1 files changed, 9 insertions, 1 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ee8a90c7c46c..e8525fa72823 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1314,7 +1314,15 @@ static void cfq_exit_single_io_context(struct io_context *ioc,
                 unsigned long flags;
 
                 spin_lock_irqsave(q->queue_lock, flags);
-                __cfq_exit_single_io_context(cfqd, cic);
+
+                /*
+                 * Ensure we get a fresh copy of the ->key to prevent
+                 * race between exiting task and queue
+                 */
+                smp_read_barrier_depends();
+                if (cic->key)
+                        __cfq_exit_single_io_context(cfqd, cic);
+
                 spin_unlock_irqrestore(q->queue_lock, flags);
         }
 }