1 files changed, 25 insertions, 13 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index e2e294d997e0..e3c0f38acbe6 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -98,7 +98,7 @@ struct cpuset {
 
 	/* user-configured CPUs and Memory Nodes allow to tasks */
 	cpumask_var_t cpus_allowed;
-	cpumask_var_t cpus_requested;
+	cpumask_var_t cpus_requested;   /* CPUS requested, but not used because of hotplug */
 	nodemask_t mems_allowed;
 
 	/* effective CPUs and Memory Nodes allow to tasks */
@@ -325,8 +325,7 @@ static struct file_system_type cpuset_fs_type = {
 /*
  * Return in pmask the portion of a cpusets's cpus_allowed that
  * are online.  If none are online, walk up the cpuset hierarchy
- * until we find one that does have some online cpus.  The top
- * cpuset always has some cpus online.
+ * until we find one that does have some online cpus.
  *
  * One way or another, we guarantee to return some non-empty subset
  * of cpu_online_mask.
@@ -335,8 +334,20 @@ static struct file_system_type cpuset_fs_type = {
  */
 static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
 {
-	while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask))
+	while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask)) {
 		cs = parent_cs(cs);
+		if (unlikely(!cs)) {
+			/*
+			 * The top cpuset doesn't have any online cpu as a
+			 * consequence of a race between cpuset_hotplug_work
+			 * and cpu hotplug notifier.  But we know the top
+			 * cpuset's effective_cpus is on its way to to be
+			 * identical to cpu_online_mask.
+			 */
+			cpumask_copy(pmask, cpu_online_mask);
+			return;
+		}
+	}
 	cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
 }
 
@@ -1945,11 +1956,11 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 	if (!cs)
 		return ERR_PTR(-ENOMEM);
 	if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL))
-		goto free_cs;
-	if (!alloc_cpumask_var(&cs->cpus_requested, GFP_KERNEL))
-		goto free_allowed;
+		goto error_allowed;
 	if (!alloc_cpumask_var(&cs->effective_cpus, GFP_KERNEL))
-		goto free_requested;
+		goto error_effective;
+	if (!alloc_cpumask_var(&cs->cpus_requested, GFP_KERNEL))
+		goto error_requested;
 
 	set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 	cpumask_clear(cs->cpus_allowed);
@@ -1962,11 +1973,11 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
 
 	return &cs->css;
 
-free_requested:
-	free_cpumask_var(cs->cpus_requested);
-free_allowed:
+error_requested:
+	free_cpumask_var(cs->effective_cpus);
+error_effective:
 	free_cpumask_var(cs->cpus_allowed);
-free_cs:
+error_allowed:
 	kfree(cs);
 	return ERR_PTR(-ENOMEM);
 }
@@ -2268,7 +2279,8 @@ retry:
 		goto retry;
 	}
 
-	cpumask_and(&new_cpus, cs->cpus_requested, parent_cs(cs)->effective_cpus);
+	cpumask_and(&new_cpus, cs->cpus_requested,
+						parent_cs(cs)->effective_cpus);
 	nodes_and(new_mems, cs->mems_allowed, parent_cs(cs)->effective_mems);
 
 	cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);