linux-kernel - Re: [PATCH v3 07/22] rcu: Mark rcu_dynticks_curr_cpu_in

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Message-ID: <20200219163934.GA2935@paulmck-ThinkPad-P72>
Date:   Wed, 19 Feb 2020 08:39:34 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        rostedt@...dmis.org, mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        luto@...nel.org, tony.luck@...el.com, frederic@...nel.org,
        dan.carpenter@...cle.com, mhiramat@...nel.org
Subject: Re: [PATCH v3 07/22] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline

On Wed, Feb 19, 2020 at 03:47:31PM +0100, Peter Zijlstra wrote:
> Since rcu_is_watching() is notrace (and needs to be, as it can be
> called from the tracers), make sure everything it in turn calls is
> notrace too.
> 
> To that effect, mark rcu_dynticks_curr_cpu_in_eqs() inline, which
> implies notrace, as the function is tiny.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

There was some controversy over inline vs. notrace, leading me to
ask whether we should use both inline and notrace here.  ;-)

Assuming that the usual tracing suspects are OK with it:

Reviewed-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  kernel/rcu/tree.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -294,7 +294,7 @@ static void rcu_dynticks_eqs_online(void
>   *
>   * No ordering, as we are sampling CPU-local information.
>   */
> -static bool rcu_dynticks_curr_cpu_in_eqs(void)
> +static inline bool rcu_dynticks_curr_cpu_in_eqs(void)
>  {
>  	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
>  
> 
>