Messages in this thread | | | Date | Fri, 2 Feb 2018 13:52:31 +0100 | From | Juri Lelli <> | Subject | Re: [PATCH V2 2/7] cpuset: Rebuild root domain deadline accounting information |
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Hi Mathieu,
On 01/02/18 09:51, Mathieu Poirier wrote: > When the topology of root domains is modified by CPUset or CPUhotplug > operations information about the current deadline bandwidth held in the > root domain is lost. > > This patch address the issue by recalculating the lost deadline > bandwidth information by circling through the deadline tasks held in > CPUsets and adding their current load to the root domain they are > associated with. > > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> > ---
[...]
> +static void update_tasks_root_domain(struct cpuset *cs) > +{ > + struct css_task_iter it; > + struct task_struct *task; > + > + css_task_iter_start(&cs->css, 0, &it); > + > + while ((task = css_task_iter_next(&it))) > + dl_add_task_root_domain(task); > + > + css_task_iter_end(&it); > +} > + > +/* > + * Called with cpuset_mutex held (rebuild_sched_domains()) > + * Called with hotplug lock held (rebuild_sched_domains_locked()) > + * Called with sched_domains_mutex held (partition_and_rebuild_domains()) > + */ > +static void rebuild_root_domains(void) > +{ > + struct cpuset *cs = NULL; > + struct cgroup_subsys_state *pos_css; > + > + rcu_read_lock(); > + > + /* > + * Clear default root domain DL accounting, it will be computed again > + * if a task belongs to it. > + */ > + dl_clear_root_domain(&def_root_domain);
Can't a __sched_setscheduler sneak in at this point, set a task to DEADLINE, add its bandwidth to the rd...
> + > + cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) { > + > + if (cpumask_empty(cs->effective_cpus)) { > + pos_css = css_rightmost_descendant(pos_css); > + continue; > + } > + > + css_get(&cs->css); > + > + rcu_read_unlock(); > + > + update_tasks_root_domain(cs);
... and this adds it again?
> + > + rcu_read_lock(); > + css_put(&cs->css); > + } > + rcu_read_unlock(); > +}
Best,
- Juri
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