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From:   Binglei Wang <l3b2w1@gmail.com>
To:     tj@kernel.org, jiangshanlai@gmail.com
Cc:     linux-kernel@vger.kernel.org, Binglei Wang <l3b2w1@gmail.com>
Subject: [PATCH] workqueue: make workers threads stick to HK_TYPE_KTHREAD cpumask
Date:   Thu,  3 Nov 2022 11:09:33 +0800
Message-Id: <20221103030933.840989-1-l3b2w1@gmail.com>
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From: Binglei Wang <l3b2w1@gmail.com>

When new worker thread created, set its affinity to HK_TYPE_KTHREAD
cpumask.
When hotplug cpu online, rebind workers's affinity to HK_TYPE_KTHREAD
cpumask.
Make workers threads stick to HK_TYPE_KTHREAD cpumask all the time.

Signed-off-by: Binglei Wang <l3b2w1@gmail.com>
---
 kernel/workqueue.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7cd5f5e7e..77b303f5e 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1928,6 +1928,7 @@ static struct worker *create_worker(struct worker_pool *pool)
 	struct worker *worker;
 	int id;
 	char id_buf[16];
+	const struct cupmask *cpumask = NULL;
 
 	/* ID is needed to determine kthread name */
 	id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
@@ -1952,7 +1953,10 @@ static struct worker *create_worker(struct worker_pool *pool)
 		goto fail;
 
 	set_user_nice(worker->task, pool->attrs->nice);
-	kthread_bind_mask(worker->task, pool->attrs->cpumask);
+
+	if (housekeeping_enabled(HK_TYPE_KTHREAD))
+		cpumask = housekeeping_cpumask(HK_TYPE_KTHREAD);
+	kthread_bind_mask(worker->task, cpumask ? cpumask : pool->attrs->cpumask);
 
 	/* successful, attach the worker to the pool */
 	worker_attach_to_pool(worker, pool);
@@ -5027,20 +5031,26 @@ static void unbind_workers(int cpu)
 static void rebind_workers(struct worker_pool *pool)
 {
 	struct worker *worker;
+	const struct cpumask *cpumask = NULL;
 
 	lockdep_assert_held(&wq_pool_attach_mutex);
 
+	if (housekeeping_enabled(HK_TYPE_KTHREAD))
+		cpumask = housekeeping_cpumask(HK_TYPE_KTHREAD);
+
 	/*
 	 * Restore CPU affinity of all workers.  As all idle workers should
 	 * be on the run-queue of the associated CPU before any local
 	 * wake-ups for concurrency management happen, restore CPU affinity
 	 * of all workers first and then clear UNBOUND.  As we're called
 	 * from CPU_ONLINE, the following shouldn't fail.
+	 *
+	 * Also consider the housekeeping HK_TYPE_KTHREAD cpumask.
 	 */
 	for_each_pool_worker(worker, pool) {
 		kthread_set_per_cpu(worker->task, pool->cpu);
 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
-						  pool->attrs->cpumask) < 0);
+						  cpumask ? cpumask : pool->attrs->cpumask) < 0);
 	}
 
 	raw_spin_lock_irq(&pool->lock);
-- 
2.27.0