[Intel-gfx] [PATCH 1/3] drm/i915: Remove struct_mutex for destroying framebuffers

[Chris Wilson]

On Wed, Feb 15, 2017 at 03:59:23PM +0200, Joonas Lahtinen wrote:
> On ke, 2017-02-15 at 10:59 +0000, Chris Wilson wrote:
> > We do not need to hold struct_mutex for destroying drm_i915_gem_objects
> > any longer, and with a little care taken over tracking
> > obj->framebuffer_references, we can relinquish BKL locking around the
> > destroy of intel_framebuffer.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> <SNIP>
> 
> > @@ -14266,14 +14266,14 @@ static void intel_setup_outputs(struct drm_i915_private *dev_priv)
> >  
> >  static void intel_user_framebuffer_destroy(struct drm_framebuffer *fb)
> >  {
> > -	struct drm_device *dev = fb->dev;
> >  	struct intel_framebuffer *intel_fb = to_intel_framebuffer(fb);
> >  
> >  	drm_framebuffer_cleanup(fb);
> > -	mutex_lock(&dev->struct_mutex);
> > -	WARN_ON(!intel_fb->obj->framebuffer_references--);
> > +
> > +	WARN_ON(atomic_read(&intel_fb->obj->framebuffer_references) == 0);
> > +	atomic_dec(&intel_fb->obj->framebuffer_references);
> 
> Umm isn't the point of atomicity that you do this in one step?

Sure, just wasn't actually thinking of it a as real atomic.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre