sched/fair: Introduce is_rd_overutilized() helper function to access root_domain::overutilized

The root_domain::overutilized field is READ_ONCE() accessed in
multiple places, which could be simplified with a helper function.

This might also make it more apparent that it needs to be used
only in case of EAS.

No change in functionality intended.
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Qais Yousef <qyousef@layalina.io>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240307085725.444486-3-sshegde@linux.ibm.com

kernel/sched/fair.c

@@ -6685,6 +6685,15 @@ static inline bool cpu_overutilized(int cpu)
 	return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
 }
 
+/*
+ * Ensure that caller can do EAS. overutilized value
+ * make sense only if EAS is enabled
+ */
+static inline int is_rd_overutilized(struct root_domain *rd)
+{
+	return READ_ONCE(rd->overutilized);
+}
+
 static inline void set_rd_overutilized_status(struct root_domain *rd,
 					      unsigned int status)
 {
@@ -6704,7 +6713,7 @@ static inline void check_update_overutilized_status(struct rq *rq)
 	if (!sched_energy_enabled())
 		return;
 
-	if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
+	if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
 		set_rd_overutilized_status(rq->rd, SG_OVERUTILIZED);
 }
 #else
@@ -7990,7 +7999,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 
 	rcu_read_lock();
 	pd = rcu_dereference(rd->pd);
-	if (!pd || READ_ONCE(rd->overutilized))
+	if (!pd || is_rd_overutilized(rd))
 		goto unlock;
 
 	/*
@@ -10897,7 +10906,7 @@ static struct sched_group *sched_balance_find_src_group(struct lb_env *env)
 	if (sched_energy_enabled()) {
 		struct root_domain *rd = env->dst_rq->rd;
 
-		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
+		if (rcu_dereference(rd->pd) && !is_rd_overutilized(rd))
 			goto out_balanced;
 	}