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linux/drivers/cpufreq/cpufreq_governor.h
Viresh Kumar 732b6d617a cpufreq: governor: Serialize governor callbacks 
There are several races reported in cpufreq core around governors (only
ondemand and conservative) by different people.

There are at least two race scenarios present in governor code:
 (a) Concurrent access/updates of governor internal structures.

 It is possible that fields such as 'dbs_data->usage_count', etc.  are
 accessed simultaneously for different policies using same governor
 structure (i.e. CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag unset). And
 because of this we can dereference bad pointers.

 For example consider a system with two CPUs with separate 'struct
 cpufreq_policy' instances. CPU0 governor: ondemand and CPU1: powersave.
 CPU0 switching to powersave and CPU1 to ondemand:
	CPU0				CPU1

	store*				store*

	cpufreq_governor_exit()		cpufreq_governor_init()
					dbs_data = cdata->gdbs_data;

	if (!--dbs_data->usage_count)
		kfree(dbs_data);

					dbs_data->usage_count++;
					*Bad pointer dereference*

 There are other races possible between EXIT and START/STOP/LIMIT as
 well. Its really complicated.

 (b) Switching governor state in bad sequence:

 For example trying to switch a governor to START state, when the
 governor is in EXIT state. There are some checks present in
 __cpufreq_governor() but they aren't sufficient as they compare events
 against 'policy->governor_enabled', where as we need to take governor's
 state into account, which can be used by multiple policies.

These two issues need to be solved separately and the responsibility
should be properly divided between cpufreq and governor core.

The first problem is more about the governor core, as it needs to
protect its structures properly. And the second problem should be fixed
in cpufreq core instead of governor, as its all about sequence of
events.

This patch is trying to solve only the first problem.

There are two types of data we need to protect,
- 'struct common_dbs_data': No matter what, there is going to be a
  single copy of this per governor.
- 'struct dbs_data': With CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag set, we
  will have per-policy copy of this data, otherwise a single copy.

Because of such complexities, the mutex present in 'struct dbs_data' is
insufficient to solve our problem. For example we need to protect
fetching of 'dbs_data' from different structures at the beginning of
cpufreq_governor_dbs(), to make sure it isn't currently being updated.

This can be fixed if we can guarantee serialization of event parsing
code for an individual governor. This is best solved with a mutex per
governor, and the placeholder for that is 'struct common_dbs_data'.

And so this patch moves the mutex from 'struct dbs_data' to 'struct
common_dbs_data' and takes it at the beginning and drops it at the end
of cpufreq_governor_dbs().

Tested with and without following configuration options:

CONFIG_LOCKDEP_SUPPORT=y
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_PI_LIST=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_PROVE_LOCKING=y
CONFIG_LOCKDEP=y
CONFIG_DEBUG_ATOMIC_SLEEP=y

