linux-kernel - Re: [PATCH] oom: skip frozen tasks

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Message-ID: <alpine.DEB.2.00.1108231313520.21637@chino.kir.corp.google.com>
Date:	Tue, 23 Aug 2011 13:18:14 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] oom: skip frozen tasks

On Tue, 23 Aug 2011, Konstantin Khlebnikov wrote:

> All frozen tasks are unkillable, and if one of them has TIF_MEMDIE
> we must kill something else to avoid deadlock. After this patch
> select_bad_process() will skip frozen task before checking TIF_MEMDIE.
> 

The caveat is that if the task in the refrigerator is not OOM_DISABLE and 
there are no other eligible tasks (system wide, in the cpuset, or in the 
memcg) to kill, then the machine will panic as a result of this when, in 
the past, we would simply issue the SIGKILL and keep looping in the page 
allocator until it is thawed.

So you may actually be trading a stall waiting for this thread to thaw for 
what would now be a panic, and that's not clearly better to me.
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