linux-kernel - Re: [PATCH] hung_task: recover hung task warnings in next check interval

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Message-ID: <e5c695c9-2006-f2cb-e3e2-7ea8ee465817@i-love.sakura.ne.jp>
Date:   Thu, 20 Jun 2019 19:02:57 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Yafang Shao <laoar.shao@...il.com>, akpm@...ux-foundation.org,
        dvyukov@...gle.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hung_task: recover hung task warnings in next check
 interval

On 2019/06/20 14:55, Yafang Shao wrote:
> When sys_hung_task_warnings reaches 0, the hang task messages will not
> be reported any more.

It is a common mistake that sys_hung_task_warnings is already 0 when
a real problem which should be reported occurred.

> 
> If the user want to get more hung task messages, he must reset
> kernel.hung_task_warnings to a postive integer or -1 with sysctl.

People are setting sys_hung_task_warnings to -1 in order to make sure
that the messages are printed.

> This is not a good way for the user.

But I don't think we should reset automatically.

> We'd better reset hung task warnings in the kernel, and then the user
> don't need to pay attention to this value.

I suggest changing the default value of sys_hung_task_warnings to -1.

> 
> 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).