   94.202760][  T616]  load_elf_binary+0x467/0x2180 
>>> [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
>>> [   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
>>> [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
>>> [   94.292254][  T616]  do_syscall_64+0x91/0xb47 
>>> [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>> 
>>> [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
>>> [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>> [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>> [  103.561771][   C22] ================================================================== 
>>> [  103.598005][   C41] ================================================================== 
>>> [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
>>> [  103.673408][   C41]  
>>> [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
>>> [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
>>> [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
>>> [  103.762611][   C41]  update_blocked_averages+0x585/0x630 
>>> [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
>>> [  103.812821][   C41]  __do_softirq+0xd9/0x57c 
>>> [  103.834438][   C41]  irq_exit+0xa2/0xc0 
>>> [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
>>> [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
>>> [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
>>> [  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
>>> [  103.938405][   C41]  call_cpuidle+0x23/0x40 
>>> [  103.957152][   C41]  do_idle+0x248/0x280 
>>> [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
>>> [  103.995059][   C41]  start_secondary+0x1ad/0x230 
>>> [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
>>> [  104.037376][   C41]  
>>> [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
>>> [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
>>> [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
>>> [  104.127759][   C41]  update_load_avg+0x70e/0x800 
>>> [  104.148400][   C41]  task_tick_fair+0x5c/0x680 
>>> [  104.168325][   C41]  scheduler_tick+0xab/0x120 
>>> [  104.188881][   C41]  update_process_times+0x44/0x60 
>>> [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
>>> [  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
>>> [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
>>> [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
>>> [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
>>> [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
>>> [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
>>> [  104.370100][   C41]  __read_once_size+0x1f/0xe0 
>>> [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
>>> [  104.413591][   C41]  on_each_cpu+0x46/0x90 
>>> [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
>>> [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
>>> [  104.476699][   C41]  remove_vm_area+0xf4/0x100 
>>> [  104.496763][   C41]  __vunmap+0x10a/0x460 
>>> [  104.514807][   C41]  __vfree+0x33/0x90 
>>> [  104.531597][   C41]  vfree+0x47/0x80 
>>> [  104.547600][   C41]  n_tty_close+0x56/0x80 
>>> [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
>>> [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
>>> [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
>>> [  104.627098][   C41]  tty_release_struct+0x23/0x60 
>>> [  104.648268][   C41]  tty_release+0x673/0x9c0 
>>> [  104.667517][   C41]  __fput+0x187/0x410 
>>> [  104.684357][   C41]  ____fput+0x1e/0x30 
>>> [  104.701542][   C41]  task_work_run+0xed/0x140 
>>> [  104.721358][   C41]  do_syscall_64+0x803/0xb47 
>>> [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>> 
>>> [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
>>> [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>> [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>> [  136.861974][   C34] ================================================================== 
>>> [  136.911354][    T1] ================================================================== 
>>> [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
>>> [  136.981645][    T1]  
>>> [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
>>> [  137.026513][    T1]  fill_pool+0x38/0x700 
>>> [  137.045575][    T1]  __debug_object_init+0x3f/0x900 
>>> [  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
>>> [  137.093102][    T1]  call_rcu+0x4c/0x4e0 
>>> [  137.111520][    T1]  __fput+0x23a/0x410 
>>> [  137.129618][    T1]  ____fput+0x1e/0x30 
>>> [  137.147627][    T1]  task_work_run+0xed/0x140 
>>> [  137.168322][    T1]  do_syscall_64+0x803/0xb47 
>>> [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>> [  137.215309][    T1]  
>>> [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
>>> [  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
>>> [  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
>>> [  137.306988][    T1]  call_rcu+0x4c/0x4e0 
>>> [  137.326804][    T1]  dentry_free+0x70/0xe0 
>>> [  137.347208][    T1]  __dentry_kill+0x1db/0x300 
>>> [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
>>> [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
>>> [  137.417174][    T1]  d_invalidate+0x80/0x130 
>>> [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
>>> [  137.459263][    T1]  release_task.part.21+0x156/0xb50 
>>> [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
>>> [  137.507550][    T1]  do_wait+0x25b/0x560 
>>> [  137.526175][    T1]  kernel_waitid+0x194/0x270 
>>> [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
>>> [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
>>> [  137.590291][    T1]  do_syscall_64+0x91/0xb47 
>>> [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16 17:50             ` Qian Cai
@ 2020-01-16 17:55               ` Qian Cai
  0 siblings, 0 replies; 15+ messages in thread
From: Qian Cai @ 2020-01-16 17:55 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon



> On Jan 16, 2020, at 12:50 PM, Qian Cai <cai@lca.pw> wrote:
> 
> 
> 
>> On Jan 16, 2020, at 12:40 PM, Paul E. McKenney <paulmck@kernel.org> wrote:
>> 
>> On Wed, Jan 15, 2020 at 11:37:47PM -0500, Qian Cai wrote:
>>> 
>>>> On Jan 15, 2020, at 10:39 PM, Qian Cai <cai@lca.pw> wrote:
>>>>> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
>>>>> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
>>>>>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
>>>>>>> 
>>>>>>>> --- a/kernel/kcsan/core.c
>>>>>>>> +++ b/kernel/kcsan/core.c
>>>>>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>>>>>      *      detection point of view) to simply disable preemptions to ensure
>>>>>>>>      *      as many tasks as possible run on other CPUs.
>>>>>>>>      */
>>>>>>>> -       local_irq_save(irq_flags);
>>>>>>>> +       raw_local_irq_save(irq_flags);
>>>>>>> 
>>>>>>> Please reflect the need to use raw_local_irq_save() in the comment.
>>>>>>> 
>>>>>>>> 
>>>>>>>>     watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
>>>>>>>>     if (watchpoint == NULL) {
>>>>>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
>>>>>>>> 
>>>>>>>>     kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
>>>>>>>> out_unlock:
>>>>>>>> -       local_irq_restore(irq_flags);
>>>>>>>> +       raw_local_irq_restore(irq_flags);
>>>>>>> 
>>>>>>> Ditto
>>>>>> 
>>>>>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
>>>>> 
>>>>> Alexander and Qian, could you please let me know if this fixes things
>>>>> up for you?
>>>> 
>>>> The lockdep warning is gone, so feel free to add,
>>>> 
>>>> Tested-by: Qian Cai <cai@lca.pw>
>>>> 
>>>> for that patch, but the system is still unable to boot due to spam of
>>>> warnings due to incompatible with debug_pagealloc, debugobjects, so
>>>> the warning rate limit does not help.
>>> 
>>> I set CONFIG_DEBUG_OBJECTS=n to see how further it could go, but
>>> the kernel is dead after those lines. Unable to boot any further.
>> 
>> How large a system are you running on?  The reason that I ask is that I
>> have been running it on a 12-CPU system with and without lockdep for some
>> time.  So perhaps you are running this on a large system (thus indicating
>> a need for better scalability) or are using an additional Kconfig option?
> 
> The system has 64 CPUs with additional debug options enabled,
> 
> https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config

Forgot to mention, just deselect KASAN and select KCSAN there to reproduce.

