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cpufreq: userspace: Use fine-grained mutex in userspace governor

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The userspace governor currently uses a big global mutex to avoid the
race condition on the governor_data field of cpufreq_policy structure.

This leads to a low concurrency if multiple userspace applications are
trying to set the speed of different policies at the same time.

Introduce a per-policy mutex to allow the updating of different policies
to be performed concurrently, improving overall concurrency.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Liao Chang 2023-09-12 06:10:56 +00:00 committed by Rafael J. Wysocki
parent 842c34a266
commit 285189c573
1 changed files with 39 additions and 28 deletions
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67
drivers/cpufreq/cpufreq_userspace.c
View file

@ -16,7 +16,11 @@
#include <linux/slab.h>
static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
static DEFINE_MUTEX(userspace_mutex);
struct userspace_policy {
unsigned int setspeed;
struct mutex mutex;
};
/**
* cpufreq_set - set the CPU frequency
@ -28,19 +32,19 @@ static DEFINE_MUTEX(userspace_mutex);
static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
{
int ret = -EINVAL;
unsigned int *setspeed = policy->governor_data;
struct userspace_policy *userspace = policy->governor_data;
pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
mutex_lock(&userspace_mutex);
mutex_lock(&userspace->mutex);
if (!per_cpu(cpu_is_managed, policy->cpu))
goto err;
*setspeed = freq;
userspace->setspeed = freq;
ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
err:
mutex_unlock(&userspace_mutex);
mutex_unlock(&userspace->mutex);
return ret;
}
@ -51,67 +55,74 @@ static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
{
unsigned int *setspeed;
struct userspace_policy *userspace;
setspeed = kzalloc(sizeof(*setspeed), GFP_KERNEL);
if (!setspeed)
userspace = kzalloc(sizeof(*userspace), GFP_KERNEL);
if (!userspace)
return -ENOMEM;
policy->governor_data = setspeed;
mutex_init(&userspace->mutex);
policy->governor_data = userspace;
return 0;
}
/*
* Any routine that writes to the policy struct will hold the "rwsem" of
* policy struct that means it is free to free "governor_data" here.
*/
static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
{
mutex_lock(&userspace_mutex);
kfree(policy->governor_data);
policy->governor_data = NULL;
mutex_unlock(&userspace_mutex);
}
static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
{
unsigned int *setspeed = policy->governor_data;
struct userspace_policy *userspace = policy->governor_data;
BUG_ON(!policy->cur);
pr_debug("started managing cpu %u\n", policy->cpu);
mutex_lock(&userspace_mutex);
mutex_lock(&userspace->mutex);
per_cpu(cpu_is_managed, policy->cpu) = 1;
*setspeed = policy->cur;
mutex_unlock(&userspace_mutex);
userspace->setspeed = policy->cur;
mutex_unlock(&userspace->mutex);
return 0;
}
static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
{
unsigned int *setspeed = policy->governor_data;
struct userspace_policy *userspace = policy->governor_data;
pr_debug("managing cpu %u stopped\n", policy->cpu);
mutex_lock(&userspace_mutex);
mutex_lock(&userspace->mutex);
per_cpu(cpu_is_managed, policy->cpu) = 0;
*setspeed = 0;
mutex_unlock(&userspace_mutex);
userspace->setspeed = 0;
mutex_unlock(&userspace->mutex);
}
static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
{
unsigned int *setspeed = policy->governor_data;
struct userspace_policy *userspace = policy->governor_data;
mutex_lock(&userspace_mutex);
mutex_lock(&userspace->mutex);
pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
policy->cpu, policy->min, policy->max, policy->cur, *setspeed);
policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);
if (policy->max < *setspeed)
__cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
else if (policy->min > *setspeed)
__cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
if (policy->max < userspace->setspeed)
__cpufreq_driver_target(policy, policy->max,
CPUFREQ_RELATION_H);
else if (policy->min > userspace->setspeed)
__cpufreq_driver_target(policy, policy->min,
CPUFREQ_RELATION_L);
else
__cpufreq_driver_target(policy, *setspeed, CPUFREQ_RELATION_L);
__cpufreq_driver_target(policy, userspace->setspeed,
CPUFREQ_RELATION_L);
mutex_unlock(&userspace_mutex);
mutex_unlock(&userspace->mutex);
}
static struct cpufreq_governor cpufreq_gov_userspace = {