linux-kernel - Re: [PATCH] kernel/hung_task.c: allow to set period separately from timeout

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Date:   Mon, 11 Jun 2018 15:16:34 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH] kernel/hung_task.c: allow to set period separately from timeout

On Mon, Jun 11, 2018 at 2:48 PM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> On 2018/06/11 20:16, Dmitry Vyukov wrote:
>>> timeout = 60 and period = 1 would allow hung task to be reported as soon
>>> as it remained uninterruptible for 60 seconds. That makes me easier to
>>> narrow down relevant kernel messages and syzbot program.
>>>
>>> Well, showing exact slept time, along with all threads which slept more
>>> than some threshold (e.g. timeout / 2), might be helpful.
>>
>> You mean if we report any task, then scan all tasks second time and
>> additionally report tasks that are blocked for (timeout/2 : timeout)?
>
> Yes. Something like check_memalloc_stalling_tasks() in
> http://lkml.kernel.org/r/1495331504-12480-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp .
>
>>
>> Should we do this when hung_task_show_lock? Or only when
>> sysctl_hung_task_panic? Or when?
>>
>
> I think always is more useful. That is, first round only checks whether
> there is at least one stalling task, and second round reports stalling tasks
> if at least one task is stalling.


Agree that it would be useful. But can't promise to work on this soon.