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Commit c0356db7 authored by Ulf Hansson's avatar Ulf Hansson Committed by Rafael J. Wysocki
Browse files

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: default avatarUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent e07b45cb

drivers/base/power/domain.c

+14 −23
Original line number Diff line number Diff line
@@ -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;

}

include/linux/pm_domain.h

+0 −1
Original line number Diff line number Diff line
@@ -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;

};