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Date: Tue, 5 Feb 2013 09:55:23 -0800
From: amit daniel kachhap <amit.daniel@...sung.com>
To: Zhang Rui <rui.zhang@...el.com>
Cc: Gu1 <gu1@...oxteam.fr>, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Thermal: fix iteration over CPU frequency list
On Tue, Feb 5, 2013 at 1:59 AM, Zhang Rui <rui.zhang@...el.com> wrote:
> On Mon, 2013-02-04 at 11:49 -0800, amit daniel kachhap wrote:
>> On Thu, Jan 31, 2013 at 11:59 PM, Zhang Rui <rui.zhang@...el.com> 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@...oxteam.fr>
>> >> ---
>> >> 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@...el.com>
>> > 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@...el.com>
>> > ---
>> > 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
>
> I have a question about this comment.
> it says that.
> * @level: level of frequency of the CPU
> * e.g level=1 --> 1st MAX FREQ, LEVEL=2 ---> 2nd MAX
> FREQ, ....etc"
> I think this is wrong because level equals cooling state, which starts
> from 0, rather than 1.
> IMO, it should be "level (cooling state) = 0 --> 1st MAX FREQ".
> what do you think?
Yes the comments are not correct. level 0 means 1st max freq.
Thanks,
Amit Daniel
>
>> > @@ -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.
>
> you are right. I'm proposing another patch.
>
> thanks,
> rui
>> > }
>> >
>> > /* 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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>
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