Re: SCHED_SPORADIC in Xenomai 3

On 11.06.26 09:49, Philippe Gerum wrote:
> Jan Kiszka <[email protected]> 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.

That would mean moving the accounting out of the pick callback
unconditionally as well - leaving some smaller synergies on the road.
Need to look into that closer, though.

>>
>> 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.
> 

Jan

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