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Subject[patch 4/4] cpufreq: Cleanup locking in conservative governor
Redesign the locking inside conservative driver. Make dbs_mutex handle all the
global state changes inside the driver and invent a new percpu mutex
to serialize percpu timer and frequency limit change.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
---
drivers/cpufreq/cpufreq_conservative.c | 34 ++++++++++++-------------------
1 files changed, 13 insertions(+), 21 deletions(-)
diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index 58889f2..5749050 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -63,7 +63,12 @@ struct cpu_dbs_info_s {
unsigned int down_skip;
unsigned int requested_freq;
int cpu;
- unsigned int enable:1;
+ /*
+ * percpu mutex that serializes governor limit change with
+ * do_dbs_timer invocation. We do not want do_dbs_timer to run
+ * when user is changing the governor or limits.
+ */
+ struct mutex timer_mutex;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);

@@ -71,9 +76,7 @@ static unsigned int dbs_enable; /* number of CPUs using this policy */

/*
* dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
- * different CPUs. It protects dbs_enable in governor start/stop. It also
- * serializes governor limit_change with do_dbs_timer. We do not want
- * do_dbs_timer to run when user is changing the governor or limits.
+ * different CPUs. It protects dbs_enable in governor start/stop.
*/
static DEFINE_MUTEX(dbs_mutex);

@@ -138,9 +141,6 @@ dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

struct cpufreq_policy *policy;

- if (!this_dbs_info->enable)
- return 0;
-
policy = this_dbs_info->cur_policy;

/*
@@ -483,17 +483,12 @@ static void do_dbs_timer(struct work_struct *work)

delay -= jiffies % delay;

- mutex_lock(&dbs_mutex);
-
- if (!dbs_info->enable) {
- mutex_unlock(&dbs_mutex);
- return;
- }
+ mutex_lock(&dbs_info->timer_mutex);

dbs_check_cpu(dbs_info);

queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
- mutex_unlock(&dbs_mutex);
+ mutex_unlock(&dbs_info->timer_mutex);
}

static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -502,7 +497,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
delay -= jiffies % delay;

- dbs_info->enable = 1;
INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
delay);
@@ -510,7 +504,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)

static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
{
- dbs_info->enable = 0;
cancel_delayed_work_sync(&dbs_info->work);
}

@@ -529,9 +522,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
if ((!cpu_online(cpu)) || (!policy->cur))
return -EINVAL;

- if (this_dbs_info->enable) /* Already enabled */
- break;
-
mutex_lock(&dbs_mutex);

rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
@@ -555,6 +545,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
this_dbs_info->down_skip = 0;
this_dbs_info->requested_freq = policy->cur;

+ mutex_init(&this_dbs_info->timer_mutex);
dbs_enable++;
/*
* Start the timerschedule work, when this governor
@@ -596,6 +587,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
mutex_lock(&dbs_mutex);
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;
+ mutex_destroy(&this_dbs_info->timer_mutex);

/*
* Stop the timerschedule work, when this governor
@@ -611,7 +603,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
break;

case CPUFREQ_GOV_LIMITS:
- mutex_lock(&dbs_mutex);
+ mutex_lock(&this_dbs_info->timer_mutex);
if (policy->max < this_dbs_info->cur_policy->cur)
__cpufreq_driver_target(
this_dbs_info->cur_policy,
@@ -620,7 +612,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
__cpufreq_driver_target(
this_dbs_info->cur_policy,
policy->min, CPUFREQ_RELATION_L);
- mutex_unlock(&dbs_mutex);
+ mutex_unlock(&this_dbs_info->timer_mutex);

break;
}
--
1.6.0.6
--



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