> 
>> 
>>> …
>>> [  111.345991][  T789] Reported by Kernel Concurrency Sanitizer on:
>>> [  111.373039][  T789] CPU: 44 PID: 789 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
>>> [  111.414596][  T789] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
>>> [  111.459984][  T789] ==================================================================
>>> [  111.554563][  T777] ==================================================================
>>> [  111.590304][  T777] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
>>> [  111.626392][  T777] 
>>> [  111.636881][  T777] write to 0xffffffff9a19cde0 of 8 bytes by task 796 on cpu 1:
>>> [  111.671544][  T777]  __change_page_attr+0xe9c/0x1620
>>> [  111.695067][  T777]  __change_page_attr_set_clr+0xde/0x4c0
>>> [  111.722124][  T777]  __set_pages_p+0xcc/0x100
>>> [  111.742644][  T777]  __kernel_map_pages+0x2e/0xdb
>>> [  111.765379][  T777]  prep_new_page+0x87/0x1f0
>>> [  111.785804][  T777]  get_page_from_freelist+0x1583/0x22b0
>>> [  111.810633][  T777]  __alloc_pages_nodemask+0x1b1/0x450
>>> [  111.835196][  T777]  alloc_pages_current+0xa6/0x120
>>> [  111.858619][  T777]  __vmalloc_node_range+0x338/0x480
>>> [  111.882253][  T777]  __vmalloc_node.constprop.29+0x70/0xb0
>>> [  111.908550][  T777]  vmalloc+0x69/0x80
>>> [  111.927150][  T777]  kernel_read_file+0x241/0x2b0
>>> [  111.950372][  T777]  kernel_read_file_from_fd+0x56/0x90
>>> [  111.976025][  T777]  __do_sys_finit_module+0xc7/0x190
>>> [  111.999847][  T777]  __x64_sys_finit_module+0x4c/0x60
>>> [  112.023326][  T777]  do_syscall_64+0x91/0xb47
>>> [  112.043903][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>> [  112.070954][  T777] 
>>> [  112.081261][  T777] read to 0xffffffff9a19cde0 of 8 bytes by task 777 on cpu 16:
>>> [  112.115510][  T777]  __change_page_attr+0xe81/0x1620
>>> [  112.138564][  T777]  __change_page_attr_set_clr+0xde/0x4c0
>>> [  112.164452][  T777]  __set_pages_p+0xcc/0x100
>>> [  112.185228][  T777]  __kernel_map_pages+0x2e/0xdb
>>> [  112.207122][  T777]  prep_new_page+0x87/0x1f0
>>> [  112.227507][  T777]  get_page_from_freelist+0x1583/0x22b0
>>> [  112.252947][  T777]  __alloc_pages_nodemask+0x1b1/0x450
>>> [  112.277504][  T777]  alloc_pages_current+0xa6/0x120
>>> [  112.300450][  T777]  alloc_slab_page+0x3b1/0x540
>>> [  112.322039][  T777]  allocate_slab+0x70/0x660
>>> [  112.342387][  T777]  new_slab+0x46/0x70
>>> [  112.360102][  T777]  ___slab_alloc+0x4ad/0x7d0
>>> [  112.380944][  T777]  __slab_alloc+0x43/0x70
>>> [  112.400596][  T777]  kmem_cache_alloc+0x2c3/0x420
>>> [  112.423674][  T777]  create_object+0x69/0x690
>>> [  112.447347][  T777]  kmemleak_alloc+0x7d/0xb0
>>> [  112.469100][  T777]  __kmalloc_track_caller+0x157/0x3c0
>>> [  112.493548][  T777]  kstrdup+0x3d/0x70
>>> [  112.510959][  T777]  mod_sysfs_setup+0x5e5/0xb10
>>> [  112.532234][  T777]  load_module+0x2510/0x2b60
>>> [  112.552985][  T777]  __do_sys_finit_module+0x14d/0x190
>>> [  112.577212][  T777]  __x64_sys_finit_module+0x4c/0x60
>>> [  112.601135][  T777]  do_syscall_64+0x91/0xb47
>>> [  112.621690][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>> [  112.648566][  T777] 
>>> [  112.659018][  T777] Reported by Kernel Concurrency Sanitizer on:
>>> [  112.687603][  T777] CPU: 16 PID: 777 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
>>> [  112.729082][  T777] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
>>> [  112.772563][  T777] ==================================================================
>>> [  112.810304][  T364] ==================================================================
>>> [  112.848145][  T364] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
>>> [  112.884579][  T364] 
>>> [  112.884586][  T364] read to 0xffffffff9a19cde0 of 8 bytes by task 789 on cpu 12:
>>> [  112.884595][  T364]  __change_page_attr+0xe81/0x1620
>>> [  112.884602][  T364]  __change_page_attr_set_clr+0xde/0x4c0
>>> [  112.884607][  T364]  __set_pages_p+0xcc/0x100
>>> [  112.884612][  T364]  __kernel_map_pages+0x2e/0xdb
>>>        [  112.884619][  T364]  prep_new_page+0x87/0x1f0
>>> [  112.884627][  T364]  get_page_from_freelist+0x1583/0x22b0
>>> [  112.884633][  T364]  __alloc_pages_nodemask+0x1b1/0x450
>>> [  112.884640][  T364]  alloc_pages_vma+0x8a/0x2c0
>>> [  112.884646][  T364]  wp_page_copy+0x100/0x930
>>> Starting Show Pl[  112.884653][  T364]  do_wp_page+0x107/0x7b0
>>> [  112.884660][  T364]  __handle_mm_fault+0xce6/0xd40
>>> [  112.884667][  T364]  handle_mm_fault+0xfc/0x2f0
>>> [  112.884677][  T364]  do_page_fault+0x263/0x6f9
>>> ymouth Boot Screen...
>>> perf: interrupt took too long (7468 > 7338), lowering kernel.perf_event_max_sample_rate to 26700
>>> perf: interrupt took too long (9463 > 9335), lowering kernel.perf_event_max_sample_rate to 21100
>>> 
>>>> 
>>>> [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
>>>> [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>>> [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>>> [   28.992752][  T394] =============================================================== 
>>>> [   28.992752][  T394] ================================================================== 
>>>> [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
>>>> [   28.992752][  T394]  
>>>> [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
>>>> [   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
>>>> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
>>>> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
>>>> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
>>>> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
>>>> [   28.992752][  T394]  __free_pages+0x51/0x90 
>>>> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
>>>> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
>>>> [   28.992752][  T394]  deferred_init_max21d 
>>>> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
>>>> [   28.992752][  T394]  kthread+0x1e0/0x200 
>>>> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
>>>> [   28.992752][  T394]  
>>>> [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
>>>> [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
>>>> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
>>>> [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
>>>> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
>>>> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
>>>> [   28.992752][  T394]  __free_pages+0x51/0x90 
>>>> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
>>>> [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
>>>> [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
>>>> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
>>>> [   28.992752][  T394]  kthread+0x1e0/0x200 
>>>> [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
>>>> 
>>>> 
>>>> [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
>>>> [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>>> [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>>> [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
>>>> [   93.378715][  T349] ================================================================== 
>>>> [   93.416183][  T616] ================================================================== 
>>>> [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
>>>> [   93.486775][  T616]  
>>>> [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
>>>> [   93.534139][  T616]  fill_pool+0x38/0x700 
>>>> [   93.554913][  T616]  __debug_object_init+0x3f/0x900 
>>>> [   93.579459][  T616]  debug_object_init+0x39/0x50 
>>>> [   93.601952][  T616]  __init_work+0x3e/0x50 
>>>> [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
>>>> [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
>>>> [   93.665134][  T616]  __kmalloc_node+0x60/0x300 
>>>> [   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
>>>> [   93.704235][  T616]  seq_read+0x57c/0x7a0 
>>>> [   93.722460][  T616]  proc_reg_read+0x11a/0x160 
>>>> [   93.743570][  T616]  __vfs_read+0x59/0xa0 
>>>> [   93.761660][  T616]  vfs_read+0xcf/0x1c0 
>>>> [   93.779269][  T616]  ksys_read+0x9d/0x130 
>>>> [   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
>>>> [   93.817205][  T616]  do_syscall_64+0x91/0xb47 
>>>> [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>>> [   93.864425][  T616]  
>>>> [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
>>>> [   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
>>>> [   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
>>>> [   93.954131][  T616]  call_rcu+0x4c/0x4e0 
>>>> [   93.971959][  T616]  put_object+0x6a/0x90 
>>>> [   93.989955][  T616]  __delete_object+0xb9/0xf0 
>>>> [   94.009996][  T616]  delete_object_full+0x2d/0x40 
>>>> [   94.031812][  T616]  kmemleak_free+0x5f/0x90 
>>>> [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
>>>> [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
>>>> [   94.103806][  T616]  vm_area_free+0x31/0x40 
>>>> [   94.124587][  T616]  remove_vma+0xb0/0xc0 
>>>> [   94.143484][  T616]  exit_mmap+0x14c/0x220 
>>>> [   94.163826][  T616]  mmput+0x10e/0x270 
>>>> [   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
>>>> [   94.202760][  T616]  load_elf_binary+0x467/0x2180 
>>>> [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
>>>> [   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
>>>> [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
>>>> [   94.292254][  T616]  do_syscall_64+0x91/0xb47 
>>>> [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>>> 
>>>> [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
>>>> [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>>> [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>>> [  103.561771][   C22] ================================================================== 
>>>> [  103.598005][   C41] ================================================================== 
>>>> [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
>>>> [  103.673408][   C41]  
>>>> [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
>>>> [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
>>>> [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
>>>> [  103.762611][   C41]  update_blocked_averages+0x585/0x630 
>>>> [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
>>>> [  103.812821][   C41]  __do_softirq+0xd9/0x57c 
>>>> [  103.834438][   C41]  irq_exit+0xa2/0xc0 
>>>> [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
>>>> [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
>>>> [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
>>>> [  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
>>>> [  103.938405][   C41]  call_cpuidle+0x23/0x40 
>>>> [  103.957152][   C41]  do_idle+0x248/0x280 
>>>> [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
>>>> [  103.995059][   C41]  start_secondary+0x1ad/0x230 
>>>> [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
>>>> [  104.037376][   C41]  
>>>> [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
>>>> [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
>>>> [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
>>>> [  104.127759][   C41]  update_load_avg+0x70e/0x800 
>>>> [  104.148400][   C41]  task_tick_fair+0x5c/0x680 
>>>> [  104.168325][   C41]  scheduler_tick+0xab/0x120 
>>>> [  104.188881][   C41]  update_process_times+0x44/0x60 
>>>> [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
>>>> [  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
>>>> [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
>>>> [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
>>>> [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
>>>> [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
>>>> [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
>>>> [  104.370100][   C41]  __read_once_size+0x1f/0xe0 
>>>> [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
>>>> [  104.413591][   C41]  on_each_cpu+0x46/0x90 
>>>> [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
>>>> [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
>>>> [  104.476699][   C41]  remove_vm_area+0xf4/0x100 
>>>> [  104.496763][   C41]  __vunmap+0x10a/0x460 
>>>> [  104.514807][   C41]  __vfree+0x33/0x90 
>>>> [  104.531597][   C41]  vfree+0x47/0x80 
>>>> [  104.547600][   C41]  n_tty_close+0x56/0x80 
>>>> [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
>>>> [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
>>>> [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
>>>> [  104.627098][   C41]  tty_release_struct+0x23/0x60 
>>>> [  104.648268][   C41]  tty_release+0x673/0x9c0 
>>>> [  104.667517][   C41]  __fput+0x187/0x410 
>>>> [  104.684357][   C41]  ____fput+0x1e/0x30 
>>>> [  104.701542][   C41]  task_work_run+0xed/0x140 
>>>> [  104.721358][   C41]  do_syscall_64+0x803/0xb47 
>>>> [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>>> 
>>>> [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
>>>> [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
>>>> [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
>>>> [  136.861974][   C34] ================================================================== 
>>>> [  136.911354][    T1] ================================================================== 
>>>> [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
>>>> [  136.981645][    T1]  
>>>> [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
>>>> [  137.026513][    T1]  fill_pool+0x38/0x700 
>>>> [  137.045575][    T1]  __debug_object_init+0x3f/0x900 
>>>> [  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
>>>> [  137.093102][    T1]  call_rcu+0x4c/0x4e0 
>>>> [  137.111520][    T1]  __fput+0x23a/0x410 
>>>> [  137.129618][    T1]  ____fput+0x1e/0x30 
>>>> [  137.147627][    T1]  task_work_run+0xed/0x140 
>>>> [  137.168322][    T1]  do_syscall_64+0x803/0xb47 
>>>> [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>>>> [  137.215309][    T1]  
>>>> [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
>>>> [  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
>>>> [  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
>>>> [  137.306988][    T1]  call_rcu+0x4c/0x4e0 
>>>> [  137.326804][    T1]  dentry_free+0x70/0xe0 
>>>> [  137.347208][    T1]  __dentry_kill+0x1db/0x300 
>>>> [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
>>>> [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
>>>> [  137.417174][    T1]  d_invalidate+0x80/0x130 
>>>> [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
>>>> [  137.459263][    T1]  release_task.part.21+0x156/0xb50 
>>>> [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
>>>> [  137.507550][    T1]  do_wait+0x25b/0x560 
>>>> [  137.526175][    T1]  kernel_waitid+0x194/0x270 
>>>> [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
>>>> [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
>>>> [  137.590291][    T1]  do_syscall_64+0x91/0xb47 
>>>> [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16  3:39       ` Qian Cai
  2020-01-16  4:37         ` Qian Cai
@ 2020-01-16 18:57         ` Marco Elver
  2020-01-17 16:40           ` Paul E. McKenney
  1 sibling, 1 reply; 15+ messages in thread
From: Marco Elver @ 2020-01-16 18:57 UTC (permalink / raw)
  To: Qian Cai
  Cc: Paul E. McKenney, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon

