Merge branch 'for-4.8-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo:
"Three late fixes for cgroup: Two cpuset ones, one trivial and the
other pretty obscure, and a cgroup core fix for a bug which impacts
cgroup v2 namespace users"
* 'for-4.8-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: fix invalid controller enable rejections with cgroup namespace
cpuset: fix non static symbol warning
cpuset: handle race between CPU hotplug and cpuset_hotplug_work
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5e8dab5..d6b729b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3446,9 +3446,28 @@
* Except for the root, subtree_control must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
- if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
- ret = -EBUSY;
- goto out_unlock;
+ if (enable && cgroup_parent(cgrp)) {
+ struct cgrp_cset_link *link;
+
+ /*
+ * Because namespaces pin csets too, @cgrp->cset_links
+ * might not be empty even when @cgrp is empty. Walk and
+ * verify each cset.
+ */
+ spin_lock_irq(&css_set_lock);
+
+ ret = 0;
+ list_for_each_entry(link, &cgrp->cset_links, cset_link) {
+ if (css_set_populated(link->cset)) {
+ ret = -EBUSY;
+ break;
+ }
+ }
+
+ spin_unlock_irq(&css_set_lock);
+
+ if (ret)
+ goto out_unlock;
}
/* save and update control masks and prepare csses */
@@ -3899,7 +3918,9 @@
* cgroup_task_count - count the number of tasks in a cgroup.
* @cgrp: the cgroup in question
*
- * Return the number of tasks in the cgroup.
+ * Return the number of tasks in the cgroup. The returned number can be
+ * higher than the actual number of tasks due to css_set references from
+ * namespace roots and temporary usages.
*/
static int cgroup_task_count(const struct cgroup *cgrp)
{
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c27e533..2b4c20a 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -325,8 +325,7 @@
/*
* 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 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 @@
* 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;