diff --git a/arch/um/drivers/harddog_kern.c b/arch/um/drivers/harddog_kern.c
index a9ad4bd..d332503 100644
--- a/arch/um/drivers/harddog_kern.c
+++ b/arch/um/drivers/harddog_kern.c
@@ -66,6 +66,7 @@
 	int err = -EBUSY;
 	char *sock = NULL;
 
+	lock_kernel();
 	spin_lock(&lock);
 	if(timer_alive)
 		goto err;
@@ -82,9 +83,11 @@
 
 	timer_alive = 1;
 	spin_unlock(&lock);
+	unlock_kernel();
 	return nonseekable_open(inode, file);
 err:
 	spin_unlock(&lock);
+	unlock_kernel();
 	return err;
 }