From 2071ac985d37efe496782c34318dbead93beb02f Mon Sep 17 00:00:00 2001
From: Jiada Wang <jiada_wang@mentor.com>
Date: Tue, 12 Mar 2019 15:51:28 +0900
Subject: [PATCH] PM / Domains: Avoid a potential deadlock
Lockdep warns that prepare_lock and genpd->mlock can cause a deadlock
the deadlock scenario is like following:
First thread is probing cs2000
cs2000_probe()
clk_register()
__clk_core_init()
clk_prepare_lock() ----> acquires prepare_lock
cs2000_recalc_rate()
i2c_smbus_read_byte_data()
rcar_i2c_master_xfer()
dma_request_chan()
rcar_dmac_of_xlate()
rcar_dmac_alloc_chan_resources()
pm_runtime_get_sync()
__pm_runtime_resume()
rpm_resume()
rpm_callback()
genpd_runtime_resume() ----> acquires genpd->mlock
Second thread is attaching any device to the same PM domain
genpd_add_device()
genpd_lock() ----> acquires genpd->mlock
cpg_mssr_attach_dev()
of_clk_get_from_provider()
__of_clk_get_from_provider()
__clk_create_clk()
clk_prepare_lock() ----> acquires prepare_lock
Since currently no PM provider access genpd's critical section
in .attach_dev, and .detach_dev callbacks, so there is no need to protect
these two callbacks with genpd->mlock.
This patch avoids a potential deadlock by moving out .attach_dev and .detach_dev
from genpd->mlock, so that genpd->mlock won't be held when prepare_lock is acquired
in .attach_dev and .detach_dev
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/base/power/domain.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 76c9969b7124c..96a6dc9d305c8 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1469,12 +1469,12 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
if (IS_ERR(gpd_data))
return PTR_ERR(gpd_data);
- genpd_lock(genpd);
-
ret = genpd->attach_dev ? genpd->attach_dev(genpd, dev) : 0;
if (ret)
goto out;
+ genpd_lock(genpd);
+
dev_pm_domain_set(dev, &genpd->domain);
genpd->device_count++;
@@ -1482,9 +1482,8 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
- out:
genpd_unlock(genpd);
-
+ out:
if (ret)
genpd_free_dev_data(dev, gpd_data);
else
@@ -1533,15 +1532,15 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
genpd->device_count--;
genpd->max_off_time_changed = true;
- if (genpd->detach_dev)
- genpd->detach_dev(genpd, dev);
-
dev_pm_domain_set(dev, NULL);
list_del_init(&pdd->list_node);
genpd_unlock(genpd);
+ if (genpd->detach_dev)
+ genpd->detach_dev(genpd, dev);
+
genpd_free_dev_data(dev, gpd_data);
return 0;
--
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