Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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()
+16
-13
+16
-13
kernel/sched/core.c
+16
-13
kernel/sched/core.c
···
596
596
return false;
597
597
598
598
/*
599
-
* FIFO realtime policy runs the highest priority task (after DEADLINE).
600
-
* Other runnable tasks are of a lower priority. The scheduler tick
601
-
* isn't needed.
602
-
*/
603
-
fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
604
-
if (fifo_nr_running)
605
-
return true;
606
-
607
-
/*
608
-
* Round-robin realtime tasks time slice with other tasks at the same
609
-
* realtime priority.
599
+
* If there are more than one RR tasks, we need the tick to effect the
600
+
* actual RR behaviour.
610
601
*/
611
602
if (rq->rt.rr_nr_running) {
612
603
if (rq->rt.rr_nr_running == 1)
···
606
615
return false;
607
616
}
608
617
609
-
/* Normal multitasking need periodic preemption checks */
610
-
if (rq->cfs.nr_running > 1)
618
+
/*
619
+
* If there's no RR tasks, but FIFO tasks, we can skip the tick, no
620
+
* forced preemption between FIFO tasks.
621
+
*/
622
+
fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
623
+
if (fifo_nr_running)
624
+
return true;
625
+
626
+
/*
627
+
* If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
628
+
* if there's more than one we need the tick for involuntary
629
+
* preemption.
630
+
*/
631
+
if (rq->nr_running > 1)
611
632
return false;
612
633
613
634
return true;