---

yaml
---
r: 354569
b: refs/heads/master
c: 810360a
h: refs/heads/master
i:
  354567: cc0e8fd
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fcdb6a21903bcab0b5f788ba7eb0c31dd06040fd
+refs/heads/master: 810360a03597afc0d43a45798a52cfb69b8453d3

trunk/drivers/usb/serial/usb-serial.c

@@ -361,15 +361,21 @@ static int serial_write_room(struct tty_struct *tty)
 static int serial_chars_in_buffer(struct tty_struct *tty)
 {
 	struct usb_serial_port *port = tty->driver_data;
+	struct usb_serial *serial = port->serial;
+	int count = 0;
 
 	dev_dbg(tty->dev, "%s - port %d\n", __func__, port->number);
 
+	mutex_lock(&serial->disc_mutex);
 	/* if the device was unplugged then any remaining characters
 	   fell out of the connector ;) */
-	if (port->serial->disconnected)
-		return 0;
-	/* pass on to the driver specific version of this function */
-	return port->serial->type->chars_in_buffer(tty);
+	if (serial->disconnected)
+		count = 0;
+	else
+		count = serial->type->chars_in_buffer(tty);
+	mutex_unlock(&serial->disc_mutex);
+
+	return count;
 }
 
 static void serial_throttle(struct tty_struct *tty)