On 2 February 2018 at 05:52, Juri Lelli <juri.le...@redhat.com> wrote: > 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.poir...@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...
Let me think about that one for a bit. Thanks for the review, Mathieu > >> + >> + 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