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path: root/drivers/cpufreq/cpufreq_conservative.c
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Diffstat (limited to 'drivers/cpufreq/cpufreq_conservative.c')
-rw-r--r--drivers/cpufreq/cpufreq_conservative.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index e07a35487bd..8878a154ed4 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -72,6 +72,14 @@ static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
static unsigned int dbs_enable; /* number of CPUs using this policy */
+/*
+ * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
+ * lock and dbs_mutex. cpu_hotplug lock should always be held before
+ * dbs_mutex. If any function that can potentially take cpu_hotplug lock
+ * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
+ * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
+ * is recursive for the same process. -Venki
+ */
static DEFINE_MUTEX (dbs_mutex);
static DECLARE_WORK (dbs_work, do_dbs_timer, NULL);
@@ -414,12 +422,14 @@ static void dbs_check_cpu(int cpu)
static void do_dbs_timer(void *data)
{
int i;
+ lock_cpu_hotplug();
mutex_lock(&dbs_mutex);
for_each_online_cpu(i)
dbs_check_cpu(i);
schedule_delayed_work(&dbs_work,
usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
mutex_unlock(&dbs_mutex);
+ unlock_cpu_hotplug();
}
static inline void dbs_timer_init(void)
@@ -514,6 +524,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
break;
case CPUFREQ_GOV_LIMITS:
+ lock_cpu_hotplug();
mutex_lock(&dbs_mutex);
if (policy->max < this_dbs_info->cur_policy->cur)
__cpufreq_driver_target(
@@ -524,6 +535,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
this_dbs_info->cur_policy,
policy->min, CPUFREQ_RELATION_L);
mutex_unlock(&dbs_mutex);
+ unlock_cpu_hotplug();
break;
}
return 0;