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Message-ID: <20230912061057.2516963-1-liaochang1@huawei.com>
Date: Tue, 12 Sep 2023 06:10:56 +0000
From: Liao Chang <liaochang1@...wei.com>
To: <rafael@...nel.org>, <viresh.kumar@...aro.org>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] cpufreq: userspace: Use fine-grained mutex in userspace governor
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. This
patch introduces a per-policy mutex to allow the updating of different
policies to be performed concurrently, improving overall concurrency.
Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
drivers/cpufreq/cpufreq_userspace.c | 69 +++++++++++++++++------------
1 file changed, 40 insertions(+), 29 deletions(-)
diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
index 50a4d7846580..442e31060d62 100644
--- a/drivers/cpufreq/cpufreq_userspace.c
+++ b/drivers/cpufreq/cpufreq_userspace.c
@@ -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);
-
- 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);
+ policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);
+
+ 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 = {
--
2.34.1
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