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

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Message-Id: <201509190139.GJH48908.QMSFJLFtOHOVFO@I-love.SAKURA.ne.jp>
Date:	Sat, 19 Sep 2015 01:39:53 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	oleg@...hat.com, cl@...ux.com
Cc:	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

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.
I think we need to rewrite oom_kill_process().

> 
> 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
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