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Commit fd7a4bed authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks 



Remove the direct {push,pull} balancing operations from
switched_{from,to}_rt() / prio_changed_rt() and use the balance
callback queue.

Again, err on the side of too many reschedules; since too few is a
hard bug while too many is just annoying.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124742.766832367@infradead.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 8046d680

kernel/sched/rt.c

+19 −16
Original line number Diff line number Diff line
@@ -354,16 +354,23 @@ static inline int has_pushable_tasks(struct rq *rq) 
	return !plist_head_empty(&rq->rt.pushable_tasks);

}



static DEFINE_PER_CPU(struct callback_head, rt_balance_head);

static DEFINE_PER_CPU(struct callback_head, rt_push_head);

static DEFINE_PER_CPU(struct callback_head, rt_pull_head);



static void push_rt_tasks(struct rq *);

static void pull_rt_task(struct rq *);



static inline void queue_push_tasks(struct rq *rq)

{

	if (!has_pushable_tasks(rq))

		return;



	queue_balance_callback(rq, &per_cpu(rt_balance_head, rq->cpu), push_rt_tasks);

	queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);

}



static inline void queue_pull_task(struct rq *rq)

{

	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);

}



static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
@@ -2139,7 +2146,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p) 
	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)

		return;



	pull_rt_task(rq);

	queue_pull_task(rq);

}



void __init init_sched_rt_class(void)
@@ -2160,8 +2167,6 @@ void __init init_sched_rt_class(void) 
 */

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

{

	int check_resched = 1;



	/*

	 * If we are already running, then there's nothing

	 * that needs to be done. But if we are not running
@@ -2171,13 +2176,12 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) 
	 */

	if (task_on_rq_queued(p) && rq->curr != p) {

#ifdef CONFIG_SMP

		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded &&

		    /* Don't resched if we changed runqueues */

		    push_rt_task(rq) && rq != task_rq(p))

			check_resched = 0;

#endif /* CONFIG_SMP */

		if (check_resched && p->prio < rq->curr->prio)

		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)

			queue_push_tasks(rq);

#else

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

			resched_curr(rq);

#endif /* CONFIG_SMP */

	}

}
@@ -2198,14 +2202,13 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio) 
		 * may need to pull tasks to this runqueue.

		 */

		if (oldprio < p->prio)

			pull_rt_task(rq);

			queue_pull_task(rq);



		/*

		 * If there's a higher priority task waiting to run

		 * then reschedule. Note, the above pull_rt_task

		 * can release the rq lock and p could migrate.

		 * Only reschedule if p is still on the same runqueue.

		 * then reschedule.

		 */

		if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)

		if (p->prio > rq->rt.highest_prio.curr)

			resched_curr(rq);

#else

		/* For UP simply resched on drop of prio */