linux-kernel - Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched

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Message-ID: <20190904061616.25ce79e1@oasis.local.home>
Date:   Wed, 4 Sep 2019 06:16:16 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alessio Balsini <balsini@...roid.com>, mingo@...nel.org,
        juri.lelli@...hat.com, linux-kernel@...r.kernel.org,
        dietmar.eggemann@....com, luca.abeni@...tannapisa.it,
        bristot@...hat.com, dvyukov@...gle.com, tglx@...utronix.de,
        vpillai@...italocean.com, kernel-team@...roid.com
Subject: Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on
 sched_attr::sched_period

On Mon, 2 Sep 2019 11:16:23 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> in sched_dl_period_handler(). And do:
> 
> +	preempt_disable();
> 	max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
> 	min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
> +	preempt_enable();

Hmm, I'm curious. Doesn't the preempt_disable/enable() also add
compiler barriers which would remove the need for the READ_ONCE()s here?

-- Steve