Merge branch 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

[cascardo/linux.git] / kernel / cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c27e533..2b4c20a 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -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);
 }
 
@@ -2074,7 +2085,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
  * which could have been changed by cpuset just after it inherits the
  * state from the parent and before it sits on the cgroup's task list.
  */
-void cpuset_fork(struct task_struct *task)
+static void cpuset_fork(struct task_struct *task)
 {
        if (task_css_is_root(task, cpuset_cgrp_id))
                return;