linux-kernel - Re: [PATCH 06/10] mm, oom: kill all tasks sharing the mm

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Date:	Tue, 7 Jun 2016 08:37:39 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>,
	David Rientjes <rientjes@...gle.com>
Cc:	linux-mm@...ck.org,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/10] mm, oom: kill all tasks sharing the mm

On Tue 07-06-16 01:20:08, Oleg Nesterov wrote:
> On 06/06, David Rientjes wrote:
> >
> > > There is a potential race where we kill the oom disabled task which is
> > > highly unlikely but possible. It would happen if __set_oom_adj raced
> > > with select_bad_process and then it is OK to consider the old value or
> > > with fork when it should be acceptable as well.
> > > Let's add a little note to the log so that people would tell us that
> > > this really happens in the real life and it matters.
> > >
> >
> > We cannot kill oom disabled processes at all, little race or otherwise.
> 
> But this change doesn't really make it worse?

Exactly, the race was always there. We could mitigate it to some degree
by (ab)using oom_lock in __set_oom_adj. But I guess this is just an
overkill.
-- 
Michal Hocko
SUSE Labs