Re: [LOCKDEP] cpufreq: possible circular locking dependency detected

[Michael Wang <wangyun@linux.vnet.ibm.com>]

On 07/11/2013 04:47 PM, Michael Wang wrote:
> On 07/11/2013 04:22 PM, Sergey Senozhatsky wrote:
> [snip]
>>>
>>
>> Hello Michael,
>> nice job! works fine for me.
>>
>> Reported-and-Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> 
> Thanks for the test :)
> 
> Borislav may also doing some testing, let's wait for few days and see
> whether there are any point we missed.

s /Borislav/Bartlomiej

> 
> And we should also thanks Srivatsa for catching the root issue ;-)
> 
> Regards,
> Michael Wang
> 
>>
>>
>> 	-ss
>>
>>> Regards,
>>> Michael Wang
>>>
>>> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
>>> index dc9b72e..a64b544 100644
>>> --- a/drivers/cpufreq/cpufreq_governor.c
>>> +++ b/drivers/cpufreq/cpufreq_governor.c
>>> @@ -178,13 +178,14 @@ void gov_queue_work(struct dbs_data *dbs_data, struct cpufreq_policy *policy,
>>>  {
>>>  	int i;
>>>  
>>> +	if (dbs_data->queue_stop)
>>> +		return;
>>> +
>>>  	if (!all_cpus) {
>>>  		__gov_queue_work(smp_processor_id(), dbs_data, delay);
>>>  	} else {
>>> -		get_online_cpus();
>>>  		for_each_cpu(i, policy->cpus)
>>>  			__gov_queue_work(i, dbs_data, delay);
>>> -		put_online_cpus();
>>>  	}
>>>  }
>>>  EXPORT_SYMBOL_GPL(gov_queue_work);
>>> @@ -193,12 +194,27 @@ static inline void gov_cancel_work(struct dbs_data *dbs_data,
>>>  		struct cpufreq_policy *policy)
>>>  {
>>>  	struct cpu_dbs_common_info *cdbs;
>>> -	int i;
>>> +	int i, round = 2;
>>>  
>>> +	dbs_data->queue_stop = 1;
>>> +redo:
>>> +	round--;
>>>  	for_each_cpu(i, policy->cpus) {
>>>  		cdbs = dbs_data->cdata->get_cpu_cdbs(i);
>>>  		cancel_delayed_work_sync(&cdbs->work);
>>>  	}
>>> +
>>> +	/*
>>> +	 * Since there is no lock to prvent re-queue the
>>> +	 * cancelled work, some early cancelled work might
>>> +	 * have been queued again by later cancelled work.
>>> +	 *
>>> +	 * Flush the work again with dbs_data->queue_stop
>>> +	 * enabled, this time there will be no survivors.
>>> +	 */
>>> +	if (round)
>>> +		goto redo;
>>> +	dbs_data->queue_stop = 0;
>>>  }
>>>  
>>>  /* Will return if we need to evaluate cpu load again or not */
>>> diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
>>> index e16a961..9116135 100644
>>> --- a/drivers/cpufreq/cpufreq_governor.h
>>> +++ b/drivers/cpufreq/cpufreq_governor.h
>>> @@ -213,6 +213,7 @@ struct dbs_data {
>>>  	unsigned int min_sampling_rate;
>>>  	int usage_count;
>>>  	void *tuners;
>>> +	int queue_stop;
>>>  
>>>  	/* dbs_mutex protects dbs_enable in governor start/stop */
>>>  	struct mutex mutex;
>>>
>>>>
>>>> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
>>>>
>>>> ---
>>>>
>>>>  drivers/cpufreq/cpufreq.c          |  5 +----
>>>>  drivers/cpufreq/cpufreq_governor.c | 17 +++++++++++------
>>>>  drivers/cpufreq/cpufreq_stats.c    |  2 +-
>>>>  3 files changed, 13 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>>> index 6a015ad..f8aacf1 100644
