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    SubjectRe: [PATCH v5] sched/deadline: remove useless param from setup_new_dl_entity
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    On 2016/08/05 at 18:09, Juri Lelli wrote:
    > setup_new_dl_entity() takes two parameters, but it only actually uses
    > one of them, under a different name, to setup a new dl_entity, after:
    >
    > 2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity"
    >
    > as we currently do
    >
    > setup_new_dl_entity(&p->dl, &p->dl)
    >
    > However, before Luca's change we were doing
    >
    > setup_new_dl_entity(dl_se, pi_se)
    >
    > in update_dl_entity() for a dl_se->new entity: we were using pi_se's
    > parameters (the potential PI donor) for setting up a new entity.
    >
    > This change removes the useless second parameter of setup_new_dl_entity().
    > While we are at it we also optimize things further calling setup_new_dl_
    > entity() only for already queued tasks, since (as pointed out by Xunlei)
    > we already do the very same update at tasks wakeup time anyway. By doing
    > so, we don't need to worry about a potential PI donor anymore, as rt_
    > mutex_setprio() takes care of that already for us.
    >
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: Peter Zijlstra <peterz@infradead.org>
    > Cc: Steven Rostedt <rostedt@goodmis.org>
    > Cc: Luca Abeni <luca.abeni@unitn.it>
    > Cc: Xunlei Pang <xpang@redhat.com>
    > Signed-off-by: Juri Lelli <juri.lelli@arm.com>

    Reviewed-by: Xunlei Pang <xlpang@redhat.com>


    >
    > ---
    > Changes from v4:
    > - remove dead code checking for boosted status, as never triggered
    > after rt_mutex_setprio()
    >
    > Changes from v3:
    > - call setup_new_dl_entity only if task is enqueued already
    >
    > Changes from v2:
    > - optimize by calling rt_mutex_get_top_task only if the task is
    > boosted (as suggested by Steve)
    >
    > Changes from v1:
    > - Steve pointed out that we were actually using the second parameter
    > to permorm initialization
    > - Luca confirmed that behavior is slightly changed w.r.t. before his
    > change
    > - changelog updated and original behavior restored
    > ---
    > kernel/sched/deadline.c | 35 ++++++++++++++++++++++-------------
    > 1 file changed, 22 insertions(+), 13 deletions(-)
    >
    > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
    > index fcb7f0217ff4..9491dbe039e8 100644
    > --- a/kernel/sched/deadline.c
    > +++ b/kernel/sched/deadline.c
    > @@ -346,12 +346,12 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
    > * one, and to (try to!) reconcile itself with its own scheduling
    > * parameters.
    > */
    > -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
    > - struct sched_dl_entity *pi_se)
    > +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
    > {
    > struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
    > struct rq *rq = rq_of_dl_rq(dl_rq);
    >
    > + WARN_ON(dl_se->dl_boosted);
    > WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
    >
    > /*
    > @@ -367,8 +367,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
    > * future; in fact, we must consider execution overheads (time
    > * spent on hardirq context, etc.).
    > */
    > - dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
    > - dl_se->runtime = pi_se->dl_runtime;
    > + dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
    > + dl_se->runtime = dl_se->dl_runtime;
    > }
    >
    > /*
    > @@ -1720,19 +1720,28 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
    > */
    > static void switched_to_dl(struct rq *rq, struct task_struct *p)
    > {
    > - if (dl_time_before(p->dl.deadline, rq_clock(rq)))
    > - setup_new_dl_entity(&p->dl, &p->dl);
    >
    > - if (task_on_rq_queued(p) && rq->curr != p) {
    > + if (task_on_rq_queued(p)) {
    > + /*
    > + * If p is not queued we will update its parameters at next
    > + * wakeup. If p is dl_boosted we already updated its params in
    > + * rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
    > + * p's deadline being now already after rq_clock(rq).
    > + */
    > + if (dl_time_before(p->dl.deadline, rq_clock(rq)))
    > + setup_new_dl_entity(&p->dl);
    > +
    > + if (rq->curr != p) {
    > #ifdef CONFIG_SMP
    > - if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
    > - queue_push_tasks(rq);
    > + if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
    > + queue_push_tasks(rq);
    > #else
    > - if (dl_task(rq->curr))
    > - check_preempt_curr_dl(rq, p, 0);
    > - else
    > - resched_curr(rq);
    > + if (dl_task(rq->curr))
    > + check_preempt_curr_dl(rq, p, 0);
    > + else
    > + resched_curr(rq);
    > #endif
    > + }
    > }
    > }
    >

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