linux-kernel - Re: [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick upfront in the idle loop

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Message-ID: <20180307233911.GB9367@lerouge>
Date:   Thu, 8 Mar 2018 00:39:12 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Thomas Ilsche <thomas.ilsche@...dresden.de>,
        Doug Smythies <dsmythies@...us.net>,
        Rik van Riel <riel@...riel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Mike Galbraith <mgalbraith@...e.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick
 upfront in the idle loop

On Tue, Mar 06, 2018 at 10:02:15AM +0100, Rafael J. Wysocki wrote:
> Index: linux-pm/kernel/sched/idle.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/idle.c
> +++ linux-pm/kernel/sched/idle.c
> @@ -220,13 +220,17 @@ static void do_idle(void)
>  	 */
>  
>  	__current_set_polling();
> -	tick_nohz_idle_enter();
> +	tick_nohz_idle_prepare();

Since we leave tick_nohz_idle_exit() unchanged, can we keep tick_nohz_idle_prepare()
under the name tick_nohz_idle_enter() so that we stay symetric? And then make xen call
the two functions:

    tick_nohz_idle_enter();
    tick_nohz_idle_go_idle();

Also can we rename tick_nohz_idle_go_idle() to tick_nohz_idle_stop_tick() ?
This will be more self-explanatory.

Thanks.