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-06-15 15:42:53 +02:00

279 lines
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/*
* drivers/cpufreq/cpufreq_governor.h
*
* Header file for CPUFreq governors common code
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
* (C) 2009 Alexander Clouter <alex@digriz.org.uk>
* (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _CPUFREQ_GOVERNOR_H
#define _CPUFREQ_GOVERNOR_H
#include <linux/cpufreq.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/mutex.h>
/*
* The polling frequency depends on the capability of the processor. Default
* polling frequency is 1000 times the transition latency of the processor. The
* governor will work on any processor with transition latency <= 10ms, using
* appropriate sampling rate.
*
* For CPUs with transition latency > 10ms (mostly drivers with CPUFREQ_ETERNAL)
* this governor will not work. All times here are in us (micro seconds).
*/
#define MIN_SAMPLING_RATE_RATIO (2)
#define LATENCY_MULTIPLIER (1000)
#define MIN_LATENCY_MULTIPLIER (20)
#define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)
/* Ondemand Sampling types */
enum {OD_NORMAL_SAMPLE, OD_SUB_SAMPLE};
/*
* Macro for creating governors sysfs routines
*
* - gov_sys: One governor instance per whole system
* - gov_pol: One governor instance per policy
*/
/* Create attributes */
#define gov_sys_attr_ro(_name) \
static struct global_attr _name##_gov_sys = \
__ATTR(_name, 0444, show_##_name##_gov_sys, NULL)
#define gov_sys_attr_rw(_name) \
static struct global_attr _name##_gov_sys = \
__ATTR(_name, 0644, show_##_name##_gov_sys, store_##_name##_gov_sys)
#define gov_pol_attr_ro(_name) \
static struct freq_attr _name##_gov_pol = \
__ATTR(_name, 0444, show_##_name##_gov_pol, NULL)
#define gov_pol_attr_rw(_name) \
static struct freq_attr _name##_gov_pol = \
__ATTR(_name, 0644, show_##_name##_gov_pol, store_##_name##_gov_pol)
#define gov_sys_pol_attr_rw(_name) \
gov_sys_attr_rw(_name); \
gov_pol_attr_rw(_name)
#define gov_sys_pol_attr_ro(_name) \
gov_sys_attr_ro(_name); \
gov_pol_attr_ro(_name)
/* Create show/store routines */
#define show_one(_gov, file_name) \
static ssize_t show_##file_name##_gov_sys \
(struct kobject *kobj, struct attribute *attr, char *buf) \
{ \
struct _gov##_dbs_tuners *tuners = _gov##_dbs_cdata.gdbs_data->tuners; \
return sprintf(buf, "%u\n", tuners->file_name); \
} \
\
static ssize_t show_##file_name##_gov_pol \
(struct cpufreq_policy *policy, char *buf) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
struct _gov##_dbs_tuners *tuners = dbs_data->tuners; \
return sprintf(buf, "%u\n", tuners->file_name); \
}
#define store_one(_gov, file_name) \
static ssize_t store_##file_name##_gov_sys \
(struct kobject *kobj, struct attribute *attr, const char *buf, size_t count) \
{ \
struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
return store_##file_name(dbs_data, buf, count); \
} \
\
static ssize_t store_##file_name##_gov_pol \
(struct cpufreq_policy *policy, const char *buf, size_t count) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
return store_##file_name(dbs_data, buf, count); \
}
#define show_store_one(_gov, file_name) \
show_one(_gov, file_name); \
store_one(_gov, file_name)
/* create helper routines */
#define define_get_cpu_dbs_routines(_dbs_info) \
static struct cpu_dbs_common_info *get_cpu_cdbs(int cpu) \
{ \
return &per_cpu(_dbs_info, cpu).cdbs; \
} \
\
static void *get_cpu_dbs_info_s(int cpu) \
{ \
return &per_cpu(_dbs_info, cpu); \
}
/*
* Abbreviations:
* dbs: used as a shortform for demand based switching It helps to keep variable
* names smaller, simpler
* cdbs: common dbs
* od_*: On-demand governor
* cs_*: Conservative governor
*/
/* Per cpu structures */
struct cpu_dbs_common_info {
int cpu;
u64 prev_cpu_idle;
u64 prev_cpu_wall;
u64 prev_cpu_nice;
/*
* Used to keep track of load in the previous interval. However, when
* explicitly set to zero, it is used as a flag to ensure that we copy
