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

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
...@@ -596,17 +596,8 @@ bool sched_can_stop_tick(struct rq *rq) ...@@ -596,17 +596,8 @@ bool sched_can_stop_tick(struct rq *rq)
return false; return false;
/* /*
* FIFO realtime policy runs the highest priority task (after DEADLINE). * If there are more than one RR tasks, we need the tick to effect the
* Other runnable tasks are of a lower priority. The scheduler tick * actual RR behaviour.
* 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 (rq->rt.rr_nr_running) { if (rq->rt.rr_nr_running) {
if (rq->rt.rr_nr_running == 1) if (rq->rt.rr_nr_running == 1)
...@@ -615,8 +606,20 @@ bool sched_can_stop_tick(struct rq *rq) ...@@ -615,8 +606,20 @@ bool sched_can_stop_tick(struct rq *rq)
return false; 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 false;
return true; return true;
......
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