linux-kernel - Re: [PATCH] sched/core: Use empty mask to reset cpumasks in sched

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Message-ID: <20230705093752.GW4253@hirez.programming.kicks-ass.net>
Date:   Wed, 5 Jul 2023 11:37:52 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, 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>,
        linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>,
        Brent Rowsell <browsell@...hat.com>,
        Peter Hunt <pehunt@...hat.com>
Subject: Re: [PATCH] sched/core: Use empty mask to reset cpumasks in
 sched_setaffinity()

On Mon, Jul 03, 2023 at 10:55:02AM -0400, Waiman Long wrote:

> Our OpenShift team has actually hit a problem with the recent persistent
> user provided cpu affinity change because they are relying on the fact that
> moving a task to a different cpuset will reset cpu affinity to the cpuset
> default which is no longer true. That is the main reason behind this patch
> to provide a way to reset cpu affinity to the cpuset default.

Where is the sched_setaffinity() in that story?

So somewhere this thing did a sched_setaffinity() and then starts
playing with cpusets. Instead of adding more sched_setaffinity() calls,
can't it just remove some?