linux-kernel - [PATCH v1] sched/uclamp: Initialize uclamp_rq alongside rq setup in sched

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Message-Id: <20250627074535.14064-1-zhangzihuan@kylinos.cn>
Date: Fri, 27 Jun 2025 15:45:35 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	patrick.bellasi@....com,
	qyousef@...alina.io,
	xuewen.yan@...soc.com
Cc: linux-kernel@...r.kernel.org,
	Zihuan Zhang <zhangzihuan@...inos.cn>
Subject: [PATCH v1] sched/uclamp: Initialize uclamp_rq alongside rq setup in sched_init()

uclamp_rq is currently initialized for all possible CPUs in a separate
loop within init_uclamp(). This creates a dependency on the ordering of
sched_init() and init_uclamp(), and duplicates the per-CPU iteration.

This patch simplifies the logic by moving uclamp_rq initialization into
sched_init(), immediately after each cpu_rq is initialized. This ensures
uclamprq setup is tightly coupled with rq setup and removes the need for
a redundant loop.

Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
---
 kernel/sched/core.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8988d38d46a3..a160ec8645b2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1998,7 +1998,7 @@ static void uclamp_post_fork(struct task_struct *p)
 	uclamp_update_util_min_rt_default(p);
 }
 
-static void __init init_uclamp_rq(struct rq *rq)
+static void init_uclamp_rq(struct rq *rq)
 {
 	enum uclamp_id clamp_id;
 	struct uclamp_rq *uc_rq = rq->uclamp;
@@ -2016,10 +2016,6 @@ static void __init init_uclamp(void)
 {
 	struct uclamp_se uc_max = {};
 	enum uclamp_id clamp_id;
-	int cpu;
-
-	for_each_possible_cpu(cpu)
-		init_uclamp_rq(cpu_rq(cpu));
 
 	for_each_clamp_id(clamp_id) {
 		uclamp_se_set(&init_task.uclamp_req[clamp_id],
@@ -2043,6 +2039,7 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
 static inline void uclamp_fork(struct task_struct *p) { }
 static inline void uclamp_post_fork(struct task_struct *p) { }
 static inline void init_uclamp(void) { }
+static inline void init_uclamp_rq(struct rq *rq) {}
 #endif /* CONFIG_UCLAMP_TASK */
 
 bool sched_task_on_rq(struct task_struct *p)
@@ -8586,6 +8583,7 @@ void __init sched_init(void)
 		init_cfs_rq(&rq->cfs);
 		init_rt_rq(&rq->rt);
 		init_dl_rq(&rq->dl);
+		init_uclamp_rq(rq);
 #ifdef CONFIG_FAIR_GROUP_SCHED
 		INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
 		rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
-- 
2.25.1