cpufreq: convert cpufreq_driver to using RCU

We eventually would like to remove the rwlock cpufreq_driver_lock or
convert it back to a spinlock and protect the read sections with RCU.
The first step in that direction is to make cpufreq_driver use RCU.
I don't see an easy wasy to protect the cpufreq_cpu_data structure
with RCU, so I am leaving it with the rwlock for now since under
certain configs __cpufreq_cpu_get is a hot spot with 256+ cores.

[rjw: Subject, changelog, white space]
Signed-off-by: Nathan Zimmer <nzimmer@sgi.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:
Nathan Zimmer 2013-04-04 14:53:25 +00:00 committed by Rafael J. Wysocki
parent 6eb1c37742
commit 5800043b24

View File

@ -39,7 +39,7 @@
* level driver of CPUFreq support, and its spinlock. This lock
* also protects the cpufreq_cpu_data array.
*/
static struct cpufreq_driver *cpufreq_driver;
static struct cpufreq_driver __rcu *cpufreq_driver;
static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
#ifdef CONFIG_HOTPLUG_CPU
/* This one keeps track of the previously set governor of a removed CPU */
@ -130,27 +130,35 @@ static DEFINE_MUTEX(cpufreq_governor_mutex);
bool have_governor_per_policy(void)
{
return cpufreq_driver->have_governor_per_policy;
bool have_governor_per_policy;
rcu_read_lock();
have_governor_per_policy =
rcu_dereference(cpufreq_driver)->have_governor_per_policy;
rcu_read_unlock();
return have_governor_per_policy;
}
static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
{
struct cpufreq_policy *data;
struct cpufreq_driver *driver;
unsigned long flags;
if (cpu >= nr_cpu_ids)
goto err_out;
/* get the cpufreq driver */
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (!driver)
goto err_out_unlock;
if (!try_module_get(driver->owner))
goto err_out_unlock;
read_lock_irqsave(&cpufreq_driver_lock, flags);
if (!cpufreq_driver)
goto err_out_unlock;
if (!try_module_get(cpufreq_driver->owner))
goto err_out_unlock;
/* get the CPU */
data = per_cpu(cpufreq_cpu_data, cpu);
@ -161,12 +169,14 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
goto err_out_put_module;
read_unlock_irqrestore(&cpufreq_driver_lock, flags);
rcu_read_unlock();
return data;
err_out_put_module:
module_put(cpufreq_driver->owner);
err_out_unlock:
module_put(driver->owner);
read_unlock_irqrestore(&cpufreq_driver_lock, flags);
err_out_unlock:
rcu_read_unlock();
err_out:
return NULL;
}
@ -189,7 +199,9 @@ static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs)
{
if (!sysfs)
kobject_put(&data->kobj);
module_put(cpufreq_driver->owner);
rcu_read_lock();
module_put(rcu_dereference(cpufreq_driver)->owner);
rcu_read_unlock();
}
void cpufreq_cpu_put(struct cpufreq_policy *data)
@ -257,7 +269,9 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy,
if (cpufreq_disabled())
return;
freqs->flags = cpufreq_driver->flags;
rcu_read_lock();
freqs->flags = rcu_dereference(cpufreq_driver)->flags;
rcu_read_unlock();
pr_debug("notification %u of frequency transition to %u kHz\n",
state, freqs->new);
@ -268,7 +282,7 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy,
* which is not equal to what the cpufreq core thinks is
* "old frequency".
