Commit e1313196 authored by Damien Riegel's avatar Damien Riegel Committed by Wim Van Sebroeck
Browse files

watchdog: core: add reboot notifier support 



Many watchdog drivers register a reboot notifier in order to stop the
watchdog on system reboot. Thus we can factorize this code in the
watchdog core.

For that purpose, a new notifier block is added in watchdog_device for
internal use only, as well as a new watchdog_stop_on_reboot helper
function.

If this helper is called, watchdog core registers the related notifier
block and will stop the watchdog when SYS_HALT or SYS_DOWN is received.

Since this operation can be critical on some platforms, abort the device
registration if the reboot notifier registration fails.

Suggested-by: default avatarVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: default avatarDamien Riegel <damien.riegel@savoirfairelinux.com>
Reviewed-by: default avatarVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent 0ebad1e5

Documentation/watchdog/watchdog-kernel-api.txt

+8 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ struct watchdog_device { 
	unsigned int timeout;

	unsigned int min_timeout;

	unsigned int max_timeout;

	struct notifier_block reboot_nb;

	struct notifier_block restart_nb;

	void *driver_data;

	struct mutex lock;
@@ -76,6 +77,9 @@ It contains following fields: 
* timeout: the watchdog timer's timeout value (in seconds).

* min_timeout: the watchdog timer's minimum timeout value (in seconds).

* max_timeout: the watchdog timer's maximum timeout value (in seconds).

* reboot_nb: notifier block that is registered for reboot notifications, for

  internal use only. If the driver calls watchdog_stop_on_reboot, watchdog core

  will stop the watchdog on such notifications.

* restart_nb: notifier block that is registered for machine restart, for

  internal use only. If a watchdog is capable of restarting the machine, it

  should define ops->restart. Priority can be changed through
@@ -240,6 +244,10 @@ to set the default timeout value as timeout value in the watchdog_device and 
then use this function to set the user "preferred" timeout value.

This routine returns zero on success and a negative errno code for failure.



To disable the watchdog on reboot, the user must call the following helper:



static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd);



To change the priority of the restart handler the following helper should be

used:

drivers/watchdog/watchdog_core.c

+37 −0
Original line number Diff line number Diff line
@@ -138,6 +138,25 @@ int watchdog_init_timeout(struct watchdog_device *wdd, 
}

EXPORT_SYMBOL_GPL(watchdog_init_timeout);



static int watchdog_reboot_notifier(struct notifier_block *nb,

				    unsigned long code, void *data)

{

	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,

						   reboot_nb);



	if (code == SYS_DOWN || code == SYS_HALT) {

		if (watchdog_active(wdd)) {

			int ret;



			ret = wdd->ops->stop(wdd);

			if (ret)

				return NOTIFY_BAD;

		}

	}



	return NOTIFY_DONE;

}



static int watchdog_restart_notifier(struct notifier_block *nb,

				     unsigned long action, void *data)

{
@@ -238,6 +257,21 @@ static int __watchdog_register_device(struct watchdog_device *wdd) 
		return ret;

	}



	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {

		wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;



		ret = register_reboot_notifier(&wdd->reboot_nb);

		if (ret) {

			dev_err(wdd->dev, "Cannot register reboot notifier (%d)\n",

				ret);

			watchdog_dev_unregister(wdd);

			device_destroy(watchdog_class, devno);

			ida_simple_remove(&watchdog_ida, wdd->id);

			wdd->dev = NULL;

			return ret;

		}

	}



	if (wdd->ops->restart) {

		wdd->restart_nb.notifier_call = watchdog_restart_notifier;
@@ -286,6 +320,9 @@ static void __watchdog_unregister_device(struct watchdog_device *wdd) 
	if (wdd->ops->restart)

		unregister_restart_handler(&wdd->restart_nb);



	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))

		unregister_reboot_notifier(&wdd->reboot_nb);



	devno = wdd->cdev.dev;

	ret = watchdog_dev_unregister(wdd);

	if (ret)

include/linux/watchdog.h

+9 −0
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ struct watchdog_ops { 
 * @timeout:	The watchdog devices timeout value (in seconds).

 * @min_timeout:The watchdog devices minimum timeout value (in seconds).

 * @max_timeout:The watchdog devices maximum timeout value (in seconds).

 * @reboot_nb:	The notifier block to stop watchdog on reboot.

 * @restart_nb:	The notifier block to register a restart function.

 * @driver-data:Pointer to the drivers private data.

 * @lock:	Lock for watchdog core internal use only.
@@ -92,6 +93,7 @@ struct watchdog_device { 
	unsigned int timeout;

	unsigned int min_timeout;

	unsigned int max_timeout;

	struct notifier_block reboot_nb;

	struct notifier_block restart_nb;

	void *driver_data;

	struct mutex lock;
@@ -102,6 +104,7 @@ struct watchdog_device { 
#define WDOG_ALLOW_RELEASE	2	/* Did we receive the magic char ? */

#define WDOG_NO_WAY_OUT		3	/* Is 'nowayout' feature set ? */

#define WDOG_UNREGISTERED	4	/* Has the device been unregistered */

#define WDOG_STOP_ON_REBOOT	5	/* Should be stopped on reboot */

	struct list_head deferred;

};
@@ -121,6 +124,12 @@ static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool noway 
		set_bit(WDOG_NO_WAY_OUT, &wdd->status);

}



/* Use the following function to stop the watchdog on reboot */

static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd)

{

	set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);

}



/* Use the following function to check if a timeout value is invalid */

static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigned int t)

{

CRA Git | Maintained and supported by SUSTech CRA and CCSE