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

[Sergey Senozhatsky <sergey.senozhatsky@gmail.com>]

On (07/15/13 15:52), Michael Wang wrote:
> > 
> > And may be we could try below patch to get more info, I've moved the timing
> > of restore stop flag from 'after STOP' to 'before START', I suppose that
> > could create a window to prevent the work re-queue, it could at least provide
> > us more info...
> > 
> > I think I may need to setup a environment for debug now, what's the steps to
> > produce this WARN?
> 
> I have done some test, although I failed to reproduce this WARN, but I
> found that the work is still running and re-queue itself after STOP,
> even with my prev suggestion...
> 
> However, enlarge the stop window as my suggestion below, the work do
> stopped...I suppose it will also stop the first WARN too.
> 
> Now we need to figure out the reason...
>

Hello,

WARN is triggered during laptop suspend/hibernate phase.
I'll test your patch soon.

	-ss

> Regards,
> Michael Wang
> 
> > 
> > Regards,
> > Michael Wang
> > 
> > 
> > diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> > index dc9b72e..b1446fe 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_start)
> > +		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 +194,26 @@ 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_start = 0;
> > +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;
> >  }
> > 
> >  /* Will return if we need to evaluate cpu load again or not */
> > @@ -391,6 +406,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
> > 
> >  		/* Initiate timer time stamp */
> >  		cpu_cdbs->time_stamp = ktime_get();
> > +		dbs_data->queue_start = 1;
> > 
> >  		gov_queue_work(dbs_data, policy,
> >  				delay_for_sampling_rate(sampling_rate), true);
> > 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_start;
> > 
> >  	/* dbs_mutex protects dbs_enable in governor start/stop */
> >  	struct mutex mutex;
> > 
> > 
> > 
> >> 	-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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> > 
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