[PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[Guilherme G. Piccoli]

After a recent change introduced by Vlastimil's series [0], kernel is
able now to handle sysctl parameters on kernel command line; also, the
series introduced a simple infrastructure to convert legacy boot
parameters (that duplicate sysctls) into sysctl aliases.

This patch converts the watchdog parameters softlockup_panic and
{hard,soft}lockup_all_cpu_backtrace to use the new alias infrastructure.
It fixes the documentation too, since the alias only accepts values 0
or 1, not the full range of integers. We also took the opportunity here
to improve the documentation of the previously converted hung_task_panic
(see the patch series [0]) and put the alias table in alphabetical order.

[0] lore.kernel.org/lkml/20200427180433.7029-1-vbabka@suse.cz

Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
---


This patch is based on linux-next/akpm branch, at d0f3f6070c3a. Thanks
in advance for reviews!
Cheers,

Guilherme


 .../admin-guide/kernel-parameters.txt         | 10 ++---
 fs/proc/proc_sysctl.c                         |  7 +++-
 kernel/watchdog.c                             | 38 +++++--------------
 3 files changed, 19 insertions(+), 36 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5a44c1bf85e7..d9197499aad1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1435,7 +1435,7 @@
 	hardlockup_all_cpu_backtrace=
 			[KNL] Should the hard-lockup detector generate
 			backtraces on all cpus.
-			Format: <integer>
+			Format: 0 | 1
 
 	hashdist=	[KNL,NUMA] Large hashes allocated during boot
 			are distributed across NUMA nodes.  Defaults on
@@ -1503,7 +1503,7 @@
 
 	hung_task_panic=
 			[KNL] Should the hung task detector generate panics.
-			Format: <integer>
+			Format: 0 | 1
 
 			A value of 1 instructs the kernel to panic when a
 			hung task is detected. The default value is controlled
@@ -4643,9 +4643,9 @@
 
 	softlockup_panic=
 			[KNL] Should the soft-lockup detector generate panics.
-			Format: <integer>
+			Format: 0 | 1
 
-			A nonzero value instructs the soft-lockup detector
+			A value of 1 instructs the soft-lockup detector
 			to panic the machine when a soft-lockup occurs. It is
 			also controlled by the kernel.softlockup_panic sysctl
 			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
@@ -4654,7 +4654,7 @@
 	softlockup_all_cpu_backtrace=
 			[KNL] Should the soft-lockup detector generate
 			backtraces on all cpus.
-			Format: <integer>
+			Format: 0 | 1
 
 	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
 			See Documentation/admin-guide/laptops/sonypi.rst
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 15030784566c..5b405f32971d 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1720,8 +1720,11 @@ struct sysctl_alias {
  * parameter.
  */
 static const struct sysctl_alias sysctl_aliases[] = {
-	{"numa_zonelist_order",		"vm.numa_zonelist_order" },
-	{"hung_task_panic",		"kernel.hung_task_panic" },
+	{"hardlockup_all_cpu_backtrace",	"kernel.hardlockup_all_cpu_backtrace" },
+	{"hung_task_panic",			"kernel.hung_task_panic" },
+	{"numa_zonelist_order",			"vm.numa_zonelist_order" },
+	{"softlockup_all_cpu_backtrace",	"kernel.softlockup_all_cpu_backtrace" },
+	{"softlockup_panic",			"kernel.softlockup_panic" },
 	{ }
 };
 
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index fa5aacbfd000..1b939532fcc1 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -50,6 +50,11 @@ struct cpumask watchdog_cpumask __read_mostly;
 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
+
+# ifdef CONFIG_SMP
+int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
+# endif /* CONFIG_SMP */
+
 /*
  * Should we panic when a soft-lockup or hard-lockup occurs:
  */
@@ -82,17 +87,6 @@ static int __init hardlockup_panic_setup(char *str)
 }
 __setup("nmi_watchdog=", hardlockup_panic_setup);
 
-# ifdef CONFIG_SMP
-int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
-
-static int __init hardlockup_all_cpu_backtrace_setup(char *str)
-{
-	sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
-	return 1;
-}
-__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
-# endif /* CONFIG_SMP */
-
 atomic_t hardlockup_detected = ATOMIC_INIT(0);
 
 static inline void flush_hardlockup_messages(void)
@@ -183,6 +177,10 @@ static void lockup_detector_update_enable(void)
 
 #define SOFTLOCKUP_RESET	ULONG_MAX
 
+#ifdef CONFIG_SMP
+int __read_mostly sysctl_softlockup_all_cpu_backtrace;
+#endif
+
 /* Global variables, exported for sysctl */
 unsigned int __read_mostly softlockup_panic =
 			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
@@ -198,13 +196,6 @@ static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 static unsigned long soft_lockup_nmi_warn;
 
