diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 68404e488504..cdde9ef05ad2 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -416,6 +416,41 @@ static inline bool is_in_v2_mode(void) (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, @@ -1257,22 +1292,27 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd, 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) { @@ -1294,10 +1334,12 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd, 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; /* @@ -1322,8 +1364,8 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd, */ 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) { @@ -1425,9 +1467,15 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) /* * 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; @@ -1449,6 +1497,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) continue; } +update_parent_subparts: /* * update_parent_subparts_cpumask() should have been called * for cs already in update_cpumask(). We should also call @@ -2254,6 +2303,12 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) (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) @@ -3119,7 +3174,8 @@ hotplug_update_tasks(struct cpuset *cs, 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; @@ -3188,10 +3244,11 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) /* * 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); @@ -3202,13 +3259,15 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) } /* - * 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,