[PATCH] fix oops in usbserial_cleanup function;

[m00150988@huawei.com]

From: marui <m00150988@huawei.com>

1. I find this bug on OpenSUSE 11.3 which kernel vesion is 2.6.34, but the latest kernel vesion 2.6.36-rc7 aslo have this bug. This patch is based on the kernel of 2.6.36-rc7.
2. Bug report:
   a. Install huawei datacard dashboard on OpenSUSE 11.3
   b. Plug in huawei datacard into OpenSUSE 11.3 which kernel verison is 2.6.36-rc7
   c. After the dashboard has detected the device, I  pull out the usb datacard
   d. close datashboard,then kernel panic will happen in usbserial_cleanup function. 
 
 
3. fix the bug:
   I find usbserial_cleanup should judge the usb device wheher has been disconnected firtly.

Signed-off-by: marui<m00150988@huawei.com>


--- linux-2.6.36-rc7_orig/drivers/usb/serial/usb-serial.c	2010-10-06 16:39:52.000000000 -0400
+++ linux-2.6.36-rc7/drivers/usb/serial/usb-serial.c	2010-10-14 20:59:47.000000000 -0400
@@ -328,6 +328,20 @@ static void serial_cleanup(struct tty_st
 	/* The console is magical.  Do not hang up the console hardware
 	 * or there will be tears.
 	 */
+        dbg("%s start\n",__func__);
+        if(NULL == port)
+        {
+            dbg("%s NULL == port\n",__func__);
+            return;
+        }
+	mutex_lock(&port->serial->disc_mutex);
+	if (port->serial->disconnected)
+        {
+                dbg("%s port->serial->disconnected\n",__func__);
+                return_serial(port->serial);
+		return;
+        }
+	mutex_unlock(&port->serial->disc_mutex);
 	if (port->port.console)
 		return;