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

[Tejun Heo]

On Thu, Sep 11, 2014 at 06:30:04PM +0200, Michal Hocko wrote:
> > I am wondering if the folllowing check makes any sense with regarding
> > to rule out PM freeze:
> > 
> >         if ((!pm_nosig_freezing && !pm_freezing) &&
> >             cgroup_freezing(current) && test_thread_flag(TIF_MEMDIE))
> >                 return true;

Doesn't this mean that if PM freezing and OOM killing race each other,
the system may hang?  Driver PM operation may try to allocate memory
-> triggers OOM -> OOM killer selects an already frozen task ->
nothing happens.  I wonder whether OOM killing and PM operations
should be mutually exclusive at a higher level.  e.g. make OOM killing
always override freezing but let hibernation abort operation before
taking snapshot if OOM killing has happened since the beginning of the
PM operation.

Thanks.

-- 
tejun
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