diff options
Diffstat (limited to 'drivers/cpufreq/cpufreq_conservative.c')
| -rw-r--r-- | drivers/cpufreq/cpufreq_conservative.c | 12 |
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; |