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

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

On (07/11/13 16:47), 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.
> 
> And we should also thanks Srivatsa for catching the root issue ;-)

Sure, many thanks to everyone.
I'll perform some additional testing.

	-ss

> 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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