linux-kernel - [tip: sched/core] sched/fair: Remove superfluous rcu_read

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Message-ID: <176569840446.498.719471047587243574.tip-bot2@tip-bot2>
Date: Sun, 14 Dec 2025 07:46:44 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Remove superfluous rcu_read_lock()

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     a03fee333a2f1e065a739bdbe5edbc5512fab9a4
Gitweb:        https://git.kernel.org/tip/a03fee333a2f1e065a739bdbe5edbc5512fab9a4
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 14 Nov 2025 11:00:55 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 14 Dec 2025 08:25:02 +01:00

sched/fair: Remove superfluous rcu_read_lock()

With fair switched to rcu_dereference_all() validation, having IRQ or
preemption disabled is sufficient, remove the rcu_read_lock()
clutter.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://patch.msgid.link/20251127154725.647502625@infradead.org
---
 kernel/sched/fair.c |  9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 44a359d..496a30a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12856,21 +12856,16 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 	 */
 	rq_unpin_lock(this_rq, rf);
 
-	rcu_read_lock();
 	sd = rcu_dereference_sched_domain(this_rq->sd);
-	if (!sd) {
-		rcu_read_unlock();
+	if (!sd)
 		goto out;
-	}
 
 	if (!get_rd_overloaded(this_rq->rd) ||
 	    this_rq->avg_idle < sd->max_newidle_lb_cost) {
 
 		update_next_balance(sd, &next_balance);
-		rcu_read_unlock();
 		goto out;
 	}
-	rcu_read_unlock();
 
 	/*
 	 * Include sched_balance_update_blocked_averages() in the cost
@@ -12883,7 +12878,6 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 	rq_modified_clear(this_rq);
 	raw_spin_rq_unlock(this_rq);
 
-	rcu_read_lock();
 	for_each_domain(this_cpu, sd) {
 		u64 domain_cost;
 
@@ -12933,7 +12927,6 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 		if (pulled_task || !continue_balancing)
 			break;
 	}
-	rcu_read_unlock();
 
 	raw_spin_rq_lock(this_rq);