Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <1561010100-14080-1-git-send-email-laoar.shao@gmail.com>
 <e5c695c9-2006-f2cb-e3e2-7ea8ee465817@i-love.sakura.ne.jp>
 <CALOAHbCe9J0pOCW03dW+C4NK__amTKttAs=eNHXwvPPf5Lpwhw@mail.gmail.com> <ac52f383-697d-8102-a6af-6aa172ee2a6f@i-love.sakura.ne.jp>
In-Reply-To: <ac52f383-697d-8102-a6af-6aa172ee2a6f@i-love.sakura.ne.jp>
From:   Yafang Shao <laoar.shao@gmail.com>
Date:   Thu, 20 Jun 2019 18:47:34 +0800
Message-ID: <CALOAHbAAJ4EaZ1NaR3Kpms1Yu78gA7UBoYAfTgxDD1JxWEArmw@mail.gmail.com>
Subject: Re: [PATCH] hung_task: recover hung task warnings in next check interval
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jun 20, 2019 at 6:23 PM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> On 2019/06/20 19:10, Yafang Shao wrote:
> >>> With this patch, hung task warnings will be reset with
> >>> sys_hung_task_warnings setting in evenry check interval.
> >>
> >> Since it is uncommon that the messages are printed for more than 10
> >> times for one check_hung_uninterruptible_tasks() call, this patch is
> >> effectively changing to always print the messages (in other words,
> >> setting -1).
> >
> > If sys_hung_task_warnings can't be recovered, does it make sense to exist?
> > In which case do we need this setting ?
>
> Someone might want to print the messages up to only a few times because he/she
> does not like the ever-repeating messages.

But some new difference hung task information may be missed.
And the reason of the new hung task may be different with the old one.

So I still can't understand it.

It would be better if you could give some use cases in the real world.

> But automatically resetting will
> forbid his/her wish to print the messages for up to only a few times.
>
> >
> > Btw, why the default value of this setting is 10, instead of -1 ?
>
> I don't know. I guess just by historical reason, for this variable
> has been existed before support of -1 is added.
>

I think we'd better change the default value from 10 to -1,
because this is the common use case.
And then the user don't need to write it into sysctl.conf again.

Thanks
Yafang