linux-kernel - Re: [PATCH 1/5] oom: select_bad_process: check PF

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Message-ID: <alpine.DEB.2.00.1006011333470.13136@chino.kir.corp.google.com>
Date:	Tue, 1 Jun 2010 13:36:45 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 1/5] oom: select_bad_process: check PF_KTHREAD instead
 of !mm to skip kthreads

On Mon, 31 May 2010, KOSAKI Motohiro wrote:

> From: Oleg Nesterov <oleg@...hat.com>
> Subject: oom: select_bad_process: check PF_KTHREAD instead of !mm to skip kthreads
> 
> select_bad_process() thinks a kernel thread can't have ->mm != NULL, this
> is not true due to use_mm().
> 
> Change the code to check PF_KTHREAD.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> Acked-by: David Rientjes <rientjes@...gle.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

This is already pushed in my oom killer rewrite as patch 14/18 "check 
PF_KTHREAD instead of !mm to skip kthreads".

This does not need to be merged immediately since it's not vital: use_mm() 
is only temporary state and these kthreads will once again be excluded 
when they call unuse_mm().  The worst case scenario here is that the oom 
killer will erroneously select one of these kthreads which cannot die and 
will need to reselect another task on its next call.
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