From: Ulf Hansson <ulf.hansson@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Kevin Hilman <khilman@kernel.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
linux-pm@vger.kernel.org
Cc: Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Lina Iyer <lina.iyer@linaro.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Axel Haslam <ahaslam@baylibre.com>,
Marc Titinger <mtitinger@baylibre.com>
Subject: [PATCH] PM / Domains: Fix potential deadlock while adding/removing subdomains
Date: Fri, 15 Jan 2016 10:59:20 +0100 [thread overview]
Message-ID: <1452851960-22555-1-git-send-email-ulf.hansson@linaro.org> (raw)
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>
---
drivers/base/power/domain.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 6ac9a7f..81332a4 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1339,8 +1339,8 @@ int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
if (!link)
return -ENOMEM;
+ mutex_lock(&subdomain->lock);
mutex_lock(&genpd->lock);
- mutex_lock_nested(&subdomain->lock, SINGLE_DEPTH_NESTING);
if (genpd->status == GPD_STATE_POWER_OFF
&& subdomain->status != GPD_STATE_POWER_OFF) {
@@ -1363,8 +1363,8 @@ 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;
@@ -1385,6 +1385,7 @@ 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(&subdomain->lock);
mutex_lock(&genpd->lock);
if (!list_empty(&subdomain->slave_links) || subdomain->device_count) {
@@ -1398,22 +1399,19 @@ 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;
}
--
1.9.1
reply other threads:[~2016-01-15 9:59 UTC|newest]
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