pinctrl: Fix two deadlocks

This patch is to fix two deadlock cases.
Deadlock 1:
CPU #1
 pinctrl_register-> pinctrl_get ->
 create_pinctrl
 (Holding lock pinctrl_maps_mutex)
 -> get_pinctrl_dev_from_devname
 (Trying to acquire lock pinctrldev_list_mutex)
CPU #0
 pinctrl_unregister
 (Holding lock pinctrldev_list_mutex)
 -> pinctrl_put ->> pinctrl_free ->
 pinctrl_dt_free_maps -> pinctrl_unregister_map
 (Trying to acquire lock pinctrl_maps_mutex)

Simply to say
CPU#1 is holding lock A and trying to acquire lock B,
CPU#0 is holding lock B and trying to acquire lock A.

Deadlock 2:
CPU #3
 pinctrl_register-> pinctrl_get ->
 create_pinctrl
 (Holding lock pinctrl_maps_mutex)
 -> get_pinctrl_dev_from_devname
 (Trying to acquire lock pinctrldev_list_mutex)
CPU #2
 pinctrl_unregister
 (Holding lock pctldev->mutex)
 -> pinctrl_put ->> pinctrl_free ->
 pinctrl_dt_free_maps -> pinctrl_unregister_map
 (Trying to acquire lock pinctrl_maps_mutex)
CPU #0
 tegra_gpio_request
 (Holding lock pinctrldev_list_mutex)
 -> pinctrl_get_device_gpio_range
 (Trying to acquire lock pctldev->mutex)

Simply to say
CPU#3 is holding lock A and trying to acquire lock D,
CPU#2 is holding lock B and trying to acquire lock A,
CPU#0 is holding lock D and trying to acquire lock B.

Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Jim Lin <jilin@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index e4f65510c87e..89dca77ca038 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1801,14 +1801,15 @@ void pinctrl_unregister(struct pinctrl_dev *pctldev)
         if (pctldev == NULL)
                 return;
 
-        mutex_lock(&pinctrldev_list_mutex);
         mutex_lock(&pctldev->mutex);
-
         pinctrl_remove_device_debugfs(pctldev);
+        mutex_unlock(&pctldev->mutex);
 
         if (!IS_ERR(pctldev->p))
                 pinctrl_put(pctldev->p);
 
+        mutex_lock(&pinctrldev_list_mutex);
+        mutex_lock(&pctldev->mutex);
         /* TODO: check that no pinmuxes are still active? */
         list_del(&pctldev->node);
         /* Destroy descriptor tree */