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Commit 70b45e9f authored by Junjie Wu's avatar Junjie Wu
Browse files

PM / devfreq: governor_cache_hwmon: Fix race in monitor start/stop 



Some cache_hwmon devices can have interrupts firing at any time. The
interrupt handler would stop devfreq monitor, update its vote and
restart the monitor again. This introduces a race if
devfreq_supend/resume() or devfreq_interval_update() is called at
the same time. Since devfreq_monitor_start() re-initializes the work,
it could cause corruption while the work is being used elsewhere.

Protect governor monitor start/stops with a new lock.

Change-Id: I143aaaea86494b4c617df46e2c521a19b43861d5
Signed-off-by: default avatarJunjie Wu <junjiew@codeaurora.org>
parent cf1a92bc

drivers/devfreq/governor_cache_hwmon.c

+18 −5
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2014, The Linux Foundation. All rights reserved.

 * Copyright (c) 2014-2015, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -53,7 +53,9 @@ static LIST_HEAD(cache_hwmon_list); 
static DEFINE_MUTEX(list_lock);



static int use_cnt;

static DEFINE_MUTEX(state_lock);

static DEFINE_MUTEX(register_lock);



static DEFINE_MUTEX(monitor_lock);



#define show_attr(name) \

static ssize_t show_##name(struct device *dev,				\
@@ -185,8 +187,12 @@ int update_cache_hwmon(struct cache_hwmon *hwmon) 
	node = df->data;

	if (!node)

		return -ENODEV;

	if (!node->mon_started)



	mutex_lock(&monitor_lock);

	if (!node->mon_started) {

		mutex_unlock(&monitor_lock);

		return -EBUSY;

	}



	dev_dbg(df->dev.parent, "Got update request\n");

	devfreq_monitor_stop(df);
@@ -216,6 +222,7 @@ int update_cache_hwmon(struct cache_hwmon *hwmon) 


	devfreq_monitor_start(df);



	mutex_unlock(&monitor_lock);

	return 0;

}
@@ -289,8 +296,10 @@ static int start_monitoring(struct devfreq *df) 
		goto err_start;

	}



	mutex_lock(&monitor_lock);

	devfreq_monitor_start(df);

	node->mon_started = true;

	mutex_unlock(&monitor_lock);



	ret = sysfs_create_group(&df->dev.kobj, &dev_attr_group);

	if (ret) {
@@ -301,8 +310,10 @@ static int start_monitoring(struct devfreq *df) 
	return 0;



sysfs_fail:

	mutex_lock(&monitor_lock);

	node->mon_started = false;

	devfreq_monitor_stop(df);

	mutex_unlock(&monitor_lock);

	hw->stop_hwmon(hw);

err_start:

	df->data = node->orig_data;
@@ -317,8 +328,10 @@ static void stop_monitoring(struct devfreq *df) 
	struct cache_hwmon *hw = node->hw;



	sysfs_remove_group(&df->dev.kobj, &dev_attr_group);

	mutex_lock(&monitor_lock);

	node->mon_started = false;

	devfreq_monitor_stop(df);

	mutex_unlock(&monitor_lock);

	hw->stop_hwmon(hw);

	df->data = node->orig_data;

	node->orig_data = NULL;
@@ -391,13 +404,13 @@ int register_cache_hwmon(struct device *dev, struct cache_hwmon *hwmon) 
	node->hw = hwmon;

	node->attr_grp = &dev_attr_group;



	mutex_lock(&state_lock);

	mutex_lock(&register_lock);

	if (!use_cnt) {

		ret = devfreq_add_governor(&devfreq_cache_hwmon);

		if (!ret)

			use_cnt++;

	}

	mutex_unlock(&state_lock);

	mutex_unlock(&register_lock);



	if (!ret) {

		dev_info(dev, "Cache HWmon governor registered.\n");