From e7d841ca03b7ab668620045cd7b428eda9f41601 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 3 Dec 2012 11:36:30 +0000 Subject: drm/i915: Close race between processing unpin task and queueing the flip 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 Cc: stable@vger.kernel.org [danvet: Review the barriers a bit, we need a write barrier both before and after updating ->pending. Similarly we need a read barrier in the interrupt handler both before and after reading ->pending. With well-ordered irqs only one barrier in each place should be required, but since this patch explicitly sets out to combat spurious interrupts with is staged activation of the unpin work we need to go full-bore on the barriers, too. Discussed with Chris Wilson on irc and changes acked by him.] Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_drv.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/i915/intel_drv.h') diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 522061ca068..3915ca9abd4 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -401,7 +401,10 @@ struct intel_unpin_work { struct drm_i915_gem_object *old_fb_obj; struct drm_i915_gem_object *pending_flip_obj; struct drm_pending_vblank_event *event; - int pending; + atomic_t pending; +#define INTEL_FLIP_INACTIVE 0 +#define INTEL_FLIP_PENDING 1 +#define INTEL_FLIP_COMPLETE 2 bool enable_stall_check; }; -- cgit v1.2.3-70-g09d2