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    Subject[PATCH 3.14 048/130] sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Peter Zijlstra <peterz@infradead.org>

    commit 9916e214998a4a363b152b637245e5c958067350 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/sched/deadline.c | 34 +++++++++++++++++++++-------------
    1 file changed, 21 insertions(+), 13 deletions(-)

    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -210,16 +210,23 @@ static inline int has_pushable_dl_tasks(

    static int push_dl_task(struct rq *rq);

    -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
    @@ -247,6 +254,10 @@ void dec_dl_migration(struct sched_dl_en
    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);
    @@ -1541,7 +1552,7 @@ static void switched_from_dl(struct rq *
    * from an overloaded cpu, if any.
    */
    if (!rq->dl.dl_nr_running)
    - pull_dl_task(rq);
    + queue_pull_task(rq);
    #endif
    }

    @@ -1551,8 +1562,6 @@ static void switched_from_dl(struct rq *
    */
    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
    @@ -1563,12 +1572,12 @@ static void switched_to_dl(struct rq *rq

    if (p->on_rq || 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;
    -#endif /* CONFIG_SMP */
    - if (check_resched && task_has_dl_policy(rq->curr))
    + if (rq->dl.overloaded)
    + queue_push_tasks(rq);
    +#else
    + if (task_has_dl_policy(rq->curr))
    check_preempt_curr_dl(rq, p, 0);
    +#endif /* CONFIG_SMP */
    }
    }

    @@ -1588,15 +1597,14 @@ static void prio_changed_dl(struct rq *r
    * 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_task(p);
    #else
    /*
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