Re: SCHED_SPORADIC in Xenomai 3

[Philippe Gerum <rpm@xenomai.org>]

Jan Kiszka <jan.kiszka@siemens.com> writes:

> diff --git a/kernel/cobalt/sched.c b/kernel/cobalt/sched.c
> index d527b6be2c..6dfbf83220 100644
> --- a/kernel/cobalt/sched.c
> +++ b/kernel/cobalt/sched.c
> @@ -895,6 +895,7 @@ static inline void do_lazy_user_work(struct xnthread *curr)
>  
>  int ___xnsched_run(struct xnsched *sched)
>  {
> +	struct xnsched_class *prev_schedclass __maybe_unused;
>  	bool switched = false, leaving_inband;
>  	struct xnthread *prev, *next, *curr;
>  	spl_t s;
> @@ -933,6 +934,13 @@ int ___xnsched_run(struct xnsched *sched)
>  
>  	prev = curr;
>  
> +#ifdef CONFIG_XENO_OPT_SCHED_CLASSES
> +	prev_schedclass = prev->sched_class;
> +	if (prev_schedclass->weight < next->sched_class->weight &&
> +	    prev_schedclass->sched_out)
> +		prev_schedclass->sched_out(prev);
> +#endif

I would call the scheduling out hook unconditionally, the sched class
has all the information required to sort this out, do the right thing,
which the generic scheduler does not.
>
> Something analogous for sched-sporadic does not help. It looks broken in 
> its algorithm, specifically that is schedules consumed budget for 
> recharge on preemption, rather than reducing the remaining budget.

Since the original implementation did not account for the preemption
case in budget-tracking classes, that makes sense.

-- 
Philippe.