[tip: sched/core] sched/fair: Remove superfluous rcu_read_lock()

tip-bot2 for Peter Zijlstra
2025-12-14T07:46:47Z

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@infradead.org>
AuthorDate: Fri, 14 Nov 2025 11:00:55 +01:00
Committer: Ingo Molnar <mingo@kernel.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@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.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);