linux-kernel - Re: [PATCH 2/4] watchdog/softlockup: Use printk_cpu_sync_get

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Date: Fri, 22 Dec 2023 15:13:41 +0800
From: lizhe.67@...edance.com
To: dianders@...omium.org
Cc: akpm@...ux-foundation.org,
	john.ogness@...utronix.de,
	kernelfans@...il.com,
	lecopzer.chen@...iatek.com,
	linux-kernel@...r.kernel.org,
	lizhe.67@...edance.com,
	pmladek@...e.com
Subject: Re: [PATCH 2/4] watchdog/softlockup: Use printk_cpu_sync_get_irqsave() to serialize reporting

On Wed, 20 Dec 2023 13:15:35 -0800, dianders@...omium.org wrote: 

>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());
>-- 

Reviewed-by: Li Zhe <lizhe.67@...edance.com>