The patch titled
Subject: softlockup: serialized softlockup's log
has been added to the -mm mm-nonmm-unstable branch. Its filename is
softlockup-serialized-softlockups-log.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/softlockup-serialized-softlockups-log.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
Subject: softlockup: serialized softlockup's log
Date: Thu, 23 Nov 2023 16:40:22 +0800
If multiple CPUs trigger softlockup at the same time with
'softlockup_all_cpu_backtrace=0', the softlockup's logs will appear
staggeredly in dmesg, which will affect the viewing of the logs for
developer. Since the code path for outputting softlockup logs is not a
kernel hotspot and the performance requirements for the code are not
strict, locks are used to serialize the softlockup log output to improve
the readability of the logs.
Link: https://lkml.kernel.org/r/20231123084022.10302-1-lizhe.67@xxxxxxxxxxxxx
Signed-off-by: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Zefan Li <lizefan.x@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 3 +++
1 file changed, 3 insertions(+)
--- a/kernel/watchdog.c~softlockup-serialized-softlockups-log
+++ a/kernel/watchdog.c
@@ -448,6 +448,7 @@ static enum hrtimer_restart watchdog_tim
struct pt_regs *regs = get_irq_regs();
int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
+ static DEFINE_SPINLOCK(watchdog_output_lock);
if (!watchdog_enabled)
return HRTIMER_NORESTART;
@@ -514,6 +515,7 @@ static enum hrtimer_restart watchdog_tim
/* Start period for the next softlockup warning. */
update_report_ts();
+ spin_lock(&watchdog_output_lock);
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
@@ -523,6 +525,7 @@ static enum hrtimer_restart watchdog_tim
show_regs(regs);
else
dump_stack();
+ spin_unlock(&watchdog_output_lock);
if (softlockup_all_cpu_backtrace) {
trigger_allbutcpu_cpu_backtrace(smp_processor_id());
_
Patches currently in -mm which might be from lizhe.67@xxxxxxxxxxxxx are
softlockup-serialized-softlockups-log.patch
