drm/i915: Double check that the wait_request is not pending before warning

If we are busy, then we may have woken up the wait_request handler but
not yet serviced it before the hang check fires. So in hang check,
double check that the i915_gem_do_wait_request() is still pending the
wake-up before declaring all hope lost.

Fixes regression with e78d73b16bcde921c9cf458d2e4de8e4fc2518f3.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=30073
Reported-and-tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_irq.c

@@ -1350,17 +1350,25 @@ void i915_hangcheck_elapsed(unsigned long data)
 		i915_seqno_passed(i915_get_gem_seqno(dev,
 				&dev_priv->render_ring),
 			i915_get_tail_request(dev)->seqno)) {
+		bool missed_wakeup = false;
+
 		dev_priv->hangcheck_count = 0;
 
 		/* Issue a wake-up to catch stuck h/w. */
-		if (dev_priv->render_ring.waiting_gem_seqno |
-		    dev_priv->bsd_ring.waiting_gem_seqno) {
-			DRM_ERROR("Hangcheck timer elapsed... GPU idle, missed IRQ.\n");
-			if (dev_priv->render_ring.waiting_gem_seqno)
-				DRM_WAKEUP(&dev_priv->render_ring.irq_queue);
-			if (dev_priv->bsd_ring.waiting_gem_seqno)
-				DRM_WAKEUP(&dev_priv->bsd_ring.irq_queue);
+		if (dev_priv->render_ring.waiting_gem_seqno &&
+		    waitqueue_active(&dev_priv->render_ring.irq_queue)) {
+			DRM_WAKEUP(&dev_priv->render_ring.irq_queue);
+			missed_wakeup = true;
+		}
+
+		if (dev_priv->bsd_ring.waiting_gem_seqno &&
+		    waitqueue_active(&dev_priv->bsd_ring.irq_queue)) {
+			DRM_WAKEUP(&dev_priv->bsd_ring.irq_queue);
+			missed_wakeup = true;
 		}
+
+		if (missed_wakeup)
+			DRM_ERROR("Hangcheck timer elapsed... GPU idle, missed IRQ.\n");
 		return;
 	}