Re: [PATCH] Thermal: fix iteration over CPU frequency list

[amit daniel kachhap]

On Thu, Jan 31, 2013 at 11:59 PM, Zhang Rui <rui.zhang@xxxxxxxxx> wrote:
> On Thu, 2013-01-24 at 16:24 +0100, Gu1 wrote:
>> In different places in the Thermal code, the CPU frequency list is iterated
>> in an incorrect way, leading to endless loops when the frequency list contains
>> a CPUFREQ_TABLE_INVALID entry, which is the case by default in the the Exynos
>> 4x12 cpufreq driver, for example.
>>
>> The frequency list is iterated with a while loop, and when a
>> CPUFREQ_TABLE_INVALID entry is encountered, the continue; statement is used to
>> skip it, but the index is not incremented, causing an endless loop.
>>
>> A similar bug was fixed by hongbo.zhang in commit:
>>   Thermal: fix bug of counting cpu frequencies
>>
>> Signed-off-by: Gu1 <gu1@xxxxxxxxxxxx>
>> ---
>>  drivers/thermal/cpu_cooling.c    | 8 +++-----
>>  drivers/thermal/exynos_thermal.c | 9 +++++----
>>  2 files changed, 8 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
>> index 836828e..51acd26 100644
>> --- a/drivers/thermal/cpu_cooling.c
>> +++ b/drivers/thermal/cpu_cooling.c
>> @@ -123,7 +123,7 @@ static int is_cpufreq_valid(int cpu)
>>   */
>>  static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>>  {
>> -     int ret = 0, i = 0;
>> +     int ret = 0, i;
>>       unsigned long level_index;
>>       bool descend = false;
>>       struct cpufreq_frequency_table *table =
>> @@ -131,7 +131,7 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>>       if (!table)
>>               return ret;
>>
>> -     while (table[i].frequency != CPUFREQ_TABLE_END) {
>> +     for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
>>               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>>                       continue;
>>
>> @@ -145,7 +145,6 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>>               /*return if level matched and table in descending order*/
>>               if (descend && i == level)
>>                       return table[i].frequency;
>> -             i++;
>>       }
>>       i--;
>>
>> @@ -154,13 +153,12 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>>       level_index = i - level;
>>
>>       /*Scan the table in reverse order and match the level*/
>> -     while (i >= 0) {
>> +     for (; i >= 0; i--) {
>>               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>>                       continue;
>>               /*return if level matched*/
>>               if (i == level_index)
>>                       return table[i].frequency;
>> -             i--;
>>       }
>>       return ret;
>>  }
>
> so the "level" parameter is the index in the frequency table, right?
>
>> diff --git a/drivers/thermal/exynos_thermal.c b/drivers/thermal/exynos_thermal.c
>> index 224751e..fa9e1d7 100644
>> --- a/drivers/thermal/exynos_thermal.c
>> +++ b/drivers/thermal/exynos_thermal.c
>> @@ -233,7 +233,8 @@ static int exynos_get_crit_temp(struct thermal_zone_device *thermal,
>>
>>  static int exynos_get_frequency_level(unsigned int cpu, unsigned int freq)
>>  {
>> -     int i = 0, ret = -EINVAL;
>> +     int i, ret = -EINVAL;
>> +     unsigned int count = 0;
>>       struct cpufreq_frequency_table *table = NULL;
>>  #ifdef CONFIG_CPU_FREQ
>>       table = cpufreq_frequency_get_table(cpu);
>> @@ -241,12 +242,12 @@ static int exynos_get_frequency_level(unsigned int cpu, unsigned int freq)
>>       if (!table)
>>               return ret;
>>
>> -     while (table[i].frequency != CPUFREQ_TABLE_END) {
>> +     for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
>>               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>>                       continue;
>>               if (table[i].frequency == freq)
>> -                     return i;
>> -             i++;
>> +                     return count;
>> +             count++;
>>       }
>>       return ret;
>>  }
>
> but we ignore the invalid entry here.
>
> take the following cpufreq table for example, with your patch,
> entry  frequency
>  0     2.4G
>  1     invalid
>  2     2G
>  3     invalid
>  4     1.6G
>  5     end
>
> in exynos_get_frequency_level(), freq 1.6G is translated to level 2,
> because count is increased only twice, for entry 0 and entry 2, right?

Hi Rui,

Gui fixes looks fine for infinite loop issue. After Gui's fixes 1.6G
in translated to level 4 which is fine.

