linux-kernel - [RFC PATCH 01/19] sched/fair: Simplify set_cpu_sd_state

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Message-ID: <20250904041516.3046-2-kprateek.nayak@amd.com>
Date: Thu, 4 Sep 2025 04:14:57 +0000
From: K Prateek Nayak <kprateek.nayak@....com>
To: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
	<vincent.guittot@...aro.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner
	<tglx@...utronix.de>, <linux-kernel@...r.kernel.org>
CC: Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt
	<rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, K Prateek Nayak
	<kprateek.nayak@....com>, "Gautham R. Shenoy" <gautham.shenoy@....com>,
	Swapnil Sapkal <swapnil.sapkal@....com>
Subject: [RFC PATCH 01/19] sched/fair: Simplify set_cpu_sd_state_*() with guards

Simplify set_cpu_sd_state_{busy,idle}() using guard(rcu).

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
 kernel/sched/fair.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df8dc389af8e..61b59fd75ced 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12449,16 +12449,14 @@ static void set_cpu_sd_state_busy(int cpu)
 {
 	struct sched_domain *sd;
 
-	rcu_read_lock();
-	sd = rcu_dereference(per_cpu(sd_llc, cpu));
+	guard(rcu)();
 
+	sd = rcu_dereference(per_cpu(sd_llc, cpu));
 	if (!sd || !sd->nohz_idle)
-		goto unlock;
-	sd->nohz_idle = 0;
+		return;
 
+	sd->nohz_idle = 0;
 	atomic_inc(&sd->shared->nr_busy_cpus);
-unlock:
-	rcu_read_unlock();
 }
 
 void nohz_balance_exit_idle(struct rq *rq)
@@ -12479,16 +12477,14 @@ static void set_cpu_sd_state_idle(int cpu)
 {
 	struct sched_domain *sd;
 
-	rcu_read_lock();
-	sd = rcu_dereference(per_cpu(sd_llc, cpu));
+	guard(rcu)();
 
+	sd = rcu_dereference(per_cpu(sd_llc, cpu));
 	if (!sd || sd->nohz_idle)
-		goto unlock;
-	sd->nohz_idle = 1;
+		return;
 
+	sd->nohz_idle = 1;
 	atomic_dec(&sd->shared->nr_busy_cpus);
-unlock:
-	rcu_read_unlock();
 }
 
 /*
-- 
2.34.1