• Chris Wilson's avatar
    drm/i915: Close race between processing unpin task and queueing the flip · e7d841ca
    Chris Wilson authored
    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: default avatarChris Wilson <chris@chris-wilson.co.uk>
    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: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    e7d841ca
i915_irq.c 75.7 KB