static void mct_u232_close (struct usb_serial_port *port, struct file *filp)
 {
        unsigned int c_cflag;
-       unsigned long flags;
        unsigned int control_state;
        struct mct_u232_private *priv = usb_get_serial_port_data(port);
        dbg("%s port %d", __FUNCTION__, port->number);
 
        if (port->tty) {
                c_cflag = port->tty->termios->c_cflag;
-               if (c_cflag & HUPCL) {
-                  /* drop DTR and RTS */
-                  spin_lock_irqsave(&priv->lock, flags);
-                  priv->control_state &= ~(TIOCM_DTR | TIOCM_RTS);
-                  control_state = priv->control_state;
-                  spin_unlock_irqrestore(&priv->lock, flags);
-                  mct_u232_set_modem_ctrl(port->serial, control_state);
+               mutex_lock(&port->serial->disc_mutex);
+               if (c_cflag & HUPCL && !port->serial->disconnected) {
+                       /* drop DTR and RTS */
+                       spin_lock_irq(&priv->lock);
+                       priv->control_state &= ~(TIOCM_DTR | TIOCM_RTS);
+                       control_state = priv->control_state;
+                       spin_unlock_irq(&priv->lock);
+                       mct_u232_set_modem_ctrl(port->serial, control_state);
                }
+               mutex_unlock(&port->serial->disc_mutex);
        }
 
 
 
        portdata->dtr_state = 0;
 
        if (serial->dev) {
-               option_send_setup(port);
+               mutex_lock(&serial->disc_mutex);
+               if (!serial->disconnected)
+                       option_send_setup(port);
+               mutex_unlock(&serial->disc_mutex);
 
                /* Stop reading/writing urbs */
                for (i = 0; i < N_IN_URB; i++)
 
        portdata->dtr_state = 0;
 
        if (serial->dev) {
-               sierra_send_setup(port);
+               mutex_lock(&serial->disc_mutex);
+               if (!serial->disconnected)
+                       sierra_send_setup(port);
+               mutex_unlock(&serial->disc_mutex);
 
                /* Stop reading/writing urbs */
                for (i = 0; i < N_IN_URB; i++)
 
        usb_kill_urb(port->read_urb);
        usb_kill_urb(port->interrupt_in_urb);
 
-       /* Try to send shutdown message, if the device is gone, this will just fail. */
-       transfer_buffer =  kmalloc (0x12, GFP_KERNEL);
-       if (transfer_buffer) {
-               usb_control_msg (port->serial->dev,
-                                usb_rcvctrlpipe(port->serial->dev, 0),
-                                VISOR_CLOSE_NOTIFICATION, 0xc2,
-                                0x0000, 0x0000, 
-                                transfer_buffer, 0x12, 300);
-               kfree (transfer_buffer);
+       mutex_lock(&port->serial->disc_mutex);
+       if (!port->serial->disconnected) {
+               /* Try to send shutdown message, unless the device is gone */
+               transfer_buffer =  kmalloc (0x12, GFP_KERNEL);
+               if (transfer_buffer) {
+                       usb_control_msg (port->serial->dev,
+                                        usb_rcvctrlpipe(port->serial->dev, 0),
+                                        VISOR_CLOSE_NOTIFICATION, 0xc2,
+                                        0x0000, 0x0000,
+                                        transfer_buffer, 0x12, 300);
+                       kfree (transfer_buffer);
+               }
        }
+       mutex_lock(&port->serial->disc_mutex);
 
        if (stats)
                dev_info(&port->dev, "Bytes In = %d  Bytes Out = %d\n",
 
        struct list_head *tmp2;
 
        dbg("%s - port %d", __FUNCTION__, port->number);
-       
+
+       mutex_lock(&port->serial->disc_mutex);
        /* filp is NULL when called from usb_serial_disconnect */
-       if (filp && (tty_hung_up_p(filp))) {
+       if ((filp && (tty_hung_up_p(filp))) || port->serial->disconnected) {
+               mutex_unlock(&port->serial->disc_mutex);
                return;
        }
+       mutex_unlock(&port->serial->disc_mutex);
 
        port->tty->closing = 1;