linux-kernel - Re: [PATCH 3/3] sched/nohz: Remove weird error handling from find_new

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Message-ID: <20231006103858.GB36277@noisy.programming.kicks-ass.net>
Date:   Fri, 6 Oct 2023 12:38:58 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/3] sched/nohz: Remove weird error handling from
 find_new_ilb()

On Fri, Oct 06, 2023 at 12:25:18PM +0200, Ingo Molnar wrote:
> find_new_ilb() returns nr_cpu_ids on failure - which is a weird
> choice in itself: not only is it a global variable, it is
> a +1 out of bounds CPU index...

FWIW this is what all the cpumask bitops return when they've exhausted
the mask. Eg. no bits left set etc..