linux-kernel - Re: [PATCH v14 05/12] cpuset: Add an error state to cpuset.sched.partition

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Message-ID: <3542ae87-5e58-93cb-8f95-04b6101f1a33@redhat.com>
Date:   Wed, 7 Nov 2018 18:13:26 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...com, pjt@...gle.com, luto@...capital.net,
        Mike Galbraith <efault@....de>, torvalds@...ux-foundation.org,
        Roman Gushchin <guro@...com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Tom Hromatka <tom.hromatka@...cle.com>
Subject: Re: [PATCH v14 05/12] cpuset: Add an error state to
 cpuset.sched.partition

On 11/06/2018 06:40 AM, Peter Zijlstra wrote:
> On Mon, Oct 15, 2018 at 04:29:30PM -0400, Waiman Long wrote:
>> +				spin_lock_irq(&callback_lock);
>> +				clear_bit(CS_CPU_EXCLUSIVE, &cp->flags);
>> +				spin_unlock_irq(&callback_lock);
> A single atomic bitop wrapped in a spinlock..  maybe it is correct, but
> it looks suspicous.

Yes, you are right. The spin_lock() should not be needed in this case.

Thanks,
Longman