ENGR00161643-3 UTP : bugfix

[karo-tx-linux.git] / block / blk-cgroup.c

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b9f4cc494ecefbf2560483bdc4685bb98d59b5d3..28d227c5ca7781aed5bb15cf37d3b0f1dcaa8d79 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -872,6 +872,13 @@ void blkcg_drain_queue(struct request_queue *q)
 {
        lockdep_assert_held(q->queue_lock);
 
+       /*
+        * @q could be exiting and already have destroyed all blkgs as
+        * indicated by NULL root_blkg.  If so, don't confuse policies.
+        */
+       if (!q->root_blkg)
+               return;
+
        blk_throtl_drain(q);
 }