linux-kernel - Re: [PATCH v4] Sched/fair: Block nohz tick

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Message-ID: <20230703121009.GH4253@hirez.programming.kicks-ass.net>
Date:   Mon, 3 Jul 2023 14:10:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Phil Auld <pauld@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Valentin Schneider <vschneid@...hat.com>,
        Ben Segall <bsegall@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH v4] Sched/fair: Block nohz tick_stop when cfs bandwidth
 in use

On Fri, Jun 30, 2023 at 12:29:10PM -0400, Phil Auld wrote:

> I think you are agreeing that I need the pick next code but need to remove
> the hierarchy walks, right?

Yeah, the dequeue case makes we have to care about pick, not sure we
then also need to care about sched_update_tick_dependency() though.
There is indeed a window where these two will 'race', but afaict it is
benign.