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Date: Fri, 26 Aug 2011 16:44:49 +0400
From: Konstantin Khlebnikov <khlebnikov@openvz.org>
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To: Michal Hocko <mhocko@suse.cz>
CC: David Rientjes <rientjes@google.com>, Oleg Nesterov <oleg@redhat.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.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>
Subject: Re: [PATCH] oom: skip frozen tasks
References: <alpine.DEB.2.00.1108231313520.21637@chino.kir.corp.google.com> <20110824101927.GB3505@tiehlicka.suse.cz> <alpine.DEB.2.00.1108241226550.31357@chino.kir.corp.google.com> <20110825091920.GA22564@tiehlicka.suse.cz> <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> <4E576F65.5060009@openvz.org> <20110826104827.GC9083@tiehlicka.suse.cz>
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Michal Hocko wrote:
> On Fri 26-08-11 14:03:17, Konstantin Khlebnikov wrote:
>> Michal Hocko wrote:
>>
>>> @@ -450,6 +459,10 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
>>>   			pr_err("Kill process %d (%s) sharing same memory\n",
>>>   				task_pid_nr(q), q->comm);
>>>   			task_unlock(q);
>>> +
>>> +			if (frozen(q))
>>> +				thaw_process(q);
>>> +
>>
>> We must thaw task strictly after sending SIGKILL.
>
> Sounds reasonable.
>
>> But anyway I think this is a bad idea.
>
> Why?

Refrigerator may be used for digging in task's internal structures,
so such digger may be very surprised if somebody suddenly thaws this task.

>
>>
>>>   			force_sig(SIGKILL, q);
>>>   		}
>>>
>