linux-kernel - Re: [PATCH] kernel/hung_task.c: force ignore

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Date:   Wed, 12 Dec 2018 11:17:33 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     "Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/hung_task.c: force ignore_loglevel before panic

On Wed 2018-12-12 01:16:11, Liu, Chuansheng wrote:
> 
> 
> > -----Original Message-----
> > From: Tetsuo Handa [mailto:penguin-kernel@...ove.sakura.ne.jp]
> > Sent: Tuesday, December 11, 2018 6:02 PM
> > To: Liu, Chuansheng <chuansheng.liu@...el.com>; Sergey Senozhatsky
> > <sergey.senozhatsky.work@...il.com>
> > Cc: akpm@...ux-foundation.org; pmladek@...e.com;
> > sergey.senozhatsky@...il.com; rostedt@...dmis.org; dvyukov@...gle.com;
> > linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH] kernel/hung_task.c: force ignore_loglevel before panic
> > 
> > On 2018/12/11 10:16, Liu, Chuansheng wrote:
> > > We may enhance it by:
> > > -       if (sysctl_hung_task_warnings) {
> > > +       if (sysctl_hung_task_panic || sysctl_hung_task_warnings) {
> > >                 if (sysctl_hung_task_warnings > 0)
> > >                         sysctl_hung_task_warnings--;
> > 
> > Why ignore sysctl_hung_task_warnings? The administrator can already
> > configure as sysctl_hung_task_warnings == -1 && sysctl_hung_task_panic == 1
> > if he/she does not want to suppress neither sched_show_task() nor
> > debug_show_all_locks()/trigger_all_cpu_backtrace(). Someone might want that
> > sysctl_hung_task_warnings == 0 (which is a request to suppress only
> > sched_show_task()) should not be ignored by sysctl_hung_task_panic == 1
> > (which is a request to trigger panic).
> 
> 
> My complete idea is in patch V1 which has been sent. Paste here:
> If sysctl_hung_task_panic == 1, I will force sched_show_task(t) and set
> hung_task_call_panic = true
> hung_task_show_lock = true

Please, do not mix two changes into one patch.

Add console_verbose() in one patch. It is simple and
everyone has agreed with it so far.

Force sched_show_task() when hung_task_call_panic == 1 in
another patch. It seems to be controversial and should be
discussed/changed separately.

Best Regards,
Petr