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cpuset: Track cpusets that use parent's effective_cpus

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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: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2018-11-08 10:08:40 -05:00 committed by Tejun Heo
parent 3881b86128
commit 4716909cc5
1 changed files with 70 additions and 1 deletions
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71
kernel/cgroup/cpuset.c
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@ -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);