linux-kernel - Re: [PATCH 06/10] cpuidle: Remove unnecessary current_clr_polling_and

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Message-ID: <CAJZ5v0gOU7cC+QsYWik5-6ePRnq8h6Qba3TWDSQQvsN92s34fw@mail.gmail.com>
Date:   Fri, 11 Aug 2023 19:39:32 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: Re: [PATCH 06/10] cpuidle: Remove unnecessary current_clr_polling_and_test()
 from haltpoll

On Fri, Aug 11, 2023 at 7:01 PM Frederic Weisbecker <frederic@...nel.org> wrote:
>
> When cpuidle drivers ->enter() callback are called, the TIF_NR_POLLING
> flag is cleared already and TIF_NEED_RESCHED checked by call_cpuidle().
>
> Therefore calling current_clr_polling_and_test() is redundant here and
> further setting of TIF_NEED_RESCHED will result in an IPI and thus an
> idle loop exit. This call can be safely removed.
>
> Cc: Marcelo Tosatti <mtosatti@...hat.com>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Acked-by: Rafael J. Wysocki <rafael@...nel.org>

> ---
>  drivers/cpuidle/cpuidle-haltpoll.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
> index e66df22f9695..b641bc535102 100644
> --- a/drivers/cpuidle/cpuidle-haltpoll.c
> +++ b/drivers/cpuidle/cpuidle-haltpoll.c
> @@ -28,11 +28,8 @@ static enum cpuhp_state haltpoll_hp_state;
>  static int default_enter_idle(struct cpuidle_device *dev,
>                               struct cpuidle_driver *drv, int index)
>  {
> -       if (current_clr_polling_and_test()) {
> -               local_irq_enable();
> -               return index;
> -       }
>         arch_cpu_idle();
> +
>         return index;
>  }
>
> --
> 2.34.1
>