1 files changed, 27 insertions, 9 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 746d1eeb5dbe..ba96349aa522 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1990,6 +1990,32 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
 }
 
 /*
+ * Helper function to traverse cpusets.
+ * It can be used to walk the cpuset tree from top to bottom, completing
+ * one layer before dropping down to the next (thus always processing a
+ * node before any of its children).
+ */
+static struct cpuset *cpuset_next(struct list_head *queue)
+{
+        struct cpuset *cp;
+        struct cpuset *child;   /* scans child cpusets of cp */
+        struct cgroup *cont;
+
+        if (list_empty(queue))
+                return NULL;
+
+        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);
+        }
+
+        return cp;
+}
+
+
+/*
  * Walk the specified cpuset subtree and look for empty cpusets.
  * The tasks of such cpuset must be moved to a parent cpuset.
  *
@@ -2008,19 +2034,11 @@ static void scan_for_empty_cpusets(struct cpuset *root)
 {
         LIST_HEAD(queue);
         struct cpuset *cp;      /* scans cpusets being updated */
-        struct cpuset *child;   /* scans child cpusets of cp */
-        struct cgroup *cont;
         static nodemask_t oldmems;      /* protected by cgroup_mutex */
 
         list_add_tail((struct list_head *)&root->stack_list, &queue);
 
-        while (!list_empty(&queue)) {
-                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);
-                }
+        while ((cp = cpuset_next(&queue)) != NULL) {
 
                 /* Continue past cpusets with all cpus, mems online */
                 if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&