linux-kernel - [RFC PATCH 2/4] kernel/workqueue: Bind rescuer to unbound cpumask for WQ

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Date: Tue, 16 Jan 2024 17:19:27 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: Lai Jiangshan <jiangshanlai@...il.com>,
	Aaron Tomlin <atomlin@...mlin.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Waiman Long <longman@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/4] kernel/workqueue: Bind rescuer to unbound cpumask for WQ_UNBOUND

At the time they are created unbound workqueues rescuers currently use
cpu_possible_mask as their affinity, but this can be too wide in case a
workqueue unbound mask has been set as a subset of cpu_possible_mask.

Make new rescuers use their associated workqueue unbound cpumask from
the start.

Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
---
 kernel/workqueue.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 76e60faed8923..3a1d5a67bd66a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4652,7 +4652,10 @@ static int init_rescuer(struct workqueue_struct *wq)
 	}
 
 	wq->rescuer = rescuer;
-	kthread_bind_mask(rescuer->task, cpu_possible_mask);
+	if (wq->flags & WQ_UNBOUND)
+		kthread_bind_mask(rescuer->task, wq->unbound_attrs->cpumask);
+	else
+		kthread_bind_mask(rescuer->task, cpu_possible_mask);
 	wake_up_process(rescuer->task);
 
 	return 0;
-- 
2.43.0