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softlockup: serialized softlockup's log

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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@bytedance.com
Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Li Zhe 2023-11-23 16:40:22 +08:00 committed by Andrew Morton
parent b3ba234171
commit 9d02330abd
1 changed files with 3 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
kernel/watchdog.c
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@ -448,6 +448,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
struct pt_regs *regs = get_irq_regs(); struct pt_regs *regs = get_irq_regs();
int duration; int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
static DEFINE_SPINLOCK(watchdog_output_lock);
if (!watchdog_enabled) if (!watchdog_enabled)
return HRTIMER_NORESTART; return HRTIMER_NORESTART;
@ -514,6 +515,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
/* Start period for the next softlockup warning. */ /* Start period for the next softlockup warning. */
update_report_ts(); update_report_ts();
spin_lock(&watchdog_output_lock);
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration, smp_processor_id(), duration,
current->comm, task_pid_nr(current)); current->comm, task_pid_nr(current));
@ -523,6 +525,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
show_regs(regs); show_regs(regs);
else else
dump_stack(); dump_stack();
spin_unlock(&watchdog_output_lock);
if (softlockup_all_cpu_backtrace) { if (softlockup_all_cpu_backtrace) {
trigger_allbutcpu_cpu_backtrace(smp_processor_id()); trigger_allbutcpu_cpu_backtrace(smp_processor_id());