Re: [PATCH 2/2] rt: Increase/decrease the nr of migratory tasks when enabling/disabling migration

From: Ingo Molnar
Date: Thu Jun 22 2017 - 04:38:44 EST



* Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote:

> void migrate_disable(void)
> {
> struct task_struct *p = current;
> + struct rq *rq;
> + struct rq_flags rf;
> +
>
> if (in_atomic() || irqs_disabled()) {
> #ifdef CONFIG_SCHED_DEBUG
> @@ -7593,10 +7596,21 @@ void migrate_disable(void)
> preempt_disable();
> preempt_lazy_disable();
> pin_current_cpu();
> - p->migrate_disable = 1;
>
> - p->cpus_ptr = cpumask_of(smp_processor_id());
> + rq = task_rq_lock(p, &rf);
> + if (unlikely((p->sched_class == &rt_sched_class ||
> + p->sched_class == &dl_sched_class) &&
> + p->nr_cpus_allowed > 1)) {
> + if (p->sched_class == &rt_sched_class)
> + task_rq(p)->rt.rt_nr_migratory--;
> + else
> + task_rq(p)->dl.dl_nr_migratory--;
> + }
> p->nr_cpus_allowed = 1;
> + task_rq_unlock(rq, p, &rf);
> + p->cpus_ptr = cpumask_of(smp_processor_id());
> + p->migrate_disable = 1;
> +
>
> preempt_enable();
> }
> @@ -7605,6 +7619,9 @@ EXPORT_SYMBOL(migrate_disable);
> void migrate_enable(void)
> {
> struct task_struct *p = current;
> + struct rq *rq;
> + struct rq_flags rf;
> +
>
> if (in_atomic() || irqs_disabled()) {
> #ifdef CONFIG_SCHED_DEBUG
> @@ -7628,17 +7645,24 @@ void migrate_enable(void)
>
> preempt_disable();
>
> - p->cpus_ptr = &p->cpus_mask;
> - p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
> p->migrate_disable = 0;
> + p->cpus_ptr = &p->cpus_mask;
>
> - if (p->migrate_disable_update) {
> - struct rq *rq;
> - struct rq_flags rf;
> + rq = task_rq_lock(p, &rf);
> + p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
> + if (unlikely((p->sched_class == &rt_sched_class ||
> + p->sched_class == &dl_sched_class) &&
> + p->nr_cpus_allowed > 1)) {
> + if (p->sched_class == &rt_sched_class)
> + task_rq(p)->rt.rt_nr_migratory++;
> + else
> + task_rq(p)->dl.dl_nr_migratory++;
> + }
> + task_rq_unlock(rq, p, &rf);

The fix looks good to me, but AFAICS the repeat pattern introduced here could be
factored out into a helper function instead, right?

Thanks,

Ingo