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    Subject[PATCH AUTOSEL 5.4 03/50] sched/core: Don't skip remote tick for idle CPUs
    Date
    From: Scott Wood <swood@redhat.com>

    [ Upstream commit 488603b815a7514c7009e6fc339d74ed4a30f343 ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 dfaefb175ba05..5cbf64db4e0a3 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -3667,22 +3667,24 @@ 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:
    --
    2.20.1
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