Hello.
On Sat, Jul 01, 2023 at 02:50:49PM +0800, Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1806,9 +1806,12 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
> cpuset_for_each_child(cp, css, parent)
> if (is_partition_valid(cp) &&
> cpumask_intersects(trialcs->cpus_allowed, cp->cpus_allowed)) {
> + if (!css_tryget_online(&cp->css))
> + continue;
> rcu_read_unlock();
> update_parent_subparts_cpumask(cp, partcmd_invalidate, NULL, &tmp);
> rcu_read_lock();
> + css_put(&cp->css);
Apologies for a possibly noob question -- why is RCU read lock
temporarily dropped within the loop?
(Is it only because of callback_lock or cgroup_file_kn_lock (via
notify_partition_change()) on PREEMPT_RT?)
[
OT question:
cpuset_for_each_child(cp, css, parent) (1)
if (is_partition_valid(cp) &&
cpumask_intersects(trialcs->cpus_allowed, cp->cpus_allowed)) {
if (!css_tryget_online(&cp->css))
continue;
rcu_read_unlock();
update_parent_subparts_cpumask(cp, partcmd_invalidate, NULL, &tmp);
...
update_tasks_cpumask(cp->parent)
...
css_task_iter_start(&cp->parent->css, 0, &it); (2)
...
rcu_read_lock();
css_put(&cp->css);
}
May this touch each task same number of times as its depth within
herarchy?
]
Thanks,
Michal
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