Re: [PATCH V7 09/11] sched: Add nodelay scheduling

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, Jul 24 2025 at 16:16, Prakash Sangappa wrote:
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c

You forgot dl.c :)

> @@ -1027,7 +1027,7 @@ static void update_curr_rt(struct rq *rq)
>  			rt_rq->rt_time += delta_exec;
>  			exceeded = sched_rt_runtime_exceeded(rt_rq);
>  			if (exceeded)
> -				resched_curr(rq);
> +				resched_curr_nodelay(rq, rq->curr);

How is this possibly correct?

If the current task has nodelay set, then this means it asks not to be
affected by a slice extension of a lower priority task.

But that aside, I agree with Sebastian, that this is overly complex and
yet another TIF RESCHED flag is just horrible. We should avoid it in the
first place unless there is a real use case.

RT uses the LAZY flag for non-RT tasks, which means if the regular
RESCHED is set on RT, then we just go and preempt and decline the
extension.

If there is a real use case somewhere down the road, we can revisit the
problem later. Keep it simple for now.

Thanks,

        tglx