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Thu, 05 Feb 2026 23:06:58 -0800 (PST) From: Qiliang Yuan Date: Fri, 06 Feb 2026 02:04:33 -0500 Subject: [PATCH RFC 12/12] sched/isolation: Bridge isolcpus and support runtime tick offload init Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260206-feature-dynamic_isolcpus_dhei-v1-12-00a711eb0c74@gmail.com> References: <20260206-feature-dynamic_isolcpus_dhei-v1-0-00a711eb0c74@gmail.com> In-Reply-To: <20260206-feature-dynamic_isolcpus_dhei-v1-0-00a711eb0c74@gmail.com> To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Thomas Gleixner , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Tejun Heo , Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Anna-Maria Behnsen , Ingo Molnar Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org, Qiliang Yuan , Qiliang Yuan X-Mailer: b4 0.14.3 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 Signed-off-by: Qiliang Yuan --- 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