ttm: Return -ERESTART when a signal interrupts bo eviction.

A bug caused the ttm code to just terminate the wait when a signal
was received while waiting for the GPU to release a buffer object that
was to be evicted.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -527,9 +527,12 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo, unsigned mem_type,
 	ret = ttm_bo_wait(bo, false, interruptible, no_wait);
 	spin_unlock(&bo->lock);
 
-	if (ret && ret != -ERESTART) {
-		printk(KERN_ERR TTM_PFX "Failed to expire sync object before "
-		       "buffer eviction.\n");
+	if (unlikely(ret != 0)) {
+		if (ret != -ERESTART) {
+			printk(KERN_ERR TTM_PFX
+			       "Failed to expire sync object before "
+			       "buffer eviction.\n");
+		}
 		goto out;
 	}