Thanks,
Amit Daniel

>
> but then, in get_cpu_frequency(), level 2 is translated to 2G HZ, which
> I do not think is what we want.
>
> I think we are doing something wrong here, and here is a cleanup patch I made
> to fix this issue, please review.
>
> From a868d68fdcd94a29ac9d3998283119a453decb4b Mon Sep 17 00:00:00 2001
> From: Zhang Rui <rui.zhang@xxxxxxxxx>
> Date: Fri, 1 Feb 2013 15:41:47 +0800
> Subject: [PATCH] Thermal cpu_cooling: fix inconsistent use of CPU frequency
>  table
>
> there are three kinds of entries in CPU frequency table.
> 1. invalid entry, its frequency is CPUFREQ_ENTRY_INVALID.
> 2. duplicate entry, two entry may share the same frequency,
>    And we should treat it as on valid entry.
> 3. valid entry with a proper frequency.
>
> And when talking about cpufreq cooling device cooling state,
> it should be the same thing, in both cpu_cooling.c and its users,
> AKA, max_cooling_state of a cpufreq cooling device equals the
> number of VALID entries (type #3 above) in CPU frequency table.
> And when setting a cpufreq cooling device to state X, it means set
> the cpufreq cooling device to Xth maximum frequency in the
> cpufreq frequency table.
>
> This patch does a cleanup in both drivers/thermal/cpu_cooling.c
> and drivers/thermal/exynos_thermal.c to make them be consistent
> in using cpu level/cpufreq cooling state.
>
> Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
> ---
>  drivers/thermal/cpu_cooling.c    |  122 ++++++++++++++++++++++++--------------
>  drivers/thermal/exynos_thermal.c |   17 +-----
>  include/linux/cpu_cooling.h      |   12 ++++
>  3 files changed, 91 insertions(+), 60 deletions(-)
>
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index 836828e..c16795b 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -116,6 +116,40 @@ static int is_cpufreq_valid(int cpu)
>  }
>
>  /**
> + * cpufreq_cooling_get_max_level - function to get max valid cpufreq levels
> + * @cpu: cpu for which frequency is fetched.
> + */
> +int cpufreq_cooling_get_max_level(unsigned int cpu)
> +{
> +       int i, level;
> +       unsigned int freq = CPUFREQ_ENTRY_INVALID;
> +       struct cpufreq_frequency_table *table =
> +                                       cpufreq_frequency_get_table(cpu);
> +
> +       if (!table)
> +               return -EINVAL;
> +
> +       for (i = 0, level = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
> +               /* Invalid entry */
> +               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> +                       continue;
> +
> +               /* Duplicate entry */
> +               if (freq == table[i].frequency)
> +                       continue;
> +
> +               /* First valid entry */
> +               if (freq == CPUFREQ_ENTRY_INVALID)
> +                       freq = table[i].frequency;
> +
> +               level++;
> +       }
> +
> +       return level;
> +}
> +EXPORT_SYMBOL(cpufreq_cooling_get_max_level);
> +
> +/**
>   * get_cpu_frequency - get the absolute value of frequency from level.
>   * @cpu: cpu for which frequency is fetched.
>   * @level: level of frequency of the CPU
> @@ -123,46 +157,58 @@ static int is_cpufreq_valid(int cpu)
>   */
>  static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
>  {
> -       int ret = 0, i = 0;
> -       unsigned long level_index;
> +       int i, count;
> +       int max_level;
> +       unsigned int freq = CPUFREQ_ENTRY_INVALID;
>         bool descend = false;
>         struct cpufreq_frequency_table *table =
>                                         cpufreq_frequency_get_table(cpu);
> -       if (!table)
> -               return ret;
>
> -       while (table[i].frequency != CPUFREQ_TABLE_END) {
> +       max_level = cpufreq_cooling_get_max_level(cpu);
> +
> +       if (max_level < 0)
> +               return max_level;
> +
> +       if (level > max_level)
> +               return -EINVAL;
> +
> +       for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
>                 if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>                         continue;
>
> -               /*check if table in ascending or descending order*/
> -               if ((table[i + 1].frequency != CPUFREQ_TABLE_END) &&
> -                       (table[i + 1].frequency < table[i].frequency)
> -                       && !descend) {
> -                       descend = true;
> +               if (freq == CPUFREQ_ENTRY_INVALID)
> +                       /* first valid entry */
> +                       freq = table[i].frequency;
> +               else if (freq == table[i].frequency)
> +                       /* duplicate entry */
> +                       continue;
> +               else {
> +                       /* two valid entries, check frequency order */
> +                       descend = !!(freq > table[i].frequency);
