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Commit fc560a26 authored by Tejun Heo's avatar Tejun Heo
Browse files

cpuset: replace cpuset->stack_list with cpuset_for_each_descendant_pre() 



Implement cpuset_for_each_descendant_pre() and replace the
cpuset-specific tree walking using cpuset->stack_list with it.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 5d21cc2d

kernel/cpuset.c

+48 −75
Original line number Diff line number Diff line
@@ -103,9 +103,6 @@ struct cpuset { 
	/* for custom sched domain */

	int relax_domain_level;



	/* used for walking a cpuset hierarchy */

	struct list_head stack_list;



	struct work_struct hotplug_work;

};
@@ -207,6 +204,20 @@ static struct cpuset top_cpuset = { 
	cgroup_for_each_child((pos_cgrp), (parent_cs)->css.cgroup)	\

		if (is_cpuset_online(((child_cs) = cgroup_cs((pos_cgrp)))))



/**

 * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants

 * @des_cs: loop cursor pointing to the current descendant

 * @pos_cgrp: used for iteration

 * @root_cs: target cpuset to walk ancestor of

 *

 * Walk @des_cs through the online descendants of @root_cs.  Must be used

 * with RCU read locked.  The caller may modify @pos_cgrp by calling

 * cgroup_rightmost_descendant() to skip subtree.

 */

#define cpuset_for_each_descendant_pre(des_cs, pos_cgrp, root_cs)	\

	cgroup_for_each_descendant_pre((pos_cgrp), (root_cs)->css.cgroup) \

		if (is_cpuset_online(((des_cs) = cgroup_cs((pos_cgrp)))))



/*

 * There are two global mutexes guarding cpuset structures - cpuset_mutex

 * and callback_mutex.  The latter may nest inside the former.  We also
@@ -507,31 +518,24 @@ update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c) 
	return;

}



static void

update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)

static void update_domain_attr_tree(struct sched_domain_attr *dattr,

				    struct cpuset *root_cs)

{

	LIST_HEAD(q);



	list_add(&c->stack_list, &q);

	while (!list_empty(&q)) {

	struct cpuset *cp;

		struct cgroup *cont;

		struct cpuset *child;

	struct cgroup *pos_cgrp;



		cp = list_first_entry(&q, struct cpuset, stack_list);

		list_del(q.next);



		if (cpumask_empty(cp->cpus_allowed))

	rcu_read_lock();

	cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {

		/* skip the whole subtree if @cp doesn't have any CPU */

		if (cpumask_empty(cp->cpus_allowed)) {

			pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);

			continue;

		}



		if (is_sched_load_balance(cp))

			update_domain_attr(dattr, cp);



		rcu_read_lock();

		cpuset_for_each_child(child, cont, cp)

			list_add_tail(&child->stack_list, &q);

		rcu_read_unlock();

	}

	rcu_read_unlock();

}



/*
@@ -591,7 +595,6 @@ update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c) 
static int generate_sched_domains(cpumask_var_t **domains,

			struct sched_domain_attr **attributes)

{

	LIST_HEAD(q);		/* queue of cpusets to be scanned */

	struct cpuset *cp;	/* scans q */

	struct cpuset **csa;	/* array of all cpuset ptrs */

	int csn;		/* how many cpuset ptrs in csa so far */
@@ -600,6 +603,7 @@ static int generate_sched_domains(cpumask_var_t **domains, 
	struct sched_domain_attr *dattr;  /* attributes for custom domains */

	int ndoms = 0;		/* number of sched domains in result */

	int nslot;		/* next empty doms[] struct cpumask slot */

	struct cgroup *pos_cgrp;



	doms = NULL;

	dattr = NULL;
@@ -627,33 +631,27 @@ static int generate_sched_domains(cpumask_var_t **domains, 
		goto done;

	csn = 0;



	list_add(&top_cpuset.stack_list, &q);

	while (!list_empty(&q)) {

		struct cgroup *cont;

		struct cpuset *child;   /* scans child cpusets of cp */



		cp = list_first_entry(&q, struct cpuset, stack_list);

		list_del(q.next);



		if (cpumask_empty(cp->cpus_allowed))

			continue;



	rcu_read_lock();

	cpuset_for_each_descendant_pre(cp, pos_cgrp, &top_cpuset) {

		/*

		 * All child cpusets contain a subset of the parent's cpus, so

		 * just skip them, and then we call update_domain_attr_tree()

		 * to calc relax_domain_level of the corresponding sched

		 * domain.

		 * Continue traversing beyond @cp iff @cp has some CPUs and

		 * isn't load balancing.  The former is obvious.  The

		 * latter: All child cpusets contain a subset of the

		 * parent's cpus, so just skip them, and then we call

		 * update_domain_attr_tree() to calc relax_domain_level of

		 * the corresponding sched domain.

		 */

		if (is_sched_load_balance(cp)) {

			csa[csn++] = cp;

		if (!cpumask_empty(cp->cpus_allowed) &&

		    !is_sched_load_balance(cp))

			continue;

		}



		rcu_read_lock();

		cpuset_for_each_child(child, cont, cp)

			list_add_tail(&child->stack_list, &q);

		rcu_read_unlock();

		if (is_sched_load_balance(cp))

			csa[csn++] = cp;



		/* skip @cp's subtree */

		pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);

	}

	rcu_read_unlock();



	for (i = 0; i < csn; i++)

		csa[i]->pn = i;
@@ -2068,31 +2066,6 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs) 
	move_member_tasks_to_cpuset(cs, parent);

}



/*

 * Helper function to traverse cpusets.

 * It can be used to walk the cpuset tree from top to bottom, completing

 * one layer before dropping down to the next (thus always processing a

 * node before any of its children).

 */

static struct cpuset *cpuset_next(struct list_head *queue)

{

	struct cpuset *cp;

	struct cpuset *child;	/* scans child cpusets of cp */

	struct cgroup *cont;



	if (list_empty(queue))

		return NULL;



	cp = list_first_entry(queue, struct cpuset, stack_list);

	list_del(queue->next);

	rcu_read_lock();

	cpuset_for_each_child(child, cont, cp)

		list_add_tail(&child->stack_list, queue);

	rcu_read_unlock();



	return cp;

}



/**

 * cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset

 * @cs: cpuset in interest
@@ -2229,12 +2202,12 @@ static void cpuset_hotplug_workfn(struct work_struct *work) 
	/* if cpus or mems went down, we need to propagate to descendants */

	if (cpus_offlined || mems_offlined) {

		struct cpuset *cs;

		LIST_HEAD(queue);

		struct cgroup *pos_cgrp;



		list_add_tail(&top_cpuset.stack_list, &queue);

		while ((cs = cpuset_next(&queue)))

			if (cs != &top_cpuset)

		rcu_read_lock();

		cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)

			schedule_cpuset_propagate_hotplug(cs);

		rcu_read_unlock();

	}



	mutex_unlock(&cpuset_mutex);