cpufreq: Fix NULL reference crash while accessing policy->governor_data

[mirror_ubuntu-artful-kernel.git] / drivers / cpufreq / cpufreq_governor.c

/*
 * drivers/cpufreq/cpufreq_governor.c
 *
 * CPUFREQ governors common code
 *
 * Copyright    (C) 2001 Russell King
 *              (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
 *              (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
 *              (C) 2009 Alexander Clouter <alex@digriz.org.uk>
 *              (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/export.h>
#include <linux/kernel_stat.h>
#include <linux/slab.h>

#include "cpufreq_governor.h"

static struct attribute_group *get_sysfs_attr(struct dbs_data *dbs_data)
{
        if (have_governor_per_policy())
                return dbs_data->cdata->attr_group_gov_pol;
        else
                return dbs_data->cdata->attr_group_gov_sys;
}

void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
{
        struct cpu_dbs_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
        struct cpufreq_policy *policy = cdbs->shared->policy;
        unsigned int sampling_rate;
        unsigned int max_load = 0;
        unsigned int ignore_nice;
        unsigned int j;

        if (dbs_data->cdata->governor == GOV_ONDEMAND) {
                struct od_cpu_dbs_info_s *od_dbs_info =
                                dbs_data->cdata->get_cpu_dbs_info_s(cpu);

                /*
                 * Sometimes, the ondemand governor uses an additional
                 * multiplier to give long delays. So apply this multiplier to
                 * the 'sampling_rate', so as to keep the wake-up-from-idle
                 * detection logic a bit conservative.
                 */
                sampling_rate = od_tuners->sampling_rate;
                sampling_rate *= od_dbs_info->rate_mult;

                ignore_nice = od_tuners->ignore_nice_load;
        } else {
                sampling_rate = cs_tuners->sampling_rate;
                ignore_nice = cs_tuners->ignore_nice_load;
        }

        /* Get Absolute Load */
        for_each_cpu(j, policy->cpus) {
                struct cpu_dbs_info *j_cdbs;
                u64 cur_wall_time, cur_idle_time;
                unsigned int idle_time, wall_time;
                unsigned int load;
                int io_busy = 0;

                j_cdbs = dbs_data->cdata->get_cpu_cdbs(j);

                /*
                 * For the purpose of ondemand, waiting for disk IO is
                 * an indication that you're performance critical, and
                 * not that the system is actually idle. So do not add
                 * the iowait time to the cpu idle time.
                 */
                if (dbs_data->cdata->governor == GOV_ONDEMAND)
                        io_busy = od_tuners->io_is_busy;
                cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);

                wall_time = (unsigned int)
                        (cur_wall_time - j_cdbs->prev_cpu_wall);
                j_cdbs->prev_cpu_wall = cur_wall_time;

                idle_time = (unsigned int)
                        (cur_idle_time - j_cdbs->prev_cpu_idle);
                j_cdbs->prev_cpu_idle = cur_idle_time;

                if (ignore_nice) {
                        u64 cur_nice;
                        unsigned long cur_nice_jiffies;

                        cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
                                         cdbs->prev_cpu_nice;
                        /*
                         * Assumption: nice time between sampling periods will
                         * be less than 2^32 jiffies for 32 bit sys
                         */
                        cur_nice_jiffies = (unsigned long)
                                        cputime64_to_jiffies64(cur_nice);

                        cdbs->prev_cpu_nice =
                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];
                        idle_time += jiffies_to_usecs(cur_nice_jiffies);
                }

                if (unlikely(!wall_time || wall_time < idle_time))
                        continue;

                /*
                 * If the CPU had gone completely idle, and a task just woke up
                 * on this CPU now, it would be unfair to calculate 'load' the
                 * usual way for this elapsed time-window, because it will show
                 * near-zero load, irrespective of how CPU intensive that task
                 * actually is. This is undesirable for latency-sensitive bursty
                 * workloads.
                 *
                 * To avoid this, we reuse the 'load' from the previous
                 * time-window and give this task a chance to start with a
                 * reasonably high CPU frequency. (However, we shouldn't over-do
                 * this copy, lest we get stuck at a high load (high frequency)
                 * for too long, even when the current system load has actually
                 * dropped down. So we perform the copy only once, upon the
                 * first wake-up from idle.)
                 *
                 * Detecting this situation is easy: the governor's deferrable
                 * timer would not have fired during CPU-idle periods. Hence
                 * an unusually large 'wall_time' (as compared to the sampling
                 * rate) indicates this scenario.
                 *
                 * prev_load can be zero in two cases and we must recalculate it
                 * for both cases:
                 * - during long idle intervals
                 * - explicitly set to zero
                 */
                if (unlikely(wall_time > (2 * sampling_rate) &&
                             j_cdbs->prev_load)) {
                        load = j_cdbs->prev_load;

