diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 88b2074..fc1cea4 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -487,21 +487,22 @@
 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);
 	}
 
 
diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index bbbe1b9..5e8bf1b 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -641,7 +641,10 @@
 	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++)
diff --git a/drivers/usb/serial/sierra.c b/drivers/usb/serial/sierra.c
index 953bdf8..4c925e3 100644
--- a/drivers/usb/serial/sierra.c
+++ b/drivers/usb/serial/sierra.c
@@ -597,7 +597,10 @@
 	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++)
diff --git a/drivers/usb/serial/visor.c b/drivers/usb/serial/visor.c
index 7ee087f..c234799 100644
--- a/drivers/usb/serial/visor.c
+++ b/drivers/usb/serial/visor.c
@@ -349,16 +349,20 @@
 	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",
diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index f5033d4..38726ef 100644
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -658,11 +658,14 @@
 	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;