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