Re: [PATCH] drm/i915: Fix locking in DRRS flush/invalidate hooks

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Apr 09, 2015 at 12:52:19PM +0300, Jani Nikula wrote:
> On Thu, 09 Apr 2015, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > We must acquire the mutex before we can check drrs.dp, otherwise
> > someone might sneak in with a modeset, clear the pointer after we've
> > checked it and then the code will Oops.
> >
> > This issue has been introduced in
> >
> > commit a93fad0f7fb8a3ff12e8814b630648f6d187954c
> > Author: Vandana Kannan <vandana.kannan@intel.com>
> > Date:   Sat Jan 10 02:25:59 2015 +0530
> >
> >     drm/i915: DRRS calls based on frontbuffer
> >
> > Cc: Ramalingam C <ramalingam.c@intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Vandana Kannan <vandana.kannan@intel.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 
> Missed 4.0 so this is

Fortunately so since it makes my BSW deadlock on module load. And Mika
says his IVB is showing similar symptoms.

> 
> Cc: stable@vger.kernel.org
> 
> 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 17 ++++++++++-------
> >  1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 1b87969536ff..e265a0dee479 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -5170,7 +5170,6 @@ static void intel_edp_drrs_downclock_work(struct work_struct *work)
> >  			downclock_mode->vrefresh);
> >  
> >  unlock:
> > -
> >  	mutex_unlock(&dev_priv->drrs.mutex);
> >  }
> >  
> > @@ -5192,12 +5191,14 @@ void intel_edp_drrs_invalidate(struct drm_device *dev,
> >  	struct drm_crtc *crtc;
> >  	enum pipe pipe;
> >  
> > -	if (!dev_priv->drrs.dp)
> > -		return;
> > -
> >  	cancel_delayed_work_sync(&dev_priv->drrs.work);
> >  
> >  	mutex_lock(&dev_priv->drrs.mutex);
> > +	if (!dev_priv->drrs.dp) {
> > +		mutex_unlock(&dev_priv->drrs.mutex);
> > +		return;
> > +	}
> > +
> >  	crtc = dp_to_dig_port(dev_priv->drrs.dp)->base.base.crtc;
> >  	pipe = to_intel_crtc(crtc)->pipe;
> >  
> > @@ -5231,12 +5232,14 @@ void intel_edp_drrs_flush(struct drm_device *dev,
> >  	struct drm_crtc *crtc;
> >  	enum pipe pipe;
> >  
> > -	if (!dev_priv->drrs.dp)
> > -		return;
> > -
> >  	cancel_delayed_work_sync(&dev_priv->drrs.work);
> >  
> >  	mutex_lock(&dev_priv->drrs.mutex);
> > +	if (!dev_priv->drrs.dp) {
> > +		mutex_unlock(&dev_priv->drrs.mutex);
> > +		return;
> > +	}
> > +
> >  	crtc = dp_to_dig_port(dev_priv->drrs.dp)->base.base.crtc;
> >  	pipe = to_intel_crtc(crtc)->pipe;
> >  	dev_priv->drrs.busy_frontbuffer_bits &= ~frontbuffer_bits;
> > -- 
> > 2.1.4
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
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