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[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:
venkatesh.pallipadi@intel.com 2009-07-02 17:08:30 -07:00 committed by Dave Jones
parent faf80d62e4
commit 7d26e2d5e2
3 changed files with 24 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/cpufreq/cpufreq.c
View File

@ -1070,8 +1070,6 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
#endif
unlock_policy_rwsem_write(cpu);
if (cpufreq_driver->target)
__cpufreq_governor(data, CPUFREQ_GOV_STOP);
@ -1088,6 +1086,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
if (cpufreq_driver->exit)
cpufreq_driver->exit(data);
unlock_policy_rwsem_write(cpu);
free_cpumask_var(data->related_cpus);
free_cpumask_var(data->cpus);
kfree(data);

27
drivers/cpufreq/cpufreq_conservative.c
View File

@ -70,15 +70,10 @@ 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
* DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
* would deadlock with cancel_delayed_work_sync(), which is needed for proper
* raceless workqueue teardown.
* dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
* different CPUs. It protects dbs_enable in governor start/stop. It also
* serializes governor limit_change with do_dbs_timer. We do not want
* do_dbs_timer to run when user is changing the governor or limits.
*/
static DEFINE_MUTEX(dbs_mutex);
@ -488,18 +483,17 @@ static void do_dbs_timer(struct work_struct *work)
delay -= jiffies % delay;
if (lock_policy_rwsem_write(cpu) < 0)
return;
mutex_lock(&dbs_mutex);
if (!dbs_info->enable) {
unlock_policy_rwsem_write(cpu);
mutex_unlock(&dbs_mutex);
return;
}
dbs_check_cpu(dbs_info);
queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
unlock_policy_rwsem_write(cpu);
mutex_unlock(&dbs_mutex);
}
static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@ -590,15 +584,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
&dbs_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
}
dbs_timer_init(this_dbs_info);
mutex_unlock(&dbs_mutex);
dbs_timer_init(this_dbs_info);
break;
case CPUFREQ_GOV_STOP:
mutex_lock(&dbs_mutex);
dbs_timer_exit(this_dbs_info);
mutex_lock(&dbs_mutex);
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;

27
drivers/cpufreq/cpufreq_ondemand.c
View File

@ -78,15 +78,10 @@ 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
* DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
* would deadlock with cancel_delayed_work_sync(), which is needed for proper
* raceless workqueue teardown.
* dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
* different CPUs. It protects dbs_enable in governor start/stop. It also
* serializes governor limit_change with do_dbs_timer. We do not want
* do_dbs_timer to run when user is changing the governor or limits.
*/
static DEFINE_MUTEX(dbs_mutex);
@ -494,11 +489,10 @@ static void do_dbs_timer(struct work_struct *work)
delay -= jiffies % delay;
if (lock_policy_rwsem_write(cpu) < 0)
return;
mutex_lock(&dbs_mutex);
if (!dbs_info->enable) {
unlock_policy_rwsem_write(cpu);
mutex_unlock(&dbs_mutex);
return;
}
@ -517,7 +511,7 @@ static void do_dbs_timer(struct work_struct *work)
dbs_info->freq_lo, CPUFREQ_RELATION_H);
}
queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
unlock_policy_rwsem_write(cpu);
mutex_unlock(&dbs_mutex);
}
static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@ -598,14 +592,15 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
max(min_sampling_rate,
latency * LATENCY_MULTIPLIER);
}
dbs_timer_init(this_dbs_info);
mutex_unlock(&dbs_mutex);
dbs_timer_init(this_dbs_info);
break;
case CPUFREQ_GOV_STOP:
mutex_lock(&dbs_mutex);
dbs_timer_exit(this_dbs_info);
mutex_lock(&dbs_mutex);
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;
mutex_unlock(&dbs_mutex);