linux-kernel - Re: [PATCH] mm/oom_kill.c: don't kill TASK

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Message-ID: <20150918165441.GA20665@redhat.com>
Date:	Fri, 18 Sep 2015 18:54:42 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	cl@...ux.com, kwalker@...hat.com, akpm@...ux-foundation.org,
	mhocko@...e.cz, rientjes@...gle.com, hannes@...xchg.org,
	vdavydov@...allels.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, skozina@...hat.com
Subject: Re: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks

On 09/19, Tetsuo Handa wrote:
>
> Oleg Nesterov wrote:
> > To simplify the discussion lets ignore PF_FROZEN, this is another issue.
> >
> > I am not sure this change is enough, we need to ensure that
> > select_bad_process() won't pick the same task (or its sub-thread) again.
>
> SysRq-f is sometimes unusable because it continues choosing the same thread.
> oom_kill_process() should not choose a thread which already has TIF_MEMDIE.

So I was right, this is really not enough...

> I think we need to rewrite oom_kill_process().

Heh. I can only ack the intent and wish you good luck ;)

> > And perhaps something like
> >
> > 	wait_event_timeout(oom_victims_wait, !oom_victims,
> > 				configurable_timeout);
> >
> > before select_bad_process() makes sense?
>
> I think you should not sleep for long with oom_lock mutex held.
> http://marc.info/?l=linux-mm&m=143031212312459

Yes, yes, sure, I didn't mean we should wait under oom_lock.

Oleg.

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