Commit 9d02330a authored by Li Zhe's avatar Li Zhe Committed by Andrew Morton
Browse files

softlockup: serialized softlockup's log 

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: default avatarLi Zhe <lizhe.67@bytedance.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Reviewed-by: default avatarDouglas 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b3ba2341

kernel/watchdog.c

+3 −0
Original line number Diff line number Diff line
@@ -448,6 +448,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 
	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_timer_fn(struct hrtimer *hrtimer) 
		/* 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_timer_fn(struct hrtimer *hrtimer) 
			show_regs(regs);

		else

			dump_stack();

		spin_unlock(&watchdog_output_lock);



		if (softlockup_all_cpu_backtrace) {

			trigger_allbutcpu_cpu_backtrace(smp_processor_id());