diff --git a/block/as-iosched.c b/block/as-iosched.c
index 296708ceceb2d..e25a5d79ab271 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 67d446de0227a..01820b1094e9f 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();
 }