Re: [PATCH 3/4] OOM, PM: OOM killed task shouldn't escape PM suspend

[Michal Hocko]

On Thu 06-11-14 11:12:11, Tejun Heo wrote:
> On Thu, Nov 06, 2014 at 05:01:58PM +0100, Michal Hocko wrote:
> > Yes, OOM killer simply kicks the process sets TIF_MEMDIE and terminates.
> > That will release the read_lock, allow this to take the write lock and
> > check whether it the current has been killed without any races.
> > OOM killer doesn't wait for the killed task. The allocation is retried.
> > 
> > Does this explain your concern?
> 
> Draining oom killer then doesn't mean anything, no?  OOM killer may
> have been disabled and drained but the killed tasks might wake up
> after the PM freezer considers them to be frozen, right?  What am I
> missing?

The mutual exclusion between OOM and the freezer will cause that the
victim will have TIF_MEMDIE already set when try_to_freeze_tasks even
starts. Then freezing_slow_path wouldn't allow the task to enter the
fridge so the wake up moment is not really that important.

-- 
Michal Hocko
SUSE Labs
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