linux-kernel - Re: [PATCH/for-next v4 3/4] cgroup/cpuset: Call housekeeping_update() without holding cpus_read

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Message-ID: <b1193a25-f38d-4f4f-bee0-565fc7b7402b@redhat.com>
Date: Tue, 10 Feb 2026 09:39:30 -0500
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, Waiman Long <llong@...hat.com>,
 Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 Anna-Maria Behnsen <anna-maria@...utronix.de>,
 Frederic Weisbecker <frederic@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Shuah Khan <shuah@...nel.org>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH/for-next v4 3/4] cgroup/cpuset: Call housekeeping_update()
 without holding cpus_read_lock


On 2/9/26 8:39 PM, Chen Ridong wrote:
>
> On 2026/2/10 4:20, Waiman Long wrote:
>> On 2/9/26 2:23 AM, Chen Ridong wrote:
>>> On 2026/2/7 4:37, Waiman Long wrote:
>>>> +static cpumask_var_t    isolated_hk_cpus;    /* T */
>>> Can we get this from isolation.c instead?
>>>
>>> The name probably shouldn't include 'hk', since it refers to the inverse
>>> (housekeeping CPUs) of isolated CPUs, right?
>> The housekeeping_update() will create an inverse of the pass-in isolated
>> cpumasks. As for the name, I add hk to indicate this cpumask is for passing to
>> housekeeping_update() to update housekeeping cpumask. It is not directly related
>> to the cpumasks in sched/isolation.c. Please let me know if you have  a
>> suggestion for the name.
>>
> I understand the intent. However, when reading both cpuset.c and
> sched/isolation.c, it can be confusing whether isolated_hk_cpus is an inverse
> mask, since in sched/isolation.c “hk” consistently refers to the inverse.
>
> How about isolated_cpus_applied?

Applied to what? I did add a comment to describe isolated_hk_cpus as a 
copy of isolated_cpus to be passed to housekeeping_update(). "hk" in the 
name refers to its role for being passed to that function. I can't use 
"isolated_cpus" for now as it may get modified by CPU hotplug 
concurrently. In the future, if CPU hotplug no longer modify 
isolated_cpus, I will remove isolated_hk_cpus and pass isolated_cpus 
directly to housekeeping_update(). I don't think we need to spend extra 
time bikeshedding what the right name should be.

Cheers,
Longman