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Date: Thu, 11 Jul 2013 12:01:13 +0300
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To: Michael Wang <wangyun@...ux.vnet.ibm.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...en8.de>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Viresh Kumar <viresh.kumar@...aro.org>,
"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: Re: [LOCKDEP] cpufreq: possible circular locking dependency detected
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@...il.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@...il.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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