On Fri, Nov 07, 2025 at 07:51:49AM +0100, Juri Lelli wrote:
> On 06/11/25 17:39, Andrea Righi wrote:
> > On Thu, Nov 06, 2025 at 08:13:39AM +0100, Juri Lelli wrote:
>
> ...
>
> > > > @@ -376,8 +378,11 @@ static ssize_t sched_fair_server_write(struct file
> > > > *filp, const char __user *ubu
> > > > return -EINVAL;
> > > > }
> > > >
> > > > - update_rq_clock(rq);
> > > > - dl_server_stop(&rq->fair_server);
> > > > + is_active = dl_server_active(&rq->fair_server);
> > > > + if (is_active) {
> > > > + update_rq_clock(rq);
> > > > + dl_server_stop(&rq->fair_server);
> > > > + }
> > > >
> > > > retval = dl_server_apply_params(&rq->fair_server,
> > > > runtime, period, 0);
> > > >
> > > > @@ -385,7 +390,7 @@ static ssize_t sched_fair_server_write(struct file
> > > > *filp, const char __user *ubu
> > > > printk_deferred("Fair server disabled in CPU
> > > > %d, system may crash due to starvation.\n",
> > > > cpu_of(rq));
> > > >
> > > > - if (rq->cfs.h_nr_queued)
> > > > + if (is_active)
> > > > dl_server_start(&rq->fair_server);
> > >
> > > Something that I noticed while reviewing this series is that we still
> > > start back a server even if the user put its runtime to zero (disabling
> > > it) and I don't think we want to do that. It's not of course related to
> > > this change or this series per-se, but something we probably want to fix
> > > independently.
> >
> > Should we just call dl_server_remove_params() when runtime is zero?
>
> Looking again at it I actually wonder if wouldn't it be better to use
> dl_server_apply_params(dl_se, 0, dl_se->dl_period, false) in both cases.
> dl_rq_change_utilization() deals with dl_non_contending (inactive_timer
> armed) case already (even though sub-optimally, but we can fix/change it
> later), so we can probably remove the special handling you do in
> dl_server_remove_params(). The WARN_ON_ONCE(on_dl_rq()) could be moved
> to dl_server_apply_params() as well.
>
> What do you think?
As you said, it's probably sub-optimal, but I think it's still better than
missing scx dl_server entirely. :)
I'll give this approach a try and check if everything works as expected.
Thanks (and sorry for the late response)!
-Andrea