On Thu, 16 Jan 2020 at 04:39, Qian Cai <cai@lca.pw> wrote:
>
>
>
> > On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> >> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> >>>
> >>>> --- a/kernel/kcsan/core.c
> >>>> +++ b/kernel/kcsan/core.c
> >>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>         *      detection point of view) to simply disable preemptions to ensure
> >>>>         *      as many tasks as possible run on other CPUs.
> >>>>         */
> >>>> -       local_irq_save(irq_flags);
> >>>> +       raw_local_irq_save(irq_flags);
> >>>
> >>> Please reflect the need to use raw_local_irq_save() in the comment.
> >>>
> >>>>
> >>>>        watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> >>>>        if (watchpoint == NULL) {
> >>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>
> >>>>        kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> >>>> out_unlock:
> >>>> -       local_irq_restore(irq_flags);
> >>>> +       raw_local_irq_restore(irq_flags);
> >>>
> >>> Ditto
> >>
> >> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> >
> > Alexander and Qian, could you please let me know if this fixes things
> > up for you?
>
> The lockdep warning is gone, so feel free to add,
>
> Tested-by: Qian Cai <cai@lca.pw>

Thank you for testing!

> for that patch, but the system is still unable to boot due to spam of
> warnings due to incompatible with debug_pagealloc, debugobjects, so
> the warning rate limit does not help.

You may also try to set CONFIG_KCSAN_REPORT_ONCE_IN_MS to something
large, say 1000000000 (effectively reporting each data race once).

That being said, there are 2 options here:

Option 1. If that still isn't satisfactory, we can try to make the
system somehow tolerate the excessive number of data race reports
(there may indeed be other printk limits based on rate or context we
are hitting). More important appears to be the below...

Option 2. Investigate and fix the bugs, or declare them "benign" to
the tool. Compared to option (1) this will have much bigger impact on
the kernel, as it not only improves the kernel with all the debugging
tools enabled, but more importantly, improves the kernel *without* the
debugging tools. This is what should be our goal here.

With that in mind, I tried to fix debugobjects data races:
  http://lkml.kernel.org/r/20200116185529.11026-1-elver@google.com
Feel free to test, and reply to that patch with comments.

Thanks,
-- Marco






> [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on:
> [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3
> [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [   28.992752][  T394] ===============================================================
> [   28.992752][  T394] ==================================================================
> [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [   28.992752][  T394]
> [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16:
> [   28.992752][  T394]  __change_page_attr+0xe81/0x1620
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> [   28.992752][  T394]  __free_pages+0x51/0x90
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> [   28.992752][  T394]  deferred_init_max21d
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> [   28.992752][  T394]  kthread+0x1e0/0x200
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> [   28.992752][  T394]
> [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0:
> [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> [   28.992752][  T394]  __free_pages+0x51/0x90
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> [   28.992752][  T394]  kthread+0x1e0/0x200
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50
>
>
> [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on:
> [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3
> [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func
> [   93.378715][  T349] ==================================================================
> [   93.416183][  T616] ==================================================================
> [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> [   93.486775][  T616]
> [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12:
> [   93.534139][  T616]  fill_pool+0x38/0x700
> [   93.554913][  T616]  __debug_object_init+0x3f/0x900
> [   93.579459][  T616]  debug_object_init+0x39/0x50
> [   93.601952][  T616]  __init_work+0x3e/0x50
> [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480
> [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0
> [   93.665134][  T616]  __kmalloc_node+0x60/0x300
> [   93.685094][  T616]  kvmalloc_node+0x83/0xa0
> [   93.704235][  T616]  seq_read+0x57c/0x7a0
> [   93.722460][  T616]  proc_reg_read+0x11a/0x160
> [   93.743570][  T616]  __vfs_read+0x59/0xa0
> [   93.761660][  T616]  vfs_read+0xcf/0x1c0
> [   93.779269][  T616]  ksys_read+0x9d/0x130
> [   93.797267][  T616]  __x64_sys_read+0x4c/0x60
> [   93.817205][  T616]  do_syscall_64+0x91/0xb47
> [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [   93.864425][  T616]
> [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61:
> [   93.908534][  T616]  __debug_object_init+0x6e5/0x900
> [   93.931018][  T616]  debug_object_activate+0x1fc/0x350
> [   93.954131][  T616]  call_rcu+0x4c/0x4e0
> [   93.971959][  T616]  put_object+0x6a/0x90
> [   93.989955][  T616]  __delete_object+0xb9/0xf0
> [   94.009996][  T616]  delete_object_full+0x2d/0x40
> [   94.031812][  T616]  kmemleak_free+0x5f/0x90
> [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0
> [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0
> [   94.103806][  T616]  vm_area_free+0x31/0x40
> [   94.124587][  T616]  remove_vma+0xb0/0xc0
> [   94.143484][  T616]  exit_mmap+0x14c/0x220
> [   94.163826][  T616]  mmput+0x10e/0x270
> [   94.181736][  T616]  flush_old_exec+0x572/0xfe0
> [   94.202760][  T616]  load_elf_binary+0x467/0x2180
> [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0
> [   94.248735][  T616]  __do_execve_file+0xb61/0x1080
> [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70
> [   94.292254][  T616]  do_syscall_64+0x91/0xb47
> [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on:
> [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3
> [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  103.561771][   C22] ==================================================================
> [  103.598005][   C41] ==================================================================
> [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util
> [  103.673408][   C41]
> [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2:
> [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40
> [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160
> [  103.762611][   C41]  update_blocked_averages+0x585/0x630
> [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240
> [  103.812821][   C41]  __do_softirq+0xd9/0x57c
> [  103.834438][   C41]  irq_exit+0xa2/0xc0
> [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480
> [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20
> [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0
> [  103.919324][   C41]  cpuidle_enter+0x69/0xc0
> [  103.938405][   C41]  call_cpuidle+0x23/0x40
> [  103.957152][   C41]  do_idle+0x248/0x280
> [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f
> [  103.995059][   C41]  start_secondary+0x1ad/0x230
> [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0
> [  104.037376][   C41]
> [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41:
> [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40
> [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160
> [  104.127759][   C41]  update_load_avg+0x70e/0x800
> [  104.148400][   C41]  task_tick_fair+0x5c/0x680
> [  104.168325][   C41]  scheduler_tick+0xab/0x120
> [  104.188881][   C41]  update_process_times+0x44/0x60
> [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0
> [  104.231137][   C41]  tick_sched_timer+0x45/0xc0
> [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800
> [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0
> [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480
> [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20
> [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120
> [  104.370100][   C41]  __read_once_size+0x1f/0xe0
> [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0
> [  104.413591][   C41]  on_each_cpu+0x46/0x90
> [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0
> [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0
> [  104.476699][   C41]  remove_vm_area+0xf4/0x100
> [  104.496763][   C41]  __vunmap+0x10a/0x460
> [  104.514807][   C41]  __vfree+0x33/0x90
> [  104.531597][   C41]  vfree+0x47/0x80
> [  104.547600][   C41]  n_tty_close+0x56/0x80
> [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0
> [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0
> [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0
> [  104.627098][   C41]  tty_release_struct+0x23/0x60
> [  104.648268][   C41]  tty_release+0x673/0x9c0
> [  104.667517][   C41]  __fput+0x187/0x410
> [  104.684357][   C41]  ____fput+0x1e/0x30
> [  104.701542][   C41]  task_work_run+0xed/0x140
> [  104.721358][   C41]  do_syscall_64+0x803/0xb47
> [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on:
> [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3
> [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  136.861974][   C34] ==================================================================
> [  136.911354][    T1] ==================================================================
> [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> [  136.981645][    T1]
> [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25:
> [  137.026513][    T1]  fill_pool+0x38/0x700
> [  137.045575][    T1]  __debug_object_init+0x3f/0x900
> [  137.068826][    T1]  debug_object_activate+0x1fc/0x350
> [  137.093102][    T1]  call_rcu+0x4c/0x4e0
> [  137.111520][    T1]  __fput+0x23a/0x410
> [  137.129618][    T1]  ____fput+0x1e/0x30
> [  137.147627][    T1]  task_work_run+0xed/0x140
> [  137.168322][    T1]  do_syscall_64+0x803/0xb47
> [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  137.215309][    T1]
> [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7:
> [  137.259867][    T1]  __debug_object_init+0x6e5/0x900
> [  137.283065][    T1]  debug_object_activate+0x1fc/0x350
> [  137.306988][    T1]  call_rcu+0x4c/0x4e0
> [  137.326804][    T1]  dentry_free+0x70/0xe0
> [  137.347208][    T1]  __dentry_kill+0x1db/0x300
> [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0
> [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320
> [  137.417174][    T1]  d_invalidate+0x80/0x130
> [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0
> [  137.459263][    T1]  release_task.part.21+0x156/0xb50
> [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960
> [  137.507550][    T1]  do_wait+0x25b/0x560
> [  137.526175][    T1]  kernel_waitid+0x194/0x270
> [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0
> [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90
> [  137.590291][    T1]  do_syscall_64+0x91/0xb47
> [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-16 18:57         ` Marco Elver
@ 2020-01-17 16:40           ` Paul E. McKenney
  2020-01-17 16:59             ` Qian Cai
  2020-01-17 22:54             ` Marco Elver
  0 siblings, 2 replies; 15+ messages in thread
From: Paul E. McKenney @ 2020-01-17 16:40 UTC (permalink / raw)
  To: Marco Elver
  Cc: Qian Cai, Alexander Potapenko, Andrey Konovalov, Dmitriy Vyukov,
	kasan-dev, LKML, Peter Zijlstra, Ingo Molnar, Will Deacon

