[PATCH v2 02/12] sched/isolation: Introduce housekeeping notifier infrastructure

Qiliang Yuan
2026-04-13T07:43:45Z

Subsystems currently rely on static housekeeping masks determined at
boot. Supporting runtime reconfiguration (DHM v2) 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 triggered by cpusets.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
---
include/linux/sched/isolation.h | 21 +++++++++++++++++++++
kernel/sched/isolation.c | 26 ++++++++++++++++++++++++++
2 files changed, 47 insertions(+)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index b9a041247565c..aea1dbc4d7486 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -4,6 +4,7 @@
#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/tick.h>
+#include <linux/notifier.h>

enum hk_type {
/* Inverse of boot-time isolcpus= argument */
@@ -28,6 +29,13 @@ enum hk_type {

#define HK_TYPE_KERNEL_NOISE HK_TYPE_TICK

+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);
@@ -38,6 +46,9 @@ extern bool housekeeping_test_cpu(int cpu, enum hk_type type);
extern int housekeeping_update(struct cpumask *isol_mask);
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)
@@ -65,6 +76,16 @@ static inline bool housekeeping_test_cpu(int cpu, enum hk_type type)

static inline int housekeeping_update(struct cpumask *isol_mask) { return 0; }
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 e05ed5118e651..0462b41807161 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -10,6 +10,7 @@
#include <linux/sched/isolation.h>
#include <linux/pci.h>
#include "sched.h"
+#include <linux/notifier.h>

enum hk_flags {
HK_FLAG_DOMAIN_BOOT = BIT(HK_TYPE_DOMAIN_BOOT),
@@ -26,6 +27,8 @@ enum hk_flags {
#define HK_FLAG_KERNEL_NOISE (HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | \
HK_FLAG_MISC | HK_FLAG_WQ | HK_FLAG_KTHREAD)

+static BLOCKING_NOTIFIER_HEAD(housekeeping_notifier_list);
+
DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
EXPORT_SYMBOL_GPL(housekeeping_overridden);

@@ -170,6 +173,29 @@ int housekeeping_update(struct cpumask *isol_mask)
return 0;
}

+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);
+
+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);
+}
+EXPORT_SYMBOL_GPL(housekeeping_update_notify);
+
void __init housekeeping_init(void)
{
enum hk_type type;

--
2.43.0