USB: kl5kusb105 don't flush to logically disconnected devices

If disconnect() is called for a logical disconnect, no more IO must be
done after disconnect() returns, or the old and new drivers may conflict.
This patch avoids this by using the flag and lock introduced by the earlier
patch for the mos7720 driver.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/kl5kusb105.c

@@ -461,6 +461,8 @@ static void klsi_105_close (struct usb_serial_port *port, struct file *filp)
 
 	dbg("%s port %d", __FUNCTION__, port->number);
 
+	mutex_lock(&port->serial->disc_mutex);
+	if (!port->serial->disconnected) {
 		/* send READ_OFF */
 		rc = usb_control_msg (port->serial->dev,
 				      usb_sndctrlpipe(port->serial->dev, 0),
@@ -472,6 +474,8 @@ static void klsi_105_close (struct usb_serial_port *port, struct file *filp)
 				      KLSI_TIMEOUT);
 		if (rc < 0)
 			err("Disabling read failed (error = %d)", rc);
+	}
+	mutex_unlock(&port->serial->disc_mutex);
 
 	/* shutdown our bulk reads and writes */
 	usb_kill_urb(port->write_urb);