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    Subject[PATCH for v3.18.25 6/6] sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks
    Date
    From: Peter Zijlstra <peterz@infradead.org>

    Remove the direct {push,pull} balancing operations from
    switched_{from,to}_dl() / prio_changed_dl() and use the balance
    callback queue.

    Again, err on the side of too many reschedules; since too few is a
    hard bug while too many is just annoying.

    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/20150611124742.968262663@infradead.org
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Byungchul Park <byungchul.park@lge.com>

    Conflicts:
    kernel/sched/deadline.c
    ---
    kernel/sched/deadline.c | 42 +++++++++++++++++++++++-------------------
    1 file changed, 23 insertions(+), 19 deletions(-)

    diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
    index 1242e5b..6762024 100644
    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -213,16 +213,23 @@ static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
    return dl_task(prev);
    }

    -static DEFINE_PER_CPU(struct callback_head, dl_balance_head);
    +static DEFINE_PER_CPU(struct callback_head, dl_push_head);
    +static DEFINE_PER_CPU(struct callback_head, dl_pull_head);

    static void push_dl_tasks(struct rq *);
    +static void pull_dl_task(struct rq *);

    static inline void queue_push_tasks(struct rq *rq)
    {
    if (!has_pushable_dl_tasks(rq))
    return;

    - queue_balance_callback(rq, &per_cpu(dl_balance_head, rq->cpu), push_dl_tasks);
    + queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
    +}
    +
    +static inline void queue_pull_task(struct rq *rq)
    +{
    + queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
    }

    #else
    @@ -259,6 +266,10 @@ static inline void pull_dl_task(struct rq *rq)
    static inline void queue_push_tasks(struct rq *rq)
    {
    }
    +
    +static inline void queue_pull_task(struct rq *rq)
    +{
    +}
    #endif /* CONFIG_SMP */

    static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
    @@ -975,8 +986,6 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
    resched_curr(rq);
    }

    -static void pull_dl_task(struct rq *this_rq);
    -
    #endif /* CONFIG_SMP */

    /*
    @@ -1586,7 +1595,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
    * from an overloaded cpu, if any.
    */
    if (!rq->dl.dl_nr_running)
    - pull_dl_task(rq);
    + queue_pull_task(rq);
    #endif
    }

    @@ -1596,8 +1605,6 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
    */
    static void switched_to_dl(struct rq *rq, struct task_struct *p)
    {
    - int check_resched = 1;
    -
    /*
    * If p is throttled, don't consider the possibility
    * of preempting rq->curr, the check will be done right
    @@ -1608,16 +1615,14 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)

    if (task_on_rq_queued(p) && rq->curr != p) {
    #ifdef CONFIG_SMP
    - if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
    - /* Only reschedule if pushing failed */
    - check_resched = 0;
    + if (rq->dl.overloaded)
    + queue_push_tasks(rq);
    +#else
    + if (dl_task(rq->curr))
    + check_preempt_curr_dl(rq, p, 0);
    + else
    + resched_curr(rq);
    #endif /* CONFIG_SMP */
    - if (check_resched) {
    - if (dl_task(rq->curr))
    - check_preempt_curr_dl(rq, p, 0);
    - else
    - resched_curr(rq);
    - }
    }
    }

    @@ -1637,15 +1642,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
    * or lowering its prio, so...
    */
    if (!rq->dl.overloaded)
    - pull_dl_task(rq);
    + queue_pull_task(rq);

    /*
    * If we now have a earlier deadline task than p,
    * then reschedule, provided p is still on this
    * runqueue.
    */
    - if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
    - rq->curr == p)
    + if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
    resched_curr(rq);
    #else
    /*
    --
    1.9.1


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