                        /*
                         * Perform a destructive copy, to ensure that we copy
                         * the previous load only once, upon the first wake-up
                         * from idle.
                         */
                        j_cdbs->prev_load = 0;
                } else {
                        load = 100 * (wall_time - idle_time) / wall_time;
                        j_cdbs->prev_load = load;
                }

                if (load > max_load)
                        max_load = load;
        }

        dbs_data->cdata->gov_check_cpu(cpu, max_load);
}
EXPORT_SYMBOL_GPL(dbs_check_cpu);

static inline void __gov_queue_work(int cpu, struct dbs_data *dbs_data,
                unsigned int delay)
{
        struct cpu_dbs_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);

        mod_delayed_work_on(cpu, system_wq, &cdbs->dwork, delay);
}

void gov_queue_work(struct dbs_data *dbs_data, struct cpufreq_policy *policy,
                unsigned int delay, bool all_cpus)
{
        int i;

        if (!all_cpus) {
                /*
                 * Use raw_smp_processor_id() to avoid preemptible warnings.
                 * We know that this is only called with all_cpus == false from
                 * works that have been queued with *_work_on() functions and
                 * 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);
        } else {
                for_each_cpu(i, policy->cpus)
                        __gov_queue_work(i, dbs_data, delay);
        }
}
EXPORT_SYMBOL_GPL(gov_queue_work);

static inline void gov_cancel_work(struct dbs_data *dbs_data,
                struct cpufreq_policy *policy)
{
        struct cpu_dbs_info *cdbs;
        int i;

        for_each_cpu(i, policy->cpus) {
                cdbs = dbs_data->cdata->get_cpu_cdbs(i);
                cancel_delayed_work_sync(&cdbs->dwork);
        }
}

/* Will return if we need to evaluate cpu load again or not */
static bool need_load_eval(struct cpu_common_dbs_info *shared,
                           unsigned int sampling_rate)
{
        if (policy_is_shared(shared->policy)) {
                ktime_t time_now = ktime_get();
                s64 delta_us = ktime_us_delta(time_now, shared->time_stamp);

                /* Do nothing if we recently have sampled */
                if (delta_us < (s64)(sampling_rate / 2))
                        return false;
                else
                        shared->time_stamp = time_now;
        }

        return true;
}

static void dbs_timer(struct work_struct *work)
{
        struct cpu_dbs_info *cdbs = container_of(work, struct cpu_dbs_info,
                                                 dwork.work);
        struct cpu_common_dbs_info *shared = cdbs->shared;
        struct cpufreq_policy *policy;
        struct dbs_data *dbs_data;
        unsigned int sampling_rate, delay;
        bool modify_all = true;

        mutex_lock(&shared->timer_mutex);

        policy = shared->policy;

        /*
         * Governor might already be disabled and there is no point continuing
         * with the work-handler.
         */
        if (!policy)
                goto unlock;

        dbs_data = policy->governor_data;

        if (dbs_data->cdata->governor == GOV_CONSERVATIVE) {
                struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;

                sampling_rate = cs_tuners->sampling_rate;
        } else {
                struct od_dbs_tuners *od_tuners = dbs_data->tuners;

                sampling_rate = od_tuners->sampling_rate;
        }

        if (!need_load_eval(cdbs->shared, sampling_rate))
                modify_all = false;

        delay = dbs_data->cdata->gov_dbs_timer(cdbs, dbs_data, modify_all);
        gov_queue_work(dbs_data, policy, delay, modify_all);

unlock:
        mutex_unlock(&shared->timer_mutex);
}

static void set_sampling_rate(struct dbs_data *dbs_data,
                unsigned int sampling_rate)
{
        if (dbs_data->cdata->governor == GOV_CONSERVATIVE) {
                struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
                cs_tuners->sampling_rate = sampling_rate;
        } else {
                struct od_dbs_tuners *od_tuners = dbs_data->tuners;
                od_tuners->sampling_rate = sampling_rate;
        }
}

static int alloc_common_dbs_info(struct cpufreq_policy *policy,
                                 struct common_dbs_data *cdata)
{
        struct cpu_common_dbs_info *shared;
        int j;

        /* Allocate memory for the common information for policy->cpus */
        shared = kzalloc(sizeof(*shared), GFP_KERNEL);
        if (!shared)
                return -ENOMEM;

