diff --git a/drivers/char/mwave/mwavedd.c b/drivers/char/mwave/mwavedd.c
index 8d14823b0514..50243fcd87e8 100644
--- a/drivers/char/mwave/mwavedd.c
+++ b/drivers/char/mwave/mwavedd.c
@@ -56,6 +56,7 @@
 #include <linux/serial.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
+#include <linux/smp_lock.h>
 #include <linux/delay.h>
 #include <linux/serial_8250.h>
 #include "smapi.h"
@@ -100,6 +101,7 @@ static int mwave_open(struct inode *inode, struct file *file)
 	PRINTK_2(TRACE_MWAVE,
 		"mwavedd::mwave_open, exit return retval %x\n", retval);
 
+	cycle_kernel_lock();
 	return retval;
 }