diff --git a/kernel/smp.c b/kernel/smp.c
index 8e451f3ff51b818796bf5ca4e4b3189a215b367a..b320622543e901741eda59d636ed812b4329d60a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -109,7 +109,7 @@ static void csd_lock_wait(struct call_single_data *data)
 static void csd_lock(struct call_single_data *data)
 {
 	csd_lock_wait(data);
-	data->flags = CSD_FLAG_LOCK;
+	data->flags |= CSD_FLAG_LOCK;
 
 	/*
 	 * prevent CPU from reordering the above assignment