On 11/07/2014 09:00 PM, Rafael J. Wysocki wrote:
> On Wednesday, November 05, 2014 09:53:59 AM Prarit Bhargava wrote:
>> Add some additional debug to capture failures in the locking scheme for
>> cpufreq. Instead of just a NULL pointer, these warnings will capture failure
>> points if the locking scheme for cpufreq is broken.
>>
>> Cc: "Rafael J. Wysocki" <[email protected]>
>> Cc: Viresh Kumar <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Prarit Bhargava <[email protected]>
>> ---
>> drivers/cpufreq/cpufreq_governor.c | 32 +++++++++++++++++++++++++++-----
>> 1 file changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq_governor.c
>> b/drivers/cpufreq/cpufreq_governor.c
>> index b1ee597..f158882 100644
>> --- a/drivers/cpufreq/cpufreq_governor.c
>> +++ b/drivers/cpufreq/cpufreq_governor.c
>> @@ -161,9 +161,18 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
>> EXPORT_SYMBOL_GPL(dbs_check_cpu);
>>
>> static inline void __gov_queue_work(int cpu, struct dbs_data *dbs_data,
>> - unsigned int delay)
>> + unsigned int delay,
>> + struct cpufreq_policy *policy)
>> {
>> - struct cpu_dbs_common_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
>> + struct cpu_dbs_common_info *cdbs;
>> +
>> + if (!dbs_data->cdata) {
>> + pr_emerg("common_dbs_data is NULL for %s but initialized = %d",
>> + policy->governor->name,
>> + atomic_read(&policy->governor->initialized));
>> + BUG();
>
> Is it necessary to crash the kernel here?
Yes. dbs_data->cdata is referenced right below.
>
>> + }
>> + cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
and we'll NULL pointer panic right here without any of the debug info above :(
>>
>> mod_delayed_work_on(cpu, system_wq, &cdbs->work, delay);
>> }
>> @@ -185,10 +194,11 @@ void gov_queue_work(struct dbs_data *dbs_data, struct
>> cpufreq_policy *policy,
>> * those works are canceled during CPU_DOWN_PREPARE so they
>> * can't possibly run on any other CPU.
>> */
>> - __gov_queue_work(raw_smp_processor_id(), dbs_data, delay);
>> + __gov_queue_work(raw_smp_processor_id(), dbs_data, delay,
>> + policy);
>> } else {
>> for_each_cpu(i, policy->cpus)
>> - __gov_queue_work(i, dbs_data, delay);
>> + __gov_queue_work(i, dbs_data, delay, policy);
>> }
>>
>> out_unlock:
>> @@ -258,7 +268,13 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>> else
>> dbs_data = cdata->gdbs_data;
>>
>> - WARN_ON(!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT));
>> + if (!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT)) {
>> + pr_emerg("governor_data is NULL but governor %s is initialized
>> = %d [governor_enabled = %d event = %u]\n",
>> + policy->governor->name,
>> + atomic_read(&policy->governor->initialized),
>> + policy->governor_enabled, event);
>> + BUG();
>
> And here?
>
Ditto -- dbs_data is dereferenced in the call path and will NULL pointer panic.
P.
>> + }
>>
>> switch (event) {
>> case CPUFREQ_GOV_POLICY_INIT:
>> @@ -329,6 +345,12 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>> case CPUFREQ_GOV_POLICY_EXIT:
>> mutex_lock(&dbs_data->usage_count_mutex);
>> if (atomic_dec_and_test(&dbs_data->usage_count)) {
>> + if (atomic_read(&policy->governor->initialized) > 1) {
>> + pr_emerg("Removing governor %s but initialized
>> = %d, dbs_data->usage_count = 0\n",
>> + policy->governor->name,
>> + atomic_read(&policy->governor->initialized));
>> + BUG();
>> + }
>> sysfs_remove_group(get_governor_parent_kobj(policy),
>> get_sysfs_attr(dbs_data));
>>
>>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
