diff options
| author | Douglas Anderson <dianders@chromium.org> | 2023-12-20 13:15:35 -0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-12-29 12:22:30 -0800 |
| commit | 896260a6d69d01ceb1aad8cfe4298bd837a67432 (patch) | |
| tree | 6e1f18d7259b9d58bb1016144dbf5806b5c2c954 /kernel/watchdog.c | |
| parent | 6dcde5d5f248291c5ff6cbe00a7fa6ae400d1aa9 (diff) | |
watchdog/softlockup: use printk_cpu_sync_get_irqsave() to serialize reporting
Instead of introducing a spinlock, use printk_cpu_sync_get_irqsave() and
printk_cpu_sync_put_irqrestore() to serialize softlockup reporting. Alone
this doesn't have any real advantage over the spinlock, but this will
allow us to use the same function in a future change to also serialize
hardlockup crawls.
NOTE: for the most part this serialization is important because we often
end up in the show_regs() path and that has no built-in serialization if
there are multiple callers at once. However, even in the case where we
end up in the dump_stack() path this still has some advantages because the
stack will be guaranteed to be together in the logs with the lockup
message with no interleaving.
NOTE: the fact that printk_cpu_sync_get_irqsave() is allowed to be called
multiple times on the same CPU is important here. Specifically we hold
the "lock" while calling dump_stack() which also gets the same "lock".
This is explicitly documented to be OK and means we don't need to
introduce a variant of dump_stack() that doesn't grab the lock.
Link: https://lkml.kernel.org/r/20231220131534.2.Ia5906525d440d8e8383cde31b7c61c2aadc8f907@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Li Zhe <lizhe.67@bytedance.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'kernel/watchdog.c')
| -rw-r--r-- | kernel/watchdog.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index b4fd2f12137f..526041a1100a 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -454,7 +454,7 @@ 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); + unsigned long flags; if (!watchdog_enabled) return HRTIMER_NORESTART; @@ -521,7 +521,7 @@ 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); + printk_cpu_sync_get_irqsave(flags); pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); @@ -531,7 +531,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) show_regs(regs); else dump_stack(); - spin_unlock(&watchdog_output_lock); + printk_cpu_sync_put_irqrestore(flags); if (softlockup_all_cpu_backtrace) { trigger_allbutcpu_cpu_backtrace(smp_processor_id()); |