linux-kernel - [RFC][PATCH v0.3 1/6] cpufreq/sched: schedutil: Add helper for governor checks

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Message-ID: <1840739.VLH7GnMWUR@rjwysocki.net>
Date: Fri, 07 Mar 2025 20:15:42 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Peter Zijlstra <peterz@...radead.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Morten Rasmussen <morten.rasmussen@....com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Pierre Gondois <pierre.gondois@....com>,
 Christian Loehle <christian.loehle@....com>,
 Viresh Kumar <viresh.kumar@...aro.org>
Subject:
 [RFC][PATCH v0.3 1/6] cpufreq/sched: schedutil: Add helper for governor
 checks

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Add a helper for checking if schedutil is the current governor for
a given cpufreq policy and use it in sched_is_eas_possible() to avoid
accessing cpufreq policy internals directly from there.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 include/linux/cpufreq.h          |    9 +++++++++
 kernel/sched/cpufreq_schedutil.c |    9 +++++++--
 kernel/sched/sched.h             |    2 --
 kernel/sched/topology.c          |    6 +++---
 4 files changed, 19 insertions(+), 7 deletions(-)

--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -641,6 +641,15 @@
 struct cpufreq_governor *cpufreq_default_governor(void);
 struct cpufreq_governor *cpufreq_fallback_governor(void);
 
+#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
+bool sugov_is_cpufreq_governor(struct cpufreq_policy *policy);
+#else
+static inline bool sugov_is_cpufreq_governor(struct cpufreq_policy *policy)
+{
+	return false;
+}
+#endif
+
 static inline void cpufreq_policy_apply_limits(struct cpufreq_policy *policy)
 {
 	if (policy->max < policy->cur)
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -604,7 +604,7 @@
 
 /********************** cpufreq governor interface *********************/
 
-struct cpufreq_governor schedutil_gov;
+static struct cpufreq_governor schedutil_gov;
 
 static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
 {
@@ -874,7 +874,7 @@
 	sg_policy->limits_changed = true;
 }
 
-struct cpufreq_governor schedutil_gov = {
+static struct cpufreq_governor schedutil_gov = {
 	.name			= "schedutil",
 	.owner			= THIS_MODULE,
 	.flags			= CPUFREQ_GOV_DYNAMIC_SWITCHING,
@@ -892,4 +892,9 @@
 }
 #endif
 
+bool sugov_is_cpufreq_governor(struct cpufreq_policy *policy)
+{
+	return policy->governor == &schedutil_gov;
+}
+
 cpufreq_governor_init(schedutil_gov);
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3552,8 +3552,6 @@
 	return static_branch_unlikely(&sched_energy_present);
 }
 
-extern struct cpufreq_governor schedutil_gov;
-
 #else /* ! (CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL) */
 
 #define perf_domain_span(pd) NULL
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -216,7 +216,7 @@
 {
 	bool any_asym_capacity = false;
 	struct cpufreq_policy *policy;
-	struct cpufreq_governor *gov;
+	bool policy_is_ready;
 	int i;
 
 	/* EAS is enabled for asymmetric CPU capacity topologies. */
@@ -261,9 +261,9 @@
 			}
 			return false;
 		}
-		gov = policy->governor;
+		policy_is_ready = sugov_is_cpufreq_governor(policy);
 		cpufreq_cpu_put(policy);
-		if (gov != &schedutil_gov) {
+		if (!policy_is_ready) {
 			if (sched_debug()) {
 				pr_info("rd %*pbl: Checking EAS, schedutil is mandatory\n",
 					cpumask_pr_args(cpu_mask));