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From:   Uros Bizjak <ubizjak@gmail.com>
Date:   Tue, 4 Apr 2023 08:04:09 +0200
Message-ID: <CAFULd4YYFNfN7uQeutP94j69LXwZQ-utveTFv3MVfZ9nt681rg@mail.gmail.com>
Subject: Re: [PATCH] sched/core: Use do-while instead of for loop in set_nr_if_polling
To:     linux-kernel@vger.kernel.org
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Christian Brauner <brauner@kernel.org>
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I would like to ping for the patch below. The patch normalizes
try_cmpxchg loop to a more readable "while" instead of "for (;;)"
loop, otherwise it is a nop.

https://lore.kernel.org/lkml/20230228161426.4508-1-ubizjak@gmail.com/

Uros.


On Tue, Feb 28, 2023 at 5:14=E2=80=AFPM Uros Bizjak <ubizjak@gmail.com> wro=
te:
>
> Use equivalent do-while loop instead of infinite for loop.
>
> There are no asm code changes.
>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Christian Brauner <brauner@kernel.org>
> ---
>  kernel/sched/core.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index af017e038b48..349c018eaf09 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -899,14 +899,13 @@ static bool set_nr_if_polling(struct task_struct *p=
)
>         struct thread_info *ti =3D task_thread_info(p);
>         typeof(ti->flags) val =3D READ_ONCE(ti->flags);
>
> -       for (;;) {
> +       do {
>                 if (!(val & _TIF_POLLING_NRFLAG))
>                         return false;
>                 if (val & _TIF_NEED_RESCHED)
>                         return true;
> -               if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED=
))
> -                       break;
> -       }
> +       } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))=
;
> +
>         return true;
>  }
>
> --
> 2.39.2
>