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From:   Joel Fernandes <joel@joelfernandes.org>
Date:   Sun, 6 Aug 2023 17:39:24 -0400
Message-ID: <CAEXW_YSJ-G_zUKLzLgvCkxAY-dg_Zxo6n=bEXyeEmo9hEMcZpg@mail.gmail.com>
Subject: Re: [PATCH 1/9] sched: Simplify get_nohz_timer_target()
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     mingo@redhat.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, vschneid@redhat.com,
        linux-kernel@vger.kernel.org
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On Sun, Aug 6, 2023 at 9:52=E2=80=AFAM Peter Zijlstra <peterz@infradead.org=
> wrote:
>
> Use guards to reduce gotos and simplify control flow.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  kernel/sched/core.c |   15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1097,25 +1097,22 @@ int get_nohz_timer_target(void)
>
>         hk_mask =3D housekeeping_cpumask(HK_TYPE_TIMER);
>
> -       rcu_read_lock();
> +       guard(rcu)();
> +
>         for_each_domain(cpu, sd) {
>                 for_each_cpu_and(i, sched_domain_span(sd), hk_mask) {
>                         if (cpu =3D=3D i)
>                                 continue;
>
> -                       if (!idle_cpu(i)) {
> -                               cpu =3D i;
> -                               goto unlock;
> -                       }
> +                       if (!idle_cpu(i))
> +                               return i;
>                 }
>         }
>
>         if (default_cpu =3D=3D -1)
>                 default_cpu =3D housekeeping_any_cpu(HK_TYPE_TIMER);
> -       cpu =3D default_cpu;
> -unlock:
> -       rcu_read_unlock();
> -       return cpu;
> +
> +       return default_cpu;
>  }

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

I haven't looked into the actual implementation of the guard stuff,
but rcu_read_lock_guarded() is less of an eyesore to me than
guard(rcu)(); TBH.

thanks,

 - Joel