linux-kernel - Re: [PATCHv4 2/2] sched/deadline: Walk up cpuset hierarchy to decide root domain when hot-unplug

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Message-ID: <5d755e54-ff86-4cd0-87bf-86290d4f13de@redhat.com>
Date: Mon, 3 Nov 2025 22:42:05 -0500
From: Waiman Long <llong@...hat.com>
To: Pingfan Liu <piliu@...hat.com>, Juri Lelli <juri.lelli@...hat.com>
Cc: Waiman Long <llong@...hat.com>, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
 Pierre Gondois <pierre.gondois@....com>,
 Frederic Weisbecker <frederic@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCHv4 2/2] sched/deadline: Walk up cpuset hierarchy to decide
 root domain when hot-unplug

On 11/3/25 10:34 PM, Pingfan Liu wrote:
>> If that is the case, and assuming nobody touched the sleeping task
>> affinity (p->cpus_ptr), can't we just use another online cpu from
> In fact, IIUC, the change will be always propagated through the cpuset
> hier into cpus_ptr by cpuset_update_tasks_cpumask() in cpuset v2.
> (Ridong, please correct me if my understanding is wrong)

For kthreads, changes to p->cpus_ptr via cpuset is going to be updated 
with a new set of kthread patch [1] being reviewed right now.

[1] https://lore.kernel.org/lkml/20251013203146.10162-1-frederic@kernel.org/

Cheers,
Longman