sync iocbs need to actually wake_up_process the waiter (as spotted by Suparna).

fs/aio.c

@@ -552,6 +552,9 @@ int aio_complete(struct kiocb *iocb, long res, long res2)
 		iocb->ki_users--;
 		ret = (0 == iocb->ki_users);
 		spin_unlock_irq(&ctx->ctx_lock);
+
+		/* sync iocbs put the task here for us */
+		wake_up_process(iocb->ki_user_obj);
 		return ret;
 	}