*/
if (!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
if (!(freqs->flags & CPUFREQ_CONST_LOOPS)) {
if ((policy) && (policy->cpu == freqs->cpu) &&
(policy->cur) && (policy->cur != freqs->old)) {
pr_debug("Warning: CPU frequency is"
@ -334,11 +348,21 @@ static int cpufreq_parse_governor(char *str_governor, unsigned int *policy,
struct cpufreq_governor **governor)
{
int err = -EINVAL;
struct cpufreq_driver *driver;
bool has_setpolicy;
bool has_target;
if (!cpufreq_driver)
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (!driver) {
rcu_read_unlock();
goto out;
}
has_setpolicy = driver->setpolicy ? true : false;
has_target = driver->target ? true : false;
rcu_read_unlock();
if (cpufreq_driver->setpolicy) {
if (has_setpolicy) {
if (!strnicmp(str_governor, "performance", CPUFREQ_NAME_LEN)) {
*policy = CPUFREQ_POLICY_PERFORMANCE;
err = 0;
@ -347,7 +371,7 @@ static int cpufreq_parse_governor(char *str_governor, unsigned int *policy,
*policy = CPUFREQ_POLICY_POWERSAVE;
err = 0;
}
} else if (cpufreq_driver->target) {
} else if (has_target) {
struct cpufreq_governor *t;
mutex_lock(&cpufreq_governor_mutex);
@ -498,7 +522,12 @@ static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
*/
static ssize_t show_scaling_driver(struct cpufreq_policy *policy, char *buf)
{
return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n", cpufreq_driver->name);
ssize_t size;
rcu_read_lock();
size = scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n",
rcu_dereference(cpufreq_driver)->name);
rcu_read_unlock();
return size;
}
/**
@ -510,10 +539,13 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
ssize_t i = 0;
struct cpufreq_governor *t;
if (!cpufreq_driver->target) {
rcu_read_lock();
if (!rcu_dereference(cpufreq_driver)->target) {
rcu_read_unlock();
i += sprintf(buf, "performance powersave");
goto out;
}
rcu_read_unlock();
list_for_each_entry(t, &cpufreq_governor_list, governor_list) {
if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char))
@ -591,9 +623,15 @@ static ssize_t show_scaling_setspeed(struct cpufreq_policy *policy, char *buf)
static ssize_t show_bios_limit(struct cpufreq_policy *policy, char *buf)
{
unsigned int limit;
int (*bios_limit)(int cpu, unsigned int *limit);
int ret;
if (cpufreq_driver->bios_limit) {
ret = cpufreq_driver->bios_limit(policy->cpu, &limit);
rcu_read_lock();
bios_limit = rcu_dereference(cpufreq_driver)->bios_limit;
rcu_read_unlock();
if (bios_limit) {
ret = bios_limit(policy->cpu, &limit);
if (!ret)
return sprintf(buf, "%u\n", limit);
}
@ -736,6 +774,7 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
{
struct cpufreq_policy new_policy;
struct freq_attr **drv_attr;
struct cpufreq_driver *driver;
unsigned long flags;
int ret = 0;
unsigned int j;
@ -747,28 +786,31 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
return ret;
/* set up files for this cpu device */
drv_attr = cpufreq_driver->attr;
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
drv_attr = driver->attr;
while ((drv_attr) && (*drv_attr)) {
ret = sysfs_create_file(&policy->kobj, &((*drv_attr)->attr));
if (ret)
goto err_out_kobj_put;
goto err_out_unlock;
drv_attr++;
}
if (cpufreq_driver->get) {
if (driver->get) {
ret = sysfs_create_file(&policy->kobj, &cpuinfo_cur_freq.attr);
if (ret)
goto err_out_kobj_put;
goto err_out_unlock;
}
if (cpufreq_driver->target) {
if (driver->target) {
ret = sysfs_create_file(&policy->kobj, &scaling_cur_freq.attr);
if (ret)
goto err_out_kobj_put;
goto err_out_unlock;
}
if (cpufreq_driver->bios_limit) {
if (driver->bios_limit) {
ret = sysfs_create_file(&policy->kobj, &bios_limit.attr);
if (ret)
goto err_out_kobj_put;
goto err_out_unlock;
}
rcu_read_unlock();
write_lock_irqsave(&cpufreq_driver_lock, flags);
for_each_cpu(j, policy->cpus) {
@ -791,12 +833,20 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
policy->user_policy.governor = policy->governor;
