linux-kernel - Re: Subject: [PATCH] [PATCH] time: tick-sched: use bool for tick

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Date:   Tue, 10 Apr 2018 10:00:01 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     yuankuiz@...eaurora.org
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        aulmck@...ux.vnet.ibm.com, Ingo Molnar <mingo@...nel.org>,
        Len Brown <len.brown@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Subject: [PATCH] [PATCH] time: tick-sched: use bool for tick_stopped

On Tue, Apr 10, 2018 at 9:33 AM,  <yuankuiz@...eaurora.org> wrote:
> From: John Zhao <yuankuiz@...eaurora.org>
>
> Variable tick_stopped returned by tick_nohz_tick_stopped
> can have only true / forse values. Since the return type
> of the tick_nohz_tick_stopped is also bool, variable
> tick_stopped nice to have data type as bool in place of int.
> Moreover, the executed instructions cost could be minimal
> without potiential data type conversion.
>
> Signed-off-by: John Zhao <yuankuiz@...eaurora.org>
> ---
>  kernel/time/tick-sched.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
> index 6de959a..4d34309 100644
> --- a/kernel/time/tick-sched.h
> +++ b/kernel/time/tick-sched.h
> @@ -48,8 +48,8 @@ struct tick_sched {
>         unsigned long                   check_clocks;
>         enum tick_nohz_mode             nohz_mode;
>
> +       bool                            tick_stopped    : 1;
>         unsigned int                    inidle          : 1;
> -       unsigned int                    tick_stopped    : 1;
>         unsigned int                    idle_active     : 1;
>         unsigned int                    do_timer_last   : 1;
>         unsigned int                    got_idle_tick   : 1;

I don't think this is a good idea at all.

Please see https://lkml.org/lkml/2017/11/21/384 for example.

Thanks!