linux-kernel - Re: [PATCH] sched/deadline: Replace rq_of_dl_rq(dl_rq_of_se(dl_se)) with ... ...task_rq(dl_task_of(dl

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Message-ID: <20201013154800.GV2611@hirez.programming.kicks-ass.net>
Date:   Tue, 13 Oct 2020 17:48:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qi Zheng <arch0.zheng@...il.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/deadline: Replace rq_of_dl_rq(dl_rq_of_se(dl_se))
 with ... ...task_rq(dl_task_of(dl_se))

On Tue, Oct 13, 2020 at 10:31:40PM +0800, Qi Zheng wrote:
> The rq is already obtained in the dl_rq_of_se() function:
> 	struct task_struct *p = dl_task_of(dl_se);
>         struct rq *rq = task_rq(p);
> So there is no need to do extra conversion.
> 
> Signed-off-by: Qi Zheng <arch0.zheng@...il.com>
> ---
>  kernel/sched/deadline.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 6d93f4518734..f64e577f6aba 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1152,7 +1152,7 @@ void init_dl_task_timer(struct sched_dl_entity *dl_se)
>  static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
>  {
>  	struct task_struct *p = dl_task_of(dl_se);
> -	struct rq *rq = rq_of_dl_rq(dl_rq_of_se(dl_se));
> +	struct rq *rq = task_rq(p);
>  
>  	if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
>  	    dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
> @@ -1498,7 +1498,7 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
>  		replenish_dl_entity(dl_se, pi_se);
>  	} else if ((flags & ENQUEUE_RESTORE) &&
>  		  dl_time_before(dl_se->deadline,
> -				 rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
> +				 rq_clock(task_rq(dl_task_of(dl_se))))) {
>  		setup_new_dl_entity(dl_se);
>  	}

Consider where we're going:

  https://lkml.kernel.org/r/20200807095051.385985-1-juri.lelli@redhat.com

then a dl_entity is no longer immediately a task and the above is no
longer true.