Re: [PATCH V2 2/6] cpufreq: Remove cpufreq_frequency_get_table()

From: Javi Merino
Date: Thu Jun 02 2016 - 10:59:13 EST

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In reply to: Viresh Kumar: "[PATCH V2 2/6] cpufreq: Remove cpufreq_frequency_get_table()"
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Hi Viresh,

On Thu, Jun 02, 2016 at 07:34:56PM +0530, Viresh Kumar wrote:
> Most of the callers of cpufreq_frequency_get_table() already have the
> pointer to a valid 'policy' structure and they don't really need to go
> through the per-cpu variable first and then a check to validate the
> frequency, in order to find the freq-table for the policy.
>
> Directly use the policy->freq_table field instead for them.
>
> Only one user of that API is left after above changes, cpu_cooling.c and
> it accesses the freq_table in a racy way as the policy can get freed in
> between.
>
> Fix it by using cpufreq_cpu_get() properly.

In 5a31d594a973 ("cpufreq: Allow freq_table to be obtained for offline
CPUs") you did the opposite: don't use cpufreq_cpu_get_raw() because
it won't give you the policy of a cpu that is offline. Now you are
arguing that we should go back to cpufreq_cpu_get() which implicitly
calls cpufreq_cpu_get_raw(). Won't we hit the same issue that
5a31d594a973 was trying to prevent: that we can't get a freq_table for
a cpu that is offline?