if (ret) {
int (*exit)(struct cpufreq_policy *policy);
pr_debug("setting policy failed\n");
if (cpufreq_driver->exit)
cpufreq_driver->exit(policy);
rcu_read_lock();
exit = rcu_dereference(cpufreq_driver)->exit;
rcu_read_unlock();
if (exit)
exit(policy);
}
return ret;
err_out_unlock:
rcu_read_unlock();
err_out_kobj_put:
kobject_put(&policy->kobj);
wait_for_completion(&policy->kobj_unregister);
@ -854,6 +904,8 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
unsigned int j, cpu = dev->id;
int ret = -ENOMEM;
struct cpufreq_policy *policy;
struct cpufreq_driver *driver;
int (*init)(struct cpufreq_policy *policy);
unsigned long flags;
#ifdef CONFIG_HOTPLUG_CPU
struct cpufreq_governor *gov;
@ -888,10 +940,15 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
#endif
#endif
if (!try_module_get(cpufreq_driver->owner)) {
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (!try_module_get(driver->owner)) {
rcu_read_unlock();
ret = -EINVAL;
goto module_out;
}
init = driver->init;
rcu_read_unlock();
policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
if (!policy)
@ -916,7 +973,7 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
/* call driver. From then on the cpufreq must be able
* to accept all calls to ->verify and ->setpolicy for this CPU
*/
ret = cpufreq_driver->init(policy);
ret = init(policy);
if (ret) {
pr_debug("initialization failed\n");
goto err_set_policy_cpu;
@ -951,7 +1008,9 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
goto err_out_unregister;
kobject_uevent(&policy->kobj, KOBJ_ADD);
module_put(cpufreq_driver->owner);
rcu_read_lock();
module_put(rcu_dereference(cpufreq_driver)->owner);
rcu_read_unlock();
pr_debug("initialization complete\n");
return 0;
@ -973,7 +1032,9 @@ err_free_cpumask:
err_free_policy:
kfree(policy);
nomem_out:
module_put(cpufreq_driver->owner);
rcu_read_lock();
module_put(rcu_dereference(cpufreq_driver)->owner);
rcu_read_unlock();
module_out:
return ret;
}
@ -1007,9 +1068,12 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
unsigned int cpu = dev->id, ret, cpus;
unsigned long flags;
struct cpufreq_policy *data;
struct cpufreq_driver *driver;
struct kobject *kobj;
struct completion *cmp;
struct device *cpu_dev;
bool has_target;
int (*exit)(struct cpufreq_policy *policy);
pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
@ -1025,14 +1089,19 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
return -EINVAL;
}
if (cpufreq_driver->target)
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
has_target = driver->target ? true : false;
exit = driver->exit;
if (has_target)
__cpufreq_governor(data, CPUFREQ_GOV_STOP);
#ifdef CONFIG_HOTPLUG_CPU
if (!cpufreq_driver->setpolicy)
if (!driver->setpolicy)
strncpy(per_cpu(cpufreq_cpu_governor, cpu),
data->governor->name, CPUFREQ_NAME_LEN);
#endif
rcu_read_unlock();
WARN_ON(lock_policy_rwsem_write(cpu));
cpus = cpumask_weight(data->cpus);
@ -1091,13 +1160,13 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
wait_for_completion(cmp);
pr_debug("wait complete\n");
if (cpufreq_driver->exit)
cpufreq_driver->exit(data);
if (exit)
exit(data);
free_cpumask_var(data->related_cpus);
free_cpumask_var(data->cpus);
kfree(data);
} else if (cpufreq_driver->target) {
} else if (has_target) {
__cpufreq_governor(data, CPUFREQ_GOV_START);
__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
}
@ -1171,10 +1240,18 @@ static void cpufreq_out_of_sync(unsigned int cpu, unsigned int old_freq,
unsigned int cpufreq_quick_get(unsigned int cpu)
{
struct cpufreq_policy *policy;
struct cpufreq_driver *driver;
unsigned int (*get)(unsigned int cpu);
unsigned int ret_freq = 0;
if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
return cpufreq_driver->get(cpu);
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (driver && driver->setpolicy && driver->get) {
get = driver->get;
rcu_read_unlock();
return get(cpu);
