linux-kernel - Re: [PATCH v8 4/6] cpuset: Make generate_sched_domains() recognize isolated

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Date:   Mon, 28 May 2018 21:12:55 -0400
From:   Waiman Long <longman@...hat.com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.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>
Subject: Re: [PATCH v8 4/6] cpuset: Make generate_sched_domains() recognize
 isolated_cpus

On 05/24/2018 06:28 AM, Juri Lelli wrote:
> On 17/05/18 16:55, Waiman Long wrote:
>
> [...]
>
>> @@ -849,7 +860,12 @@ static void rebuild_sched_domains_locked(void)
>>  	 * passing doms with offlined cpu to partition_sched_domains().
>>  	 * Anyways, hotplug work item will rebuild sched domains.
>>  	 */
>> -	if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
>> +	if (!top_cpuset.isolation_count &&
>> +	    !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
>> +		goto out;
>> +
>> +	if (top_cpuset.isolation_count &&
>> +	   !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
>>  		goto out;
> Do we cover the case in which hotplug removed one of the isolated cpus
> from cpu_active_mask?

Yes, you are right. That is the remnant of my original patch that allows
only one isolated_cpus at root. Thanks for spotting that.

Cheers,
Longman