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

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Message-ID: <20140909152336.GB8890@mtj.dyndns.org>
Date:	Wed, 10 Sep 2014 00:23:36 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Cong Wang <xiyou.wangcong@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch v4 1/2] freezer: check OOM kill while being frozen

On Tue, Sep 09, 2014 at 05:16:55PM +0200, Michal Hocko wrote:
> But OOM killer doesn't kill kernel threads as they do not own any
> memory. So the check should be safe, no?

Even for userland tasks, try_to_freeze() can currently be anywhere in
the kernel.  The frequently used ones are few but there are some odd
ones out, and, again, there's nothing enforcing any structure on
try_to_freeze() usage.  The other thing is that we may do quite a bit
during exiting including allocating memory.  Are those safe for system
PM?  Rafael, what exactly are the rules for PM?  What shouldn't
change?

Thanks.

-- 
tejun
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