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Commit 17d25a33 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fix from Ingo Molnar:
 "This contains a single fix that fixes a nohz tick stopping bug when
  mixed-poliocy SCHED_FIFO and SCHED_RR tasks are present on a runqueue"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  nohz/full, sched/rt: Fix missed tick-reenabling bug in sched_can_stop_tick()
parents 18fb92c3 2548d546

kernel/sched/core.c

+16 −13
Original line number Diff line number Diff line
@@ -596,17 +596,8 @@ bool sched_can_stop_tick(struct rq *rq) 
		return false;



	/*

	 * FIFO realtime policy runs the highest priority task (after DEADLINE).

	 * Other runnable tasks are of a lower priority. The scheduler tick

	 * isn't needed.

	 */

	fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;

	if (fifo_nr_running)

		return true;



	/*

	 * Round-robin realtime tasks time slice with other tasks at the same

	 * realtime priority.

	 * If there are more than one RR tasks, we need the tick to effect the

	 * actual RR behaviour.

	 */

	if (rq->rt.rr_nr_running) {

		if (rq->rt.rr_nr_running == 1)
@@ -615,8 +606,20 @@ bool sched_can_stop_tick(struct rq *rq) 
			return false;

	}



	/* Normal multitasking need periodic preemption checks */

	if (rq->cfs.nr_running > 1)

	/*

	 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no

	 * forced preemption between FIFO tasks.

	 */

	fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;

	if (fifo_nr_running)

		return true;



	/*

	 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;

	 * if there's more than one we need the tick for involuntary

	 * preemption.

	 */

	if (rq->nr_running > 1)

		return false;



	return true;