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

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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: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ulf Hansson 2016-01-27 09:10:37 +01:00 committed by Rafael J. Wysocki
parent 0106ef5146
commit cdb300a041
1 changed files with 6 additions and 8 deletions
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14
drivers/base/power/domain.c
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@ -1340,8 +1340,8 @@ int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
if (!link)
return -ENOMEM;
mutex_lock(&genpd->lock);
mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);
mutex_lock(&subdomain->lock);
mutex_lock_nested(&genpd->lock, SINGLE_DEPTH_NESTING);
if (genpd->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);
out:
mutex_unlock(&subdomain->lock);
mutex_unlock(&genpd->lock);
mutex_unlock(&subdomain->lock);
if (ret)
kfree(link);
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))
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) {
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)
continue;
mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);
list_del(&link->master_node);
list_del(&link->slave_node);
kfree(link);
if (subdomain->status != GPD_STATE_POWER_OFF)
genpd_sd_counter_dec(genpd);
mutex_unlock(&subdomain->lock);
ret = 0;
break;
}
out:
mutex_unlock(&genpd->lock);
mutex_unlock(&subdomain->lock);
return ret;
}