>>>> --- a/drivers/cpufreq/cpufreq.c
>>>> +++ b/drivers/cpufreq/cpufreq.c
>>>> @@ -1943,13 +1943,10 @@ static int __cpuinit cpufreq_cpu_callback(struct notifier_block *nfb,
>>>>  		case CPU_ONLINE:
>>>>  			cpufreq_add_dev(dev, NULL);
>>>>  			break;
>>>> -		case CPU_DOWN_PREPARE:
>>>> +		case CPU_POST_DEAD:
>>>>  		case CPU_UP_CANCELED_FROZEN:
>>>>  			__cpufreq_remove_dev(dev, NULL);
>>>>  			break;
>>>> -		case CPU_DOWN_FAILED:
>>>> -			cpufreq_add_dev(dev, NULL);
>>>> -			break;
>>>>  		}
>>>>  	}
>>>>  	return NOTIFY_OK;
>>>> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
>>>> index 4645876..681d5d6 100644
>>>> --- a/drivers/cpufreq/cpufreq_governor.c
>>>> +++ b/drivers/cpufreq/cpufreq_governor.c
>>>> @@ -125,7 +125,11 @@ static inline void __gov_queue_work(int cpu, struct dbs_data *dbs_data,
>>>>  		unsigned int delay)
>>>>  {
>>>>  	struct cpu_dbs_common_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
>>>> -
>>>> +	/* cpu offline might block existing gov_queue_work() user,
>>>> +	 * unblocking it after CPU_DEAD and before CPU_POST_DEAD.
>>>> +	 * thus potentially we can hit offlined CPU */
>>>> +	if (unlikely(cpu_is_offline(cpu)))
>>>> +		return;
>>>>  	mod_delayed_work_on(cpu, system_wq, &cdbs->work, delay);
>>>>  }
>>>>
>>>> @@ -133,15 +137,14 @@ void gov_queue_work(struct dbs_data *dbs_data, struct cpufreq_policy *policy,
>>>>  		unsigned int delay, bool all_cpus)
>>>>  {
>>>>  	int i;
>>>> -
>>>> +	get_online_cpus();
>>>>  	if (!all_cpus) {
>>>>  		__gov_queue_work(smp_processor_id(), dbs_data, delay);
>>>>  	} else {
>>>> -		get_online_cpus();
>>>>  		for_each_cpu(i, policy->cpus)
>>>>  			__gov_queue_work(i, dbs_data, delay);
>>>> -		put_online_cpus();
>>>>  	}
>>>> +	put_online_cpus();
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(gov_queue_work);
>>>>
>>>> @@ -354,8 +357,10 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>>>>  		/* Initiate timer time stamp */
>>>>  		cpu_cdbs->time_stamp = ktime_get();
>>>>
>>>> -		gov_queue_work(dbs_data, policy,
>>>> -				delay_for_sampling_rate(sampling_rate), true);
>>>> +		/* hotplug lock already held */
>>>> +		for_each_cpu(j, policy->cpus)
>>>> +			__gov_queue_work(j, dbs_data,
>>>> +				delay_for_sampling_rate(sampling_rate));
>>>>  		break;
>>>>
>>>>  	case CPUFREQ_GOV_STOP:
>>>> diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
>>>> index cd9e817..833816e 100644
>>>> --- a/drivers/cpufreq/cpufreq_stats.c
>>>> +++ b/drivers/cpufreq/cpufreq_stats.c
>>>> @@ -355,7 +355,7 @@ static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,
>>>>  	case CPU_DOWN_PREPARE:
>>>>  		cpufreq_stats_free_sysfs(cpu);
>>>>  		break;
>>>> -	case CPU_DEAD:
>>>> +	case CPU_POST_DEAD:
>>>>  		cpufreq_stats_free_table(cpu);
>>>>  		break;
>>>>  	case CPU_UP_CANCELED_FROZEN:
>>>> --
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>>>
>> --
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>