diff --git a/arch/um/drivers/mmapper_kern.c b/arch/um/drivers/mmapper_kern.c
index 67b2f55a602f6db174f95f4e0b843f4adda97d2e..eb240323c40ad6a52883b079f2324c57ae9eb09f 100644
--- a/arch/um/drivers/mmapper_kern.c
+++ b/arch/um/drivers/mmapper_kern.c
@@ -16,6 +16,7 @@
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include "mem_user.h"
 
@@ -77,6 +78,7 @@ static int mmapper_mmap(struct file *file, struct vm_area_struct *vma)
 
 static int mmapper_open(struct inode *inode, struct file *file)
 {
+	cycle_kernel_lock();
 	return 0;
 }