> +                       break;
>                 }
> -
> -               /*return if level matched and table in descending order*/
> -               if (descend && i == level)
> -                       return table[i].frequency;
> -               i++;
>         }
> -       i--;
>
> -       if (level > i || descend)
> -               return ret;
> -       level_index = i - level;
> +       /* level equals "the index of valid entries" in cpufreq table */
> +       level = descend ? level : max_level - level + 1;
>
> -       /*Scan the table in reverse order and match the level*/
> -       while (i >= 0) {
> +       freq = CPUFREQ_ENTRY_INVALID;
> +       for (i = 0, count = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
> +               /* ignore invalid entry */
>                 if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>                         continue;
> -               /*return if level matched*/
> -               if (i == level_index)
> +
> +               if (freq == CPUFREQ_ENTRY_INVALID)
> +                       /* first valid entry */
> +                       freq = table[i].frequency;
> +               else if (freq == table[i].frequency)
> +                       /* ignore duplicate entry */
> +                       continue;
> +               count++;
> +               if (level == count)
>                         return table[i].frequency;
> -               i--;
>         }
> -       return ret;
> +       return -ENODEV;
>  }
>
>  /**
> @@ -244,29 +290,17 @@ static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
>         struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
>         struct cpumask *maskPtr = &cpufreq_device->allowed_cpus;
>         unsigned int cpu;
> -       struct cpufreq_frequency_table *table;
> -       unsigned long count = 0;
> -       int i = 0;
> +       int max_level;
>
>         cpu = cpumask_any(maskPtr);
> -       table = cpufreq_frequency_get_table(cpu);
> -       if (!table) {
> -               *state = 0;
> -               return 0;
> -       }
> -
> -       for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
> -               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> -                       continue;
> -               count++;
> -       }
>
> -       if (count > 0) {
> -               *state = --count;
> -               return 0;
> -       }
> +       max_level = cpufreq_cooling_get_max_level(cpu);
>
> -       return -EINVAL;
> +       if (max_level < 0)
> +               return max_level;
> +       else
> +               *state = max_level;
> +       return 0;
>  }
>
>  /**
> diff --git a/drivers/thermal/exynos_thermal.c b/drivers/thermal/exynos_thermal.c
> index cd71e24..5ac2de1 100644
> --- a/drivers/thermal/exynos_thermal.c
> +++ b/drivers/thermal/exynos_thermal.c
> @@ -241,22 +241,7 @@ static int exynos_get_crit_temp(struct thermal_zone_device *thermal,
>
>  static int exynos_get_frequency_level(unsigned int cpu, unsigned int freq)
>  {
> -       int i = 0, ret = -EINVAL;
> -       struct cpufreq_frequency_table *table = NULL;
> -#ifdef CONFIG_CPU_FREQ
> -       table = cpufreq_frequency_get_table(cpu);
> -#endif
> -       if (!table)
> -               return ret;
> -
> -       while (table[i].frequency != CPUFREQ_TABLE_END) {
> -               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> -                       continue;
> -               if (table[i].frequency == freq)
> -                       return i;
> -               i++;
> -       }
> -       return ret;
> +       return cpufreq_cooling_get_max_level(cpu);
This is not correct as it always gives the highest level.
>  }
>
>  /* Bind callback functions for thermal zone */
> diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
> index 40b4ef5..2de9319 100644
> --- a/include/linux/cpu_cooling.h
> +++ b/include/linux/cpu_cooling.h
> @@ -42,6 +42,14 @@ struct thermal_cooling_device *cpufreq_cooling_register(
>   * @cdev: thermal cooling device pointer.
>   */
>  void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev);
> +
> +/**
> + * cpufreq_cooling_get_max_level - function to get maxinum cooling state
> + *                                of a cpufreq cooling device
> + * @cpu: cpu of which frequency is fetched.
> + */
> +int cpufreq_cooling_get_max_level(unsigned int cpu);
> +
>  #else /* !CONFIG_CPU_THERMAL */
>  static inline struct thermal_cooling_device *cpufreq_cooling_register(
>         const struct cpumask *clip_cpus)
> @@ -53,6 +61,10 @@ static inline void cpufreq_cooling_unregister(
>  {
>         return;
>  }
> +static inline int cpufreq_cooling_get_max_level(unsigned int cpu)
> +{
> +       return -ENODEV;
> +}
>  #endif /* CONFIG_CPU_THERMAL */
>
>  #endif /* __CPU_COOLING_H__ */
> --
> 1.7.9.5
>
>
>
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