linux-kernel - Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend

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Message-ID: <20141105170111.GG14386@htj.dyndns.org>
Date:	Wed, 5 Nov 2014 12:01:11 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Cong Wang <xiyou.wangcong@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend

On Wed, Nov 05, 2014 at 11:54:28AM -0500, Tejun Heo wrote:
> > Still not following. How do you want to detect an on-going OOM without
> > any interface around out_of_memory?
> 
> I thought you were using oom_killer_allowed_start() outside OOM path.
> Ugh.... why is everything weirdly structured?  oom_killer_disabled
> implies that oom killer may fail, right?  Why is
> __alloc_pages_slowpath() checking it directly?  If whether oom killing
> failed or not is relevant to its users, make out_of_memory() return an
> error code.  There's no reason for the exclusion detail to leak out of
> the oom killer proper.  The only interface should be disable/enable
> and whether oom killing failed or not.

And what's implemented is wrong.  What happens if oom killing is
already in progress and then a task blocks trying to write-lock the
rwsem and then that task is selected as the OOM victim?  disable()
call must be able to fail.

-- 
tejun
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