Subject: Re: [PATCH v3] watchdog: Add warning message when the newcpumask
 contains nohz_full cores
To:     frederic@kernel.org, pmladek@suse.com
Cc:     akpm@linux-foundation.org, linux-kernel@vger.kernel.org
References: <20211118031046.32632-1-qiang.zhang1211@gmail.com>
From:   Zqiang <qiang.zhang1211@gmail.com>
Message-ID: <c4adfc53-9471-6cb9-c263-5f462469db1a@gmail.com>
Date:   Mon, 22 Nov 2021 19:13:20 +0800
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On 2021/11/18 上午11:10, Zqiang wrote:
> The watchdog default is disabled on nohz_full cores, however when
> override the cpumask, if new cpumask contains nohz_full cores,
> add warning message.
>
> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
> ---
>   v1->v2:
>   if watchdog_cpumask became empty, set housekeeping_cpumask.
>   v2->v3:
>   only print a warning when a nohz_full CPU is included in new cpumask.
>
>   kernel/watchdog.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index ad912511a0c0..37a978d8ff06 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -629,6 +629,7 @@ static void proc_watchdog_update(void)
>   {
>   	/* Remove impossible cpus to keep sysctl output clean. */
>   	cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
> +	WARN_ONCE(!cpumask_subset(&watchdog_cpumask, housekeeping_cpumask(HK_FLAG_TIMER)), "Enabling watchdog on nohz_full cores\n");
>   	lockup_detector_reconfigure();
>   }
>   

Hello Frederic

Can you give some suggestions?

Thanks

Zqiang