drm/i915: Convert BUG_ON(pin_count) from an impossible condition

Also spotted by Dan Carpenter.

obj->pin_count is unsigned so the BUG_ON(obj->pin_count<0) will never
trigger.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7569b77..08f57ae 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4128,12 +4128,7 @@ i915_gem_object_pin(struct drm_gem_object *obj, uint32_t alignment,
                        return ret;
        }
 
-       obj_priv->pin_count++;
-
-       /* If the object is not active and not pending a flush,
-        * remove it from the inactive list
-        */
-       if (obj_priv->pin_count == 1) {
+       if (obj_priv->pin_count++ == 0) {
                i915_gem_info_add_pin(dev_priv, obj, mappable);
                if (!obj_priv->active)
                        list_move_tail(&obj_priv->mm_list,
@@ -4153,15 +4148,10 @@ i915_gem_object_unpin(struct drm_gem_object *obj)
        struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
 
        WARN_ON(i915_verify_lists(dev));
-       obj_priv->pin_count--;
-       BUG_ON(obj_priv->pin_count < 0);
+       BUG_ON(obj_priv->pin_count == 0);
        BUG_ON(obj_priv->gtt_space == NULL);
 
-       /* If the object is no longer pinned, and is
-        * neither active nor being flushed, then stick it on
-        * the inactive list
-        */
-       if (obj_priv->pin_count == 0) {
+       if (--obj_priv->pin_count == 0) {
                if (!obj_priv->active)
                        list_move_tail(&obj_priv->mm_list,
                                       &dev_priv->mm.inactive_list);