diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index b008e2b38d543e5709f68dcdfce036f7a3177cd5..adbd9acf817f1594b04357274355714b99c6ea7d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -275,6 +275,7 @@ int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 	return 0;
 }
 
+/* Caller must hold tty_lock */
 static int check_tty_count(struct tty_struct *tty, const char *routine)
 {
 #ifdef CHECK_TTY_COUNT