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authorMatthew Wilcox <mawilcox@microsoft.com>2017-03-10 21:33:28 +0300
committerZhang Rui <rui.zhang@intel.com>2017-03-13 05:06:04 +0300
commit088db931e065bd3b159fa2e588eab859ef0d9d23 (patch)
tree7211f7bc220cfc430e37dc4fa37dec978efbe0f7 /drivers/thermal/cpu_cooling.c
parent4495c08e84729385774601b5146d51d9e5849f81 (diff)
downloadlinux-088db931e065bd3b159fa2e588eab859ef0d9d23.tar.xz
thermal: Fix potential deadlock in cpu_cooling
cooling_list_lock is covering not just cpufreq_dev_count, but also the calls to cpufreq_register_notifier() and cpufreq_unregister_notifier(). Since cooling_list_lock is also used within cpufreq_thermal_notifier(), lockdep reports a potential deadlock. Fix it by testing the condition under cooling_list_lock and dropping the lock before calling cpufreq_register_notifier(). And variable cpufreq_dev_count is removed at the same time, because it's no longer needed after the fix. Fixes: ae606089621e ("thermal: convert cpu_cooling to use an IDA") Reported-and-Tested-by: Russell King <linux@armlinux.org.uk> Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Diffstat (limited to 'drivers/thermal/cpu_cooling.c')
-rw-r--r--drivers/thermal/cpu_cooling.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 91048eeca28b..11b5ea685518 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -107,8 +107,6 @@ struct cpufreq_cooling_device {
};
static DEFINE_IDA(cpufreq_ida);
-static unsigned int cpufreq_dev_count;
-
static DEFINE_MUTEX(cooling_list_lock);
static LIST_HEAD(cpufreq_dev_list);
@@ -771,6 +769,7 @@ __cpufreq_cooling_register(struct device_node *np,
unsigned int freq, i, num_cpus;
int ret;
struct thermal_cooling_device_ops *cooling_ops;
+ bool first;
if (!alloc_cpumask_var(&temp_mask, GFP_KERNEL))
return ERR_PTR(-ENOMEM);
@@ -874,13 +873,14 @@ __cpufreq_cooling_register(struct device_node *np,
cpufreq_dev->cool_dev = cool_dev;
mutex_lock(&cooling_list_lock);
+ /* Register the notifier for first cpufreq cooling device */
+ first = list_empty(&cpufreq_dev_list);
list_add(&cpufreq_dev->node, &cpufreq_dev_list);
+ mutex_unlock(&cooling_list_lock);
- /* Register the notifier for first cpufreq cooling device */
- if (!cpufreq_dev_count++)
+ if (first)
cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
CPUFREQ_POLICY_NOTIFIER);
- mutex_unlock(&cooling_list_lock);
goto put_policy;
@@ -1021,6 +1021,7 @@ EXPORT_SYMBOL(of_cpufreq_power_cooling_register);
void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
{
struct cpufreq_cooling_device *cpufreq_dev;
+ bool last;
if (!cdev)
return;
@@ -1028,14 +1029,15 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
cpufreq_dev = cdev->devdata;
mutex_lock(&cooling_list_lock);
+ list_del(&cpufreq_dev->node);
/* Unregister the notifier for the last cpufreq cooling device */
- if (!--cpufreq_dev_count)
+ last = list_empty(&cpufreq_dev_list);
+ mutex_unlock(&cooling_list_lock);
+
+ if (last)
cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
CPUFREQ_POLICY_NOTIFIER);
- list_del(&cpufreq_dev->node);
- mutex_unlock(&cooling_list_lock);
-
thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
ida_simple_remove(&cpufreq_ida, cpufreq_dev->id);
kfree(cpufreq_dev->dyn_power_table);