linux-kernel - [PATCH 2/2] cpufreq: serialize calls to __cpufreq

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Message-Id: <80c4bd8c577e5da0aa63342671773be5cdc26a9a.1378012620.git.viresh.kumar@linaro.org>
Date:	Sun,  1 Sep 2013 10:56:02 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	rjw@...k.pl, sboyd@...eaurora.org
Cc:	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH 2/2] cpufreq: serialize calls to __cpufreq_governor()

We can't take a big lock around __cpufreq_governor() as this causes recursive
locking for some cases. But calls to this routine must be serialized for every
policy.

Lets introduce another variable which would guarantee serialization here.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq.c | 7 ++++++-
 include/linux/cpufreq.h   | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index f320a20..4d5723db 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1692,13 +1692,15 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
 						policy->cpu, event);
 
 	mutex_lock(&cpufreq_governor_lock);
-	if ((policy->governor_enabled && (event == CPUFREQ_GOV_START)) ||
+	if (policy->governor_busy ||
+		(policy->governor_enabled && (event == CPUFREQ_GOV_START)) ||
 		(!policy->governor_enabled && ((event == CPUFREQ_GOV_LIMITS) ||
 					       (event == CPUFREQ_GOV_STOP)))) {
 		mutex_unlock(&cpufreq_governor_lock);
 		return -EBUSY;
 	}
 
+	policy->governor_busy = true;
 	if (event == CPUFREQ_GOV_STOP)
 		policy->governor_enabled = false;
 	else if (event == CPUFREQ_GOV_START)
@@ -1727,6 +1729,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
 			((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
 		module_put(policy->governor->owner);
 
+	mutex_lock(&cpufreq_governor_lock);
+	policy->governor_busy = false;
+	mutex_unlock(&cpufreq_governor_lock);
 	return ret;
 }
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index d568f39..cca885d 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -76,6 +76,7 @@ struct cpufreq_policy {
 	struct cpufreq_governor	*governor; /* see below */
 	void			*governor_data;
 	bool			governor_enabled; /* governor start/stop flag */
+	bool			governor_busy;
 
 	struct work_struct	update; /* if update_policy() needs to be
 					 * called, but you're in IRQ context */
-- 
1.7.12.rc2.18.g61b472e

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