diff mbox

[V2,05/14] cpufreq: stats: get rid of per-cpu cpufreq_stats_table

Message ID b7d24dcbe2aecf8627d5fbe0666ec88b8d8076d3.1420177186.git.viresh.kumar@linaro.org
State New
Headers show

Commit Message

Viresh Kumar Jan. 2, 2015, 5:46 a.m. UTC 
Because all CPUs in a policy share clock line, they share stats as well.  But
cpufreq-stats maintains a per-cpu list of tables for managing this. Get rid of
it by assigning a special field for stats in 'struct cpufreq_policy'.

Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/cpufreq/cpufreq_stats.c | 51 ++++++++++++++++++-----------------------
 include/linux/cpufreq.h         |  3 +++
 2 files changed, 25 insertions(+), 29 deletions(-)

Comments

Viresh Kumar Jan. 5, 2015, 4:23 a.m. UTC | #1 
On 4 January 2015 at 03:50, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:

All comments accepted before this ..

>> @@ -293,15 +281,19 @@ static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
>>               unsigned long val, void *data)
>>  {
>>       struct cpufreq_freqs *freq = data;
>> +     struct cpufreq_policy *policy = cpufreq_cpu_get(freq->cpu);
>>       struct cpufreq_stats *stat;
>>       int old_index, new_index;
>>
>>       if (val != CPUFREQ_POSTCHANGE)
>>               return 0;
>>
>> -     stat = per_cpu(cpufreq_stats_table, freq->cpu);
>> -     if (!stat)
>> -             return 0;
>> +     if (!policy) {
>> +             pr_err("%s: No policy found\n", __func__);
>
> Do we need the extra message here?  If so, can it be pr_debug()?

Because we are in the POSTCHANGE stage right now, the policy
isn't allowed to be NULL. And so this is an error and I used pr_err.

>> +             return -ENODEV;
>> +     }
>
> This changes the behavior in a subtle way.  Instead of returning 0 when stats
> are not present, we'll now return an error code for a missing policy.  Are you
> sure that this isn't going to break anything?

Something I didn't looked at earlier. This *can* break things a bit.
If I understand it clearly now, the notifiers aren't allowed to return these
errors. They should return:

NOTIFY_DONE or NOTIFY_OK or NOTIFY_BAD

And this is what the notifier chain does to the return value:

    if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
            break;

So, if the return error has its 15th bit set, then we will break the loop.
(NOTIFY_STOP_MASK 0x8000).

It wouldn't happen in this case, but probably we should just return
NOTIFY_DONE (0)..

Right ?

>> +
>> +     stat = policy->stats_data;
>
> Is stat guaraneed to be a valid pointer at this point?

We better check it as well for some corner cases where we failed
to create a table.

>> +     void                    *stats_data;
>
> Why isn't that
>
>         struct cpufreq_stats    *stats;

It will be.
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diff mbox

Patch

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index ebd9e4c5c124..106c89ccef30 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -31,8 +31,6 @@  struct cpufreq_stats {
 #endif
 };
 
-static DEFINE_PER_CPU(struct cpufreq_stats *, cpufreq_stats_table);
-
 struct cpufreq_stats_attribute {
 	struct attribute attr;
 	ssize_t(*show) (struct cpufreq_stats *, char *);
@@ -53,20 +51,17 @@  static int cpufreq_stats_update(struct cpufreq_stats *stat)
 
 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
 {
-	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
-	if (!stat)
-		return 0;
-	return sprintf(buf, "%d\n",
-			per_cpu(cpufreq_stats_table, stat->cpu)->total_trans);
+	struct cpufreq_stats *stat = policy->stats_data;
+
+	return sprintf(buf, "%d\n", stat->total_trans);
 }
 
 static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
 {
+	struct cpufreq_stats *stat = policy->stats_data;
 	ssize_t len = 0;
 	int i;
-	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
-	if (!stat)
-		return 0;
+
 	cpufreq_stats_update(stat);
 	for (i = 0; i < stat->state_num; i++) {
 		len += sprintf(buf + len, "%u %llu\n", stat->freq_table[i],
@@ -79,12 +74,10 @@  static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
 {
+	struct cpufreq_stats *stat = policy->stats_data;
 	ssize_t len = 0;
 	int i, j;
 
