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    Subject[PATCH for v3.14.58 4/7] sched,rt: Remove return value from pull_rt_task()
    Date
    From: Peter Zijlstra <peterz@infradead.org>

    In order to be able to use pull_rt_task() from a callback, we need to
    do away with the return value.

    Since the return value indicates if we should reschedule, do this
    inside the function. Since not all callers currently do this, this can
    increase the number of reschedules due rt balancing.

    Too many reschedules is not a correctness issues, too few are.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: ktkhai@parallels.com
    Cc: rostedt@goodmis.org
    Cc: juri.lelli@gmail.com
    Cc: pang.xunlei@linaro.org
    Cc: oleg@redhat.com
    Cc: wanpeng.li@linux.intel.com
    Cc: umgwanakikbuti@gmail.com
    Link: http://lkml.kernel.org/r/20150611124742.679002000@infradead.org
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Byungchul Park <byungchul.park@lge.com>

    Conflicts:
    kernel/sched/rt.c
    ---
    kernel/sched/rt.c | 15 ++++++++-------
    1 file changed, 8 insertions(+), 7 deletions(-)

    diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
    index 2b980d0..d235fd7 100644
    --- a/kernel/sched/rt.c
    +++ b/kernel/sched/rt.c
    @@ -1652,14 +1652,15 @@ static void push_rt_tasks(struct rq *rq)
    ;
    }

    -static int pull_rt_task(struct rq *this_rq)
    +static void pull_rt_task(struct rq *this_rq)
    {
    - int this_cpu = this_rq->cpu, ret = 0, cpu;
    + int this_cpu = this_rq->cpu, cpu;
    + bool resched = false;
    struct task_struct *p;
    struct rq *src_rq;

    if (likely(!rt_overloaded(this_rq)))
    - return 0;
    + return;

    /*
    * Match the barrier from rt_set_overloaded; this guarantees that if we
    @@ -1716,7 +1717,7 @@ static int pull_rt_task(struct rq *this_rq)
    if (p->prio < src_rq->curr->prio)
    goto skip;

    - ret = 1;
    + resched = true;

    deactivate_task(src_rq, p, 0);
    set_task_cpu(p, this_cpu);
    @@ -1732,7 +1733,8 @@ skip:
    double_unlock_balance(this_rq, src_rq);
    }

    - return ret;
    + if (resched)
    + resched_task(this_rq->curr);
    }

    static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
    @@ -1835,8 +1837,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
    if (!p->on_rq || rq->rt.rt_nr_running)
    return;

    - if (pull_rt_task(rq))
    - resched_task(rq->curr);
    + pull_rt_task(rq);
    }

    void init_sched_rt_class(void)
    --
    1.9.1


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