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Date: Mon, 2 Mar 2026 12:49:22 +0100
From: Frederic Weisbecker <frederic@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Chen Ridong <chenridong@huaweicloud.com>, Tejun Heo <tj@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>, Shuah Khan <shuah@kernel.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v6 7/8] cgroup/cpuset: Defer housekeeping_update() calls
 from CPU hotplug to workqueue
Message-ID: <aaV5Qvl4HDFEtFj4@lothringen>
References: <20260221185418.29319-1-longman@redhat.com>
 <20260221185418.29319-8-longman@redhat.com>
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In-Reply-To: <20260221185418.29319-8-longman@redhat.com>

On Sat, Feb 21, 2026 at 01:54:17PM -0500, Waiman Long wrote:
> The cpuset_handle_hotplug() may need to invoke housekeeping_update(),
> for instance, when an isolated partition is invalidated because its
> last active CPU has been put offline.
> 
> As we are going to enable dynamic update to the nozh_full housekeeping
> cpumask (HK_TYPE_KERNEL_NOISE) soon with the help of CPU hotplug,
> allowing the CPU hotplug path to call into housekeeping_update() directly
> from update_isolation_cpumasks() will likely cause deadlock.

It would be nice to describe the deadlock scenario here.

Thanks.