linux-kernel - Re: [PATCH v2 10/12] sched: Use lock guard in sched_ttwu

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Message-ID: <CAKfTPtD-7kjB_0JHvo2CoEVPAcug2r3NxFga9F2ucD1UPH4iyg@mail.gmail.com>
Date: Thu, 10 Jul 2025 18:51:55 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...hat.com, juri.lelli@...hat.com, dietmar.eggemann@....com, 
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	clm@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/12] sched: Use lock guard in sched_ttwu_pending()

On Wed, 2 Jul 2025 at 14:12, Peter Zijlstra <peterz@...radead.org> wrote:
>
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/sched/core.c |   11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3827,22 +3827,26 @@ void sched_ttwu_pending(void *arg)
>         struct llist_node *llist = arg;
>         struct rq *rq = this_rq();
>         struct task_struct *p, *t;
> -       struct rq_flags rf;
>
>         if (!llist)
>                 return;
>
> -       rq_lock_irqsave(rq, &rf);
> +       CLASS(rq_lock_irqsave, guard)(rq);
>         update_rq_clock(rq);
>
>         llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
> +               int wake_flags = WF_TTWU;

Adding WF_TTWU is not part of using lock guard but for patch 12 with
ttwu_delayed -> select_task_rq()


> +
>                 if (WARN_ON_ONCE(p->on_cpu))
>                         smp_cond_load_acquire(&p->on_cpu, !VAL);
>
>                 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
>                         set_task_cpu(p, cpu_of(rq));
>
> -               ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
> +               if (p->sched_remote_wakeup)
> +                       wake_flags |= WF_MIGRATED;
> +
> +               ttwu_do_activate(rq, p, wake_flags, &guard.rf);
>         }
>
>         /*
> @@ -3856,7 +3860,6 @@ void sched_ttwu_pending(void *arg)
>          * Since now nr_running > 0, idle_cpu() will always get correct result.
>          */
>         WRITE_ONCE(rq->ttwu_pending, 0);
> -       rq_unlock_irqrestore(rq, &rf);
>  }
>
>  /*
>
>