/*
* 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.
*/
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);
}
mutex_unlock(&cpuset_mutex);
}
+/*
+ * Make sure the new task conform to the current state of its parent,
+ * 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.
+ */
+static void cpuset_fork(struct task_struct *task)
+{
+ if (task_css_is_root(task, cpuset_cgrp_id))
+ return;
+
+ set_cpus_allowed_ptr(task, ¤t->cpus_allowed);
+ task->mems_allowed = current->mems_allowed;
+}
+
struct cgroup_subsys cpuset_cgrp_subsys = {
.css_alloc = cpuset_css_alloc,
.css_online = cpuset_css_online,
.attach = cpuset_attach,
.post_attach = cpuset_post_attach,
.bind = cpuset_bind,
+ .fork = cpuset_fork,
.legacy_cftypes = files,
.early_init = true,
};