[PATCH 02/15] sched/isolation: Introduce housekeeping notifier infrastructure

[Qiliang Yuan <realwujing@gmail.com>]

Subsystems currently rely on static housekeeping masks determined at
boot. Supporting runtime reconfiguration (DHEI) requires a mechanism
to broadcast mask changes to affected kernel components.

Implement a blocking notifier chain for housekeeping mask updates.

This infrastructure enables subsystems like genirq, workqueues, and RCU
to react dynamically to isolation changes.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
---
 include/linux/sched/isolation.h | 21 +++++++++++++++++++++
 kernel/sched/isolation.c        | 24 ++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index d8501f4709b58..9df55237d3901 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -5,6 +5,7 @@
 #include <linux/cpuset.h>
 #include <linux/init.h>
 #include <linux/tick.h>
+#include <linux/notifier.h>
 
 enum hk_type {
 	HK_TYPE_DOMAIN,
@@ -24,6 +25,13 @@ enum hk_type {
 	HK_TYPE_KTHREAD = HK_TYPE_KERNEL_NOISE
 };
 
+struct housekeeping_update {
+	enum hk_type type;
+	const struct cpumask *new_mask;
+};
+
+#define HK_UPDATE_MASK	0x01
+
 #ifdef CONFIG_CPU_ISOLATION
 DECLARE_STATIC_KEY_FALSE(housekeeping_overridden);
 extern int housekeeping_any_cpu(enum hk_type type);
@@ -33,6 +41,9 @@ extern void housekeeping_affine(struct task_struct *t, enum hk_type type);
 extern bool housekeeping_test_cpu(int cpu, enum hk_type type);
 extern void __init housekeeping_init(void);
 
+extern int housekeeping_register_notifier(struct notifier_block *nb);
+extern int housekeeping_unregister_notifier(struct notifier_block *nb);
+
 #else
 
 static inline int housekeeping_any_cpu(enum hk_type type)
@@ -59,6 +70,16 @@ static inline bool housekeeping_test_cpu(int cpu, enum hk_type type)
 }
 
 static inline void housekeeping_init(void) { }
+
+static inline int housekeeping_register_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int housekeeping_unregister_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
 #endif /* CONFIG_CPU_ISOLATION */
 
 static inline bool housekeeping_cpu(int cpu, enum hk_type type)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 67a5ff273ea08..e7a21023726df 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -9,6 +9,7 @@
  */
 #include <linux/sched/isolation.h>
 #include <linux/mutex.h>
+#include <linux/notifier.h>
 #include "sched.h"
 
 enum hk_flags {
@@ -18,6 +19,7 @@ enum hk_flags {
 };
 
 static DEFINE_MUTEX(housekeeping_mutex);
+static BLOCKING_NOTIFIER_HEAD(housekeeping_notifier_list);
 DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
 EXPORT_SYMBOL_GPL(housekeeping_overridden);
 
@@ -86,6 +88,28 @@ bool housekeeping_test_cpu(int cpu, enum hk_type type)
 }
 EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
 
+int housekeeping_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&housekeeping_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(housekeeping_register_notifier);
+
+int housekeeping_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&housekeeping_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(housekeeping_unregister_notifier);
+
+static int housekeeping_update_notify(enum hk_type type, const struct cpumask *new_mask)
+{
+	struct housekeeping_update update = {
+		.type = type,
+		.new_mask = new_mask,
+	};
+
+	return blocking_notifier_call_chain(&housekeeping_notifier_list, HK_UPDATE_MASK, &update);
+}
+
 void __init housekeeping_init(void)
 {
 	enum hk_type type;

-- 
2.43.0