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Subject[PATCH 5/5] cpufreq, add BUG() messages in critical paths to aid debugging failures
Date
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" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
---
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();
+ }
+ cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);

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();
+ }

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));

--
1.7.9.3


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