--- linux-2.6.30.9/drivers/usb/serial/usb-serial.c	2009-10-05 18:38:08.000000000 +0300
+++ linux-2.6.30.9-rsdk/drivers/usb/serial/usb-serial.c	2013-05-02 01:47:56.923226799 +0300
@@ -35,6 +35,8 @@
 #include <linux/usb/serial.h>
 #include "pl2303.h"
 
+#include <linux/smp_lock.h> /* brucehou, 2010/05/21, for lock_kernel & unlock_kernel */
+
 /*
  * Version Information
  */