-static int __init softlockup_panic_setup(char *str)
-{
-	softlockup_panic = simple_strtoul(str, NULL, 0);
-	return 1;
-}
-__setup("softlockup_panic=", softlockup_panic_setup);
-
 static int __init nowatchdog_setup(char *str)
 {
 	watchdog_user_enabled = 0;
@@ -226,17 +217,6 @@ static int __init watchdog_thresh_setup(char *str)
 }
 __setup("watchdog_thresh=", watchdog_thresh_setup);
 
-#ifdef CONFIG_SMP
-int __read_mostly sysctl_softlockup_all_cpu_backtrace;
-
-static int __init softlockup_all_cpu_backtrace_setup(char *str)
-{
-	sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
-	return 1;
-}
-__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
-#endif
-
 static void __lockup_detector_cleanup(void);
 
 /*
-- 
2.25.2

Re: [PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[Andrew Morton]

On Thu,  7 May 2020 18:46:24 -0300 "Guilherme G. Piccoli" <gpiccoli@canonical.com> wrote:

> After a recent change introduced by Vlastimil's series [0], kernel is
> able now to handle sysctl parameters on kernel command line; also, the
> series introduced a simple infrastructure to convert legacy boot
> parameters (that duplicate sysctls) into sysctl aliases.
> 
> This patch converts the watchdog parameters softlockup_panic and
> {hard,soft}lockup_all_cpu_backtrace to use the new alias infrastructure.
> It fixes the documentation too, since the alias only accepts values 0
> or 1, not the full range of integers. We also took the opportunity here
> to improve the documentation of the previously converted hung_task_panic
> (see the patch series [0]) and put the alias table in alphabetical order.

We have a lot of sysctls.  What is the motivation for converting these
particular ones?

Re: [PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[Guilherme G. Piccoli]

On Thu, May 7, 2020 at 8:06 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> We have a lot of sysctls.  What is the motivation for converting these
> particular ones?

No stronger motivation than a regular clean-up - I just liked the
infrastructure provided by Vlastmil and thought in using it. I know we
have plenty of sysctls, but not all of them have identical/duplicate
boot params, so I went with the obvious ones, that I use more.
Cheers,

Guilherme

Re: [PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[Vlastimil Babka]

On 5/7/20 11:46 PM, Guilherme G. Piccoli wrote:
> After a recent change introduced by Vlastimil's series [0], kernel is
> able now to handle sysctl parameters on kernel command line; also, the
> series introduced a simple infrastructure to convert legacy boot
> parameters (that duplicate sysctls) into sysctl aliases.
> 
> This patch converts the watchdog parameters softlockup_panic and
> {hard,soft}lockup_all_cpu_backtrace to use the new alias infrastructure.
> It fixes the documentation too, since the alias only accepts values 0
> or 1, not the full range of integers. We also took the opportunity here
> to improve the documentation of the previously converted hung_task_panic
> (see the patch series [0]) and put the alias table in alphabetical order.
> 
> [0] lore.kernel.org/lkml/20200427180433.7029-1-vbabka@suse.cz
> 
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com>

Ah, so I did miss some, as the Documentation file doesn't mention there is also
a sysctl for those parameters. Maybe it should?

Anyway, thanks.
Acked-by: Vlastimil Babka <vbabka@suse.cz>

Re: [PATCH] kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases

[Vlastimil Babka]

On 5/8/20 1:06 AM, Andrew Morton wrote:
> On Thu,  7 May 2020 18:46:24 -0300 "Guilherme G. Piccoli" <gpiccoli@canonical.com> wrote:
> 
>> After a recent change introduced by Vlastimil's series [0], kernel is
>> able now to handle sysctl parameters on kernel command line; also, the
>> series introduced a simple infrastructure to convert legacy boot
>> parameters (that duplicate sysctls) into sysctl aliases.
>> 
>> This patch converts the watchdog parameters softlockup_panic and
>> {hard,soft}lockup_all_cpu_backtrace to use the new alias infrastructure.
>> It fixes the documentation too, since the alias only accepts values 0
>> or 1, not the full range of integers. We also took the opportunity here
>> to improve the documentation of the previously converted hung_task_panic
>> (see the patch series [0]) and put the alias table in alphabetical order.
> 
> We have a lot of sysctls.  What is the motivation for converting these
> particular ones?

It's not converting sysctls, it's converting legacy boot parameters that have a
sysctl counterpart. There's not a lot of those, and new ones shouldn't be added
with the generic infrastructure in place. I would have converted them myself if
I found them :)