linux-kernel - Re: [PATCH] sched: Prevent raising SCHED

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Date:   Wed, 16 Dec 2020 09:19:04 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH] sched: Prevent raising SCHED_SOFTIRQ when CPU is !active

On Tue, Dec 15, 2020 at 06:52:49PM +0100, Thomas Gleixner wrote:
> I might be missing something, but how is the CPU which runs the pinned
> kernel thread, i.e. the hotplug thread, supposed to go idle between the
> two calls?

Take a mutex or something other daft. My disabling preemption around it
we basically assert the two functions are non-blocking and none of that
cruft matters.