linux-kernel - Re: [PATCH] watchdog: ignore nohz

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Date:   Tue, 16 Nov 2021 14:04:57 +0800
From:   Zqiang <qiang.zhang1211@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     akpm@...ux-foundation.org, frederic@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: ignore nohz_full cores in new cpumask


On 2021/11/15 下午11:31, Petr Mladek wrote:
> On Fri 2021-11-12 13:14:34, Zqiang wrote:
>> If the nohz_full is enabled, when update watchdog_mask, the
>> nohz_full cores should be ignored.
>>
>> Signed-off-by: Zqiang <qiang.zhang1211@...il.com>
>> ---
>>   kernel/watchdog.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
>> index ad912511a0c0..3ef11a94783c 100644
>> --- a/kernel/watchdog.c
>> +++ b/kernel/watchdog.c
>> @@ -628,7 +628,9 @@ void lockup_detector_soft_poweroff(void)
>>   static void proc_watchdog_update(void)
>>   {
>>   	/* Remove impossible cpus to keep sysctl output clean. */
>> -	cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
>> +	cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
>> housekeeping_cpumask(HK_FLAG_TIMER));
> I am not familiar with nozh_full code but this looks fine.
>
>
>> +	if (cpumask_empty(&watchdog_cpumask))
>> +		return;
> But this looks looks wrong. Is there any reason for this?
>
> We need to stop the watchdog when it was running before.
>
> I mean that lockup_detector_reconfigure() must be called anytime
> when the mask has changed even when it became empty.

Thanks Petr

I will resend patch v2.

>
>
>>   	lockup_detector_reconfigure();
>>   }
> Best Regards,
> Petr