Re: [PATCH v3 1/3] sched_ext: Fix pnt_seq calculation

['Tejun Heo' <tj@kernel.org>]

Hello,

On Mon, Aug 11, 2025 at 02:03:16PM -1000, 'Tejun Heo' wrote:
...
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 0fb9bf995..50d757e92 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -8887,6 +8887,9 @@ pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
> >  
> >  	__put_prev_set_next_dl_server(rq, prev, p);
> >  
> > +	if (scx_enabled())
> > +		scx_put_prev_set_next(rq, prev, p);
> > +
> >  	/*
> >  	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
> >  	 * likely that a next task is from the same cgroup as the current.
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index 47972f34e..bcb7f175c 100644
> > @@ -2465,6 +2470,9 @@ static inline void put_prev_set_next_task(struct rq *rq,
> >  
> >  	__put_prev_set_next_dl_server(rq, prev, next);
> >  
> > +	if (scx_enabled())
> > +		scx_put_prev_set_next(rq, prev, next);
> > +
> >  	if (next == prev)
> >  		return;
> 
> I'm not sure these are the best spots to call this function. How about
> putting it in the CONFIG_SCHED_CLASS_EXT section in prev_balance()? The goal
> of the seq counter is to wait for scheduler path to be entered, so that's
> good enough a spot and there already is scx specific section, so it doesn't
> add too much noise.

Strike that. I see that we need a hook after task is picked to resolve the
bug around cpu_released. Can you please move scx_enabled() test into
scx_put_prev_set_next() and add a helper which calls both
__put_prev_set_next_dl_server() and scx_put_prev_set_next() so that the call
doesn't have to be added to two places?

Thanks.

-- 
tejun