linux-kernel - Re: [PATCH] kernel/sysrq: reset watchdog on all CPUs while processing sysrq-w

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Date:	Wed, 8 Jun 2016 15:13:24 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/sysrq: reset watchdog on all CPUs while
 processing sysrq-w


* Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:

> Lengthy output of sysrq-w may take a lot of time on slow serial console.
> Currently we reset NMI-watchdog on the current CPU to avoid softlockup.
> Sometimes this doesn't work since watchdog might trigger on the other
> CPU which is waiting for an IPI to proceed.
> 
> Reset watchdog on all CPUs to prevent spurious softlockup messages.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> ---
>  kernel/sched/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7f2cae4..c135eee 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5134,7 +5134,7 @@ void show_state_filter(unsigned long state_filter)
>  		 * reset the NMI-timeout, listing all files on a slow
>  		 * console might take a lot of time:
>  		 */
> -		touch_nmi_watchdog();
> +		touch_all_softlockup_watchdogs();

So don't we want both?

Thanks,

	Ingo