Commit f12e1488 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched/fair: Prepare pick_next_task() for delayed dequeue 



Delayed dequeue's natural end is when it gets picked again. Ensure
pick_next_task() knows what to do with delayed tasks.

Note, this relies on the earlier patch that made pick_next_task()
state invariant -- it will restart the pick on dequeue, because
obviously the just dequeued task is no longer eligible.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarValentin Schneider <vschneid@redhat.com>
Tested-by: default avatarValentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.747330118@infradead.org
parent 2e0199df

kernel/sched/fair.c

+19 −4
Original line number Diff line number Diff line
@@ -5473,6 +5473,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 
	se->prev_sum_exec_runtime = se->sum_exec_runtime;

}



static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags);



/*

 * Pick the next process, keeping these things in mind, in this order:

 * 1) keep things fair between processes/task groups
@@ -5481,16 +5483,27 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 
 * 4) do not run the "skip" process, if something else is available

 */

static struct sched_entity *

pick_next_entity(struct cfs_rq *cfs_rq)

pick_next_entity(struct rq *rq, struct cfs_rq *cfs_rq)

{

	/*

	 * Enabling NEXT_BUDDY will affect latency but not fairness.

	 */

	if (sched_feat(NEXT_BUDDY) &&

	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))

	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next)) {

		/* ->next will never be delayed */

		SCHED_WARN_ON(cfs_rq->next->sched_delayed);

		return cfs_rq->next;

	}



	struct sched_entity *se = pick_eevdf(cfs_rq);

	if (se->sched_delayed) {

		dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED);

		SCHED_WARN_ON(se->sched_delayed);

		SCHED_WARN_ON(se->on_rq);



	return pick_eevdf(cfs_rq);

		return NULL;

	}

	return se;

}



static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
@@ -8507,7 +8520,9 @@ static struct task_struct *pick_task_fair(struct rq *rq) 
		if (unlikely(check_cfs_rq_runtime(cfs_rq)))

			goto again;



		se = pick_next_entity(cfs_rq);

		se = pick_next_entity(rq, cfs_rq);

		if (!se)

			goto again;

		cfs_rq = group_cfs_rq(se);

	} while (cfs_rq);