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Commit cdb300a0 authored by Ulf Hansson's avatar Ulf Hansson Committed by Rafael J. Wysocki
Browse files

PM / Domains: Fix potential deadlock while adding/removing subdomains 



We must preserve the same order of how we acquire and release the lock for
genpd, as otherwise we may encounter deadlocks.

The power on phase of a genpd starts by acquiring its lock. Then it walks
the hierarchy of its parent domains to be able to power on these first, as
per design of genpd.

From a locking perspective this means the locks of the parents becomes
acquired after the lock of the subdomain.

Let's fix pm_genpd_add|remove_subdomain() to maintain the same order of
acquiring/releasing the genpd lock as being applied in the power on/off
sequence.

Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 0106ef51

drivers/base/power/domain.c

+6 −8
Original line number Original line Diff line number Diff line
@@ -1340,8 +1340,8 @@ int pm_genpd_add_subdomain(struct generic_pm_domain *genpd, 
	if (!link)

	if (!link)

		return -ENOMEM;

		return -ENOMEM;





	mutex_lock(&genpd->lock);

	mutex_lock(&subdomain->lock);

	mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);

	mutex_lock_nested(&genpd->lock, SINGLE_DEPTH_NESTING);





	if (genpd->status == GPD_STATE_POWER_OFF

	if (genpd->status == GPD_STATE_POWER_OFF

	    &&  subdomain->status != GPD_STATE_POWER_OFF) {

	    &&  subdomain->status != GPD_STATE_POWER_OFF) {
@@ -1364,8 +1364,8 @@ int pm_genpd_add_subdomain(struct generic_pm_domain *genpd, 
		genpd_sd_counter_inc(genpd);

		genpd_sd_counter_inc(genpd);





 out:

 out:

	mutex_unlock(&subdomain->lock);

	mutex_unlock(&genpd->lock);

	mutex_unlock(&genpd->lock);

	mutex_unlock(&subdomain->lock);

	if (ret)

	if (ret)

		kfree(link);

		kfree(link);

	return ret;

	return ret;
@@ -1386,7 +1386,8 @@ int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd, 
	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(subdomain))

	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(subdomain))

		return -EINVAL;

		return -EINVAL;





	mutex_lock(&genpd->lock);

	mutex_lock(&subdomain->lock);

	mutex_lock_nested(&genpd->lock, SINGLE_DEPTH_NESTING);





	if (!list_empty(&subdomain->slave_links) || subdomain->device_count) {

	if (!list_empty(&subdomain->slave_links) || subdomain->device_count) {

		pr_warn("%s: unable to remove subdomain %s\n", genpd->name,

		pr_warn("%s: unable to remove subdomain %s\n", genpd->name,
@@ -1399,22 +1400,19 @@ int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd, 
		if (link->slave != subdomain)

		if (link->slave != subdomain)

			continue;

			continue;





		mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);



		list_del(&link->master_node);

		list_del(&link->master_node);

		list_del(&link->slave_node);

		list_del(&link->slave_node);

		kfree(link);

		kfree(link);

		if (subdomain->status != GPD_STATE_POWER_OFF)

		if (subdomain->status != GPD_STATE_POWER_OFF)

			genpd_sd_counter_dec(genpd);

			genpd_sd_counter_dec(genpd);





		mutex_unlock(&subdomain->lock);



		ret = 0;

		ret = 0;

		break;

		break;

	}

	}





out:

out:

	mutex_unlock(&genpd->lock);

	mutex_unlock(&genpd->lock);

	mutex_unlock(&subdomain->lock);





	return ret;

	return ret;

}

}