Commit 7ebefa8c authored by Dmitry Adamushko's avatar Dmitry Adamushko Committed by Ingo Molnar
Browse files

sched: rework of "prioritize non-migratable tasks over migratable ones" 

(1) handle in a generic way all cases when a newly woken-up task is
not migratable (not just a corner case when "rt_se->nr_cpus_allowed ==
1")

(2) if current is to be preempted, then make sure "p" will be picked
up by pick_next_task_rt().
i.e. move task's group at the head of its list as well.

currently, it's not a case for the group-scheduling case as described
here: http://www.ussg.iu.edu/hypermail/linux/kernel/0807.0/0134.html



Signed-off-by: default avatarDmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 13b40c1e

kernel/sched_rt.c

+40 −28
Original line number Diff line number Diff line
@@ -599,11 +599,7 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se) 
	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))

		return;



	if (rt_se->nr_cpus_allowed == 1)

		list_add(&rt_se->run_list, queue);

	else

	list_add_tail(&rt_se->run_list, queue);



	__set_bit(rt_se_prio(rt_se), array->bitmap);



	inc_rt_tasks(rt_se, rt_rq);
@@ -688,32 +684,34 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep) 
 * Put task to the end of the run list without the overhead of dequeue

 * followed by enqueue.

 */

static

void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)

static void

requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)

{

	if (on_rt_rq(rt_se)) {

		struct rt_prio_array *array = &rt_rq->active;

		struct list_head *queue = array->queue + rt_se_prio(rt_se);



	if (on_rt_rq(rt_se)) {

		list_del_init(&rt_se->run_list);

		list_add_tail(&rt_se->run_list,

			      array->queue + rt_se_prio(rt_se));

		if (head)

			list_move(&rt_se->run_list, queue);

		else

			list_move_tail(&rt_se->run_list, queue);

	}

}



static void requeue_task_rt(struct rq *rq, struct task_struct *p)

static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)

{

	struct sched_rt_entity *rt_se = &p->rt;

	struct rt_rq *rt_rq;



	for_each_sched_rt_entity(rt_se) {

		rt_rq = rt_rq_of_se(rt_se);

		requeue_rt_entity(rt_rq, rt_se);

		requeue_rt_entity(rt_rq, rt_se, head);

	}

}



static void yield_task_rt(struct rq *rq)

{

	requeue_task_rt(rq, rq->curr);

	requeue_task_rt(rq, rq->curr, 0);

}



#ifdef CONFIG_SMP
@@ -753,6 +751,30 @@ static int select_task_rq_rt(struct task_struct *p, int sync) 
	 */

	return task_cpu(p);

}



static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)

{

	cpumask_t mask;



	if (rq->curr->rt.nr_cpus_allowed == 1)

		return;



	if (p->rt.nr_cpus_allowed != 1

	    && cpupri_find(&rq->rd->cpupri, p, &mask))

		return;



	if (!cpupri_find(&rq->rd->cpupri, rq->curr, &mask))

		return;



	/*

	 * There appears to be other cpus that can accept

	 * current and none to run 'p', so lets reschedule

	 * to try and push current away:

	 */

	requeue_task_rt(rq, p, 1);

	resched_task(rq->curr);

}



#endif /* CONFIG_SMP */



/*
@@ -778,18 +800,8 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p) 
	 * to move current somewhere else, making room for our non-migratable

	 * task.

	 */

	if((p->prio == rq->curr->prio)

	   && p->rt.nr_cpus_allowed == 1

	   && rq->curr->rt.nr_cpus_allowed != 1) {

		cpumask_t mask;



		if (cpupri_find(&rq->rd->cpupri, rq->curr, &mask))

			/*

			 * There appears to be other cpus that can accept

			 * current, so lets reschedule to try and push it away

			 */

			resched_task(rq->curr);

	}

	if (p->prio == rq->curr->prio && !need_resched())

		check_preempt_equal_prio(rq, p);

#endif

}
@@ -1415,7 +1427,7 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued) 
	 * on the queue:

	 */

	if (p->rt.run_list.prev != p->rt.run_list.next) {

		requeue_task_rt(rq, p);

		requeue_task_rt(rq, p, 0);

		set_tsk_need_resched(p);

	}

}

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