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Date: Sun, 14 Jul 2013 15:06:29 +0300
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To: Michael Wang <wangyun@...ux.vnet.ibm.com>
Cc: 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 (07/14/13 14:47), Sergey Senozhatsky wrote:
>
> Now, as I fixed radeon kms, I can see:
>
> [ 806.660530] ------------[ cut here ]------------
> [ 806.660539] WARNING: CPU: 0 PID: 2389 at arch/x86/kernel/smp.c:124
> native_smp_send_reschedule+0x57/0x60()
Well, this one is obviously not a lockdep error, I meant that previous
tests with disabled lockdep were invalid. Will re-do.
-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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