Re: [PATCH] sched/eevdf: Delayed dequeue task can't preempt

[Vincent Guittot]

On Thu, 2 Jul 2026 at 11:01, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Thu, Jul 02, 2026 at 09:53:13AM +0200, Vincent Guittot wrote:
> > On Thu, 2 Jul 2026 at 09:43, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > >
> > > On Wed, Jul 01, 2026 at 06:49:20PM +0200, Vincent Guittot wrote:
> > > > Load balancing can migrate delayed dequeue tasks to even the load between
> > > > CPUs.
> > > >
> > > > sched_balance_rq()
> > > >   -> detach_task()
> > > >     -> deactivate_task(DEQUEUE_NOCLOCK)
> > > >     -> set_task_cpu(dst_cpu)
> > > >
> > > >   -> attach_task()
> > > >     -> activate_task(ENQUEUE_NOCLOCK)
> > > >     -> wakeup_preempt()
> > > >
> > > > A delayed task with shorter slice can be dequeued during pick_next_entity()
> > > > but then jump to preempt because eligible.
> > >
> > > Cute.
> > >
> > > Perhaps we can look at enqueue()'s place entity and determine
> > > eligibility there and complete the delayed dequeue there. But that's
> > > definitely something for after the holidays I suppose.
> > >
> > > I'll go stick it in tip/sched/core.
> >
> > Maybe better in tip/sched/urgent because of the warn triggered in set_next_buddy
>
> Hmm, but the Fixes tag you gave it reference a patch in sched/core; is
> that tag wrong? Or do I just need to imbibe more wakeup juice?

No, I need more wakeup juice. Yeah it's tip/sched/core not 7.2-rc1