Re: [PATCH 03/12] sched: Fold sched_class::switch{ing,ed}_{to,from}() into the change pattern

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Oct 09, 2025 at 06:50:55PM +0200, Dietmar Eggemann wrote:

> Yes, but there seems to be more ... missing DEQUEUE_SAVE (a.k.a.
> ENQUEUE_RESTORE) in
> 
>   enqueue_dl_entity()
> 
>     if (flags & (ENQUEUE_RESTORE|ENQUEUE_MIGRATING))
>                  ^^^^^^^^^^^^^^^
>       ...
>       add_running_bw(dl_se, dl_rq)
> 
> and
> 
>   __sched_setscheduler()
> 
>     ...
>     if (prev_class != next_class)
>       queue_flags |= DEQUEUE_CLASS;
>       queue_flags &= ~(DEQUEUE_SAVE | DEQUEUE_MOVE);
>                        ^^^^^^^^^^^^
> 
> as well as
> 
>   sched_change_begin()
> 
>     ...
>     if (flags & DEQUEUE_CLASS) {
>       if (WARN_ON_ONCE(flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)))
>         flags &= ~(DEQUEUE_SAVE | DEQUEUE_MOVE);
>                    ^^^^^^^^^^^^
> 

Urgh.. SAVE/RESTORE while changing CLASS is so weird.

But yeah, let me take that bit out for now -- I'll make a note in a
comment that we should look at perhaps cleaning that up instead.