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SubjectRe: [RFC][PATCH 04/13] sched/{rt,deadline}: Fix set_next_task vs pick_next_task
Hi,

On 26/07/19 16:54, Peter Zijlstra wrote:
> Because pick_next_task() implies set_curr_task() and some of the
> details haven't matter too much, some of what _should_ be in
> set_curr_task() ended up in pick_next_task, correct this.
>
> This prepares the way for a pick_next_task() variant that does not
> affect the current state; allowing remote picking.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> kernel/sched/deadline.c | 23 ++++++++++++-----------
> kernel/sched/rt.c | 27 ++++++++++++++-------------
> 2 files changed, 26 insertions(+), 24 deletions(-)
>
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1694,12 +1694,21 @@ static void start_hrtick_dl(struct rq *r
> }
> #endif
>
> -static inline void set_next_task(struct rq *rq, struct task_struct *p)
> +static void set_next_task_dl(struct rq *rq, struct task_struct *p)
> {
> p->se.exec_start = rq_clock_task(rq);
>
> /* You can't push away the running task */
> dequeue_pushable_dl_task(rq, p);
> +
> + if (hrtick_enabled(rq))
> + start_hrtick_dl(rq, p);
> +
> + if (rq->curr->sched_class != &dl_sched_class)
> + update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
> +
> + if (rq->curr != p)
> + deadline_queue_push_tasks(rq);

It's a minor thing, but I was wondering why you added the check on curr.
deadline_queue_push_tasks() already checks if are there pushable tasks,
plus curr can still be of a different class at this point?

Thanks,

Juri

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