linux-kernel - Re: can't oom-kill zap the victim's memory?

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Message-Id: <201510071943.DCJ01080.JOFOFFOtLSMQHV@I-love.SAKURA.ne.jp>
Date:	Wed, 7 Oct 2015 19:43:08 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	vbabka@...e.cz
Cc:	mhocko@...nel.org, torvalds@...ux-foundation.org,
	rientjes@...gle.com, oleg@...hat.com, kwalker@...hat.com,
	cl@...ux.com, akpm@...ux-foundation.org, hannes@...xchg.org,
	vdavydov@...allels.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, skozina@...hat.com
Subject: Re: can't oom-kill zap the victim's memory?

Vlastimil Babka wrote:
> On 5.10.2015 16:44, Michal Hocko wrote:
> > So I can see basically only few ways out of this deadlock situation.
> > Either we face the reality and allow small allocations (withtout
> > __GFP_NOFAIL) to fail after all attempts to reclaim memory have failed
> > (so after even OOM killer hasn't made any progress).
> 
> Note that small allocations already *can* fail if they are done in the context
> of a task selected as OOM victim (i.e. TIF_MEMDIE). And yeah I've seen a case
> when they failed in a code that "handled" the allocation failure with a
> BUG_ON(!page).
> 
Did You hit a race described below?
http://lkml.kernel.org/r/201508272249.HDH81838.FtQOLMFFOVSJOH@I-love.SAKURA.ne.jp

Where was the BUG_ON(!page) ? Maybe it is a candidate for adding __GFP_NOFAIL.
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