USB: make sure usb serial drivers 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>

1 files changed, 9 insertions, 8 deletions

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 88b2074867c5..fc1cea4aba13 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -487,21 +487,22 @@ error:
 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);
         }