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

From: Rafael J. Wysocki
Date: Tue Sep 09 2014 - 16:29:09 EST


On Wednesday, September 10, 2014 12:23:36 AM Tejun Heo wrote:
> 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?

We can't make any assumptions regarding the availability of any devices.
That is, whatever can end up in device access may potentially fail.

Rafael

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