[Intel-gfx] [PATCH 1/2] drm/i915: fix possible RPM ref leaking during RPS disabling

[Imre Deak]

On Tue, 2014-05-13 at 15:54 +0200, Daniel Vetter wrote:
> On Tue, May 13, 2014 at 04:46:10PM +0300, Imre Deak wrote:
> > On Mon, 2014-05-12 at 19:51 +0200, Daniel Vetter wrote:
> > > On Mon, May 12, 2014 at 06:35:04PM +0300, Imre Deak wrote:
> > > > In
> > > > 
> > > > commit c6df39b5ea6342323a42edfbeeca0a28c643d7ae
> > > > Author: Imre Deak <imre.deak at intel.com>
> > > > Date:   Mon Apr 14 20:24:29 2014 +0300
> > > > 
> > > >     drm/i915: get a runtime PM ref for the deferred GT powersave enabling
> > > > 
> > > > I added an RPM get-ref when enabling RPS from a deferred work, but forgot
> > > > to add the corresponding put-ref when canceling the work. This may leave
> > > > RPM disabled.
> > > > 
> > > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > 
> > > Could we intentionally hit this by e.g. racing a suspend/resume against
> > > runtime pm? E.g.
> > > 1. disable all outputs, make sure we've entered runtime pm
> > > 2. set runtime autosuspend delay to 0
> > > 3. suspend/resume
> > > 4. autosuspend (hopefully, my understanding is a bit unclear)
> > > 
> > > ->Boom
> > > 
> > > Would look nice as an igt subtest if it works ;-)
> > 
> > Yep, works consistently as expected both before and after the fix. I
> > pushed the new subtest, please add here:
> > Testcase: igt/pm_pc8/system-suspend
> 
> Now I'm confused: I expected this to blow up without your fix here, and
> not work with or without it?! Please unconfuse ...

Blows up consistently before the fix and passes consistently after.

--Imre

> -Daniel

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