cpuset: a bit cleanup for scan_for_empty_cpusets()

clean up hierarchy traversal code
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Cliff Wickman <cpw@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/cpuset.c

@@ -1833,24 +1833,21 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
  */
 static void scan_for_empty_cpusets(const struct cpuset *root)
 {
+	LIST_HEAD(queue);
 	struct cpuset *cp;	/* scans cpusets being updated */
 	struct cpuset *child;	/* scans child cpusets of cp */
-	struct list_head queue;
 	struct cgroup *cont;
 	nodemask_t oldmems;
 
-	INIT_LIST_HEAD(&queue);
-
 	list_add_tail((struct list_head *)&root->stack_list, &queue);
 
 	while (!list_empty(&queue)) {
-		cp = container_of(queue.next, struct cpuset, stack_list);
+		cp = list_first_entry(&queue, struct cpuset, stack_list);
 		list_del(queue.next);
 		list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
 			child = cgroup_cs(cont);
 			list_add_tail(&child->stack_list, &queue);
 		}
-		cont = cp->css.cgroup;
 
 		/* Continue past cpusets with all cpus, mems online */
 		if (cpus_subset(cp->cpus_allowed, cpu_online_map) &&