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![Viresh Kumar](/assets/img/avatar_default.png)
There is no possibility of any race on updating last_index, trans_table or total_trans as these are updated only by cpufreq_stat_notifier_trans() which will be called sequentially. The only place where locking is still relevant is: cpufreq_stats_update(), which updates time_in_state and last_time. This can be called by two thread in parallel, that may result in races. The two threads being: - sysfs read of time_in_state - and frequency transition that calls cpufreq_stat_notifier_trans(). Remove locking from the first case mentioned above. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
357 lines
8.3 KiB
C
357 lines
8.3 KiB
C
/*
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* drivers/cpufreq/cpufreq_stats.c
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*
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* Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
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* (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/cpu.h>
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#include <linux/cpufreq.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/cputime.h>
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static spinlock_t cpufreq_stats_lock;
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struct cpufreq_stats {
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unsigned int total_trans;
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unsigned long long last_time;
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unsigned int max_state;
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unsigned int state_num;
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unsigned int last_index;
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u64 *time_in_state;
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unsigned int *freq_table;
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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unsigned int *trans_table;
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#endif
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};
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static int cpufreq_stats_update(struct cpufreq_stats *stats)
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{
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unsigned long long cur_time = get_jiffies_64();
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spin_lock(&cpufreq_stats_lock);
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stats->time_in_state[stats->last_index] += cur_time - stats->last_time;
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stats->last_time = cur_time;
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spin_unlock(&cpufreq_stats_lock);
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return 0;
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}
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static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
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{
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return sprintf(buf, "%d\n", policy->stats->total_trans);
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}
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static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
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{
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struct cpufreq_stats *stats = policy->stats;
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ssize_t len = 0;
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int i;
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cpufreq_stats_update(stats);
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for (i = 0; i < stats->state_num; i++) {
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len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
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(unsigned long long)
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jiffies_64_to_clock_t(stats->time_in_state[i]));
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}
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return len;
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}
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
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{
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struct cpufreq_stats *stats = policy->stats;
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ssize_t len = 0;
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int i, j;
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len += snprintf(buf + len, PAGE_SIZE - len, " From : To\n");
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len += snprintf(buf + len, PAGE_SIZE - len, " : ");
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for (i = 0; i < stats->state_num; i++) {
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if (len >= PAGE_SIZE)
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break;
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len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
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stats->freq_table[i]);
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}
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if (len >= PAGE_SIZE)
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return PAGE_SIZE;
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len += snprintf(buf + len, PAGE_SIZE - len, "\n");
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for (i = 0; i < stats->state_num; i++) {
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if (len >= PAGE_SIZE)
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break;
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len += snprintf(buf + len, PAGE_SIZE - len, "%9u: ",
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stats->freq_table[i]);
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for (j = 0; j < stats->state_num; j++) {
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if (len >= PAGE_SIZE)
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break;
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len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
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stats->trans_table[i*stats->max_state+j]);
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}
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if (len >= PAGE_SIZE)
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break;
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len += snprintf(buf + len, PAGE_SIZE - len, "\n");
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}
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if (len >= PAGE_SIZE)
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return PAGE_SIZE;
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return len;
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}
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cpufreq_freq_attr_ro(trans_table);
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#endif
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cpufreq_freq_attr_ro(total_trans);
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cpufreq_freq_attr_ro(time_in_state);
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static struct attribute *default_attrs[] = {
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&total_trans.attr,
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&time_in_state.attr,
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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&trans_table.attr,
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#endif
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NULL
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};
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static struct attribute_group stats_attr_group = {
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.attrs = default_attrs,
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.name = "stats"
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};
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static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq)
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{
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int index;
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for (index = 0; index < stats->max_state; index++)
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if (stats->freq_table[index] == freq)
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return index;
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return -1;
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}
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static void __cpufreq_stats_free_table(struct cpufreq_policy *policy)
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{
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struct cpufreq_stats *stats = policy->stats;
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/* Already freed */
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if (!stats)
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return;
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pr_debug("%s: Free stats table\n", __func__);
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sysfs_remove_group(&policy->kobj, &stats_attr_group);
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kfree(stats->time_in_state);
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kfree(stats);
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policy->stats = NULL;
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}
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static void cpufreq_stats_free_table(unsigned int cpu)
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{
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struct cpufreq_policy *policy;
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policy = cpufreq_cpu_get(cpu);
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if (!policy)
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return;
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__cpufreq_stats_free_table(policy);
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cpufreq_cpu_put(policy);
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}
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static int __cpufreq_stats_create_table(struct cpufreq_policy *policy)
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{
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unsigned int i = 0, count = 0, ret = -ENOMEM;
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struct cpufreq_stats *stats;
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unsigned int alloc_size;
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unsigned int cpu = policy->cpu;
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struct cpufreq_frequency_table *pos, *table;
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/* We need cpufreq table for creating stats table */
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table = cpufreq_frequency_get_table(cpu);
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if (unlikely(!table))
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return 0;