        /* Set shared for all CPUs, online+offline */
        for_each_cpu(j, policy->related_cpus)
                cdata->get_cpu_cdbs(j)->shared = shared;

        return 0;
}

static void free_common_dbs_info(struct cpufreq_policy *policy,
                                 struct common_dbs_data *cdata)
{
        struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(policy->cpu);
        struct cpu_common_dbs_info *shared = cdbs->shared;
        int j;

        for_each_cpu(j, policy->cpus)
                cdata->get_cpu_cdbs(j)->shared = NULL;

        kfree(shared);
}

static int cpufreq_governor_init(struct cpufreq_policy *policy,
                                 struct dbs_data *dbs_data,
                                 struct common_dbs_data *cdata)
{
        unsigned int latency;
        int ret;

        /* State should be equivalent to EXIT */
        if (policy->governor_data)
                return -EBUSY;

        if (dbs_data) {
                if (WARN_ON(have_governor_per_policy()))
                        return -EINVAL;

                ret = alloc_common_dbs_info(policy, cdata);
                if (ret)
                        return ret;

                dbs_data->usage_count++;
                policy->governor_data = dbs_data;
                return 0;
        }

        dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
        if (!dbs_data)
                return -ENOMEM;

        ret = alloc_common_dbs_info(policy, cdata);
        if (ret)
                goto free_dbs_data;

        dbs_data->cdata = cdata;
        dbs_data->usage_count = 1;

        ret = cdata->init(dbs_data, !policy->governor->initialized);
        if (ret)
                goto free_common_dbs_info;

        /* policy latency is in ns. Convert it to us first */
        latency = policy->cpuinfo.transition_latency / 1000;
        if (latency == 0)
                latency = 1;

        /* Bring kernel and HW constraints together */
        dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate,
                                          MIN_LATENCY_MULTIPLIER * latency);
        set_sampling_rate(dbs_data, max(dbs_data->min_sampling_rate,
                                        latency * LATENCY_MULTIPLIER));

        if (!have_governor_per_policy())
                cdata->gdbs_data = dbs_data;

        policy->governor_data = dbs_data;

        ret = sysfs_create_group(get_governor_parent_kobj(policy),
                                 get_sysfs_attr(dbs_data));
        if (ret)
                goto reset_gdbs_data;

        return 0;

reset_gdbs_data:
        policy->governor_data = NULL;

        if (!have_governor_per_policy())
                cdata->gdbs_data = NULL;
        cdata->exit(dbs_data, !policy->governor->initialized);
free_common_dbs_info:
        free_common_dbs_info(policy, cdata);
free_dbs_data:
        kfree(dbs_data);
        return ret;
}

static int cpufreq_governor_exit(struct cpufreq_policy *policy,
                                 struct dbs_data *dbs_data)
{
        struct common_dbs_data *cdata = dbs_data->cdata;
        struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(policy->cpu);

        /* State should be equivalent to INIT */
        if (!cdbs->shared || cdbs->shared->policy)
                return -EBUSY;

        if (!--dbs_data->usage_count) {
                sysfs_remove_group(get_governor_parent_kobj(policy),
                                   get_sysfs_attr(dbs_data));

                policy->governor_data = NULL;

                if (!have_governor_per_policy())
                        cdata->gdbs_data = NULL;

                cdata->exit(dbs_data, policy->governor->initialized == 1);
                kfree(dbs_data);
        } else {
                policy->governor_data = NULL;
        }

        free_common_dbs_info(policy, cdata);
        return 0;
}

static int cpufreq_governor_start(struct cpufreq_policy *policy,
                                  struct dbs_data *dbs_data)
{
        struct common_dbs_data *cdata = dbs_data->cdata;
        unsigned int sampling_rate, ignore_nice, j, cpu = policy->cpu;
        struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);
        struct cpu_common_dbs_info *shared = cdbs->shared;
        int io_busy = 0;

        if (!policy->cur)
                return -EINVAL;

