2 files changed, 6 insertions, 4 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 296708ceceb2..e25a5d79ab27 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1844,9 +1844,10 @@ static void __exit as_exit(void)
         DECLARE_COMPLETION(all_gone);
         elv_unregister(&iosched_as);
         ioc_gone = &all_gone;
-        barrier();
+        /* ioc_gone's update must be visible before reading ioc_count */
+        smp_wmb();
         if (atomic_read(&ioc_count))
-                complete(ioc_gone);
+                wait_for_completion(ioc_gone);
         synchronize_rcu();
         kmem_cache_destroy(arq_pool);
 }
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 67d446de0227..01820b1094e9 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2439,9 +2439,10 @@ static void __exit cfq_exit(void)
         DECLARE_COMPLETION(all_gone);
         elv_unregister(&iosched_cfq);
         ioc_gone = &all_gone;
-        barrier();
+        /* ioc_gone's update must be visible before reading ioc_count */
+        smp_wmb();
         if (atomic_read(&ioc_count))
-                complete(ioc_gone);
+                wait_for_completion(ioc_gone);
         synchronize_rcu();
         cfq_slab_kill();
 }