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Subject[tip: sched/core] sched/core: Don't skip remote tick for idle CPUs
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 488603b815a7514c7009e6fc339d74ed4a30f343
Gitweb: https://git.kernel.org/tip/488603b815a7514c7009e6fc339d74ed4a30f343
Author: Scott Wood <swood@redhat.com>
AuthorDate: Sat, 11 Jan 2020 04:53:38 -05:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 28 Jan 2020 21:36:16 +01:00

sched/core: Don't skip remote tick for idle CPUs

This will be used in the next patch to get a loadavg update from
nohz cpus. The delta check is skipped because idle_sched_class
doesn't update se.exec_start.

Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/1578736419-14628-2-git-send-email-swood@redhat.com
---
kernel/sched/core.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fc1dfc0..cf8b33d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3669,22 +3669,24 @@ static void sched_tick_remote(struct work_struct *work)
* statistics and checks timeslices in a time-independent way, regardless
* of when exactly it is running.
*/
- if (idle_cpu(cpu) || !tick_nohz_tick_stopped_cpu(cpu))
+ if (!tick_nohz_tick_stopped_cpu(cpu))
goto out_requeue;

rq_lock_irq(rq, &rf);
curr = rq->curr;
- if (is_idle_task(curr) || cpu_is_offline(cpu))
+ if (cpu_is_offline(cpu))
goto out_unlock;

update_rq_clock(rq);
- delta = rq_clock_task(rq) - curr->se.exec_start;

- /*
- * Make sure the next tick runs within a reasonable
- * amount of time.
- */
- WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+ if (!is_idle_task(curr)) {
+ /*
+ * Make sure the next tick runs within a reasonable
+ * amount of time.
+ */
+ delta = rq_clock_task(rq) - curr->se.exec_start;
+ WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+ }
curr->sched_class->task_tick(rq, curr, 0);

out_unlock:
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