diff --git a/[refs] b/[refs]
index 05418443af7f..d22597f69cc7 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9bd0a077122a6b15069aab7a59c8f50f736fa1dd
+refs/heads/master: 137d1a26c842a384c98dd2a6a605014fddf5c777
diff --git a/trunk/arch/um/kernel/reboot.c b/trunk/arch/um/kernel/reboot.c
index 66d754c46e7b..1411f4e79f9a 100644
--- a/trunk/arch/um/kernel/reboot.c
+++ b/trunk/arch/um/kernel/reboot.c
@@ -25,10 +25,13 @@ static void kill_off_processes(void)
 
 		read_lock(&tasklist_lock);
 		for_each_process(p) {
-			if (p->mm == NULL)
+			task_lock(p);
+			if (!p->mm) {
+				task_unlock(p);
 				continue;
-
+			}
 			pid = p->mm->context.id.u.pid;
+			task_unlock(p);
 			os_kill_ptraced_process(pid, 1);
 		}
 		read_unlock(&tasklist_lock);