On Thu, Jan 16, 2020 at 07:57:30PM +0100, Marco Elver wrote:
> On Thu, 16 Jan 2020 at 04:39, Qian Cai <cai@lca.pw> wrote:
> > > On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> > > On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> > >> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> > >>>
> > >>>> --- a/kernel/kcsan/core.c
> > >>>> +++ b/kernel/kcsan/core.c
> > >>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > >>>>         *      detection point of view) to simply disable preemptions to ensure
> > >>>>         *      as many tasks as possible run on other CPUs.
> > >>>>         */
> > >>>> -       local_irq_save(irq_flags);
> > >>>> +       raw_local_irq_save(irq_flags);
> > >>>
> > >>> Please reflect the need to use raw_local_irq_save() in the comment.
> > >>>
> > >>>>
> > >>>>        watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> > >>>>        if (watchpoint == NULL) {
> > >>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > >>>>
> > >>>>        kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> > >>>> out_unlock:
> > >>>> -       local_irq_restore(irq_flags);
> > >>>> +       raw_local_irq_restore(irq_flags);
> > >>>
> > >>> Ditto
> > >>
> > >> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> > >
> > > Alexander and Qian, could you please let me know if this fixes things
> > > up for you?
> >
> > The lockdep warning is gone, so feel free to add,
> >
> > Tested-by: Qian Cai <cai@lca.pw>
> 
> Thank you for testing!
> 
> > for that patch, but the system is still unable to boot due to spam of
> > warnings due to incompatible with debug_pagealloc, debugobjects, so
> > the warning rate limit does not help.
> 
> You may also try to set CONFIG_KCSAN_REPORT_ONCE_IN_MS to something
> large, say 1000000000 (effectively reporting each data race once).
> 
> That being said, there are 2 options here:
> 
> Option 1. If that still isn't satisfactory, we can try to make the
> system somehow tolerate the excessive number of data race reports
> (there may indeed be other printk limits based on rate or context we
> are hitting). More important appears to be the below...
> 
> Option 2. Investigate and fix the bugs, or declare them "benign" to
> the tool. Compared to option (1) this will have much bigger impact on
> the kernel, as it not only improves the kernel with all the debugging
> tools enabled, but more importantly, improves the kernel *without* the
> debugging tools. This is what should be our goal here.

True enough, but even if we reach the nirvana state where there is general
agreement on what constitutes a data race in need of fixing and KCSAN
faithfully checks based on that data-race definition, we need to handle
the case where someone introduces a bug that results in a destructive
off-CPU access to a per-CPU variable, which is exactly the sort of thing
that KCSAN is supposed to detect.  But suppose that this variable is
frequently referenced from functions that are inlined all over the place.

Then that one bug might result in huge numbers of data-race reports in
a very short period of time, especially on a large system.

So, yes, option 2 is important, but it is in no way a substitute for
KCSAN doing a good job of handling of option 1.

And given limited console bandwidth, there will be cases where data-race
reports
must be dropped.  After all, in such cases, the only other option is to
hang the system.  There are ways to reduce the number of such cases, and
of course your recent (and much appreciated!) patches merging identical
reports is a great example of this.  But Qian's experience indicates that
this does not cover all cases -- nor would I expect it to have done so.

> With that in mind, I tried to fix debugobjects data races:
>   http://lkml.kernel.org/r/20200116185529.11026-1-elver@google.com
> Feel free to test, and reply to that patch with comments.

Very good!

For my part, I am quite a bit closer to having RCU free of KCSAN reports.
One of the remaining ones looks related to a bug in rcu_barrier()'s
handling of no-CBs CPUs that shows up once per few hundred hours
of rcutorture testing of TREE04.  KCSAN did find some real bugs, so
thank you!  Sadly, it does not (yet) find this one, but it does find
consequences of it, which will at least reduce the testing burden once
I do get it fixed.

(So, yes, if anyone is seeing rcu_barrier() returning too soon on systems
with CONFIG_RCU_NOCB_CPU=y on a system whose console output includes the
string "Offload RCU callbacks from CPUs" with at least one CPU listed
(as opposed to the string "(none)", please do let me know!  My best
guess is that this was introduced in v5.4.)

