linux-kernel - [PATCH v4 05/19] workqueue: Manually break affinity on hotplug

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Date:   Fri, 23 Oct 2020 12:12:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     tglx@...utronix.de, mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org, bigeasy@...utronix.de,
        qais.yousef@....com, swood@...hat.com, peterz@...radead.org,
        valentin.schneider@....com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vincent.donnefort@....com, tj@...nel.org,
        ouwen210@...mail.com
Subject: [PATCH v4 05/19] workqueue: Manually break affinity on hotplug

Don't rely on the scheduler to force break affinity for us -- it will
stop doing that for per-cpu-kthreads.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Tejun Heo <tj@...nel.org>
---
 kernel/workqueue.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4905,6 +4905,10 @@ static void unbind_workers(int cpu)
 		pool->flags |= POOL_DISASSOCIATED;
 
 		raw_spin_unlock_irq(&pool->lock);
+
+		for_each_pool_worker(worker, pool)
+			WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_active_mask) < 0);
+
 		mutex_unlock(&wq_pool_attach_mutex);
 
 		/*