diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 939e198d7670..a3afa0c387cd 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1263,7 +1263,9 @@ static int tty_reopen(struct tty_struct *tty)
 	tty->count++;
 	tty->driver = driver; /* N.B. why do this every time?? */
 
+	mutex_lock(&tty->ldisc_mutex);
 	WARN_ON(!test_bit(TTY_LDISC, &tty->flags));
+	mutex_unlock(&tty->ldisc_mutex);
 
 	return 0;
 }