[PATCH 08/15] workqueue: Support dynamic housekeeping mask updates

[Qiliang Yuan <realwujing@gmail.com>]

Unbound workqueues use HK_TYPE_WQ and HK_TYPE_DOMAIN to determine
their default CPU affinity. These boundaries are currently static and
only enforced during early boot.

Implement a housekeeping notifier to update unbound workqueue affinity.

This enables unbound workqueue tasks to respect dynamic isolation
boundaries at runtime.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
---
 kernel/workqueue.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 253311af47c6d..ef3ef7e3fe81f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -7904,6 +7904,47 @@ static void __init wq_cpu_intensive_thresh_init(void)
 	wq_cpu_intensive_thresh_us = thresh;
 }
 
+static int wq_housekeeping_reconfigure(struct notifier_block *nb,
+				     unsigned long action, void *data)
+{
+	if (action == HK_UPDATE_MASK) {
+		struct housekeeping_update *upd = data;
+		unsigned int type = upd->type;
+
+		if (type == HK_TYPE_WQ || type == HK_TYPE_DOMAIN) {
+			cpumask_var_t cpumask;
+
+			if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) {
+				pr_warn("workqueue: failed to allocate cpumask for housekeeping update\n");
+				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,
+};
+
 /**
  * workqueue_init - bring workqueue subsystem fully online
  *
@@ -7964,6 +8005,7 @@ void __init workqueue_init(void)
 
 	wq_online = true;
 	wq_watchdog_init();
+	housekeeping_register_notifier(&wq_housekeeping_nb);
 }
 
 /*

-- 
2.43.0