}
rcu_read_unlock();
policy = cpufreq_cpu_get(cpu);
if (policy) {
@ -1210,15 +1287,26 @@ EXPORT_SYMBOL(cpufreq_quick_get_max);
static unsigned int __cpufreq_get(unsigned int cpu)
{
struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
struct cpufreq_driver *driver;
unsigned int (*get)(unsigned int cpu);
unsigned int ret_freq = 0;
u8 flags;
if (!cpufreq_driver->get)
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (!driver->get) {
rcu_read_unlock();
return ret_freq;
}
flags = driver->flags;
get = driver->get;
rcu_read_unlock();
ret_freq = cpufreq_driver->get(cpu);
ret_freq = get(cpu);
if (ret_freq && policy->cur &&
!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
!(flags & CPUFREQ_CONST_LOOPS)) {
/* verify no discrepancy between actual and
saved value exists */
if (unlikely(ret_freq != policy->cur)) {
@ -1274,6 +1362,7 @@ static struct subsys_interface cpufreq_interface = {
*/
static int cpufreq_bp_suspend(void)
{
int (*suspend)(struct cpufreq_policy *policy);
int ret = 0;
int cpu = smp_processor_id();
@ -1286,8 +1375,11 @@ static int cpufreq_bp_suspend(void)
if (!cpu_policy)
return 0;
if (cpufreq_driver->suspend) {
ret = cpufreq_driver->suspend(cpu_policy);
rcu_read_lock();
suspend = rcu_dereference(cpufreq_driver)->suspend;
rcu_read_unlock();
if (suspend) {
ret = suspend(cpu_policy);
if (ret)
printk(KERN_ERR "cpufreq: suspend failed in ->suspend "
"step on CPU %u\n", cpu_policy->cpu);
@ -1313,6 +1405,7 @@ static int cpufreq_bp_suspend(void)
static void cpufreq_bp_resume(void)
{
int ret = 0;
int (*resume)(struct cpufreq_policy *policy);
int cpu = smp_processor_id();
struct cpufreq_policy *cpu_policy;
@ -1324,8 +1417,12 @@ static void cpufreq_bp_resume(void)
if (!cpu_policy)
return;
if (cpufreq_driver->resume) {
ret = cpufreq_driver->resume(cpu_policy);
rcu_read_lock();
resume = rcu_dereference(cpufreq_driver)->resume;
rcu_read_unlock();
if (resume) {
ret = resume(cpu_policy);
if (ret) {
printk(KERN_ERR "cpufreq: resume failed in ->resume "
"step on CPU %u\n", cpu_policy->cpu);
@ -1352,10 +1449,14 @@ static struct syscore_ops cpufreq_syscore_ops = {
*/
const char *cpufreq_get_current_driver(void)
{
if (cpufreq_driver)
return cpufreq_driver->name;
return NULL;
struct cpufreq_driver *driver;
const char *name = NULL;
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
if (driver)
name = driver->name;
rcu_read_unlock();
return name;
}
EXPORT_SYMBOL_GPL(cpufreq_get_current_driver);
@ -1449,6 +1550,9 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
{
int retval = -EINVAL;
unsigned int old_target_freq = target_freq;
int (*target)(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation);
if (cpufreq_disabled())
return -ENODEV;
@ -1465,8 +1569,11 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
if (target_freq == policy->cur)
return 0;
if (cpufreq_driver->target)
retval = cpufreq_driver->target(policy, target_freq, relation);
rcu_read_lock();
target = rcu_dereference(cpufreq_driver)->target;
rcu_read_unlock();
if (target)
retval = target(policy, target_freq, relation);
return retval;
}
@ -1499,18 +1606,24 @@ EXPORT_SYMBOL_GPL(cpufreq_driver_target);
int __cpufreq_driver_getavg(struct cpufreq_policy *policy, unsigned int cpu)
{
int ret = 0;
unsigned int (*getavg)(struct cpufreq_policy *policy,
unsigned int cpu);
if (cpufreq_disabled())
return ret;
if (!cpufreq_driver->getavg)
rcu_read_lock();
getavg = rcu_dereference(cpufreq_driver)->getavg;
rcu_read_unlock();
if (!getavg)
return 0;
policy = cpufreq_cpu_get(policy->cpu);
if (!policy)
return -EINVAL;
ret = cpufreq_driver->getavg(policy, cpu);
ret = getavg(policy, cpu);
cpufreq_cpu_put(policy);
return ret;
@ -1668,6 +1781,9 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
struct cpufreq_policy *policy)
{
int ret = 0, failed = 1;
struct cpufreq_driver *driver;
int (*verify)(struct cpufreq_policy *policy);
