linux-kernel - Re: [PATCH v7 4/7] sched/core: Prevent race condition between cpuset and __sched

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Message-ID: <20190405123645.GT12232@hirez.programming.kicks-ass.net>
Date:   Fri, 5 Apr 2019 14:36:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     mingo@...hat.com, rostedt@...dmis.org, tj@...nel.org,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, lizefan@...wei.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v7 4/7] sched/core: Prevent race condition between cpuset
 and __sched_setscheduler()

On Wed, Apr 03, 2019 at 10:46:47AM +0200, Juri Lelli wrote:
> +static inline void cpuset_read_only_lock(unsigned long *flags)
> +{
> +	local_irq_save(*flags);
> +	preempt_disable();
> +}
> +
> +static inline void cpuset_read_only_unlock(unsigned long *flags)
> +{
> +	local_irq_restore(*flags);
> +	preempt_enable();
> +}

You can ditch the preempt stuff. IRQs disabled already very much implies
!preemptible.