linux-kernel - [PATCH 2/11] cpufreq: governor: Use common mutex for dbs

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Message-ID: <1529283.0IedZktI9q@vostro.rjw.lan>
Date:	Thu, 04 Feb 2016 00:16:05 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Linux PM list <linux-pm@...r.kernel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Juri Lelli <juri.lelli@....com>,
	Steve Muckle <steve.muckle@...aro.org>,
	Saravana Kannan <skannan@...eaurora.org>
Subject: [PATCH 2/11] cpufreq: governor: Use common mutex for dbs_data protection

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

Every governor relying on the common code in cpufreq_governor.c
has to provide its own mutex in struct common_dbs_data.  However,
those mutexes are never used at the same time and doing it this
way makes it rather difficult to follow the code.  Moreover,
if two governor modules are loaded we end up with two mutexes
used for the same purpose one at a time.

Introduce a single common mutex for that instead and drop the
mutex field from struct common_dbs_data.  That at least will
ensure that the mutex is always present and initialized regardless
of what the particular governors do.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpufreq/cpufreq_conservative.c |    1 -
 drivers/cpufreq/cpufreq_governor.c     |    7 +++++--
 drivers/cpufreq/cpufreq_governor.h     |    6 +-----
 drivers/cpufreq/cpufreq_ondemand.c     |    5 ++---
 4 files changed, 8 insertions(+), 11 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
+++ linux-pm/drivers/cpufreq/cpufreq_governor.c
@@ -22,6 +22,9 @@
 
 #include "cpufreq_governor.h"
 
+DEFINE_MUTEX(dbs_data_mutex);
+EXPORT_SYMBOL_GPL(dbs_data_mutex);
+
 static struct attribute_group *get_sysfs_attr(struct dbs_data *dbs_data)
 {
 	if (have_governor_per_policy())
@@ -542,7 +545,7 @@ int cpufreq_governor_dbs(struct cpufreq_
 	int ret;
 
 	/* Lock governor to block concurrent initialization of governor */
-	mutex_lock(&cdata->mutex);
+	mutex_lock(&dbs_data_mutex);
 
 	if (have_governor_per_policy())
 		dbs_data = policy->governor_data;
@@ -575,7 +578,7 @@ int cpufreq_governor_dbs(struct cpufreq_
 	}
 
 unlock:
-	mutex_unlock(&cdata->mutex);
+	mutex_unlock(&dbs_data_mutex);
 
 	return ret;
 }
Index: linux-pm/drivers/cpufreq/cpufreq_governor.h
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_governor.h
+++ linux-pm/drivers/cpufreq/cpufreq_governor.h
@@ -223,11 +223,6 @@ struct common_dbs_data {
 
 	/* Governor specific ops, see below */
 	void *gov_ops;
-
-	/*
-	 * Protects governor's data (struct dbs_data and struct common_dbs_data)
-	 */
-	struct mutex mutex;
 };
 
 /* Governor Per policy data */
@@ -272,6 +267,7 @@ static ssize_t show_sampling_rate_min_go
 	return sprintf(buf, "%u\n", dbs_data->min_sampling_rate);	\
 }
 
+extern struct mutex dbs_data_mutex;
 extern struct mutex cpufreq_governor_lock;
 void gov_set_update_util(struct cpu_common_dbs_info *shared,
 			 unsigned int delay_us);
Index: linux-pm/drivers/cpufreq/cpufreq_ondemand.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_ondemand.c
+++ linux-pm/drivers/cpufreq/cpufreq_ondemand.c
@@ -251,7 +251,7 @@ static void update_sampling_rate(struct
 	/*
 	 * Lock governor so that governor start/stop can't execute in parallel.
 	 */
-	mutex_lock(&od_dbs_cdata.mutex);
+	mutex_lock(&dbs_data_mutex);
 
 	cpumask_copy(&cpumask, cpu_online_mask);
 
@@ -304,7 +304,7 @@ static void update_sampling_rate(struct
 		}
 	}
 
-	mutex_unlock(&od_dbs_cdata.mutex);
+	mutex_unlock(&dbs_data_mutex);
 }
 
 static ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf,
@@ -550,7 +550,6 @@ static struct common_dbs_data od_dbs_cda
 	.gov_ops = &od_ops,
 	.init = od_init,
 	.exit = od_exit,
-	.mutex = __MUTEX_INITIALIZER(od_dbs_cdata.mutex),
 };
 
 static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
Index: linux-pm/drivers/cpufreq/cpufreq_conservative.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_conservative.c
+++ linux-pm/drivers/cpufreq/cpufreq_conservative.c
@@ -368,7 +368,6 @@ static struct common_dbs_data cs_dbs_cda
 	.gov_check_cpu = cs_check_cpu,
 	.init = cs_init,
 	.exit = cs_exit,
-	.mutex = __MUTEX_INITIALIZER(cs_dbs_cdata.mutex),
 };
 
 static int cs_cpufreq_governor_dbs(struct cpufreq_policy *policy,