linux-kernel - Re: [PATCH 1/2] oom: do not live lock on frozen tasks

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Date:	Tue, 27 Sep 2011 11:30:13 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Michal Hocko <mhocko@...e.cz>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Oleg Nesterov <oleg@...hat.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH 1/2] oom: do not live lock on frozen tasks

On Tue, 27 Sep 2011, Michal Hocko wrote:

> I guess you mean a situation when select_bad_process picks up a process
> which is not marked as frozen yet but we send SIGKILL right before
> schedule is called in refrigerator. 
> In that case either schedule should catch it by signal_pending_state
> check or we will pick it up next OOM round when we pick up the same
> process (if nothing else is eligible). Or am I missing something?
>  

That doesn't close the race, the oom killer will see the presence of an 
eligible TIF_MEMDIE thread in select_bad_process() and simply return to 
the page allocator.  You'd need to thaw it there as well and hope that 
nothing now or in the future will get into an endless thaw-freeze-thaw 
loop in the exit path.
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