Commit 4716909c authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cpuset: Track cpusets that use parent's effective_cpus 



In the default hierarchy, a cpuset will use the parent's effective_cpus
if none of the requested CPUs can be granted from the parent. That can
be a problem if a parent is a partition root with children partition
roots. Changes to a parent's effective_cpus list due to changes in a
child partition root may not be properly reflected in a child cpuset
that use parent's effective_cpus because the cpu_exclusive rule of a
partition root will not guard against that.

In order to avoid the mismatch, two new tracking variables are added to
the cpuset structure to track if a cpuset uses parent's effective_cpus
and the number of children cpusets that use its effective_cpus. So
whenever cpumask changes are made to a parent, it will also check to
see if it has other children cpusets that use its effective_cpus and
call update_cpumasks_hier() if that is the case.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 3881b861

kernel/cgroup/cpuset.c

+70 −1
Original line number Diff line number Diff line
@@ -147,6 +147,14 @@ struct cpuset { 


	/* partition root state */

	int partition_root_state;



	/*

	 * Default hierarchy only:

	 * use_parent_ecpus - set if using parent's effective_cpus

	 * child_ecpus_count - # of children with use_parent_ecpus set

	 */

	int use_parent_ecpus;

	int child_ecpus_count;

};



/*
@@ -1227,8 +1235,17 @@ 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.

		 */

		if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus))

		if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus)) {

			cpumask_copy(tmp->new_cpus, parent->effective_cpus);

			if (!cp->use_parent_ecpus) {

				cp->use_parent_ecpus = true;

				parent->child_ecpus_count++;

			}

		} else if (cp->use_parent_ecpus) {

			cp->use_parent_ecpus = false;

			WARN_ON_ONCE(!parent->child_ecpus_count);

			parent->child_ecpus_count--;

		}



		/*

		 * Skip the whole subtree if the cpumask remains the same
@@ -1345,6 +1362,35 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) 
		rebuild_sched_domains_locked();

}



/**

 * update_sibling_cpumasks - Update siblings cpumasks

 * @parent:  Parent cpuset

 * @cs:      Current cpuset

 * @tmp:     Temp variables

 */

static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,

				    struct tmpmasks *tmp)

{

	struct cpuset *sibling;

	struct cgroup_subsys_state *pos_css;



	/*

	 * Check all its siblings and call update_cpumasks_hier()

	 * if their use_parent_ecpus flag is set in order for them

	 * to use the right effective_cpus value.

	 */

	rcu_read_lock();

	cpuset_for_each_child(sibling, pos_css, parent) {

		if (sibling == cs)

			continue;

		if (!sibling->use_parent_ecpus)

			continue;



		update_cpumasks_hier(sibling, tmp);

	}

	rcu_read_unlock();

}



/**

 * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it

 * @cs: the cpuset to consider
@@ -1420,6 +1466,17 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, 
	spin_unlock_irq(&callback_lock);



	update_cpumasks_hier(cs, &tmp);



	if (cs->partition_root_state) {

		struct cpuset *parent = parent_cs(cs);



		/*

		 * For partition root, update the cpumasks of sibling

		 * cpusets if they use parent's effective_cpus.

		 */

		if (parent->child_ecpus_count)

			update_sibling_cpumasks(parent, cs, &tmp);

	}

	return 0;

}
@@ -1856,6 +1913,9 @@ static int update_prstate(struct cpuset *cs, int val) 
	if (parent != &top_cpuset)

		update_tasks_cpumask(parent);



	if (parent->child_ecpus_count)

		update_sibling_cpumasks(parent, cs, &tmp);



	rebuild_sched_domains_locked();

out:

	free_cpumasks(NULL, &tmp);
@@ -2550,6 +2610,8 @@ static int cpuset_css_online(struct cgroup_subsys_state *css) 
	if (is_in_v2_mode()) {

		cpumask_copy(cs->effective_cpus, parent->effective_cpus);

		cs->effective_mems = parent->effective_mems;

		cs->use_parent_ecpus = true;

		parent->child_ecpus_count++;

	}

	spin_unlock_irq(&callback_lock);
@@ -2613,6 +2675,13 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css) 
	    is_sched_load_balance(cs))

		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);



	if (cs->use_parent_ecpus) {

		struct cpuset *parent = parent_cs(cs);



		cs->use_parent_ecpus = false;

		parent->child_ecpus_count--;

	}



	cpuset_dec();

	clear_bit(CS_ONLINE, &cs->flags);

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