diff --git a/kernel/events/core.c b/kernel/events/core.c
index e4aee51..2293e0b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -748,6 +748,7 @@
 
 /*
  * Update the total_time_enabled and total_time_running fields for a event.
+ * The caller of this function needs to hold the ctx->lock.
  */
 static void update_event_times(struct perf_event *event)
 {