(cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
}
+/**
+ * partition_is_populated - check if partition has tasks
+ * @cs: partition root to be checked
+ * @excluded_child: a child cpuset to be excluded in task checking
+ * Return: true if there are tasks, false otherwise
+ *
+ * It is assumed that @cs is a valid partition root. @excluded_child should
+ * be non-NULL when this cpuset is going to become a partition itself.
+ */
+static inline bool partition_is_populated(struct cpuset *cs,
+ struct cpuset *excluded_child)
+{
+ struct cgroup_subsys_state *css;
+ struct cpuset *child;
+
+ if (cs->css.cgroup->nr_populated_csets)
+ return true;
+ if (!excluded_child && !cs->nr_subparts_cpus)
+ return cgroup_is_populated(cs->css.cgroup);
+
+ rcu_read_lock();
+ cpuset_for_each_child(child, css, cs) {
+ if (child == excluded_child)
+ continue;
+ if (is_partition_valid(child))
+ continue;
+ if (cgroup_is_populated(child->css.cgroup)) {
+ rcu_read_unlock();
+ return true;
+ }
+ }
+ rcu_read_unlock();
+ return false;
+}
+
/*
* Return in pmask the portion of a task's cpusets's cpus_allowed that
* are online and are capable of running the task. If none are found,
return -EBUSY;
/*
- * Enabling partition root is not allowed if not all the CPUs
- * can be granted from parent's effective_cpus or at least one
- * CPU will be left after that.
- */
- if ((cmd == partcmd_enable) &&
- (!cpumask_subset(cs->cpus_allowed, parent->effective_cpus) ||
- cpumask_equal(cs->cpus_allowed, parent->effective_cpus)))
- return -EINVAL;
-
- /*
- * A cpumask update cannot make parent's effective_cpus become empty.
* new_prs will only be changed for the partcmd_update command.
*/
adding = deleting = false;
old_prs = new_prs = cs->partition_root_state;
if (cmd == partcmd_enable) {
+ /*
+ * Enabling partition root is not allowed if not all the CPUs
+ * can be granted from parent's effective_cpus.
+ */
+ if (!cpumask_subset(cs->cpus_allowed, parent->effective_cpus))
+ return -EINVAL;
+
+ /*
+ * A parent can be left with no CPU as long as there is no
+ * task directly associated with the parent partition. For
+ * such a parent, no new task can be moved into it.
+ */
+ if (cpumask_equal(cs->cpus_allowed, parent->effective_cpus) &&
+ partition_is_populated(parent, cs))
+ return -EINVAL;
+
cpumask_copy(tmp->addmask, cs->cpus_allowed);
adding = true;
} else if (cmd == partcmd_disable) {
adding = cpumask_andnot(tmp->addmask, tmp->addmask,
parent->subparts_cpus);
/*
- * Return error if the new effective_cpus could become empty.
+ * Return error if the new effective_cpus could become empty
+ * and there are tasks in the parent.
*/
if (adding &&
- cpumask_equal(parent->effective_cpus, tmp->addmask)) {
+ cpumask_equal(parent->effective_cpus, tmp->addmask) &&
+ partition_is_populated(parent, cs)) {
if (!deleting)
return -EINVAL;
/*
*/
adding = cpumask_and(tmp->addmask, cs->cpus_allowed,
parent->effective_cpus);
- part_error = cpumask_equal(tmp->addmask,
- parent->effective_cpus);
+ part_error = cpumask_equal(tmp->addmask, parent->effective_cpus) &&
+ partition_is_populated(parent, cs);
}
if (cmd == partcmd_update) {
/*
* If it becomes empty, inherit the effective mask of the
- * parent, which is guaranteed to have some CPUs.
+ * parent, which is guaranteed to have some CPUs unless
+ * it is a partition root that has explicitly distributed
+ * out all its CPUs.
*/
if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus)) {
+ if (is_partition_valid(cp) &&
+ cpumask_equal(cp->cpus_allowed, cp->subparts_cpus))
+ goto update_parent_subparts;
+
cpumask_copy(tmp->new_cpus, parent->effective_cpus);
if (!cp->use_parent_ecpus) {
cp->use_parent_ecpus = true;
continue;
}
+update_parent_subparts:
/*
* update_parent_subparts_cpumask() should have been called
* for cs already in update_cpumask(). We should also call
(cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
goto out_unlock;
+ /*
+ * Task cannot be moved to a cpuset with empty effective cpus.
+ */
+ if (cpumask_empty(cs->effective_cpus))
+ goto out_unlock;
+
cgroup_taskset_for_each(task, css, tset) {
ret = task_can_attach(task, cs->effective_cpus);
if (ret)
struct cpumask *new_cpus, nodemask_t *new_mems,
bool cpus_updated, bool mems_updated)
{
- if (cpumask_empty(new_cpus))
+ /* A partition root is allowed to have empty effective cpus */
+ if (cpumask_empty(new_cpus) && !is_partition_valid(cs))
cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
if (nodes_empty(*new_mems))
*new_mems = parent_cs(cs)->effective_mems;
/*
* In the unlikely event that a partition root has empty
- * effective_cpus or its parent becomes invalid, we have to
- * transition it to the invalid state.
+ * effective_cpus with tasks or its parent becomes invalid, we
+ * have to transition it to the invalid state.
*/
- if (is_partition_valid(cs) && (cpumask_empty(&new_cpus) ||
+ if (is_partition_valid(cs) &&
+ ((cpumask_empty(&new_cpus) && partition_is_populated(cs, NULL)) ||
is_partition_invalid(parent))) {
if (cs->nr_subparts_cpus) {
spin_lock_irq(&callback_lock);
}
/*
- * If the effective_cpus is empty because the child
- * partitions take away all the CPUs, we can keep
- * the current partition and let the child partitions
- * fight for available CPUs.
+ * Force the partition to become invalid if either one of
+ * the following conditions hold:
+ * 1) empty effective cpus but not valid empty partition.
+ * 2) parent is invalid or doesn't grant any cpus to child
+ * partitions.
*/
if (is_partition_invalid(parent) ||
- cpumask_empty(&new_cpus)) {
+ (cpumask_empty(&new_cpus) &&
+ partition_is_populated(cs, NULL))) {
int old_prs;
update_parent_subparts_cpumask(cs, partcmd_disable,