-	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
-	if (!stat)
-		return 0;
 	cpufreq_stats_update(stat);
 	len += snprintf(buf + len, PAGE_SIZE - len, "   From  :    To\n");
 	len += snprintf(buf + len, PAGE_SIZE - len, "         : ");
@@ -150,8 +143,9 @@  static int freq_table_get_index(struct cpufreq_stats *stat, unsigned int freq)
 
 static void __cpufreq_stats_free_table(struct cpufreq_policy *policy)
 {
-	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
+	struct cpufreq_stats *stat = policy->stats_data;
 
+	/* Already freed */
 	if (!stat)
 		return;
 
@@ -160,7 +154,7 @@  static void __cpufreq_stats_free_table(struct cpufreq_policy *policy)
 	sysfs_remove_group(&policy->kobj, &stats_attr_group);
 	kfree(stat->time_in_state);
 	kfree(stat);
-	per_cpu(cpufreq_stats_table, policy->cpu) = NULL;
+	policy->stats_data = NULL;
 }
 
 static void cpufreq_stats_free_table(unsigned int cpu)
@@ -189,7 +183,7 @@  static int __cpufreq_stats_create_table(struct cpufreq_policy *policy)
 		return 0;
 
 	/* stats already initialized */
-	if (per_cpu(cpufreq_stats_table, cpu))
+	if (policy->stats_data)
 		return -EEXIST;
 
 	stat = kzalloc(sizeof(*stat), GFP_KERNEL);
@@ -201,7 +195,7 @@  static int __cpufreq_stats_create_table(struct cpufreq_policy *policy)
 		goto error_out;
 
 	stat->cpu = cpu;
-	per_cpu(cpufreq_stats_table, cpu) = stat;
+	policy->stats_data = stat;
 
 	cpufreq_for_each_valid_entry(pos, table)
 		count++;
@@ -236,7 +230,7 @@  static int __cpufreq_stats_create_table(struct cpufreq_policy *policy)
 	sysfs_remove_group(&policy->kobj, &stats_attr_group);
 error_out:
 	kfree(stat);
-	per_cpu(cpufreq_stats_table, cpu) = NULL;
+	policy->stats_data = NULL;
 	return ret;
 }
 
@@ -259,14 +253,8 @@  static void cpufreq_stats_create_table(unsigned int cpu)
 
 static void cpufreq_stats_update_policy_cpu(struct cpufreq_policy *policy)
 {
-	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table,
-			policy->last_cpu);
-
-	pr_debug("Updating stats_table for new_cpu %u from last_cpu %u\n",
-			policy->cpu, policy->last_cpu);
-	per_cpu(cpufreq_stats_table, policy->cpu) = per_cpu(cpufreq_stats_table,
-			policy->last_cpu);
-	per_cpu(cpufreq_stats_table, policy->last_cpu) = NULL;
+	struct cpufreq_stats *stat = policy->stats_data;
+
 	stat->cpu = policy->cpu;
 }
 
@@ -293,15 +281,19 @@  static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
 		unsigned long val, void *data)
 {
 	struct cpufreq_freqs *freq = data;
+	struct cpufreq_policy *policy = cpufreq_cpu_get(freq->cpu);
 	struct cpufreq_stats *stat;
 	int old_index, new_index;
 
 	if (val != CPUFREQ_POSTCHANGE)
 		return 0;
 
-	stat = per_cpu(cpufreq_stats_table, freq->cpu);
-	if (!stat)
-		return 0;
+	if (!policy) {
+		pr_err("%s: No policy found\n", __func__);
+		return -ENODEV;
+	}
+
+	stat = policy->stats_data;
 
 	old_index = stat->last_index;
 	new_index = freq_table_get_index(stat, freq->new);
@@ -322,6 +314,7 @@  static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
 #endif
 	stat->total_trans++;
 	spin_unlock(&cpufreq_stats_lock);
+	cpufreq_cpu_put(policy);
 	return 0;
 }
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 4d078cebafd2..3cb097b86d20 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -113,6 +113,9 @@  struct cpufreq_policy {
 	wait_queue_head_t	transition_wait;
 	struct task_struct	*transition_task; /* Task which is doing the transition */
 
+	/* cpufreq-stats data */
+	void			*stats_data;
+
 	/* For cpufreq driver's internal use */
 	void			*driver_data;
 };