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Commit 000fa7cf authored by Mario Kleiner's avatar Mario Kleiner Committed by Dave Airlie
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drm-vblank: Always return true vblank count of scheduled vblank event. 



This patch tries to make sure that the vbl.reply.sequence
vblank count for a queued or emitted vblank event always
corresponds to the true vblank count of queueing/emission, so
the ddx can rely on the returned target_msc for consistency
checks and implementation of swap_intervals in glXSwapBuffers().

Without this there is a small race-condition between the
userspace ddx queueing a vblank event and the vblank
counter incrementing before the event gets queued in
the kernel.

Signed-off-by: default avatarMario Kleiner <mario.kleiner@tuebingen.mpg.de>
Acked-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 3ce05168

drivers/gpu/drm/drm_irq.c

+3 −0
Original line number Diff line number Diff line
@@ -1086,15 +1086,18 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe, 


	e->event.sequence = vblwait->request.sequence;

	if ((seq - vblwait->request.sequence) <= (1 << 23)) {

		e->event.sequence = seq;

		e->event.tv_sec = now.tv_sec;

		e->event.tv_usec = now.tv_usec;

		drm_vblank_put(dev, e->pipe);

		list_add_tail(&e->base.link, &e->base.file_priv->event_list);

		wake_up_interruptible(&e->base.file_priv->event_wait);

		vblwait->reply.sequence = seq;

		trace_drm_vblank_event_delivered(current->pid, pipe,

						 vblwait->request.sequence);

	} else {

		list_add_tail(&e->base.link, &dev->vblank_event_list);

		vblwait->reply.sequence = vblwait->request.sequence;

	}



	spin_unlock_irqrestore(&dev->event_lock, flags);