Cheers,
Javi

> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> drivers/cpufreq/cpufreq.c | 38 +++++++++++++----------------------
> drivers/cpufreq/cpufreq_ondemand.c | 2 +-
> drivers/cpufreq/cpufreq_stats.c | 3 +--
> drivers/cpufreq/freq_table.c | 9 +++------
> drivers/cpufreq/ppc_cbe_cpufreq_pmi.c | 3 +--
> drivers/thermal/cpu_cooling.c | 22 +++++++++++++++-----
> include/linux/cpufreq.h | 2 --
> 7 files changed, 37 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index fbc97b1fa371..1833eda1f9d4 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -126,15 +126,6 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy)
> }
> EXPORT_SYMBOL_GPL(get_governor_parent_kobj);
>
> -struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu)
> -{
> - struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
> -
> - return policy && !policy_is_inactive(policy) ?
> - policy->freq_table : NULL;
> -}
> -EXPORT_SYMBOL_GPL(cpufreq_frequency_get_table);
> -
> static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
> {
> u64 idle_time;
> @@ -1950,7 +1941,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
> if (!cpufreq_driver->target_index)
> return -EINVAL;
>
> - freq_table = cpufreq_frequency_get_table(policy->cpu);
> + freq_table = policy->freq_table;
> if (unlikely(!freq_table)) {
> pr_err("%s: Unable to find freq_table\n", __func__);
> return -EINVAL;
> @@ -2345,26 +2336,25 @@ static struct notifier_block __refdata cpufreq_cpu_notifier = {
> *********************************************************************/
> static int cpufreq_boost_set_sw(int state)
> {
> - struct cpufreq_frequency_table *freq_table;
> struct cpufreq_policy *policy;
> int ret = -EINVAL;
>
> for_each_active_policy(policy) {
> - freq_table = cpufreq_frequency_get_table(policy->cpu);
> - if (freq_table) {
> - ret = cpufreq_frequency_table_cpuinfo(policy,
> - freq_table);
> - if (ret) {
> - pr_err("%s: Policy frequency update failed\n",
> - __func__);
> - break;
> - }
> + if (!policy->freq_table)
> + continue;
>
> - down_write(&policy->rwsem);
> - policy->user_policy.max = policy->max;
> - cpufreq_governor_limits(policy);
> - up_write(&policy->rwsem);
> + ret = cpufreq_frequency_table_cpuinfo(policy,
> + policy->freq_table);
> + if (ret) {
> + pr_err("%s: Policy frequency update failed\n",
> + __func__);
> + break;
> }
> +
> + down_write(&policy->rwsem);
> + policy->user_policy.max = policy->max;
> + cpufreq_governor_limits(policy);
> + up_write(&policy->rwsem);
> }
>
> return ret;
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> index c84fc2240d49..4d2fe2710c5d 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -113,7 +113,7 @@ static void ondemand_powersave_bias_init(struct cpufreq_policy *policy)
> {
> struct od_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);
>
> - dbs_info->freq_table = cpufreq_frequency_get_table(policy->cpu);
> + dbs_info->freq_table = policy->freq_table;
> dbs_info->freq_lo = 0;
> }
>
> diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
> index c6e7f81a0397..06d3abdffd3a 100644
> --- a/drivers/cpufreq/cpufreq_stats.c
> +++ b/drivers/cpufreq/cpufreq_stats.c
> @@ -157,11 +157,10 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy)
> unsigned int i = 0, count = 0, ret = -ENOMEM;
> struct cpufreq_stats *stats;
> unsigned int alloc_size;
> - unsigned int cpu = policy->cpu;
> struct cpufreq_frequency_table *pos, *table;
>
> /* We need cpufreq table for creating stats table */
> - table = cpufreq_frequency_get_table(cpu);
> + table = policy->freq_table;
> if (unlikely(!table))
> return;
>
> diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
> index 4e5c5dbfed7a..f52b5473b1f4 100644
> --- a/drivers/cpufreq/freq_table.c
> +++ b/drivers/cpufreq/freq_table.c
> @@ -106,12 +106,10 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_verify);
> */
> int cpufreq_generic_frequency_table_verify(struct cpufreq_policy *policy)
> {
> - struct cpufreq_frequency_table *table =
> - cpufreq_frequency_get_table(policy->cpu);
> - if (!table)
> + if (!policy->freq_table)
> return -ENODEV;
>
> - return cpufreq_frequency_table_verify(policy, table);
> + return cpufreq_frequency_table_verify(policy, policy->freq_table);
> }
> EXPORT_SYMBOL_GPL(cpufreq_generic_frequency_table_verify);
>
> @@ -210,9 +208,8 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_target);
> int cpufreq_frequency_table_get_index(struct cpufreq_policy *policy,
> unsigned int freq)
> {
> - struct cpufreq_frequency_table *pos, *table;
> + struct cpufreq_frequency_table *pos, *table = policy->freq_table;
>
> - table = cpufreq_frequency_get_table(policy->cpu);
> if (unlikely(!table)) {
> pr_debug("%s: Unable to find frequency table\n", __func__);
> return -ENOENT;
> diff --git a/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c b/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> index 7c4cd5c634f2..dc112481a408 100644
> --- a/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> +++ b/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> @@ -94,7 +94,7 @@ static int pmi_notifier(struct notifier_block *nb,
> unsigned long event, void *data)
> {
> struct cpufreq_policy *policy = data;
> - struct cpufreq_frequency_table *cbe_freqs;
> + struct cpufreq_frequency_table *cbe_freqs = policy->freq_table;
> u8 node;
>
> /* Should this really be called for CPUFREQ_ADJUST and CPUFREQ_NOTIFY
> @@ -103,7 +103,6 @@ static int pmi_notifier(struct notifier_block *nb,
> if (event == CPUFREQ_START)
> return 0;
>
> - cbe_freqs = cpufreq_frequency_get_table(policy->cpu);
> node = cbe_cpu_to_node(policy->cpu);
>
> pr_debug("got notified, event=%lu, node=%u\n", event, node);
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index 6ceac4f2d4b2..63f760869651 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -787,6 +787,7 @@ __cpufreq_cooling_register(struct device_node *np,
> const struct cpumask *clip_cpus, u32 capacitance,
> get_static_t plat_static_func)
> {
> + struct cpufreq_policy *policy;
> struct thermal_cooling_device *cool_dev;
> struct cpufreq_cooling_device *cpufreq_dev;
> char dev_name[THERMAL_NAME_LENGTH];
> @@ -794,15 +795,24 @@ __cpufreq_cooling_register(struct device_node *np,
> unsigned int freq, i, num_cpus;
> int ret;
>
> - table = cpufreq_frequency_get_table(cpumask_first(clip_cpus));
> + policy = cpufreq_cpu_get(cpumask_first(clip_cpus));
> + if (!policy) {
> + pr_debug("%s: CPUFreq policy not found\n", __func__);
> + return ERR_PTR(-EPROBE_DEFER);
> + }
> +
> + table = policy->freq_table;
> if (!table) {
> pr_debug("%s: CPUFreq table not found\n", __func__);
> - return ERR_PTR(-EPROBE_DEFER);
> + cool_dev = ERR_PTR(-ENODEV);
> + goto put_policy;
> }
>
> cpufreq_dev = kzalloc(sizeof(*cpufreq_dev), GFP_KERNEL);
> - if (!cpufreq_dev)
> - return ERR_PTR(-ENOMEM);
> + if (!cpufreq_dev) {
> + cool_dev = ERR_PTR(-ENOMEM);
> + goto put_policy;
> + }
>
> num_cpus = cpumask_weight(clip_cpus);
> cpufreq_dev->time_in_idle = kcalloc(num_cpus,
> @@ -892,7 +902,7 @@ __cpufreq_cooling_register(struct device_node *np,
> CPUFREQ_POLICY_NOTIFIER);
> mutex_unlock(&cooling_cpufreq_lock);
>
> - return cool_dev;
> + goto put_policy;
>
> remove_idr:
> release_idr(&cpufreq_idr, cpufreq_dev->id);
> @@ -906,6 +916,8 @@ __cpufreq_cooling_register(struct device_node *np,
> kfree(cpufreq_dev->time_in_idle);
> free_cdev:
> kfree(cpufreq_dev);
> +put_policy:
> + cpufreq_cpu_put(policy);
>
> return cool_dev;
> }
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 7ed93c310c08..1342cbc0f25e 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -632,8 +632,6 @@ static inline bool policy_has_boost_freq(struct cpufreq_policy *policy)
> return false;
> }
> #endif
> -/* the following funtion is for cpufreq core use only */
> -struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu);
>
> /* the following are really really optional */
> extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
> --
> 2.7.1.410.g6faf27b
>

Next message: Andrew Lunn: "Re: [PATCH] r8152: Add support for setting MAC to system's Auxiliary MAC address"
Previous message: Tejun Heo: "Re: [PATCH] scsi: device_handler: Remove create_workqueue"
In reply to: Viresh Kumar: "[PATCH V2 2/6] cpufreq: Remove cpufreq_frequency_get_table()"
Next in thread: Viresh Kumar: "Re: [PATCH V2 2/6] cpufreq: Remove cpufreq_frequency_get_table()"
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