linux-kernel - Re: [PATCH v7 19/21] timer: Implement the hierarchical pull model

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Message-ID: <ZIcr9Y5yTpJxzF-h@2a01cb0980221ec3a67fd23915238df5.ipv6.abo.wanadoo.fr>
Date:   Mon, 12 Jun 2023 16:30:13 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Lukasz Luba <lukasz.luba@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>
Subject: Re: [PATCH v7 19/21] timer: Implement the hierarchical pull model

Le Mon, Jun 12, 2023 at 02:29:25PM +0200, Anna-Maria Behnsen a écrit :
> On Wed, 7 Jun 2023, Frederic Weisbecker wrote:
> Right. It will never stop the propagation - but the condition could be
> fulfilled when call site is tmigr_inactive_up(). My proposal for expanding
> the comment is the following:
> 
> 	/*
> 	 * Walking the hierarchy is required in any case when a
> 	 * remote expiry was done before. This ensures to not lose
> 	 * already queued events in non active groups (see section
> 	 * "Required event and timerqueue update after remote
> 	 * expiry" in documentation at the top).
> 	 *
> 	 * The two call sites which are executed without a remote expiry
> 	 * before, are not prevented from propagating changes through
> 	 * the hierarchy by the return:
> 	 *  - When entering this path by tmigr_new_timer(), evt->ignore
> 	 *    is never set.
> 	 *  - tmigr_inactive_up() takes care of propagation by itself
> 	 *    and ignores return value. But an immediate return is
> 	 *    required because nothing has to be done in this level as
> 	 *    event could be ignored.
> 	 */

Yes, very good!

Thanks.