linux-kernel - Re: [Patch v4 1/2] freezer: check OOM kill while being frozen

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Date:	Mon, 8 Sep 2014 16:00:41 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch v4 1/2] freezer: check OOM kill while being frozen

On Mon, Sep 8, 2014 at 4:15 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Tuesday, September 09, 2014 07:50:12 AM Tejun Heo wrote:
>> Hello,
>>
>> On Tue, Sep 09, 2014 at 12:48:28AM +0200, Rafael J. Wysocki wrote:
>> > Well, not exactly from anywhere.  Just from where try_to_freeze() is called
>> > I suppose?
>>
>> Yeap, anywhere try_to_freeze() may be called.
>>
>> > Which means that if this is a user space task, it won't to a lot before dying,
>> > will it?
>>
>> Userland tasks aren't likely to a lot of damages before dying but then
>> again there's no guarantee.  As it currently stands, try_to_freeze()
>> can be anywhere.
>
> Well, in that case the TIF_MEMDIE test alone is not sufficient in my opinion,
> because we can't guarantee that the task will not do something it was frozen
> to prevent it from doing.
>
>

That is true, there is a small window between TIF_MEMDIE is set
and SIGKILL is handled (aka process is killed), but this seems to
be a general signal handling issue not related with freezer after all
OOM relies on SIGKILL to function. No?
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