linux-kernel - Re: [PATCH v2 14/44] cpuidle,cpu_pm: Remove RCU fiddling from cpu_pm

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Message-ID: <CAPDyKFquBVkYmKsriPD+BfVrrz62ih7oCxb7HwOML+Zzs-5U_Q@mail.gmail.com>
Date:   Tue, 4 Oct 2022 13:04:57 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
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Subject: Re: [PATCH v2 14/44] cpuidle,cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}()

On Mon, 19 Sept 2022 at 12:17, Peter Zijlstra <peterz@...radead.org> wrote:
>
> All callers should still have RCU enabled.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Acked-by: Mark Rutland <mark.rutland@....com>

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  kernel/cpu_pm.c |    9 ---------
>  1 file changed, 9 deletions(-)
>
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -30,16 +30,9 @@ static int cpu_pm_notify(enum cpu_pm_eve
>  {
>         int ret;
>
> -       /*
> -        * This introduces a RCU read critical section, which could be
> -        * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
> -        * this.
> -        */
> -       ct_irq_enter_irqson();
>         rcu_read_lock();
>         ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
>         rcu_read_unlock();
> -       ct_irq_exit_irqson();
>
>         return notifier_to_errno(ret);
>  }
> @@ -49,11 +42,9 @@ static int cpu_pm_notify_robust(enum cpu
>         unsigned long flags;
>         int ret;
>
> -       ct_irq_enter_irqson();
>         raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
>         ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
>         raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
> -       ct_irq_exit_irqson();
>
>         return notifier_to_errno(ret);
>  }
>
>