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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>
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842c34a266
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285189c573
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@ -16,7 +16,11 @@
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#include <linux/slab.h>
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static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
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static DEFINE_MUTEX(userspace_mutex);
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struct userspace_policy {
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unsigned int setspeed;
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struct mutex mutex;
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};
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/**
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* cpufreq_set - set the CPU frequency
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@ -28,19 +32,19 @@ static DEFINE_MUTEX(userspace_mutex);
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static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
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{
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int ret = -EINVAL;
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unsigned int *setspeed = policy->governor_data;
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struct userspace_policy *userspace = policy->governor_data;
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pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
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mutex_lock(&userspace_mutex);
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mutex_lock(&userspace->mutex);
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if (!per_cpu(cpu_is_managed, policy->cpu))
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goto err;
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*setspeed = freq;
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userspace->setspeed = freq;
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ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
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err:
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mutex_unlock(&userspace_mutex);
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mutex_unlock(&userspace->mutex);
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return ret;
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}
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@ -51,67 +55,74 @@ static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
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static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
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{
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unsigned int *setspeed;
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struct userspace_policy *userspace;
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setspeed = kzalloc(sizeof(*setspeed), GFP_KERNEL);
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if (!setspeed)
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userspace = kzalloc(sizeof(*userspace), GFP_KERNEL);
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if (!userspace)
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return -ENOMEM;
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policy->governor_data = setspeed;
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mutex_init(&userspace->mutex);
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policy->governor_data = userspace;
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return 0;
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}
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/*
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* Any routine that writes to the policy struct will hold the "rwsem" of
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* policy struct that means it is free to free "governor_data" here.
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*/
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static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
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{
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mutex_lock(&userspace_mutex);
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kfree(policy->governor_data);
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policy->governor_data = NULL;
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mutex_unlock(&userspace_mutex);
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}
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static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
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{
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unsigned int *setspeed = policy->governor_data;
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struct userspace_policy *userspace = policy->governor_data;
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BUG_ON(!policy->cur);
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pr_debug("started managing cpu %u\n", policy->cpu);
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mutex_lock(&userspace_mutex);
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mutex_lock(&userspace->mutex);
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per_cpu(cpu_is_managed, policy->cpu) = 1;
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*setspeed = policy->cur;
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mutex_unlock(&userspace_mutex);
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userspace->setspeed = policy->cur;
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mutex_unlock(&userspace->mutex);
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return 0;
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}
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static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
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{
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unsigned int *setspeed = policy->governor_data;
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struct userspace_policy *userspace = policy->governor_data;
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pr_debug("managing cpu %u stopped\n", policy->cpu);
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mutex_lock(&userspace_mutex);
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mutex_lock(&userspace->mutex);
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per_cpu(cpu_is_managed, policy->cpu) = 0;
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*setspeed = 0;
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mutex_unlock(&userspace_mutex);
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userspace->setspeed = 0;
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mutex_unlock(&userspace->mutex);
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}
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static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
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{
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unsigned int *setspeed = policy->governor_data;
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struct userspace_policy *userspace = policy->governor_data;
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mutex_lock(&userspace_mutex);
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mutex_lock(&userspace->mutex);
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pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
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policy->cpu, policy->min, policy->max, policy->cur, *setspeed);
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policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);
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if (policy->max < *setspeed)
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__cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
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else if (policy->min > *setspeed)
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__cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
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if (policy->max < userspace->setspeed)
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__cpufreq_driver_target(policy, policy->max,
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CPUFREQ_RELATION_H);
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else if (policy->min > userspace->setspeed)
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__cpufreq_driver_target(policy, policy->min,
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CPUFREQ_RELATION_L);
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else
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__cpufreq_driver_target(policy, *setspeed, CPUFREQ_RELATION_L);
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__cpufreq_driver_target(policy, userspace->setspeed,
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CPUFREQ_RELATION_L);
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mutex_unlock(&userspace_mutex);
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mutex_unlock(&userspace->mutex);
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}
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static struct cpufreq_governor cpufreq_gov_userspace = {
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