							Thanx, Paul

> Thanks,
> -- Marco
> 
> 
> 
> 
> 
> 
> > [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on:
> > [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3
> > [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > [   28.992752][  T394] ===============================================================
> > [   28.992752][  T394] ==================================================================
> > [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> > [   28.992752][  T394]
> > [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16:
> > [   28.992752][  T394]  __change_page_attr+0xe81/0x1620
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > [   28.992752][  T394]  __free_pages+0x51/0x90
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > [   28.992752][  T394]  deferred_init_max21d
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > [   28.992752][  T394]  kthread+0x1e0/0x200
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> > [   28.992752][  T394]
> > [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0:
> > [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > [   28.992752][  T394]  __free_pages+0x51/0x90
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > [   28.992752][  T394]  kthread+0x1e0/0x200
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> >
> >
> > [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on:
> > [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3
> > [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func
> > [   93.378715][  T349] ==================================================================
> > [   93.416183][  T616] ==================================================================
> > [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > [   93.486775][  T616]
> > [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12:
> > [   93.534139][  T616]  fill_pool+0x38/0x700
> > [   93.554913][  T616]  __debug_object_init+0x3f/0x900
> > [   93.579459][  T616]  debug_object_init+0x39/0x50
> > [   93.601952][  T616]  __init_work+0x3e/0x50
> > [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480
> > [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0
> > [   93.665134][  T616]  __kmalloc_node+0x60/0x300
> > [   93.685094][  T616]  kvmalloc_node+0x83/0xa0
> > [   93.704235][  T616]  seq_read+0x57c/0x7a0
> > [   93.722460][  T616]  proc_reg_read+0x11a/0x160
> > [   93.743570][  T616]  __vfs_read+0x59/0xa0
> > [   93.761660][  T616]  vfs_read+0xcf/0x1c0
> > [   93.779269][  T616]  ksys_read+0x9d/0x130
> > [   93.797267][  T616]  __x64_sys_read+0x4c/0x60
> > [   93.817205][  T616]  do_syscall_64+0x91/0xb47
> > [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > [   93.864425][  T616]
> > [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61:
> > [   93.908534][  T616]  __debug_object_init+0x6e5/0x900
> > [   93.931018][  T616]  debug_object_activate+0x1fc/0x350
> > [   93.954131][  T616]  call_rcu+0x4c/0x4e0
> > [   93.971959][  T616]  put_object+0x6a/0x90
> > [   93.989955][  T616]  __delete_object+0xb9/0xf0
> > [   94.009996][  T616]  delete_object_full+0x2d/0x40
> > [   94.031812][  T616]  kmemleak_free+0x5f/0x90
> > [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0
> > [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0
> > [   94.103806][  T616]  vm_area_free+0x31/0x40
> > [   94.124587][  T616]  remove_vma+0xb0/0xc0
> > [   94.143484][  T616]  exit_mmap+0x14c/0x220
> > [   94.163826][  T616]  mmput+0x10e/0x270
> > [   94.181736][  T616]  flush_old_exec+0x572/0xfe0
> > [   94.202760][  T616]  load_elf_binary+0x467/0x2180
> > [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0
> > [   94.248735][  T616]  __do_execve_file+0xb61/0x1080
> > [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70
> > [   94.292254][  T616]  do_syscall_64+0x91/0xb47
> > [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on:
> > [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3
> > [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > [  103.561771][   C22] ==================================================================
> > [  103.598005][   C41] ==================================================================
> > [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util
> > [  103.673408][   C41]
> > [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2:
> > [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40
> > [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160
> > [  103.762611][   C41]  update_blocked_averages+0x585/0x630
> > [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240
> > [  103.812821][   C41]  __do_softirq+0xd9/0x57c
> > [  103.834438][   C41]  irq_exit+0xa2/0xc0
> > [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480
> > [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20
> > [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0
> > [  103.919324][   C41]  cpuidle_enter+0x69/0xc0
> > [  103.938405][   C41]  call_cpuidle+0x23/0x40
> > [  103.957152][   C41]  do_idle+0x248/0x280
> > [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f
> > [  103.995059][   C41]  start_secondary+0x1ad/0x230
> > [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0
> > [  104.037376][   C41]
> > [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41:
> > [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40
> > [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160
> > [  104.127759][   C41]  update_load_avg+0x70e/0x800
> > [  104.148400][   C41]  task_tick_fair+0x5c/0x680
> > [  104.168325][   C41]  scheduler_tick+0xab/0x120
> > [  104.188881][   C41]  update_process_times+0x44/0x60
> > [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0
> > [  104.231137][   C41]  tick_sched_timer+0x45/0xc0
> > [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800
> > [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0
> > [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480
> > [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20
> > [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120
> > [  104.370100][   C41]  __read_once_size+0x1f/0xe0
> > [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0
> > [  104.413591][   C41]  on_each_cpu+0x46/0x90
> > [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0
> > [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0
> > [  104.476699][   C41]  remove_vm_area+0xf4/0x100
> > [  104.496763][   C41]  __vunmap+0x10a/0x460
> > [  104.514807][   C41]  __vfree+0x33/0x90
> > [  104.531597][   C41]  vfree+0x47/0x80
> > [  104.547600][   C41]  n_tty_close+0x56/0x80
> > [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0
> > [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0
> > [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0
> > [  104.627098][   C41]  tty_release_struct+0x23/0x60
> > [  104.648268][   C41]  tty_release+0x673/0x9c0
> > [  104.667517][   C41]  __fput+0x187/0x410
> > [  104.684357][   C41]  ____fput+0x1e/0x30
> > [  104.701542][   C41]  task_work_run+0xed/0x140
> > [  104.721358][   C41]  do_syscall_64+0x803/0xb47
> > [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on:
> > [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3
> > [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > [  136.861974][   C34] ==================================================================
> > [  136.911354][    T1] ==================================================================
> > [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > [  136.981645][    T1]
> > [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25:
> > [  137.026513][    T1]  fill_pool+0x38/0x700
> > [  137.045575][    T1]  __debug_object_init+0x3f/0x900
> > [  137.068826][    T1]  debug_object_activate+0x1fc/0x350
> > [  137.093102][    T1]  call_rcu+0x4c/0x4e0
> > [  137.111520][    T1]  __fput+0x23a/0x410
> > [  137.129618][    T1]  ____fput+0x1e/0x30
> > [  137.147627][    T1]  task_work_run+0xed/0x140
> > [  137.168322][    T1]  do_syscall_64+0x803/0xb47
> > [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > [  137.215309][    T1]
> > [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7:
> > [  137.259867][    T1]  __debug_object_init+0x6e5/0x900
> > [  137.283065][    T1]  debug_object_activate+0x1fc/0x350
> > [  137.306988][    T1]  call_rcu+0x4c/0x4e0
> > [  137.326804][    T1]  dentry_free+0x70/0xe0
> > [  137.347208][    T1]  __dentry_kill+0x1db/0x300
> > [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0
> > [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320
> > [  137.417174][    T1]  d_invalidate+0x80/0x130
> > [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0
> > [  137.459263][    T1]  release_task.part.21+0x156/0xb50
> > [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960
> > [  137.507550][    T1]  do_wait+0x25b/0x560
> > [  137.526175][    T1]  kernel_waitid+0x194/0x270
> > [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0
> > [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90
> > [  137.590291][    T1]  do_syscall_64+0x91/0xb47
> > [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-17 16:40           ` Paul E. McKenney
@ 2020-01-17 16:59             ` Qian Cai
  2020-01-17 22:51               ` Marco Elver
  2020-01-17 22:54             ` Marco Elver
  1 sibling, 1 reply; 15+ messages in thread
From: Qian Cai @ 2020-01-17 16:59 UTC (permalink / raw)
  To: paulmck
  Cc: Marco Elver, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon



> On Jan 17, 2020, at 11:40 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> 
> True enough, but even if we reach the nirvana state where there is general
> agreement on what constitutes a data race in need of fixing and KCSAN
> faithfully checks based on that data-race definition, we need to handle
> the case where someone introduces a bug that results in a destructive
> off-CPU access to a per-CPU variable, which is exactly the sort of thing
> that KCSAN is supposed to detect.  But suppose that this variable is
> frequently referenced from functions that are inlined all over the place.
> 
> Then that one bug might result in huge numbers of data-race reports in
> a very short period of time, especially on a large system.

It sounds like the case with debug_pagealloc where it prints a spam of those, and then the system is just dead.

[   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
[   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
[   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
[   28.992752][  T394] =============================================================== 
[   28.992752][  T394] ================================================================== 
[   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
[   28.992752][  T394]  
[   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
[   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
[   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
[   28.992752][  T394]  __set_pages_np+0xcc/0x100 
[   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
[   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
[   28.992752][  T394]  __free_pages+0x51/0x90 
[   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
[   28.992752][  T394]  deferred_free_range+0x59/0x8f 
[   28.992752][  T394]  deferred_init_max21d 
[   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
[   28.992752][  T394]  kthread+0x1e0/0x200 
[   28.992752][  T394]  ret_from_fork+0x3a/0x50 
[   28.992752][  T394]  
[   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
[   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
[   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
[   28.992752][  T394]  __set_pages_np+0xcc/0x100 
[   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
[   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
[   28.992752][  T394]  __free_pages+0x51/0x90 
[   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
[   28.992752][  T394]  deferred_free_range+0x59/0x8f 
[   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
[   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
[   28.992752][  T394]  kthread+0x1e0/0x200 
[   28.992752][  T394]  ret_from_fork+0x3a/0x50 

It point out to this,

		pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
		pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);

		cpa_inc_4k_install();
		/* Hand in lpsize = 0 to enforce the protection mechanism */
		new_prot = static_protections(new_prot, address, pfn, 1, 0,
					      CPA_PROTECT);

In static_protections(),

	/*
	 * There is no point in checking RW/NX conflicts when the requested
	 * mapping is setting the page !PRESENT.
	 */
	if (!(pgprot_val(prot) & _PAGE_PRESENT))
		return prot;

Is there a data race there?


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-17 16:59             ` Qian Cai
@ 2020-01-17 22:51               ` Marco Elver
  0 siblings, 0 replies; 15+ messages in thread
From: Marco Elver @ 2020-01-17 22:51 UTC (permalink / raw)
  To: Qian Cai
  Cc: Paul E. McKenney, Alexander Potapenko, Andrey Konovalov,
	Dmitriy Vyukov, kasan-dev, LKML, Peter Zijlstra, Ingo Molnar,
	Will Deacon

On Fri, 17 Jan 2020 at 17:59, Qian Cai <cai@lca.pw> wrote:
>
>
>
> > On Jan 17, 2020, at 11:40 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > True enough, but even if we reach the nirvana state where there is general
> > agreement on what constitutes a data race in need of fixing and KCSAN
> > faithfully checks based on that data-race definition, we need to handle
> > the case where someone introduces a bug that results in a destructive
> > off-CPU access to a per-CPU variable, which is exactly the sort of thing
> > that KCSAN is supposed to detect.  But suppose that this variable is
> > frequently referenced from functions that are inlined all over the place.
> >
> > Then that one bug might result in huge numbers of data-race reports in
> > a very short period of time, especially on a large system.
>
> It sounds like the case with debug_pagealloc where it prints a spam of those, and then the system is just dead.
>
> [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on:
> [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3
> [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [   28.992752][  T394] ===============================================================
> [   28.992752][  T394] ==================================================================
> [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [   28.992752][  T394]
> [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16:
> [   28.992752][  T394]  __change_page_attr+0xe81/0x1620
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> [   28.992752][  T394]  __free_pages+0x51/0x90
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> [   28.992752][  T394]  deferred_init_max21d
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> [   28.992752][  T394]  kthread+0x1e0/0x200
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> [   28.992752][  T394]
> [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0:
> [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620
> [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> [   28.992752][  T394]  __free_pages+0x51/0x90
> [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d
> [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> [   28.992752][  T394]  kthread+0x1e0/0x200
> [   28.992752][  T394]  ret_from_fork+0x3a/0x50
>
> It point out to this,
>
>                 pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
>                 pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
>
>                 cpa_inc_4k_install();
>                 /* Hand in lpsize = 0 to enforce the protection mechanism */
>                 new_prot = static_protections(new_prot, address, pfn, 1, 0,
>                                               CPA_PROTECT);
>
> In static_protections(),
>
>         /*
>          * There is no point in checking RW/NX conflicts when the requested
>          * mapping is setting the page !PRESENT.
>          */
>         if (!(pgprot_val(prot) & _PAGE_PRESENT))
>                 return prot;
>
> Is there a data race there?

Yes. I was finally able to reproduce this data race on linux-next (my
system doesn't crash though, maybe not enough cores?). Here is a trace
with line numbers:

read to 0xffffffffaa59a000 of 8 bytes by interrupt on cpu 7:
 cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
 __change_page_attr+0x10cf/0x1840 arch/x86/mm/pat/set_memory.c:1514
 __change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
 __set_pages_np+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2148
 __kernel_map_pages+0xb0/0xc8 arch/x86/mm/pat/set_memory.c:2178
 kernel_map_pages include/linux/mm.h:2719 [inline]
<snip>

write to 0xffffffffaa59a000 of 8 bytes by task 1 on cpu 6:
 cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
 __change_page_attr+0x10ea/0x1840 arch/x86/mm/pat/set_memory.c:1514
 __change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
 __set_pages_p+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2129
 __kernel_map_pages+0x2e/0xc8 arch/x86/mm/pat/set_memory.c:2176
 kernel_map_pages include/linux/mm.h:2719 [inline]
<snip>

Both accesses are due to the same "cpa_4k_install++" in
cpa_inc_4k_install. Now you can see that a data race here could be
potentially undesirable: depending on compiler optimizations or how
x86 executes a non-LOCK'd increment, you may lose increments, corrupt
the counter, etc. Since this counter only seems to be used for
printing some stats, this data race itself is unlikely to cause harm
to the system though.

