Workqueues use housekeeping masks (HK_TYPE_WQ and HK_TYPE_DOMAIN) to
determine the default affinity for unbound workqueues. Currently,
these masks are only applied during early boot.

Register a housekeeping notifier to dynamically update the workqueue
unbound cpumask when these housekeeping masks are changed at runtime.
This ensures that unbound workqueues are re-affined to the new
housekeeping CPUs. Also update wq_isolated_cpumask to reflect the
changes in HK_TYPE_DOMAIN.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
---
 kernel/workqueue.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 253311af47c6..b8913935d5e8 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -7913,6 +7913,44 @@ static void __init wq_cpu_intensive_thresh_init(void)
  * executing the work items yet. Populate the worker pools with the initial
  * workers and enable future kworker creations.
  */
+static int wq_housekeeping_reconfigure(struct notifier_block *nb,
+				      unsigned long action, void *data)
+{
+	if (action == HK_UPDATE_MASK) {
+		unsigned int type = (unsigned long)data;
+
+		if (type == HK_TYPE_WQ || type == HK_TYPE_DOMAIN) {
+			cpumask_var_t cpumask;
+
+			if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
+				return NOTIFY_BAD;
+
+			cpumask_copy(cpumask, cpu_possible_mask);
+			if (!cpumask_empty(housekeeping_cpumask(HK_TYPE_WQ)))
+				cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_WQ));
+			if (!cpumask_empty(housekeeping_cpumask(HK_TYPE_DOMAIN)))
+				cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
+
+			workqueue_set_unbound_cpumask(cpumask);
+
+			if (type == HK_TYPE_DOMAIN) {
+				apply_wqattrs_lock();
+				cpumask_andnot(wq_isolated_cpumask, cpu_possible_mask,
+						housekeeping_cpumask(HK_TYPE_DOMAIN));
+				apply_wqattrs_unlock();
+			}
+
+			free_cpumask_var(cpumask);
+		}
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block wq_housekeeping_nb = {
+	.notifier_call = wq_housekeeping_reconfigure,
+};
+
 void __init workqueue_init(void)
 {
 	struct workqueue_struct *wq;
@@ -7964,6 +8002,7 @@ void __init workqueue_init(void)
 
 	wq_online = true;
 	wq_watchdog_init();
+	housekeeping_register_notifier(&wq_housekeeping_nb);
 }
 
 /*

-- 
2.51.0