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Date: Mon, 15 Jul 2013 11:50:44 +0800
From: Michael Wang <wangyun@...ux.vnet.ibm.com>
To: Sergey Senozhatsky <sergey.senozhatsky@...il.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 07/14/2013 08:06 PM, Sergey Senozhatsky wrote:
> 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.
>
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?
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@...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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>>>
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