Thanks,
-- Marco

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-17 16:40           ` Paul E. McKenney
  2020-01-17 16:59             ` Qian Cai
@ 2020-01-17 22:54             ` Marco Elver
  2020-01-17 23:23               ` Paul E. McKenney
  1 sibling, 1 reply; 15+ messages in thread
From: Marco Elver @ 2020-01-17 22:54 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Qian Cai, Alexander Potapenko, Andrey Konovalov, Dmitriy Vyukov,
	kasan-dev, LKML, Peter Zijlstra, Ingo Molnar, Will Deacon

On Fri, 17 Jan 2020 at 17:40, Paul E. McKenney <paulmck@kernel.org> wrote:
>
> On Thu, Jan 16, 2020 at 07:57:30PM +0100, Marco Elver wrote:
> > On Thu, 16 Jan 2020 at 04:39, Qian Cai <cai@lca.pw> wrote:
> > > > On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> > > > On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> > > >> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> > > >>>
> > > >>>> --- a/kernel/kcsan/core.c
> > > >>>> +++ b/kernel/kcsan/core.c
> > > >>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > > >>>>         *      detection point of view) to simply disable preemptions to ensure
> > > >>>>         *      as many tasks as possible run on other CPUs.
> > > >>>>         */
> > > >>>> -       local_irq_save(irq_flags);
> > > >>>> +       raw_local_irq_save(irq_flags);
> > > >>>
> > > >>> Please reflect the need to use raw_local_irq_save() in the comment.
> > > >>>
> > > >>>>
> > > >>>>        watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> > > >>>>        if (watchpoint == NULL) {
> > > >>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > > >>>>
> > > >>>>        kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> > > >>>> out_unlock:
> > > >>>> -       local_irq_restore(irq_flags);
> > > >>>> +       raw_local_irq_restore(irq_flags);
> > > >>>
> > > >>> Ditto
> > > >>
> > > >> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> > > >
> > > > Alexander and Qian, could you please let me know if this fixes things
> > > > up for you?
> > >
> > > The lockdep warning is gone, so feel free to add,
> > >
> > > Tested-by: Qian Cai <cai@lca.pw>
> >
> > Thank you for testing!
> >
> > > for that patch, but the system is still unable to boot due to spam of
> > > warnings due to incompatible with debug_pagealloc, debugobjects, so
> > > the warning rate limit does not help.
> >
> > You may also try to set CONFIG_KCSAN_REPORT_ONCE_IN_MS to something
> > large, say 1000000000 (effectively reporting each data race once).
> >
> > That being said, there are 2 options here:
> >
> > Option 1. If that still isn't satisfactory, we can try to make the
> > system somehow tolerate the excessive number of data race reports
> > (there may indeed be other printk limits based on rate or context we
> > are hitting). More important appears to be the below...
> >
> > Option 2. Investigate and fix the bugs, or declare them "benign" to
> > the tool. Compared to option (1) this will have much bigger impact on
> > the kernel, as it not only improves the kernel with all the debugging
> > tools enabled, but more importantly, improves the kernel *without* the
> > debugging tools. This is what should be our goal here.
>
> True enough, but even if we reach the nirvana state where there is general
> agreement on what constitutes a data race in need of fixing and KCSAN
> faithfully checks based on that data-race definition, we need to handle
> the case where someone introduces a bug that results in a destructive
> off-CPU access to a per-CPU variable, which is exactly the sort of thing
> that KCSAN is supposed to detect.  But suppose that this variable is
> frequently referenced from functions that are inlined all over the place.
>
> Then that one bug might result in huge numbers of data-race reports in
> a very short period of time, especially on a large system.
>
> So, yes, option 2 is important, but it is in no way a substitute for
> KCSAN doing a good job of handling of option 1.
>
> And given limited console bandwidth, there will be cases where data-race
> reports
> must be dropped.  After all, in such cases, the only other option is to
> hang the system.  There are ways to reduce the number of such cases, and
> of course your recent (and much appreciated!) patches merging identical
> reports is a great example of this.  But Qian's experience indicates that
> this does not cover all cases -- nor would I expect it to have done so.

Agreed. And I'll keep looking into this.

> > With that in mind, I tried to fix debugobjects data races:
> >   http://lkml.kernel.org/r/20200116185529.11026-1-elver@google.com
> > Feel free to test, and reply to that patch with comments.
>
> Very good!
>
> For my part, I am quite a bit closer to having RCU free of KCSAN reports.
> One of the remaining ones looks related to a bug in rcu_barrier()'s
> handling of no-CBs CPUs that shows up once per few hundred hours
> of rcutorture testing of TREE04.  KCSAN did find some real bugs, so
> thank you!  Sadly, it does not (yet) find this one, but it does find
> consequences of it, which will at least reduce the testing burden once
> I do get it fixed.

Interesting.  I wonder if it doesn't find it because of missing
instrumentation of some arch asm?

Thanks,
-- Marco


> (So, yes, if anyone is seeing rcu_barrier() returning too soon on systems
> with CONFIG_RCU_NOCB_CPU=y on a system whose console output includes the
> string "Offload RCU callbacks from CPUs" with at least one CPU listed
> (as opposed to the string "(none)", please do let me know!  My best
> guess is that this was introduced in v5.4.)
>
>                                                         Thanx, Paul
>
> > Thanks,
> > -- Marco
> >
> >
> >
> >
> >
> >
> > > [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on:
> > > [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > [   28.992752][  T394] ===============================================================
> > > [   28.992752][  T394] ==================================================================
> > > [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> > > [   28.992752][  T394]
> > > [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16:
> > > [   28.992752][  T394]  __change_page_attr+0xe81/0x1620
> > > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > > [   28.992752][  T394]  __free_pages+0x51/0x90
> > > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > > [   28.992752][  T394]  deferred_init_max21d
> > > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > > [   28.992752][  T394]  kthread+0x1e0/0x200
> > > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> > > [   28.992752][  T394]
> > > [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0:
> > > [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620
> > > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > > [   28.992752][  T394]  __free_pages+0x51/0x90
> > > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > > [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d
> > > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > > [   28.992752][  T394]  kthread+0x1e0/0x200
> > > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> > >
> > >
> > > [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on:
> > > [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func
> > > [   93.378715][  T349] ==================================================================
> > > [   93.416183][  T616] ==================================================================
> > > [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > > [   93.486775][  T616]
> > > [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12:
> > > [   93.534139][  T616]  fill_pool+0x38/0x700
> > > [   93.554913][  T616]  __debug_object_init+0x3f/0x900
> > > [   93.579459][  T616]  debug_object_init+0x39/0x50
> > > [   93.601952][  T616]  __init_work+0x3e/0x50
> > > [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480
> > > [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0
> > > [   93.665134][  T616]  __kmalloc_node+0x60/0x300
> > > [   93.685094][  T616]  kvmalloc_node+0x83/0xa0
> > > [   93.704235][  T616]  seq_read+0x57c/0x7a0
> > > [   93.722460][  T616]  proc_reg_read+0x11a/0x160
> > > [   93.743570][  T616]  __vfs_read+0x59/0xa0
> > > [   93.761660][  T616]  vfs_read+0xcf/0x1c0
> > > [   93.779269][  T616]  ksys_read+0x9d/0x130
> > > [   93.797267][  T616]  __x64_sys_read+0x4c/0x60
> > > [   93.817205][  T616]  do_syscall_64+0x91/0xb47
> > > [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > [   93.864425][  T616]
> > > [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61:
> > > [   93.908534][  T616]  __debug_object_init+0x6e5/0x900
> > > [   93.931018][  T616]  debug_object_activate+0x1fc/0x350
> > > [   93.954131][  T616]  call_rcu+0x4c/0x4e0
> > > [   93.971959][  T616]  put_object+0x6a/0x90
> > > [   93.989955][  T616]  __delete_object+0xb9/0xf0
> > > [   94.009996][  T616]  delete_object_full+0x2d/0x40
> > > [   94.031812][  T616]  kmemleak_free+0x5f/0x90
> > > [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0
> > > [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0
> > > [   94.103806][  T616]  vm_area_free+0x31/0x40
> > > [   94.124587][  T616]  remove_vma+0xb0/0xc0
> > > [   94.143484][  T616]  exit_mmap+0x14c/0x220
> > > [   94.163826][  T616]  mmput+0x10e/0x270
> > > [   94.181736][  T616]  flush_old_exec+0x572/0xfe0
> > > [   94.202760][  T616]  load_elf_binary+0x467/0x2180
> > > [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0
> > > [   94.248735][  T616]  __do_execve_file+0xb61/0x1080
> > > [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70
> > > [   94.292254][  T616]  do_syscall_64+0x91/0xb47
> > > [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > >
> > > [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on:
> > > [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > [  103.561771][   C22] ==================================================================
> > > [  103.598005][   C41] ==================================================================
> > > [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util
> > > [  103.673408][   C41]
> > > [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2:
> > > [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40
> > > [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160
> > > [  103.762611][   C41]  update_blocked_averages+0x585/0x630
> > > [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240
> > > [  103.812821][   C41]  __do_softirq+0xd9/0x57c
> > > [  103.834438][   C41]  irq_exit+0xa2/0xc0
> > > [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480
> > > [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20
> > > [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0
> > > [  103.919324][   C41]  cpuidle_enter+0x69/0xc0
> > > [  103.938405][   C41]  call_cpuidle+0x23/0x40
> > > [  103.957152][   C41]  do_idle+0x248/0x280
> > > [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f
> > > [  103.995059][   C41]  start_secondary+0x1ad/0x230
> > > [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0
> > > [  104.037376][   C41]
> > > [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41:
> > > [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40
> > > [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160
> > > [  104.127759][   C41]  update_load_avg+0x70e/0x800
> > > [  104.148400][   C41]  task_tick_fair+0x5c/0x680
> > > [  104.168325][   C41]  scheduler_tick+0xab/0x120
> > > [  104.188881][   C41]  update_process_times+0x44/0x60
> > > [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0
> > > [  104.231137][   C41]  tick_sched_timer+0x45/0xc0
> > > [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800
> > > [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0
> > > [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480
> > > [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20
> > > [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120
> > > [  104.370100][   C41]  __read_once_size+0x1f/0xe0
> > > [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0
> > > [  104.413591][   C41]  on_each_cpu+0x46/0x90
> > > [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0
> > > [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0
> > > [  104.476699][   C41]  remove_vm_area+0xf4/0x100
> > > [  104.496763][   C41]  __vunmap+0x10a/0x460
> > > [  104.514807][   C41]  __vfree+0x33/0x90
> > > [  104.531597][   C41]  vfree+0x47/0x80
> > > [  104.547600][   C41]  n_tty_close+0x56/0x80
> > > [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0
> > > [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0
> > > [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0
> > > [  104.627098][   C41]  tty_release_struct+0x23/0x60
> > > [  104.648268][   C41]  tty_release+0x673/0x9c0
> > > [  104.667517][   C41]  __fput+0x187/0x410
> > > [  104.684357][   C41]  ____fput+0x1e/0x30
> > > [  104.701542][   C41]  task_work_run+0xed/0x140
> > > [  104.721358][   C41]  do_syscall_64+0x803/0xb47
> > > [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > >
> > > [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on:
> > > [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > [  136.861974][   C34] ==================================================================
> > > [  136.911354][    T1] ==================================================================
> > > [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > > [  136.981645][    T1]
> > > [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25:
> > > [  137.026513][    T1]  fill_pool+0x38/0x700
> > > [  137.045575][    T1]  __debug_object_init+0x3f/0x900
> > > [  137.068826][    T1]  debug_object_activate+0x1fc/0x350
> > > [  137.093102][    T1]  call_rcu+0x4c/0x4e0
> > > [  137.111520][    T1]  __fput+0x23a/0x410
> > > [  137.129618][    T1]  ____fput+0x1e/0x30
> > > [  137.147627][    T1]  task_work_run+0xed/0x140
> > > [  137.168322][    T1]  do_syscall_64+0x803/0xb47
> > > [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > [  137.215309][    T1]
> > > [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7:
> > > [  137.259867][    T1]  __debug_object_init+0x6e5/0x900
> > > [  137.283065][    T1]  debug_object_activate+0x1fc/0x350
> > > [  137.306988][    T1]  call_rcu+0x4c/0x4e0
> > > [  137.326804][    T1]  dentry_free+0x70/0xe0
> > > [  137.347208][    T1]  __dentry_kill+0x1db/0x300
> > > [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0
> > > [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320
> > > [  137.417174][    T1]  d_invalidate+0x80/0x130
> > > [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0
> > > [  137.459263][    T1]  release_task.part.21+0x156/0xb50
> > > [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960
> > > [  137.507550][    T1]  do_wait+0x25b/0x560
> > > [  137.526175][    T1]  kernel_waitid+0x194/0x270
> > > [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0
> > > [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90
> > > [  137.590291][    T1]  do_syscall_64+0x91/0xb47
> > > [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > >

