From fe41515b7ce7c7e5f572f29eb40046a1c57ce3b1 Mon Sep 17 00:00:00 2001
From: Rama Aparna Mallavarapu <aparnam@codeaurora.org>
Date: Wed, 10 Oct 2018 14:53:32 -0700
Subject: [PATCH] PM / devfreq: Fix race condition between suspend/resume and
 governor_store

There is a race condition when the event governor_store is being executed
from sysfs and the device issues a suspend. The devfreq data structures
would become stale when the suspend tries to access them in the middle
of the governor_store operation. Fix this issue by taking a lock around
suspend and resume operations so that these operations are not concurrent
with the other events from sysfs.

Also rename the sysfs_lock as event_lock since the same lock is used
for non sysfs operations like suspend and resume as well.

Change-Id: Ifa0e93915a920cec3e0429966328a1128d61098b
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>
---
 drivers/devfreq/devfreq.c | 34 ++++++++++++++++++++++------------
 include/linux/devfreq.h   |  2 +-
 2 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 5dd0acaa799f..ffcea42fd734 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -516,7 +516,7 @@ static void _remove_devfreq(struct devfreq *devfreq)
 		devfreq->profile->exit(devfreq->dev.parent);
 
 	mutex_destroy(&devfreq->lock);
-	mutex_destroy(&devfreq->sysfs_lock);
+	mutex_destroy(&devfreq->event_lock);
 	kfree(devfreq);
 }
 
@@ -573,7 +573,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 	}
 
 	mutex_init(&devfreq->lock);
-	mutex_init(&devfreq->sysfs_lock);
+	mutex_init(&devfreq->event_lock);
 	mutex_lock(&devfreq->lock);
 	devfreq->dev.parent = dev;
 	devfreq->dev.class = devfreq_class;
@@ -784,14 +784,19 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
  */
 int devfreq_suspend_device(struct devfreq *devfreq)
 {
+	int ret;
+
 	if (!devfreq)
 		return -EINVAL;
 
 	if (!devfreq->governor)
 		return 0;
 
-	return devfreq->governor->event_handler(devfreq,
+	mutex_lock(&devfreq->event_lock);
+	ret = devfreq->governor->event_handler(devfreq,
 				DEVFREQ_GOV_SUSPEND, NULL);
+	mutex_unlock(&devfreq->event_lock);
+	return ret;
 }
 EXPORT_SYMBOL(devfreq_suspend_device);
 
@@ -805,14 +810,19 @@ EXPORT_SYMBOL(devfreq_suspend_device);
  */
 int devfreq_resume_device(struct devfreq *devfreq)
 {
+	int ret;
+
 	if (!devfreq)
 		return -EINVAL;
 
 	if (!devfreq->governor)
 		return 0;
 
-	return devfreq->governor->event_handler(devfreq,
+	mutex_lock(&devfreq->event_lock);
+	ret = devfreq->governor->event_handler(devfreq,
 				DEVFREQ_GOV_RESUME, NULL);
+	mutex_unlock(&devfreq->event_lock);
+	return ret;
 }
 EXPORT_SYMBOL(devfreq_resume_device);
 
@@ -972,7 +982,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 		goto out;
 	}
 
-	mutex_lock(&df->sysfs_lock);
+	mutex_lock(&df->event_lock);
 	if (df->governor) {
 		ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
 		if (ret) {
@@ -998,7 +1008,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 	}
 
 gov_stop_out:
-	mutex_unlock(&df->sysfs_lock);
+	mutex_unlock(&df->event_lock);
 out:
 	mutex_unlock(&devfreq_list_lock);
 
@@ -1093,10 +1103,10 @@ static ssize_t polling_interval_store(struct device *dev,
 	if (ret != 1)
 		return -EINVAL;
 
-	mutex_lock(&df->sysfs_lock);
+	mutex_lock(&df->event_lock);
 	df->governor->event_handler(df, DEVFREQ_GOV_INTERVAL, &value);
 	ret = count;
-	mutex_unlock(&df->sysfs_lock);
+	mutex_unlock(&df->event_lock);
 
 	return ret;
 }
@@ -1114,7 +1124,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
 	if (ret != 1)
 		return -EINVAL;
 
-	mutex_lock(&df->sysfs_lock);
+	mutex_lock(&df->event_lock);
 	mutex_lock(&df->lock);
 	max = df->max_freq;
 	if (value && max && value > max) {
@@ -1127,7 +1137,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
 	ret = count;
 unlock:
 	mutex_unlock(&df->lock);
-	mutex_unlock(&df->sysfs_lock);
+	mutex_unlock(&df->event_lock);
 	return ret;
 }
 
@@ -1143,7 +1153,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
 	if (ret != 1)
 		return -EINVAL;
 
-	mutex_lock(&df->sysfs_lock);
+	mutex_lock(&df->event_lock);
 	mutex_lock(&df->lock);
 	min = df->min_freq;
 	if (value && min && value < min) {
@@ -1156,7 +1166,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
 	ret = count;
 unlock:
 	mutex_unlock(&df->lock);
-	mutex_unlock(&df->sysfs_lock);
+	mutex_unlock(&df->event_lock);
 	return ret;
 }
 
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index eb84ce6b9a48..85d62224fe46 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -167,7 +167,7 @@ struct devfreq {
 	struct list_head node;
 
 	struct mutex lock;
-	struct mutex sysfs_lock;
+	struct mutex event_lock;
 	struct device dev;
 	struct devfreq_dev_profile *profile;
 	const struct devfreq_governor *governor;