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

[Imre Deak <imre.deak@intel.com>]

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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@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@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

--Imre

> -Daniel
> 
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 834c49c..9170039 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -4609,7 +4609,9 @@ void intel_disable_gt_powersave(struct drm_device *dev)
> >  		ironlake_disable_drps(dev);
> >  		ironlake_disable_rc6(dev);
> >  	} else if (IS_GEN6(dev) || IS_GEN7(dev)) {
> > -		cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work);
> > +		if (cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work))
> > +			intel_runtime_pm_put(dev_priv);
> > +
> >  		cancel_work_sync(&dev_priv->rps.work);
> >  		mutex_lock(&dev_priv->rps.hw_lock);
> >  		if (IS_VALLEYVIEW(dev))
> > -- 
> > 1.8.4
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 


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