Commit 388afd85 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

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: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent e44193d3

kernel/cpuset.c

+16 −53
Original line number Diff line number Diff line
@@ -101,8 +101,6 @@ struct cpuset { 


	/* for custom sched domain */

	int relax_domain_level;



	struct work_struct hotplug_work;

};



/* Retrieve the cpuset for a cgroup */
@@ -268,12 +266,7 @@ static DEFINE_MUTEX(callback_mutex); 
/*

 * CPU / memory hotplug is handled asynchronously.

 */

static struct workqueue_struct *cpuset_propagate_hotplug_wq;



static void cpuset_hotplug_workfn(struct work_struct *work);

static void cpuset_propagate_hotplug_workfn(struct work_struct *work);

static void schedule_cpuset_propagate_hotplug(struct cpuset *cs);



static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);



static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
@@ -1554,7 +1547,6 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft, 
	 * after execution capability is restored.

	 */

	flush_work(&cpuset_hotplug_work);

	flush_workqueue(cpuset_propagate_hotplug_wq);



	mutex_lock(&cpuset_mutex);

	if (!is_cpuset_online(cs))
@@ -1821,7 +1813,6 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont) 
	cpumask_clear(cs->cpus_allowed);

	nodes_clear(cs->mems_allowed);

	fmeter_init(&cs->fmeter);

	INIT_WORK(&cs->hotplug_work, cpuset_propagate_hotplug_workfn);

	cs->relax_domain_level = -1;



	return &cs->css;
@@ -1984,18 +1975,17 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs) 
}



/**

 * cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset

 * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug

 * @cs: cpuset in interest

 *

 * Compare @cs's cpu and mem masks against top_cpuset and if some have gone

 * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,

 * all its tasks are moved to the nearest ancestor with both resources.

 */

static void cpuset_propagate_hotplug_workfn(struct work_struct *work)

static void cpuset_hotplug_update_tasks(struct cpuset *cs)

{

	static cpumask_t off_cpus;

	static nodemask_t off_mems, tmp_mems;

	struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);

	bool is_empty;



retry:
@@ -2044,34 +2034,6 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work) 
	 */

	if (is_empty)

		remove_tasks_in_empty_cpuset(cs);



	/* the following may free @cs, should be the last operation */

	css_put(&cs->css);

}



/**

 * schedule_cpuset_propagate_hotplug - schedule hotplug propagation to a cpuset

 * @cs: cpuset of interest

 *

 * Schedule cpuset_propagate_hotplug_workfn() which will update CPU and

 * memory masks according to top_cpuset.

 */

static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)

{

	/*

	 * Pin @cs.  The refcnt will be released when the work item

	 * finishes executing.

	 */

	if (!css_tryget(&cs->css))

		return;



	/*

	 * Queue @cs->hotplug_work.  If already pending, lose the css ref.

	 * cpuset_propagate_hotplug_wq is ordered and propagation will

	 * happen in the order this function is called.

	 */

	if (!queue_work(cpuset_propagate_hotplug_wq, &cs->hotplug_work))

		css_put(&cs->css);

}



/**
@@ -2084,8 +2046,8 @@ static void schedule_cpuset_propagate_hotplug(struct cpuset *cs) 
 * actively using CPU hotplug but making no active use of cpusets.

 *

 * Non-root cpusets are only affected by offlining.  If any CPUs or memory

 * nodes have been taken down, cpuset_propagate_hotplug() is invoked on all

 * descendants.

 * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on

 * all descendants.

 *

 * Note that CPU offlining during suspend is ignored.  We don't modify

 * cpusets across suspend/resume cycles at all.
@@ -2128,21 +2090,26 @@ static void cpuset_hotplug_workfn(struct work_struct *work) 
		update_tasks_nodemask(&top_cpuset, &tmp_mems, NULL);

	}



	mutex_unlock(&cpuset_mutex);



	/* if cpus or mems went down, we need to propagate to descendants */

	if (cpus_offlined || mems_offlined) {

		struct cpuset *cs;

		struct cgroup *pos_cgrp;



		rcu_read_lock();

		cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)

			schedule_cpuset_propagate_hotplug(cs);

		cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset) {

			if (!css_tryget(&cs->css))

				continue;

			rcu_read_unlock();

	}



	mutex_unlock(&cpuset_mutex);

			cpuset_hotplug_update_tasks(cs);



	/* wait for propagations to finish */

	flush_workqueue(cpuset_propagate_hotplug_wq);

			rcu_read_lock();

			css_put(&cs->css);

		}

		rcu_read_unlock();

	}



	/* rebuild sched domains if cpus_allowed has changed */

	if (cpus_updated)
@@ -2193,10 +2160,6 @@ void __init cpuset_init_smp(void) 
	top_cpuset.mems_allowed = node_states[N_MEMORY];



	register_hotmemory_notifier(&cpuset_track_online_nodes_nb);



	cpuset_propagate_hotplug_wq =

		alloc_ordered_workqueue("cpuset_hotplug", 0);

	BUG_ON(!cpuset_propagate_hotplug_wq);

}



/**