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
  2020-01-17 22:54             ` Marco Elver
@ 2020-01-17 23:23               ` Paul E. McKenney
  0 siblings, 0 replies; 15+ messages in thread
From: Paul E. McKenney @ 2020-01-17 23:23 UTC (permalink / raw)
  To: Marco Elver
  Cc: Qian Cai, Alexander Potapenko, Andrey Konovalov, Dmitriy Vyukov,
	kasan-dev, LKML, Peter Zijlstra, Ingo Molnar, Will Deacon

On Fri, Jan 17, 2020 at 11:54:47PM +0100, Marco Elver wrote:
> On Fri, 17 Jan 2020 at 17:40, Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > On Thu, Jan 16, 2020 at 07:57:30PM +0100, Marco Elver wrote:
> > > On Thu, 16 Jan 2020 at 04:39, Qian Cai <cai@lca.pw> wrote:
> > > > > On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> > > > > On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> > > > >> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> > > > >>>
> > > > >>>> --- a/kernel/kcsan/core.c
> > > > >>>> +++ b/kernel/kcsan/core.c
> > > > >>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > > > >>>>         *      detection point of view) to simply disable preemptions to ensure
> > > > >>>>         *      as many tasks as possible run on other CPUs.
> > > > >>>>         */
> > > > >>>> -       local_irq_save(irq_flags);
> > > > >>>> +       raw_local_irq_save(irq_flags);
> > > > >>>
> > > > >>> Please reflect the need to use raw_local_irq_save() in the comment.
> > > > >>>
> > > > >>>>
> > > > >>>>        watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> > > > >>>>        if (watchpoint == NULL) {
> > > > >>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> > > > >>>>
> > > > >>>>        kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> > > > >>>> out_unlock:
> > > > >>>> -       local_irq_restore(irq_flags);
> > > > >>>> +       raw_local_irq_restore(irq_flags);
> > > > >>>
> > > > >>> Ditto
> > > > >>
> > > > >> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> > > > >
> > > > > Alexander and Qian, could you please let me know if this fixes things
> > > > > up for you?
> > > >
> > > > The lockdep warning is gone, so feel free to add,
> > > >
> > > > Tested-by: Qian Cai <cai@lca.pw>
> > >
> > > Thank you for testing!
> > >
> > > > for that patch, but the system is still unable to boot due to spam of
> > > > warnings due to incompatible with debug_pagealloc, debugobjects, so
> > > > the warning rate limit does not help.
> > >
> > > You may also try to set CONFIG_KCSAN_REPORT_ONCE_IN_MS to something
> > > large, say 1000000000 (effectively reporting each data race once).
> > >
> > > That being said, there are 2 options here:
> > >
> > > Option 1. If that still isn't satisfactory, we can try to make the
> > > system somehow tolerate the excessive number of data race reports
> > > (there may indeed be other printk limits based on rate or context we
> > > are hitting). More important appears to be the below...
> > >
> > > Option 2. Investigate and fix the bugs, or declare them "benign" to
> > > the tool. Compared to option (1) this will have much bigger impact on
> > > the kernel, as it not only improves the kernel with all the debugging
> > > tools enabled, but more importantly, improves the kernel *without* the
> > > debugging tools. This is what should be our goal here.
> >
> > True enough, but even if we reach the nirvana state where there is general
> > agreement on what constitutes a data race in need of fixing and KCSAN
> > faithfully checks based on that data-race definition, we need to handle
> > the case where someone introduces a bug that results in a destructive
> > off-CPU access to a per-CPU variable, which is exactly the sort of thing
> > that KCSAN is supposed to detect.  But suppose that this variable is
> > frequently referenced from functions that are inlined all over the place.
> >
> > Then that one bug might result in huge numbers of data-race reports in
> > a very short period of time, especially on a large system.
> >
> > So, yes, option 2 is important, but it is in no way a substitute for
> > KCSAN doing a good job of handling of option 1.
> >
> > And given limited console bandwidth, there will be cases where data-race
> > reports
> > must be dropped.  After all, in such cases, the only other option is to
> > hang the system.  There are ways to reduce the number of such cases, and
> > of course your recent (and much appreciated!) patches merging identical
> > reports is a great example of this.  But Qian's experience indicates that
> > this does not cover all cases -- nor would I expect it to have done so.
> 
> Agreed. And I'll keep looking into this.

Very good, thank you!

> > > With that in mind, I tried to fix debugobjects data races:
> > >   http://lkml.kernel.org/r/20200116185529.11026-1-elver@google.com
> > > Feel free to test, and reply to that patch with comments.
> >
> > Very good!
> >
> > For my part, I am quite a bit closer to having RCU free of KCSAN reports.
> > One of the remaining ones looks related to a bug in rcu_barrier()'s
> > handling of no-CBs CPUs that shows up once per few hundred hours
> > of rcutorture testing of TREE04.  KCSAN did find some real bugs, so
> > thank you!  Sadly, it does not (yet) find this one, but it does find
> > consequences of it, which will at least reduce the testing burden once
> > I do get it fixed.
> 
> Interesting.  I wonder if it doesn't find it because of missing
> instrumentation of some arch asm?

The problem is that the large system has a gcc that is too old to
do KCSAN, and the system with a newer gcc has only 12 CPUs, and would
thus need to run for about a week and a half to have a 50% chance of
catching an actual failure.

At some point, I install a newer gcc on the large system, but I need
to do bulk testing to confirm/invalidate my guesses as to what Kconfig
options and kernel versions are needed to trigger this bug.

