linux-kernel - [PATCH 2/3] workqueue: Let DISASSOCIATED workers follow unbound wq cpumask changes

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Message-Id: <20251117030913.3084-3-jiangshanlai@gmail.com>
Date: Mon, 17 Nov 2025 11:09:12 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Waiman Long <longman@...hat.com>,
	Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH 2/3] workqueue: Let DISASSOCIATED workers follow unbound wq cpumask changes

From: Lai Jiangshan <jiangshan.ljs@...group.com>

When workqueue cpumask changes are committed, the DISASSOCIATED workers
affinity is not touched and this might be a problem down the line for
isolated setups when the DISASSOCIATED pools still have works to run
after the cpu is offline.

Make sure the workers' affinity is updated every time a workqueue cpumask
changes, so these workers can't break isolation.

Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Waiman Long <longman@...hat.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 kernel/workqueue.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9da679c621dc..ccf03a0ff122 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -6967,6 +6967,10 @@ static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
 	}
 
 	if (!ret) {
+		int cpu;
+		struct worker_pool *pool;
+		struct worker *worker;
+
 		mutex_lock(&wq_pool_attach_mutex);
 		cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
 		/* rescuer needs to respect cpumask changes when it is not attached */
@@ -6974,6 +6978,15 @@ static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
 			if (wq->rescuer && !wq->rescuer->pool)
 				unbind_worker(wq->rescuer);
 		}
+		/* DISASSOCIATED worker needs to respect wq_unbound_cpumask */
+		for_each_possible_cpu(cpu) {
+			for_each_cpu_worker_pool(pool, cpu) {
+				if (!(pool->flags & POOL_DISASSOCIATED))
+					continue;
+				for_each_pool_worker(worker, pool)
+					unbind_worker(worker);
+			}
+		}
 		mutex_unlock(&wq_pool_attach_mutex);
 	}
 	return ret;
-- 
2.19.1.6.gb485710b