cpuset: remove async hotplug propagation work
As we can drop rcu read lock while iterating cgroup hierarchy, we don't have to do propagation asynchronously via workqueue. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Li Zefan
Tejun Heo
Родитель
e44193d39e
Коммит
388afd8549
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@ -101,8 +101,6 @@ struct cpuset {
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/* for custom sched domain */
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int relax_domain_level;
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struct work_struct hotplug_work;
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};
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/* Retrieve the cpuset for a cgroup */
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@ -268,12 +266,7 @@ static DEFINE_MUTEX(callback_mutex);
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/*
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* CPU / memory hotplug is handled asynchronously.
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*/
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static struct workqueue_struct *cpuset_propagate_hotplug_wq;
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static void cpuset_hotplug_workfn(struct work_struct *work);
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static void cpuset_propagate_hotplug_workfn(struct work_struct *work);
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static void schedule_cpuset_propagate_hotplug(struct cpuset *cs);
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static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
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static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
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@ -1554,7 +1547,6 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
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* after execution capability is restored.
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*/
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flush_work(&cpuset_hotplug_work);
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flush_workqueue(cpuset_propagate_hotplug_wq);
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mutex_lock(&cpuset_mutex);
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if (!is_cpuset_online(cs))
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@ -1821,7 +1813,6 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
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cpumask_clear(cs->cpus_allowed);
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nodes_clear(cs->mems_allowed);
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fmeter_init(&cs->fmeter);
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INIT_WORK(&cs->hotplug_work, cpuset_propagate_hotplug_workfn);
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cs->relax_domain_level = -1;
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return &cs->css;
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@ -1984,18 +1975,17 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
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}
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/**
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* cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset
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* cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
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* @cs: cpuset in interest
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*
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* Compare @cs's cpu and mem masks against top_cpuset and if some have gone
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* offline, update @cs accordingly. If @cs ends up with no CPU or memory,
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* all its tasks are moved to the nearest ancestor with both resources.
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*/
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static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
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static void cpuset_hotplug_update_tasks(struct cpuset *cs)
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{
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static cpumask_t off_cpus;
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static nodemask_t off_mems, tmp_mems;
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struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
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bool is_empty;
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retry:
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@ -2044,34 +2034,6 @@ retry:
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*/
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if (is_empty)
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remove_tasks_in_empty_cpuset(cs);
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/* the following may free @cs, should be the last operation */
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css_put(&cs->css);
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}
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/**
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* schedule_cpuset_propagate_hotplug - schedule hotplug propagation to a cpuset
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* @cs: cpuset of interest
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*
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* Schedule cpuset_propagate_hotplug_workfn() which will update CPU and
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* memory masks according to top_cpuset.
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*/
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static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)
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{
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/*
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* Pin @cs. The refcnt will be released when the work item
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* finishes executing.
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*/
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if (!css_tryget(&cs->css))
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return;
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/*
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* Queue @cs->hotplug_work. If already pending, lose the css ref.
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* cpuset_propagate_hotplug_wq is ordered and propagation will
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* happen in the order this function is called.
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*/
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if (!queue_work(cpuset_propagate_hotplug_wq, &cs->hotplug_work))
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css_put(&cs->css);
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}
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/**
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@ -2084,8 +2046,8 @@ static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)
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* actively using CPU hotplug but making no active use of cpusets.
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*
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* Non-root cpusets are only affected by offlining. If any CPUs or memory
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* nodes have been taken down, cpuset_propagate_hotplug() is invoked on all
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* descendants.
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* nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
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* all descendants.
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*
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* Note that CPU offlining during suspend is ignored. We don't modify
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* cpusets across suspend/resume cycles at all.
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@ -2128,22 +2090,27 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
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update_tasks_nodemask(&top_cpuset, &tmp_mems, NULL);
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}
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mutex_unlock(&cpuset_mutex);
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/* if cpus or mems went down, we need to propagate to descendants */
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if (cpus_offlined || mems_offlined) {
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struct cpuset *cs;
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struct cgroup *pos_cgrp;
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rcu_read_lock();
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cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)
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schedule_cpuset_propagate_hotplug(cs);
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cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset) {
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if (!css_tryget(&cs->css))
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continue;
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rcu_read_unlock();
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cpuset_hotplug_update_tasks(cs);
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rcu_read_lock();
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css_put(&cs->css);
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}
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rcu_read_unlock();
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}
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mutex_unlock(&cpuset_mutex);
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/* wait for propagations to finish */
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flush_workqueue(cpuset_propagate_hotplug_wq);
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/* rebuild sched domains if cpus_allowed has changed */
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if (cpus_updated)
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rebuild_sched_domains();
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@ -2193,10 +2160,6 @@ void __init cpuset_init_smp(void)
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top_cpuset.mems_allowed = node_states[N_MEMORY];
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register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
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cpuset_propagate_hotplug_wq =
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alloc_ordered_workqueue("cpuset_hotplug", 0);
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BUG_ON(!cpuset_propagate_hotplug_wq);
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}
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/**
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