        /* State should be equivalent to INIT */
        if (!shared || shared->policy)
                return -EBUSY;

        if (cdata->governor == GOV_CONSERVATIVE) {
                struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;

                sampling_rate = cs_tuners->sampling_rate;
                ignore_nice = cs_tuners->ignore_nice_load;
        } else {
                struct od_dbs_tuners *od_tuners = dbs_data->tuners;

                sampling_rate = od_tuners->sampling_rate;
                ignore_nice = od_tuners->ignore_nice_load;
                io_busy = od_tuners->io_is_busy;
        }

        shared->policy = policy;
        shared->time_stamp = ktime_get();
        mutex_init(&shared->timer_mutex);

        for_each_cpu(j, policy->cpus) {
                struct cpu_dbs_info *j_cdbs = cdata->get_cpu_cdbs(j);
                unsigned int prev_load;

                j_cdbs->prev_cpu_idle =
                        get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy);

                prev_load = (unsigned int)(j_cdbs->prev_cpu_wall -
                                            j_cdbs->prev_cpu_idle);
                j_cdbs->prev_load = 100 * prev_load /
                                    (unsigned int)j_cdbs->prev_cpu_wall;

                if (ignore_nice)
                        j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];

                INIT_DEFERRABLE_WORK(&j_cdbs->dwork, dbs_timer);
        }

        if (cdata->governor == GOV_CONSERVATIVE) {
                struct cs_cpu_dbs_info_s *cs_dbs_info =
                        cdata->get_cpu_dbs_info_s(cpu);

                cs_dbs_info->down_skip = 0;
                cs_dbs_info->requested_freq = policy->cur;
        } else {
                struct od_ops *od_ops = cdata->gov_ops;
                struct od_cpu_dbs_info_s *od_dbs_info = cdata->get_cpu_dbs_info_s(cpu);

                od_dbs_info->rate_mult = 1;
                od_dbs_info->sample_type = OD_NORMAL_SAMPLE;
                od_ops->powersave_bias_init_cpu(cpu);
        }

        gov_queue_work(dbs_data, policy, delay_for_sampling_rate(sampling_rate),
                       true);
        return 0;
}

static int cpufreq_governor_stop(struct cpufreq_policy *policy,
                                 struct dbs_data *dbs_data)
{
        struct cpu_dbs_info *cdbs = dbs_data->cdata->get_cpu_cdbs(policy->cpu);
        struct cpu_common_dbs_info *shared = cdbs->shared;

        /* State should be equivalent to START */
        if (!shared || !shared->policy)
                return -EBUSY;

        /*
         * Work-handler must see this updated, as it should not proceed any
         * further after governor is disabled. And so timer_mutex is taken while
         * updating this value.
         */
        mutex_lock(&shared->timer_mutex);
        shared->policy = NULL;
        mutex_unlock(&shared->timer_mutex);

        gov_cancel_work(dbs_data, policy);

        mutex_destroy(&shared->timer_mutex);
        return 0;
}

static int cpufreq_governor_limits(struct cpufreq_policy *policy,
                                   struct dbs_data *dbs_data)
{
        struct common_dbs_data *cdata = dbs_data->cdata;
        unsigned int cpu = policy->cpu;
        struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);

        /* State should be equivalent to START */
        if (!cdbs->shared || !cdbs->shared->policy)
                return -EBUSY;

        mutex_lock(&cdbs->shared->timer_mutex);
        if (policy->max < cdbs->shared->policy->cur)
                __cpufreq_driver_target(cdbs->shared->policy, policy->max,
                                        CPUFREQ_RELATION_H);
        else if (policy->min > cdbs->shared->policy->cur)
                __cpufreq_driver_target(cdbs->shared->policy, policy->min,
                                        CPUFREQ_RELATION_L);
        dbs_check_cpu(dbs_data, cpu);
        mutex_unlock(&cdbs->shared->timer_mutex);

        return 0;
}

int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                         struct common_dbs_data *cdata, unsigned int event)
{
        struct dbs_data *dbs_data;
        int ret;

        /* Lock governor to block concurrent initialization of governor */
        mutex_lock(&cdata->mutex);

        if (have_governor_per_policy())
                dbs_data = policy->governor_data;
        else
                dbs_data = cdata->gdbs_data;

        if (!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT)) {
                ret = -EINVAL;
                goto unlock;
        }

        switch (event) {
        case CPUFREQ_GOV_POLICY_INIT:
                ret = cpufreq_governor_init(policy, dbs_data, cdata);
                break;
        case CPUFREQ_GOV_POLICY_EXIT:
                ret = cpufreq_governor_exit(policy, dbs_data);
                break;
        case CPUFREQ_GOV_START:
                ret = cpufreq_governor_start(policy, dbs_data);
                break;
        case CPUFREQ_GOV_STOP:
                ret = cpufreq_governor_stop(policy, dbs_data);
                break;
        case CPUFREQ_GOV_LIMITS:
                ret = cpufreq_governor_limits(policy, dbs_data);
                break;
        default:
                ret = -EINVAL;
        }

unlock:
        mutex_unlock(&cdata->mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);