diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 6c7151edd715..b0e2c4847a5d 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -110,16 +110,19 @@ static void pty_unthrottle(struct tty_struct *tty)
 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 {
 	struct tty_struct *to = tty->link;
+	unsigned long flags;
 
 	if (tty->stopped)
 		return 0;
 
 	if (c > 0) {
+		spin_lock_irqsave(&to->port->lock, flags);
 		/* Stuff the data into the input queue of the other end */
 		c = tty_insert_flip_string(to->port, buf, c);
 		/* And shovel */
 		if (c)
 			tty_flip_buffer_push(to->port);
+		spin_unlock_irqrestore(&to->port->lock, flags);
 	}
 	return c;
 }