[CPUFREQ] Eliminate the recent lockdep warnings in cpufreq
Commit b14893a62c
although it was very
much needed to properly cleanup ondemand timer, opened-up a can of worms
related to locking dependencies in cpufreq.
Patch here defines the need for dbs_mutex and cleans up its usage in
ondemand governor. This also resolves the lockdep warnings reported here
http://lkml.indiana.edu/hypermail/linux/kernel/0906.1/01925.html
http://lkml.indiana.edu/hypermail/linux/kernel/0907.0/00820.html
and few others..
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
This commit is contained in:
parent
faf80d62e4
commit
7d26e2d5e2
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@ -1070,8 +1070,6 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
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spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
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#endif
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unlock_policy_rwsem_write(cpu);
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if (cpufreq_driver->target)
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__cpufreq_governor(data, CPUFREQ_GOV_STOP);
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@ -1088,6 +1086,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
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if (cpufreq_driver->exit)
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cpufreq_driver->exit(data);
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unlock_policy_rwsem_write(cpu);
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free_cpumask_var(data->related_cpus);
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free_cpumask_var(data->cpus);
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kfree(data);
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@ -70,15 +70,10 @@ static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
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static unsigned int dbs_enable; /* number of CPUs using this policy */
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/*
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* DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
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* lock and dbs_mutex. cpu_hotplug lock should always be held before
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* dbs_mutex. If any function that can potentially take cpu_hotplug lock
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* (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
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* cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
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* is recursive for the same process. -Venki
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* DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
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* would deadlock with cancel_delayed_work_sync(), which is needed for proper
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* raceless workqueue teardown.
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* dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
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* different CPUs. It protects dbs_enable in governor start/stop. It also
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* serializes governor limit_change with do_dbs_timer. We do not want
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* do_dbs_timer to run when user is changing the governor or limits.
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*/
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static DEFINE_MUTEX(dbs_mutex);
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@ -488,18 +483,17 @@ static void do_dbs_timer(struct work_struct *work)
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delay -= jiffies % delay;
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if (lock_policy_rwsem_write(cpu) < 0)
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return;
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mutex_lock(&dbs_mutex);
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if (!dbs_info->enable) {
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unlock_policy_rwsem_write(cpu);
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mutex_unlock(&dbs_mutex);
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return;
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}
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dbs_check_cpu(dbs_info);
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queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
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unlock_policy_rwsem_write(cpu);
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mutex_unlock(&dbs_mutex);
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}
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static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
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@ -590,15 +584,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
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&dbs_cpufreq_notifier_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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}
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dbs_timer_init(this_dbs_info);
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mutex_unlock(&dbs_mutex);
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dbs_timer_init(this_dbs_info);
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break;
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case CPUFREQ_GOV_STOP:
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mutex_lock(&dbs_mutex);
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dbs_timer_exit(this_dbs_info);
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mutex_lock(&dbs_mutex);
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sysfs_remove_group(&policy->kobj, &dbs_attr_group);
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dbs_enable--;
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@ -78,15 +78,10 @@ static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
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static unsigned int dbs_enable; /* number of CPUs using this policy */
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/*
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* DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
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* lock and dbs_mutex. cpu_hotplug lock should always be held before
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* dbs_mutex. If any function that can potentially take cpu_hotplug lock
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* (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
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* cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
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* is recursive for the same process. -Venki
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* DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
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* would deadlock with cancel_delayed_work_sync(), which is needed for proper
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* raceless workqueue teardown.
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* dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
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* different CPUs. It protects dbs_enable in governor start/stop. It also
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* serializes governor limit_change with do_dbs_timer. We do not want
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* do_dbs_timer to run when user is changing the governor or limits.
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*/
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static DEFINE_MUTEX(dbs_mutex);
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@ -494,11 +489,10 @@ static void do_dbs_timer(struct work_struct *work)
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delay -= jiffies % delay;
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if (lock_policy_rwsem_write(cpu) < 0)
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return;
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mutex_lock(&dbs_mutex);
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if (!dbs_info->enable) {
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unlock_policy_rwsem_write(cpu);
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mutex_unlock(&dbs_mutex);
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return;
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}
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@ -517,7 +511,7 @@ static void do_dbs_timer(struct work_struct *work)
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dbs_info->freq_lo, CPUFREQ_RELATION_H);
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}
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queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
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unlock_policy_rwsem_write(cpu);
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mutex_unlock(&dbs_mutex);
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}
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static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
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@ -598,14 +592,15 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
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max(min_sampling_rate,
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latency * LATENCY_MULTIPLIER);
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}
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dbs_timer_init(this_dbs_info);
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mutex_unlock(&dbs_mutex);
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dbs_timer_init(this_dbs_info);
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break;
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case CPUFREQ_GOV_STOP:
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mutex_lock(&dbs_mutex);
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dbs_timer_exit(this_dbs_info);
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mutex_lock(&dbs_mutex);
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sysfs_remove_group(&policy->kobj, &dbs_attr_group);
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dbs_enable--;
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mutex_unlock(&dbs_mutex);
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