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Date: Tue, 05 Feb 2013 17:59:59 +0800
From: Zhang Rui <rui.zhang@...el.com>
To: amit daniel kachhap <amit.daniel@...sung.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 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?
> > @@ -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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