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

[Daniel Bristot de Oliveira]

On 06/22/2017 10:38 AM, Ingo Molnar wrote:
> 
> * Daniel Bristot de Oliveira <bris...@redhat.com> 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?

Like:

static inline int task_in_rt_class(struct task_struct *p)
{
        return p->sched_class == &rt_sched_class;
}

static inline int task_in_dl_class(struct task_struct *p)
{
        return p->sched_class == &dl_sched_class;
}

?

Thanks!

-- Daniel