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

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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: Junjie Wu <[email protected]>
This commit is contained in:
Junjie Wu 2019-01-16 18:32:33 -08:00 • committed by Amir Vajid
commit a3b03ca553
1 changed files with 18 additions and 5 deletions
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23
drivers/devfreq/governor_cache_hwmon.c
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@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2014, 2019 The Linux Foundation. All rights reserved.
* Copyright (c) 2014-2015, 2019, The Linux Foundation. All rights reserved.
*/
#define pr_fmt(fmt) "cache-hwmon: " fmt
@ -46,7 +46,9 @@ 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 name##_show(struct device *dev, \
@ -171,8 +173,12 @@ 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);
@ -202,6 +208,7 @@ int update_cache_hwmon(struct cache_hwmon *hwmon)
devfreq_monitor_start(df);
mutex_unlock(&monitor_lock);
return 0;
}
@ -290,8 +297,10 @@ 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 < 0) {
@ -302,8 +311,10 @@ 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;
@ -318,8 +329,10 @@ 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;
@ -388,13 +401,13 @@ 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");