From cdb300a041f5df1dfbde1367f95109b6449d1371 Mon Sep 17 00:00:00 2001 From: Ulf Hansson Date: Wed, 27 Jan 2016 09:10:37 +0100 Subject: [PATCH] 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 Signed-off-by: Rafael J. Wysocki --- drivers/base/power/domain.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index e02ddf65bc43..2ff818c2ae6b 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -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; } -- 2.30.2