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

Frederic Weisbecker
2026-03-31T09:34:38Z

Le Wed, Mar 25, 2026 at 05:09:33PM +0800, Qiliang Yuan a écrit :
> 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);
> +}

I much prefer explicit function calls over notifiers so that we control on
which order things happen. housekeeping_update() does that for HK_TYPE_DOMAIN.

Thanks.

> +
> void __init housekeeping_init(void)
> {
> enum hk_type type;
>
> --
> 2.43.0
>

--
Frederic Weisbecker
SUSE Labs