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From: Rusty Russell <rusty@rustcorp.com.au>
To: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Konstantin Khlebnikov <khlebnikov@openvz.org>, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        "Rafael J. Wysocki" <rjw@sisk.pl>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 1/2] oom: do not live lock on frozen tasks
In-Reply-To: <20110926110559.GH10156@tiehlicka.suse.cz>
References: <20110825151818.GA4003@redhat.com> <20110825164758.GB22564@tiehlicka.suse.cz> <alpine.DEB.2.00.1108251404130.18747@chino.kir.corp.google.com> <20110826070946.GA7280@tiehlicka.suse.cz> <20110826085610.GA9083@tiehlicka.suse.cz> <alpine.DEB.2.00.1108260218050.14732@chino.kir.corp.google.com> <20110826095356.GB9083@tiehlicka.suse.cz> <alpine.DEB.2.00.1108261110020.13943@chino.kir.corp.google.com> <20110926082837.GC10156@tiehlicka.suse.cz> <87sjnjk36l.fsf@rustcorp.com.au> <20110926110559.GH10156@tiehlicka.suse.cz>
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Date: Tue, 27 Sep 2011 11:51:00 +0930
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On Mon, 26 Sep 2011 13:05:59 +0200, Michal Hocko <mhocko@suse.cz> wrote:
> On Mon 26-09-11 19:58:50, Rusty Russell wrote:
> > On Mon, 26 Sep 2011 10:28:37 +0200, Michal Hocko <mhocko@suse.cz> wrote:
> > > On Fri 26-08-11 11:13:40, David Rientjes wrote:
> > > > I'd love to be able to do a thaw on a PF_FROZEN task in the oom killer 
> > > > followed by a SIGKILL if that task is selected for oom kill without an 
> > > > heuristic change.  Not sure if that's possible, so we'll wait for Rafael 
> > > > to chime in.
> > > 
> > > We have discussed that with Rafael and it should be safe to do that. See
> > > the patch bellow.
> > > The only place I am not entirely sure about is run_guest
> > > (drivers/lguest/core.c). It seems that the code is able to cope with
> > > signals but it also calls lguest_arch_run_guest after try_to_freeze.
> > 
> > Yes; if you want to kill things in the refrigerator(), then will a
> > 
> > 		if (cpu->lg->dead || task_is_dead(current))
> >                         break;
> > 
> > Work?  
> 
> The task is not dead yet. We should rather check for pending signals.
> Can we just move try_to_freeze up before the pending signals check?

Yep, that works.

Acked-by: Rusty Russell <rusty@rustcorp.com.au>

Cheers,
Rusty.