linux-kernel - [PATCH v5 12/23] PM: EM: Add helpers to read under RCU lock the EM table

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Message-Id: <20231129110853.94344-13-lukasz.luba@arm.com>
Date:   Wed, 29 Nov 2023 11:08:42 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rafael@...nel.org
Cc:     lukasz.luba@....com, dietmar.eggemann@....com, rui.zhang@...el.com,
        amit.kucheria@...durent.com, amit.kachhap@...il.com,
        daniel.lezcano@...aro.org, viresh.kumar@...aro.org,
        len.brown@...el.com, pavel@....cz, mhiramat@...nel.org,
        qyousef@...alina.io, wvw@...gle.com
Subject: [PATCH v5 12/23] PM: EM: Add helpers to read under RCU lock the EM table

To use the runtime modifiable EM table there is a need to use RCU
read locking properly. Add helper functions for the device drivers and
frameworks to make sure it's done properly.

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 include/linux/energy_model.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 520a8c8ad849..ae3ccc8b9f44 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -341,6 +341,20 @@ static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
 	return pd->nr_perf_states;
 }
 
+static inline struct em_perf_state *em_get_table(struct em_perf_domain *pd)
+{
+	struct em_perf_table __rcu *runtime_table;
+
+	rcu_read_lock();
+	runtime_table = rcu_dereference(pd->runtime_table);
+	return runtime_table->state;
+}
+
+static inline void em_put_table(void)
+{
+	rcu_read_unlock();
+}
+
 #else
 struct em_data_callback {};
 #define EM_ADV_DATA_CB(_active_power_cb, _cost_cb) { }
@@ -387,6 +401,11 @@ int em_dev_update_perf_domain(struct device *dev,
 {
 	return -EINVAL;
 }
+static inline struct em_perf_state *em_get_table(struct em_perf_domain *pd)
+{
+	return NULL;
+}
+static inline void em_put_table(void) {}
 #endif
 
 #endif
-- 
2.25.1