Commit db93facf authored Jan 08, 2015 by Jim Lin Committed by Linus Walleij Jan 14, 2015

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>

parent 53b1bfc7

drivers/pinctrl/core.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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 */

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