linux-kernel - Re: mm, oom_reaper: How to handle race with oom_killer

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Message-ID: <20160621174617.GA27527@dhcp22.suse.cz>
Date:	Tue, 21 Jun 2016 19:46:17 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	linux-mm@...ck.org, rientjes@...gle.com, oleg@...hat.com,
	vdavydov@...allels.com, mgorman@...hsingularity.net,
	hughd@...gle.com, riel@...hat.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: mm, oom_reaper: How to handle race with oom_killer_disable() ?

On Wed 22-06-16 00:32:29, Tetsuo Handa wrote:
> Michal Hocko wrote:
[...]
> > Hmm, what about the following instead. It is rather a workaround than a
> > full flaged fix but it seems much more easier and shouldn't introduce
> > new issues.
> 
> Yes, I think that will work. But I think below patch (marking signal_struct
> to ignore TIF_MEMDIE instead of clearing TIF_MEMDIE from task_struct) on top of
> current linux.git will implement no-lockup requirement. No race is possible unlike
> "[PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init".

Not really. Because without the exit_oom_victim from oom_reaper you have
no guarantee that the oom_killer_disable will ever return. I have
mentioned that in the changelog. There is simply no guarantee the oom
victim will ever reach exit_mm->exit_oom_victim.
-- 
Michal Hocko
SUSE Labs