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

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Message-ID: <alpine.DEB.2.10.1509291541010.3375@chino.kir.corp.google.com>
Date:	Tue, 29 Sep 2015 15:41:52 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Oleg Nesterov <oleg@...hat.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 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.  
Maybe process_shares_mm()?  Something to consider.
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