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: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index e02ddf6..2ff818c 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1340,8 +1340,8 @@
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 @@
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 @@
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 @@
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;
}