int (*setpolicy)(struct cpufreq_policy *policy);
pr_debug("setting new policy for CPU %u: %u - %u kHz\n", policy->cpu,
policy->min, policy->max);
@ -1681,7 +1797,13 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
}
/* verify the cpu speed can be set within this limit */
ret = cpufreq_driver->verify(policy);
rcu_read_lock();
driver = rcu_dereference(cpufreq_driver);
verify = driver->verify;
setpolicy = driver->setpolicy;
rcu_read_unlock();
ret = verify(policy);
if (ret)
goto error_out;
@ -1695,7 +1817,7 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
/* verify the cpu speed can be set within this limit,
which might be different to the first one */
ret = cpufreq_driver->verify(policy);
ret = verify(policy);
if (ret)
goto error_out;
@ -1709,10 +1831,10 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
pr_debug("new min and max freqs are %u - %u kHz\n",
data->min, data->max);
if (cpufreq_driver->setpolicy) {
if (setpolicy) {
data->policy = policy->policy;
pr_debug("setting range\n");
ret = cpufreq_driver->setpolicy(policy);
ret = setpolicy(policy);
} else {
if (policy->governor != data->governor) {
/* save old, working values */
@ -1772,6 +1894,11 @@ int cpufreq_update_policy(unsigned int cpu)
{
struct cpufreq_policy *data = cpufreq_cpu_get(cpu);
struct cpufreq_policy policy;
struct cpufreq_driver *driver;
unsigned int (*get)(unsigned int cpu);
int (*target)(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation);
int ret;
if (!data) {
@ -1793,13 +1920,18 @@ int cpufreq_update_policy(unsigned int cpu)
/* BIOS might change freq behind our back
-> ask driver for current freq and notify governors about a change */
if (cpufreq_driver->get) {
policy.cur = cpufreq_driver->get(cpu);
rcu_read_lock();
driver = rcu_access_pointer(cpufreq_driver);
get = driver->get;
target = driver->target;
rcu_read_unlock();
if (get) {
policy.cur = get(cpu);
if (!data->cur) {
pr_debug("Driver did not initialize current freq");
data->cur = policy.cur;
} else {
if (data->cur != policy.cur && cpufreq_driver->target)
if (data->cur != policy.cur && target)
cpufreq_out_of_sync(cpu, data->cur,
policy.cur);
}
@ -1878,18 +2010,19 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
driver_data->flags |= CPUFREQ_CONST_LOOPS;
write_lock_irqsave(&cpufreq_driver_lock, flags);
if (cpufreq_driver) {
if (rcu_access_pointer(cpufreq_driver)) {
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
return -EBUSY;
}
cpufreq_driver = driver_data;
rcu_assign_pointer(cpufreq_driver, driver_data);
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
synchronize_rcu();
ret = subsys_interface_register(&cpufreq_interface);
if (ret)
goto err_null_driver;
if (!(cpufreq_driver->flags & CPUFREQ_STICKY)) {
if (!(driver_data->flags & CPUFREQ_STICKY)) {
int i;
ret = -ENODEV;
@ -1916,8 +2049,9 @@ err_if_unreg:
subsys_interface_unregister(&cpufreq_interface);
err_null_driver:
write_lock_irqsave(&cpufreq_driver_lock, flags);
cpufreq_driver = NULL;
rcu_assign_pointer(cpufreq_driver, NULL);
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
synchronize_rcu();
return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_register_driver);
@ -1934,9 +2068,15 @@ EXPORT_SYMBOL_GPL(cpufreq_register_driver);
int cpufreq_unregister_driver(struct cpufreq_driver *driver)
{
unsigned long flags;
struct cpufreq_driver *old_driver;
if (!cpufreq_driver || (driver != cpufreq_driver))
rcu_read_lock();
old_driver = rcu_access_pointer(cpufreq_driver);
if (!old_driver || (driver != old_driver)) {
rcu_read_unlock();
return -EINVAL;
}
rcu_read_unlock();
pr_debug("unregistering driver %s\n", driver->name);
@ -1944,8 +2084,9 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
write_lock_irqsave(&cpufreq_driver_lock, flags);
cpufreq_driver = NULL;
rcu_assign_pointer(cpufreq_driver, NULL);
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
synchronize_rcu();
return 0;
}