linux-kernel - Re: [PATCH 2/3] preempt/dynamic: Introduce preempt mode accessors

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Message-ID: <CANpmjNPqY65ZYLFukgp779pHbiRH05yns+G7Z36QdWwrQp1WOQ@mail.gmail.com>
Date:   Mon, 14 Mar 2022 15:44:39 +0100
From:   Marco Elver <elver@...gle.com>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 2/3] preempt/dynamic: Introduce preempt mode accessors

On Mon, 14 Mar 2022 at 14:37, Frederic Weisbecker <frederic@...nel.org> wrote:
>
> From: Valentin Schneider <valentin.schneider@....com>
>
> CONFIG_PREEMPT{_NONE, _VOLUNTARY} designate either:
> o The build-time preemption model when !PREEMPT_DYNAMIC
> o The default boot-time preemption model when PREEMPT_DYNAMIC
>
> IOW, using those on PREEMPT_DYNAMIC kernels is meaningless - the actual
> model could have been set to something else by the "preempt=foo" cmdline
> parameter.
>
> Introduce a set of helpers to determine the actual preemption mode used by
> the live kernel.
>
> Suggested-by: Marco Elver <elver@...gle.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> Cc: Uladzislau Rezki <uladzislau.rezki@...y.com>
> Cc: Joel Fernandes <joel@...lfernandes.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Neeraj Upadhyay <quic_neeraju@...cinc.com>
> ---
>  include/linux/sched.h | 16 ++++++++++++++++
>  kernel/sched/core.c   | 11 +++++++++++
>  2 files changed, 27 insertions(+)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 508b91d57470..d348e886e4d0 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2096,6 +2096,22 @@ static inline void cond_resched_rcu(void)
>  #endif
>  }
>
> +#ifdef CONFIG_PREEMPT_DYNAMIC
> +
> +extern bool preempt_mode_none(void);
> +extern bool preempt_mode_voluntary(void);
> +extern bool preempt_mode_full(void);
> +
> +#else
> +
> +#define preempt_mode_none() IS_ENABLED(CONFIG_PREEMPT_NONE)
> +#define preempt_mode_voluntary() IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)
> +#define preempt_mode_full() IS_ENABLED(CONFIG_PREEMPT)
> +

Shame this was somehow forgotten.
There was a v3 of this patch that fixed a bunch of things (e.g. making
these proper functions so all builds error if accidentally used in
#if).

https://lore.kernel.org/lkml/20211112185203.280040-3-valentin.schneider@arm.com/

Is it also possible to take all the rest of that series (all 4
patches) from Valentin?

Thanks,
-- Marco