Good clean fun!  ;-)

							Thanx, Paul

> Thanks,
> -- Marco
> 
> 
> > (So, yes, if anyone is seeing rcu_barrier() returning too soon on systems
> > with CONFIG_RCU_NOCB_CPU=y on a system whose console output includes the
> > string "Offload RCU callbacks from CPUs" with at least one CPU listed
> > (as opposed to the string "(none)", please do let me know!  My best
> > guess is that this was introduced in v5.4.)
> >
> >                                                         Thanx, Paul
> >
> > > Thanks,
> > > -- Marco
> > >
> > >
> > >
> > >
> > >
> > >
> > > > [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on:
> > > > [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > > [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > > [   28.992752][  T394] ===============================================================
> > > > [   28.992752][  T394] ==================================================================
> > > > [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> > > > [   28.992752][  T394]
> > > > [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16:
> > > > [   28.992752][  T394]  __change_page_attr+0xe81/0x1620
> > > > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > > > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > > > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > > > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > > > [   28.992752][  T394]  __free_pages+0x51/0x90
> > > > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > > > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > > > [   28.992752][  T394]  deferred_init_max21d
> > > > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > > > [   28.992752][  T394]  kthread+0x1e0/0x200
> > > > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> > > > [   28.992752][  T394]
> > > > [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0:
> > > > [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620
> > > > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0
> > > > [   28.992752][  T394]  __set_pages_np+0xcc/0x100
> > > > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb
> > > > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730
> > > > [   28.992752][  T394]  __free_pages+0x51/0x90
> > > > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0
> > > > [   28.992752][  T394]  deferred_free_range+0x59/0x8f
> > > > [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d
> > > > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1
> > > > [   28.992752][  T394]  kthread+0x1e0/0x200
> > > > [   28.992752][  T394]  ret_from_fork+0x3a/0x50
> > > >
> > > >
> > > > [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on:
> > > > [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > > [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > > [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func
> > > > [   93.378715][  T349] ==================================================================
> > > > [   93.416183][  T616] ==================================================================
> > > > [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > > > [   93.486775][  T616]
> > > > [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12:
> > > > [   93.534139][  T616]  fill_pool+0x38/0x700
> > > > [   93.554913][  T616]  __debug_object_init+0x3f/0x900
> > > > [   93.579459][  T616]  debug_object_init+0x39/0x50
> > > > [   93.601952][  T616]  __init_work+0x3e/0x50
> > > > [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480
> > > > [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0
> > > > [   93.665134][  T616]  __kmalloc_node+0x60/0x300
> > > > [   93.685094][  T616]  kvmalloc_node+0x83/0xa0
> > > > [   93.704235][  T616]  seq_read+0x57c/0x7a0
> > > > [   93.722460][  T616]  proc_reg_read+0x11a/0x160
> > > > [   93.743570][  T616]  __vfs_read+0x59/0xa0
> > > > [   93.761660][  T616]  vfs_read+0xcf/0x1c0
> > > > [   93.779269][  T616]  ksys_read+0x9d/0x130
> > > > [   93.797267][  T616]  __x64_sys_read+0x4c/0x60
> > > > [   93.817205][  T616]  do_syscall_64+0x91/0xb47
> > > > [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > > [   93.864425][  T616]
> > > > [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61:
> > > > [   93.908534][  T616]  __debug_object_init+0x6e5/0x900
> > > > [   93.931018][  T616]  debug_object_activate+0x1fc/0x350
> > > > [   93.954131][  T616]  call_rcu+0x4c/0x4e0
> > > > [   93.971959][  T616]  put_object+0x6a/0x90
> > > > [   93.989955][  T616]  __delete_object+0xb9/0xf0
> > > > [   94.009996][  T616]  delete_object_full+0x2d/0x40
> > > > [   94.031812][  T616]  kmemleak_free+0x5f/0x90
> > > > [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0
> > > > [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0
> > > > [   94.103806][  T616]  vm_area_free+0x31/0x40
> > > > [   94.124587][  T616]  remove_vma+0xb0/0xc0
> > > > [   94.143484][  T616]  exit_mmap+0x14c/0x220
> > > > [   94.163826][  T616]  mmput+0x10e/0x270
> > > > [   94.181736][  T616]  flush_old_exec+0x572/0xfe0
> > > > [   94.202760][  T616]  load_elf_binary+0x467/0x2180
> > > > [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0
> > > > [   94.248735][  T616]  __do_execve_file+0xb61/0x1080
> > > > [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70
> > > > [   94.292254][  T616]  do_syscall_64+0x91/0xb47
> > > > [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > >
> > > > [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on:
> > > > [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > > [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > > [  103.561771][   C22] ==================================================================
> > > > [  103.598005][   C41] ==================================================================
> > > > [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util
> > > > [  103.673408][   C41]
> > > > [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2:
> > > > [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40
> > > > [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160
> > > > [  103.762611][   C41]  update_blocked_averages+0x585/0x630
> > > > [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240
> > > > [  103.812821][   C41]  __do_softirq+0xd9/0x57c
> > > > [  103.834438][   C41]  irq_exit+0xa2/0xc0
> > > > [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480
> > > > [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20
> > > > [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0
> > > > [  103.919324][   C41]  cpuidle_enter+0x69/0xc0
> > > > [  103.938405][   C41]  call_cpuidle+0x23/0x40
> > > > [  103.957152][   C41]  do_idle+0x248/0x280
> > > > [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f
> > > > [  103.995059][   C41]  start_secondary+0x1ad/0x230
> > > > [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0
> > > > [  104.037376][   C41]
> > > > [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41:
> > > > [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40
> > > > [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160
> > > > [  104.127759][   C41]  update_load_avg+0x70e/0x800
> > > > [  104.148400][   C41]  task_tick_fair+0x5c/0x680
> > > > [  104.168325][   C41]  scheduler_tick+0xab/0x120
> > > > [  104.188881][   C41]  update_process_times+0x44/0x60
> > > > [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0
> > > > [  104.231137][   C41]  tick_sched_timer+0x45/0xc0
> > > > [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800
> > > > [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0
> > > > [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480
> > > > [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20
> > > > [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120
> > > > [  104.370100][   C41]  __read_once_size+0x1f/0xe0
> > > > [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0
> > > > [  104.413591][   C41]  on_each_cpu+0x46/0x90
> > > > [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0
> > > > [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0
> > > > [  104.476699][   C41]  remove_vm_area+0xf4/0x100
> > > > [  104.496763][   C41]  __vunmap+0x10a/0x460
> > > > [  104.514807][   C41]  __vfree+0x33/0x90
> > > > [  104.531597][   C41]  vfree+0x47/0x80
> > > > [  104.547600][   C41]  n_tty_close+0x56/0x80
> > > > [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0
> > > > [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0
> > > > [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0
> > > > [  104.627098][   C41]  tty_release_struct+0x23/0x60
> > > > [  104.648268][   C41]  tty_release+0x673/0x9c0
> > > > [  104.667517][   C41]  __fput+0x187/0x410
> > > > [  104.684357][   C41]  ____fput+0x1e/0x30
> > > > [  104.701542][   C41]  task_work_run+0xed/0x140
> > > > [  104.721358][   C41]  do_syscall_64+0x803/0xb47
> > > > [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > >
> > > > [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on:
> > > > [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3
> > > > [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> > > > [  136.861974][   C34] ==================================================================
> > > > [  136.911354][    T1] ==================================================================
> > > > [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool
> > > > [  136.981645][    T1]
> > > > [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25:
> > > > [  137.026513][    T1]  fill_pool+0x38/0x700
> > > > [  137.045575][    T1]  __debug_object_init+0x3f/0x900
> > > > [  137.068826][    T1]  debug_object_activate+0x1fc/0x350
> > > > [  137.093102][    T1]  call_rcu+0x4c/0x4e0
> > > > [  137.111520][    T1]  __fput+0x23a/0x410
> > > > [  137.129618][    T1]  ____fput+0x1e/0x30
> > > > [  137.147627][    T1]  task_work_run+0xed/0x140
> > > > [  137.168322][    T1]  do_syscall_64+0x803/0xb47
> > > > [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > > [  137.215309][    T1]
> > > > [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7:
> > > > [  137.259867][    T1]  __debug_object_init+0x6e5/0x900
> > > > [  137.283065][    T1]  debug_object_activate+0x1fc/0x350
> > > > [  137.306988][    T1]  call_rcu+0x4c/0x4e0
> > > > [  137.326804][    T1]  dentry_free+0x70/0xe0
> > > > [  137.347208][    T1]  __dentry_kill+0x1db/0x300
> > > > [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0
> > > > [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320
> > > > [  137.417174][    T1]  d_invalidate+0x80/0x130
> > > > [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0
> > > > [  137.459263][    T1]  release_task.part.21+0x156/0xb50
> > > > [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960
> > > > [  137.507550][    T1]  do_wait+0x25b/0x560
> > > > [  137.526175][    T1]  kernel_waitid+0x194/0x270
> > > > [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0
> > > > [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90
> > > > [  137.590291][    T1]  do_syscall_64+0x91/0xb47
> > > > [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > >

^ permalink raw reply	[flat|nested] 15+ messages in thread

end of thread, other threads:[~2020-01-17 23:23 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-14 12:49 [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep Marco Elver
2020-01-14 17:24 ` Alexander Potapenko
2020-01-15 16:26   ` Marco Elver
2020-01-15 16:37     ` Paul E. McKenney
2020-01-16  3:39       ` Qian Cai
2020-01-16  4:37         ` Qian Cai
2020-01-16 17:40           ` Paul E. McKenney
2020-01-16 17:50             ` Qian Cai
2020-01-16 17:55               ` Qian Cai
2020-01-16 18:57         ` Marco Elver
2020-01-17 16:40           ` Paul E. McKenney
2020-01-17 16:59             ` Qian Cai
2020-01-17 22:51               ` Marco Elver
2020-01-17 22:54             ` Marco Elver
2020-01-17 23:23               ` Paul E. McKenney

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