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/* stats already initialized */
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if (policy->stats)
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return -EEXIST;
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stats = kzalloc(sizeof(*stats), GFP_KERNEL);
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if (!stats)
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return -ENOMEM;
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/* Find total allocation size */
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cpufreq_for_each_valid_entry(pos, table)
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count++;
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alloc_size = count * sizeof(int) + count * sizeof(u64);
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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alloc_size += count * count * sizeof(int);
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#endif
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/* Allocate memory for time_in_state/freq_table/trans_table in one go */
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stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
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if (!stats->time_in_state)
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goto free_stat;
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stats->freq_table = (unsigned int *)(stats->time_in_state + count);
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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stats->trans_table = stats->freq_table + count;
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#endif
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stats->max_state = count;
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/* Find valid-unique entries */
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cpufreq_for_each_valid_entry(pos, table)
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if (freq_table_get_index(stats, pos->frequency) == -1)
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stats->freq_table[i++] = pos->frequency;
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stats->state_num = i;
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stats->last_time = get_jiffies_64();
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stats->last_index = freq_table_get_index(stats, policy->cur);
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policy->stats = stats;
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ret = sysfs_create_group(&policy->kobj, &stats_attr_group);
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if (!ret)
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return 0;
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/* We failed, release resources */
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policy->stats = NULL;
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kfree(stats->time_in_state);
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free_stat:
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kfree(stats);
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return ret;
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}
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static void cpufreq_stats_create_table(unsigned int cpu)
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{
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struct cpufreq_policy *policy;
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/*
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* "likely(!policy)" because normally cpufreq_stats will be registered
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* before cpufreq driver
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*/
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policy = cpufreq_cpu_get(cpu);
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if (likely(!policy))
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return;
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__cpufreq_stats_create_table(policy);
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cpufreq_cpu_put(policy);
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}
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static int cpufreq_stat_notifier_policy(struct notifier_block *nb,
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unsigned long val, void *data)
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{
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int ret = 0;
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struct cpufreq_policy *policy = data;
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if (val == CPUFREQ_CREATE_POLICY)
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ret = __cpufreq_stats_create_table(policy);
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else if (val == CPUFREQ_REMOVE_POLICY)
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__cpufreq_stats_free_table(policy);
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return ret;
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}
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static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
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unsigned long val, void *data)
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{
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struct cpufreq_freqs *freq = data;
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struct cpufreq_policy *policy = cpufreq_cpu_get(freq->cpu);
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struct cpufreq_stats *stats;
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int old_index, new_index;
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if (!policy) {
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pr_err("%s: No policy found\n", __func__);
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return 0;
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}
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if (val != CPUFREQ_POSTCHANGE)
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goto put_policy;
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if (!policy->stats) {
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pr_debug("%s: No stats found\n", __func__);
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goto put_policy;
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}
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stats = policy->stats;
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old_index = stats->last_index;
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new_index = freq_table_get_index(stats, freq->new);
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/* We can't do stats->time_in_state[-1]= .. */
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if (old_index == -1 || new_index == -1)
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goto put_policy;
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if (old_index == new_index)
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goto put_policy;
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cpufreq_stats_update(stats);
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stats->last_index = new_index;
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#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
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stats->trans_table[old_index * stats->max_state + new_index]++;
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#endif
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stats->total_trans++;
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put_policy:
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cpufreq_cpu_put(policy);
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return 0;
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}
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static struct notifier_block notifier_policy_block = {
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.notifier_call = cpufreq_stat_notifier_policy
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};
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static struct notifier_block notifier_trans_block = {
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.notifier_call = cpufreq_stat_notifier_trans
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};
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static int __init cpufreq_stats_init(void)
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{
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int ret;
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unsigned int cpu;
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spin_lock_init(&cpufreq_stats_lock);
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ret = cpufreq_register_notifier(¬ifier_policy_block,
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CPUFREQ_POLICY_NOTIFIER);
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if (ret)
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return ret;
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for_each_online_cpu(cpu)
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cpufreq_stats_create_table(cpu);
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ret = cpufreq_register_notifier(¬ifier_trans_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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if (ret) {
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cpufreq_unregister_notifier(¬ifier_policy_block,
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CPUFREQ_POLICY_NOTIFIER);
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for_each_online_cpu(cpu)
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cpufreq_stats_free_table(cpu);
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return ret;
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}
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return 0;
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}
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static void __exit cpufreq_stats_exit(void)
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{
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unsigned int cpu;
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cpufreq_unregister_notifier(¬ifier_policy_block,
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CPUFREQ_POLICY_NOTIFIER);
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cpufreq_unregister_notifier(¬ifier_trans_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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for_each_online_cpu(cpu)
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cpufreq_stats_free_table(cpu);
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}
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MODULE_AUTHOR("Zou Nan hai <nanhai.zou@intel.com>");
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MODULE_DESCRIPTION("Export cpufreq stats via sysfs");
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MODULE_LICENSE("GPL");
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module_init(cpufreq_stats_init);
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module_exit(cpufreq_stats_exit);
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