[Intel-gfx] [PATCH] drm/i915: Close race between processing unpin task and queueing the flip

[Daniel Vetter]

On Mon, Dec 03, 2012 at 11:36:30AM +0000, Chris Wilson wrote:
> Before queuing the flip but crucially after attaching the unpin-work to
> the crtc, we continue to setup the unpin-work. However, should the
> hardware fire early, we see the connected unpin-work and queue the task.
> The task then promptly runs and unpins the fb before we finish taking
> the required references or even pinning it... Havoc.
> 
> To close the race, we use the flip-pending atomic to indicate when the
> flip is finally setup and enqueued. So during the flip-done processing,
> we can check more accurately whether the flip was expected.
> 
> v2: Add the appropriate mb() to ensure that the writes to the page-flip
> worker are complete prior to marking it active and emitting the MI_FLIP.
> On the read side, the mb should be enforced by the spinlocks.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: stable at vger.kernel.org

Merged to -fixes, with the barrier changes we've discussed on irc applied
(and the reasoning for why we need 2 on each sided added to my commit
message note).

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch