linux-kernel - Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in

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Message-ID: <20150930135051.GD32263@redhat.com>
Date:	Wed, 30 Sep 2015 15:50:51 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Kyle Walker <kwalker@...hat.com>,
	Michal Hocko <mhocko@...nel.org>,
	Stanislav Kozina <skozina@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 3/3] mm/oom_kill: fix the wrong task->mm == mm
	checks in

On 09/29, David Rientjes wrote:
>
> On Tue, 29 Sep 2015, Oleg Nesterov wrote:
>
> > Both "child->mm == mm" and "p->mm != mm" checks in oom_kill_process()
> > are wrong. ->mm can be if task is the exited group leader. This means
> > in particular that "kill sharing same memory" loop can miss a process
> > with a zombie leader which uses the same ->mm.
> >
> > Note: the process_has_mm(child, p->mm) check is still not 100% correct,
> > p->mm can be NULL too. This is minor, but probably deserves a fix or a
> > comment anyway.
> >
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
>
> Acked-by: David Rientjes <rientjes@...gle.com>
>
> I like this and I don't want to hold up a fix for a personal preference,
> but I find process_has_mm() to simply imply the process has a non-NULL mm.

Hmm, yes ;)

> Maybe process_shares_mm()?  Something to consider.

Agreed, will rename in v2.

Oleg.

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