[PATCH RFC 12/12] sched/isolation: Bridge isolcpus and support runtime tick offload init

[Qiliang Yuan <realwujing@gmail.com>]

Bridge the boot-time 'isolcpus' and 'nohz_full' parameters with the
DHEI sysfs interface. Ensure that housekeeping_init() correctly
initializes the isolation state and that subsequent sysfs updates
can take over management even if no isolation was configured at boot.

Remove __init from sched_tick_offload_init() and update it to be
safe for multiple calls. This allows DHEI to initialize tick offload
infrastructure at runtime when the first tick-isolated core is
configured.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
---
 kernel/sched/core.c      | 5 ++++-
 kernel/sched/isolation.c | 3 +++
 kernel/sched/sched.h     | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 045f83ad261e..d155e1132d6b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5685,8 +5685,11 @@ static void sched_tick_stop(int cpu)
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
-int __init sched_tick_offload_init(void)
+int sched_tick_offload_init(void)
 {
+	if (tick_work_cpu)
+		return 0;
+
 	tick_work_cpu = alloc_percpu(struct tick_work);
 	BUG_ON(!tick_work_cpu);
 	return 0;
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 30798e790b9f..76c039a01fb0 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -241,6 +241,9 @@ static ssize_t housekeeping_store(struct kobject *kobject,
 	housekeeping.flags |= BIT(type);
 	static_branch_enable(&housekeeping_overridden);
 	
+	if (type == HK_TYPE_TICK || type == HK_TYPE_TIMER || type == HK_TYPE_RCU)
+		sched_tick_offload_init();
+
 	housekeeping_update_notify(type, new_mask);
 	
 	err = count;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 93fce4bbff5e..0079e7210c38 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2867,7 +2867,7 @@ extern void post_init_entity_util_avg(struct task_struct *p);
 
 #ifdef CONFIG_NO_HZ_FULL
 extern bool sched_can_stop_tick(struct rq *rq);
-extern int __init sched_tick_offload_init(void);
+extern int sched_tick_offload_init(void);
 
 /*
  * Tick may be needed by tasks in the runqueue depending on their policy and

-- 
2.51.0