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.ku...@linaro.org>
> ---
>  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
> 

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