* the previous load to the current interval only once, upon the first
* wake-up from idle.
*/
unsigned int prev_load;
struct cpufreq_policy *cur_policy;
struct delayed_work work;
/*
* percpu mutex that serializes governor limit change with gov_dbs_timer
* invocation. We do not want gov_dbs_timer to run when user is changing
* the governor or limits.
*/
struct mutex timer_mutex;
ktime_t time_stamp;
};
struct od_cpu_dbs_info_s {
struct cpu_dbs_common_info cdbs;
struct cpufreq_frequency_table *freq_table;
unsigned int freq_lo;
unsigned int freq_lo_jiffies;
unsigned int freq_hi_jiffies;
unsigned int rate_mult;
unsigned int sample_type:1;
};
struct cs_cpu_dbs_info_s {
struct cpu_dbs_common_info cdbs;
unsigned int down_skip;
unsigned int requested_freq;
unsigned int enable:1;
};
/* Per policy Governors sysfs tunables */
struct od_dbs_tuners {
unsigned int ignore_nice_load;
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int powersave_bias;
unsigned int io_is_busy;
};
struct cs_dbs_tuners {
unsigned int ignore_nice_load;
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int down_threshold;
unsigned int freq_step;
};
/* Common Governor data across policies */
struct dbs_data;
struct common_dbs_data {
/* Common across governors */
#define GOV_ONDEMAND 0
#define GOV_CONSERVATIVE 1
int governor;
struct attribute_group *attr_group_gov_sys; /* one governor - system */
struct attribute_group *attr_group_gov_pol; /* one governor - policy */
/*
* Common data for platforms that don't set
* CPUFREQ_HAVE_GOVERNOR_PER_POLICY
*/
struct dbs_data *gdbs_data;
struct cpu_dbs_common_info *(*get_cpu_cdbs)(int cpu);
void *(*get_cpu_dbs_info_s)(int cpu);
void (*gov_dbs_timer)(struct work_struct *work);
void (*gov_check_cpu)(int cpu, unsigned int load);
int (*init)(struct dbs_data *dbs_data, bool notify);
void (*exit)(struct dbs_data *dbs_data, bool notify);
/* Governor specific ops, see below */
void *gov_ops;
/*
* Protects governor's data (struct dbs_data and struct common_dbs_data)
*/
struct mutex mutex;
};
/* Governor Per policy data */
struct dbs_data {
struct common_dbs_data *cdata;
unsigned int min_sampling_rate;
int usage_count;
void *tuners;
};
/* Governor specific ops, will be passed to dbs_data->gov_ops */
struct od_ops {
void (*powersave_bias_init_cpu)(int cpu);
unsigned int (*powersave_bias_target)(struct cpufreq_policy *policy,
unsigned int freq_next, unsigned int relation);
void (*freq_increase)(struct cpufreq_policy *policy, unsigned int freq);
};
static inline int delay_for_sampling_rate(unsigned int sampling_rate)
{
int delay = usecs_to_jiffies(sampling_rate);
/* We want all CPUs to do sampling nearly on same jiffy */
if (num_online_cpus() > 1)
delay -= jiffies % delay;
return delay;
}
#define declare_show_sampling_rate_min(_gov) \
static ssize_t show_sampling_rate_min_gov_sys \
(struct kobject *kobj, struct attribute *attr, char *buf) \
{ \
struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
return sprintf(buf, "%u\n", dbs_data->min_sampling_rate); \
} \
\
static ssize_t show_sampling_rate_min_gov_pol \
(struct cpufreq_policy *policy, char *buf) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
return sprintf(buf, "%u\n", dbs_data->min_sampling_rate); \
}
extern struct mutex cpufreq_governor_lock;
void dbs_check_cpu(struct dbs_data *dbs_data, int cpu);
bool need_load_eval(struct cpu_dbs_common_info *cdbs,
unsigned int sampling_rate);
int cpufreq_governor_dbs(struct cpufreq_policy *policy,
struct common_dbs_data *cdata, unsigned int event);
void gov_queue_work(struct dbs_data *dbs_data, struct cpufreq_policy *policy,
unsigned int delay, bool all_cpus);
void od_register_powersave_bias_handler(unsigned int (*f)
(struct cpufreq_policy *, unsigned int, unsigned int),
unsigned int powersave_bias);
void od_unregister_powersave_bias_handler(void);
#endif /* _CPUFREQ_GOVERNOR_H */
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