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PM / Domains: Eliminate the mutex for the generic_pm_domain_data 

While adding devices to their PM domains, dev_pm_qos_add_notifier() was
invoked while allocating the generic_pm_domain_data for the device.

Since the generic_pm_domain_data's device pointer will be assigned
after allocation, the ->genpd_dev_pm_qos_notifier() callback could be
called prior having a valid pointer to the device. Similar scenario
existed while removing a device from a genpd.

To cope with these scenarios a mutex was used to protect the pointer to
the device.

By re-order the sequence for when dev_pm_qos_add|remove_notifier() are
invoked, we make sure the ->genpd_dev_pm_qos_notifier() callback are
always called with a valid device pointer available.

In this way, we eliminate the need for protecting the pointer and thus
we can remove the mutex from the struct generic_pm_domain_data.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ulf Hansson 2015-01-27 21:13:42 +01:00 committed by Rafael J. Wysocki
parent e07b45cb98
commit c0356db7d1
2 changed files with 14 additions and 24 deletions
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37
drivers/base/power/domain.c
View File

@ -344,14 +344,7 @@ static int genpd_dev_pm_qos_notifier(struct notifier_block *nb,
struct device *dev;
gpd_data = container_of(nb, struct generic_pm_domain_data, nb);
mutex_lock(&gpd_data->lock);
dev = gpd_data->base.dev;
if (!dev) {
mutex_unlock(&gpd_data->lock);
return NOTIFY_DONE;
}
mutex_unlock(&gpd_data->lock);
for (;;) {
struct generic_pm_domain *genpd;
@ -1392,16 +1385,12 @@ static struct generic_pm_domain_data *genpd_alloc_dev_data(struct device *dev)
if (!gpd_data)
return NULL;
mutex_init(&gpd_data->lock);
gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
dev_pm_qos_add_notifier(dev, &gpd_data->nb);
return gpd_data;
}
static void genpd_free_dev_data(struct device *dev,
struct generic_pm_domain_data *gpd_data)
{
dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
kfree(gpd_data);
}
@ -1414,7 +1403,7 @@ static void genpd_free_dev_data(struct device *dev,
int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
struct gpd_timing_data *td)
{
struct generic_pm_domain_data *gpd_data_new, *gpd_data = NULL;
struct generic_pm_domain_data *gpd_data;
int ret = 0;
dev_dbg(dev, "%s()\n", __func__);
@ -1422,8 +1411,8 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
return -EINVAL;
gpd_data_new = genpd_alloc_dev_data(dev);
if (!gpd_data_new)
gpd_data = genpd_alloc_dev_data(dev);
if (!gpd_data)
return -ENOMEM;
genpd_acquire_lock(genpd);
@ -1445,7 +1434,6 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
goto out;
}
gpd_data = gpd_data_new;
dev->power.subsys_data->domain_data = &gpd_data->base;
if (td)
@ -1461,19 +1449,20 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
genpd->device_count++;
genpd->max_off_time_changed = true;
mutex_lock(&gpd_data->lock);
gpd_data->base.dev = dev;
list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
gpd_data->need_restore = -1;
gpd_data->td.constraint_changed = true;
gpd_data->td.effective_constraint_ns = -1;
mutex_unlock(&gpd_data->lock);
gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
out:
genpd_release_lock(genpd);
if (gpd_data != gpd_data_new)
genpd_free_dev_data(dev, gpd_data_new);
if (ret)
genpd_free_dev_data(dev, gpd_data);
else
dev_pm_qos_add_notifier(dev, &gpd_data->nb);
return ret;
}
@ -1509,6 +1498,11 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
|| pd_to_genpd(dev->pm_domain) != genpd)
return -EINVAL;
/* The above validation also means we have existing domain_data. */
pdd = dev->power.subsys_data->domain_data;
gpd_data = to_gpd_data(pdd);
dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
genpd_acquire_lock(genpd);
if (genpd->prepared_count > 0) {
@ -1525,16 +1519,12 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
spin_lock_irq(&dev->power.lock);
dev->pm_domain = NULL;
pdd = dev->power.subsys_data->domain_data;
list_del_init(&pdd->list_node);
gpd_data = to_gpd_data(pdd);
dev->power.subsys_data->domain_data = NULL;
spin_unlock_irq(&dev->power.lock);
mutex_lock(&gpd_data->lock);
pdd->dev = NULL;
mutex_unlock(&gpd_data->lock);
genpd_release_lock(genpd);
@ -1545,6 +1535,7 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
out:
genpd_release_lock(genpd);
dev_pm_qos_add_notifier(dev, &gpd_data->nb);
return ret;
}

1
include/linux/pm_domain.h
View File

@ -113,7 +113,6 @@ struct generic_pm_domain_data {
struct pm_domain_data base;
struct gpd_timing_data td;
struct notifier_block nb;
struct mutex lock;
int need_restore;
};