linux-kernel - Re: [PATCH v2 04/12] sched: Use lock guard in ttwu

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Message-ID: <CAKfTPtCQFCW++Rbhn=Oiq1_B7GdgfCM9BnGH+-BZ17FhXTHR9A@mail.gmail.com>
Date: Thu, 10 Jul 2025 18:48:04 +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 04/12] sched: Use lock guard in ttwu_runnable()

On Wed, 2 Jul 2025 at 14:12, Peter Zijlstra <peterz@...radead.org> wrote:
>
> Reflow and get rid of 'ret' variable.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Link: https://lkml.kernel.org/r/20250520101727.732703833@infradead.org

Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>


> ---
>  kernel/sched/core.c  |   36 ++++++++++++++++--------------------
>  kernel/sched/sched.h |    5 +++++
>  2 files changed, 21 insertions(+), 20 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3754,28 +3754,24 @@ ttwu_do_activate(struct rq *rq, struct t
>   */
>  static int ttwu_runnable(struct task_struct *p, int wake_flags)
>  {
> -       struct rq_flags rf;
> -       struct rq *rq;
> -       int ret = 0;
> +       CLASS(__task_rq_lock, guard)(p);
> +       struct rq *rq = guard.rq;
>
> -       rq = __task_rq_lock(p, &rf);
> -       if (task_on_rq_queued(p)) {
> -               update_rq_clock(rq);
> -               if (p->se.sched_delayed)
> -                       enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
> -               if (!task_on_cpu(rq, p)) {
> -                       /*
> -                        * When on_rq && !on_cpu the task is preempted, see if
> -                        * it should preempt the task that is current now.
> -                        */
> -                       wakeup_preempt(rq, p, wake_flags);
> -               }
> -               ttwu_do_wakeup(p);
> -               ret = 1;
> -       }
> -       __task_rq_unlock(rq, &rf);
> +       if (!task_on_rq_queued(p))
> +               return 0;
>
> -       return ret;
> +       update_rq_clock(rq);
> +       if (p->se.sched_delayed)
> +               enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
> +       if (!task_on_cpu(rq, p)) {
> +               /*
> +                * When on_rq && !on_cpu the task is preempted, see if
> +                * it should preempt the task that is current now.
> +                */
> +               wakeup_preempt(rq, p, wake_flags);
> +       }
> +       ttwu_do_wakeup(p);
> +       return 1;
>  }
>
>  void sched_ttwu_pending(void *arg)
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1806,6 +1806,11 @@ task_rq_unlock(struct rq *rq, struct tas
>         raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
>  }
>
> +DEFINE_LOCK_GUARD_1(__task_rq_lock, struct task_struct,
> +                   _T->rq = __task_rq_lock(_T->lock, &_T->rf),
> +                   __task_rq_unlock(_T->rq, &_T->rf),
> +                   struct rq *rq; struct rq_flags rf)
> +
>  DEFINE_LOCK_GUARD_1(task_rq_lock, struct task_struct,
>                     _T->rq = task_rq_lock(_T->lock, &_T->rf),
>                     task_rq_unlock(_T->rq, _T->lock, &_T->rf),
>
>