[intel-gem] evict_something was failing when wait_request freed objects

When i915_wait_request clears object from the active list, it may end up
freeing them and not moving them to the inactive list. This ends up
unbinding objects from the GTT without there ever being new objects visible
to i915_gem_evict_something on the inactive list. As the only success
condition required the presence of objects on the inactive list, this would
falsely assume that no GTT space had been made available, and end up
returning -ENOMEM to the application.

diff --git a/linux-core/i915_gem.c b/linux-core/i915_gem.c
index 115f8e7..b114192 100644 (file)
--- a/linux-core/i915_gem.c
+++ b/linux-core/i915_gem.c
@@ -805,7 +805,7 @@ i915_gem_evict_something(struct drm_device *dev)
        drm_i915_private_t *dev_priv = dev->dev_private;
        struct drm_gem_object *obj;
        struct drm_i915_gem_object *obj_priv;
-       int ret;
+       int ret = 0;
 
        for (;;) {
                /* If there's an inactive buffer available now, grab it
@@ -817,6 +817,13 @@ i915_gem_evict_something(struct drm_device *dev)
                                                    list);
                        obj = obj_priv->obj;
                        BUG_ON(obj_priv->pin_count != 0);
+#if WATCH_LRU
+                       DRM_INFO("%s: evicting %p\n", __func__, obj);
+#endif
+                       BUG_ON(obj_priv->active);
+
+                       /* Wait on the rendering and unbind the buffer. */
+                       ret = i915_gem_object_unbind(obj);
                        break;
                }
 
@@ -826,17 +833,21 @@ i915_gem_evict_something(struct drm_device *dev)
                 */
                if (!list_empty(&dev_priv->mm.request_list)) {
                        struct drm_i915_gem_request *request;
-                       int ret;
 
                        request = list_first_entry(&dev_priv->mm.request_list,
                                                   struct drm_i915_gem_request,
                                                   list);
 
                        ret = i915_wait_request(dev, request->seqno);
-                       if (ret != 0)
-                               return ret;
-
-                       continue;
+                       
+                       /* if waiting caused an object to become inactive,
+                        * then loop around and wait for it. Otherwise, we
+                        * assume that waiting freed and unbound something,
+                        * so there should now be some space in the GTT
+                        */
+                       if (!list_empty(&dev_priv->mm.inactive_list))
+                               continue;
+                       break;
                }
 
                /* If we didn't have anything on the request list but there
@@ -859,21 +870,15 @@ i915_gem_evict_something(struct drm_device *dev)
                        continue;
                }
 
+               DRM_ERROR("inactive empty %d request empty %d flushing empty %d\n",
+                         list_empty(&dev_priv->mm.inactive_list),
+                         list_empty(&dev_priv->mm.request_list),
+                         list_empty(&dev_priv->mm.flushing_list));
                /* If we didn't do any of the above, there's nothing to be done
                 * and we just can't fit it in.
                 */
                return -ENOMEM;
        }
-
-#if WATCH_LRU
-       DRM_INFO("%s: evicting %p\n", __func__, obj);
-#endif
-
-       BUG_ON(obj_priv->active);
-
-       /* Wait on the rendering and unbind the buffer. */
-       ret = i915_gem_object_unbind(obj);
-
        return ret;
 }
 
@@ -959,7 +964,7 @@ i915_gem_object_bind_to_gtt(struct drm_gem_object *obj, unsigned alignment)
 
                ret = i915_gem_evict_something(dev);
                if (ret != 0) {
-                       DRM_ERROR("Failed to evict a buffer\n");
+                       DRM_ERROR("Failed to evict a buffer %d\n", ret);
                        return ret;
                }
                goto search_free;