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author | Liao Chang <liaochang1@huawei.com> | 2023-09-12 06:10:56 +0000 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2023-10-06 22:01:26 +0200 |
commit | 285189c57391360701af348cd57ca0ba8cbf7ff6 (patch) | |
tree | 4b3d643adf073d191e41598df3f226fd116d349d /drivers/cpufreq/cpufreq_userspace.c | |
parent | 842c34a2668f68ebe15d0fc9dc19d33733bb428d (diff) | |
download | lwn-285189c57391360701af348cd57ca0ba8cbf7ff6.tar.gz lwn-285189c57391360701af348cd57ca0ba8cbf7ff6.zip |
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.
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>
Diffstat (limited to 'drivers/cpufreq/cpufreq_userspace.c')
-rw-r--r-- | drivers/cpufreq/cpufreq_userspace.c | 69 |
1 files 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 = { |