On Mon, 20 Apr 2015 16:22:48 +0800 Xunlei Pang <xlp...@126.com> wrote:
> + rq = task_rq(p); > + > + if (new_weight > 1 && > + rt_task(rq->curr) && > + rq->rt.rt_nr_total > 1 && > + !test_tsk_need_resched(rq->curr)) { > + /* > + * We own p->pi_lock and rq->lock. rq->lock might > + * get released when doing direct pushing, however > + * p->pi_lock is always held, so it's safe to assign > + * new_mask and new_weight to p below. > + */ > + if (!task_running(rq, p)) { > + cpumask_copy(&p->cpus_allowed, new_mask); > + p->nr_cpus_allowed = new_weight; > + direct_push = 1; > + } else if (cpumask_test_cpu(task_cpu(p), new_mask)) { > + struct task_struct *next; > + > + cpumask_copy(&p->cpus_allowed, new_mask); > + p->nr_cpus_allowed = new_weight; > + if (!cpupri_find(&rq->rd->cpupri, p, NULL)) > + goto update; > + > + /* > + * At this point, current task gets migratable most > + * likely due to the change of its affinity, let's > + * figure out if we can migrate it. > + * > + * Can we find any task with the same priority as > + * current? To accomplish this, firstly we requeue > + * current to the tail and peek next, then restore > + * current to the head. "current"? Don't you mean 'p'? > + */ > + requeue_task_rt(rq, p, 0); > + next = peek_next_task_rt(rq); > + requeue_task_rt(rq, p, 1); Actually, I'm totally confused by all this. Why are you looking at next? The running task (current) should not be in the next_task_rt() list to begin with. If p can not preempt current, and cpupri_find() finds something for p to run on, then move it there, and be done with it. I also looked at set_cpus_allowed_ptr() and think we should probably add a p->sched_class->pick_cpu() and do: if (p->sched_class->pick_cpu) dest_cpu = p->sched_class->pick_cpu(p, cpu_active_mask, new_mask); else dest_cpu = cpumask_any_and(cpu_active_mask, new_mask); Hmm, maybe all this work should be done there, or have do_set_cpus_allowed() return a value that states that the sched_class->set_cpus_allowed() did all the work for us. -- Steve > + if (next != p && next->prio == p->prio) { > + /* > + * Target found, so let's reschedule to try > + * and push current away. > + */ > + requeue_task_rt(rq, next, 1); > + preempt_push = 1; > + } > + } > + } > + > +update: > /* > * Only update if the process changes its state from whether it > * can migrate or not. > */ > - if ((p->nr_cpus_allowed > 1) == (weight > 1)) > - return; > - > - rq = task_rq(p); > + if ((old_weight > 1) == (new_weight > 1)) > + goto out; > > /* > * The process used to be able to migrate OR it can now migrate > */ > - if (weight <= 1) { > + if (new_weight <= 1) { > if (!task_current(rq, p)) > dequeue_pushable_task(rq, p); > BUG_ON(!rq->rt.rt_nr_migratory); > @@ -2129,6 +2184,12 @@ static void set_cpus_allowed_rt(struct task_struct *p, > } > > update_rt_migration(&rq->rt); > + > +out: > + if (direct_push) > + push_rt_tasks(rq); > + else if (preempt_push) > + resched_curr(rq); > } > > /* Assumes rq->lock is held */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/