pinctrl: Fix two deadlocks

commit db93facfb0ef542aa5d8079e47580b3e669a4d82 upstream.

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.

Signed-off-by: Jim Lin <jilin@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index bb7ee9cb00b1614e89b3434ee9d07671fffb59b3..9c9fc69a01b347d43cfafe2514fff8a90a1f4943 100644 (file)
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1693,14 +1693,15 @@ 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 */