drm/i915: Flush read-only buffers from the active list upon idle as well

It is possible for the active list to only contain a read-only buffer so
that the ring->gpu_write_list remains entry. This leads to an
inconsistency between i915_gpu_is_active() and i915_gpu_idle() causing
an infinite spin during the shrinker and an assertion failure that
i915_gpu_idle() does indeed flush all buffers from the active lists.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_gem.c

@@ -2172,7 +2172,7 @@ i915_gem_object_unbind(struct drm_gem_object *obj)
 static int i915_ring_idle(struct drm_device *dev,
 			  struct intel_ring_buffer *ring)
 {
-	if (list_empty(&ring->gpu_write_list))
+	if (list_empty(&ring->gpu_write_list) && list_empty(&ring->active_list))
 		return 0;
 
 	i915_gem_flush_ring(dev, NULL, ring,
@@ -2190,9 +2190,7 @@ i915_gpu_idle(struct drm_device *dev)
 	int ret;
 
 	lists_empty = (list_empty(&dev_priv->mm.flushing_list) &&
-		       list_empty(&dev_priv->render_ring.active_list) &&
-		       list_empty(&dev_priv->bsd_ring.active_list) &&
-		       list_empty(&dev_priv->blt_ring.active_list));
+		       list_empty(&dev_priv->mm.active_list));
 	if (lists_empty)
 		return 0;
 
@@ -4900,9 +4898,7 @@ i915_gpu_is_active(struct drm_device *dev)
 	int lists_empty;
 
 	lists_empty = list_empty(&dev_priv->mm.flushing_list) &&
-		      list_empty(&dev_priv->render_ring.active_list) &&
-		      list_empty(&dev_priv->bsd_ring.active_list) &&
-		      list_empty(&dev_priv->blt_ring.active_list);
+		      list_empty(&dev_priv->mm.active_list);
 
 	return !lists_empty;
 }

drivers/gpu/drm/i915/i915_gem_evict.c

@@ -165,9 +165,7 @@ i915_gem_evict_everything(struct drm_device *dev)
 
 	lists_empty = (list_empty(&dev_priv->mm.inactive_list) &&
 		       list_empty(&dev_priv->mm.flushing_list) &&
-		       list_empty(&dev_priv->render_ring.active_list) &&
-		       list_empty(&dev_priv->bsd_ring.active_list) &&
-		       list_empty(&dev_priv->blt_ring.active_list));
+		       list_empty(&dev_priv->mm.active_list));
 	if (lists_empty)
 		return -ENOSPC;
 
@@ -184,9 +182,7 @@ i915_gem_evict_everything(struct drm_device *dev)
 
 	lists_empty = (list_empty(&dev_priv->mm.inactive_list) &&
 		       list_empty(&dev_priv->mm.flushing_list) &&
-		       list_empty(&dev_priv->render_ring.active_list) &&
-		       list_empty(&dev_priv->bsd_ring.active_list) &&
-		       list_empty(&dev_priv->blt_ring.active_list));
+		       list_empty(&dev_priv->mm.active_list));
 	BUG_ON(!lists_empty);
 
 	return 0;