watchdog: Introduce WDOG_HW_RUNNING flag (ee142889) · Commits · 戴 / test

Documentation/watchdog/watchdog-kernel-api.txt

+15 −7

Original line number	Diff line number	Diff line
		@@ -137,10 +137,10 @@ are:
		* stop: with this routine the watchdog timer device is being stopped.
		The routine needs a pointer to the watchdog timer device structure as a
		parameter. It returns zero on success or a negative errno code for failure.
		Some watchdog timer hardware can only be started and not be stopped. The
		driver supporting this hardware needs to make sure that a start and stop
		routine is being provided. This can be done by using a timer in the driver
		that regularly sends a keepalive ping to the watchdog timer hardware.
		Some watchdog timer hardware can only be started and not be stopped.
		If a watchdog can not be stopped, the watchdog driver must set the
		WDOG_HW_RUNNING flag in its stop function to inform the watchdog core that
		the watchdog is still running.

		Not all watchdog timer hardware supports the same functionality. That's why
		all other routines/operations are optional. They only need to be provided if
		@@ -189,11 +189,19 @@ The 'ref' and 'unref' operations are no longer used and deprecated.
		The status bits should (preferably) be set with the set_bit and clear_bit alike
		bit-operations. The status bits that are defined are:
		* WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device
		is active or not. When the watchdog is active after booting, then you should
		set this status bit (Note: when you register the watchdog timer device with
		this bit set, then opening /dev/watchdog will skip the start operation)
		is active or not from user perspective. User space is expected to send
		heartbeat requests to the driver while this flag is set.
		* WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
		If this bit is set then the watchdog timer will not be able to stop.
		* WDOG_HW_RUNNING: Set by the watchdog driver if the hardware watchdog is
		running. The bit must be set if the watchdog timer hardware can not be
		stopped. The bit may also be set if the watchdog timer is running after
		booting, before the watchdog device is opened. If set, the watchdog
		infrastructure will send keepalives to the watchdog hardware while
		WDOG_ACTIVE is not set.
		Note: when you register the watchdog timer device with this bit set,
		then opening /dev/watchdog will skip the start operation but send a keepalive
		request instead.

		To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
		timer device) you can either:

drivers/watchdog/watchdog_dev.c

+39 −13

Original line number	Diff line number	Diff line
		@@ -92,7 +92,8 @@ static inline bool watchdog_need_worker(struct watchdog_device *wdd)
		* requests.
		* - Userspace requests a longer timeout than the hardware can handle.
		*/
		return watchdog_active(wdd) && hm && t > hm;
		return hm && ((watchdog_active(wdd) && t > hm) \|\|
		(t && !watchdog_active(wdd) && watchdog_hw_running(wdd)));
		}

		static long watchdog_next_keepalive(struct watchdog_device *wdd)
		@@ -108,6 +109,9 @@ static long watchdog_next_keepalive(struct watchdog_device *wdd)
		hw_heartbeat_ms = min(timeout_ms, wdd->max_hw_heartbeat_ms);
		keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2);

		if (!watchdog_active(wdd))
		return keepalive_interval;

		/*
		* To ensure that the watchdog times out wdd->timeout seconds
		* after the most recent ping from userspace, the last
		@@ -161,7 +165,7 @@ static int watchdog_ping(struct watchdog_device *wdd)
		{
		struct watchdog_core_data *wd_data = wdd->wd_data;

		if (!watchdog_active(wdd))
		if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
		return 0;

		wd_data->last_keepalive = jiffies;
		@@ -178,7 +182,7 @@ static void watchdog_ping_work(struct work_struct *work)

		mutex_lock(&wd_data->lock);
		wdd = wd_data->wdd;
		if (wdd && watchdog_active(wdd))
		if (wdd && (watchdog_active(wdd) \|\| watchdog_hw_running(wdd)))
		__watchdog_ping(wdd);
		mutex_unlock(&wd_data->lock);
		}
		@@ -204,6 +208,9 @@ static int watchdog_start(struct watchdog_device *wdd)
		return 0;

		started_at = jiffies;
		if (watchdog_hw_running(wdd) && wdd->ops->ping)
		err = wdd->ops->ping(wdd);
		else
		err = wdd->ops->start(wdd);
		if (err == 0) {
		set_bit(WDOG_ACTIVE, &wdd->status);
		@@ -228,8 +235,7 @@ static int watchdog_start(struct watchdog_device *wdd)

		static int watchdog_stop(struct watchdog_device *wdd)
		{
		struct watchdog_core_data *wd_data = wdd->wd_data;
		int err;
		int err = 0;

		if (!watchdog_active(wdd))
		return 0;
		@@ -243,7 +249,7 @@ static int watchdog_stop(struct watchdog_device *wdd)
		err = wdd->ops->stop(wdd);
		if (err == 0) {
		clear_bit(WDOG_ACTIVE, &wdd->status);
		cancel_delayed_work(&wd_data->work);
		watchdog_update_worker(wdd);
		}

		return err;
		@@ -641,7 +647,7 @@ static int watchdog_open(struct inode inode, struct file file)
		* If the /dev/watchdog device is open, we don't want the module
		* to be unloaded.
		*/
		if (!try_module_get(wdd->ops->owner)) {
		if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
		err = -EBUSY;
		goto out_clear;
		}
		@@ -652,6 +658,7 @@ static int watchdog_open(struct inode inode, struct file file)

		file->private_data = wd_data;

		if (!watchdog_hw_running(wdd))
		kref_get(&wd_data->kref);

		/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
		@@ -713,15 +720,22 @@ static int watchdog_release(struct inode inode, struct file file)
		}

		cancel_delayed_work_sync(&wd_data->work);
		watchdog_update_worker(wdd);

		/* make sure that /dev/watchdog can be re-opened */
		clear_bit(_WDOG_DEV_OPEN, &wd_data->status);

		done:
		mutex_unlock(&wd_data->lock);
		/* Allow the owner module to be unloaded again */
		module_put(wd_data->cdev.owner);
		/*
		* Allow the owner module to be unloaded again unless the watchdog
		* is still running. If the watchdog is still running, it can not
		* be stopped, and its driver must not be unloaded.
		*/
		if (!watchdog_hw_running(wdd)) {
		module_put(wdd->ops->owner);
		kref_put(&wd_data->kref, watchdog_core_data_release);
		}
		return 0;
		}

		@@ -798,10 +812,22 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
		old_wd_data = NULL;
		kref_put(&wd_data->kref, watchdog_core_data_release);
		}
		}
		return err;
		}

		/*
		* If the watchdog is running, prevent its driver from being unloaded,
		* and schedule an immediate ping.
		*/
		if (watchdog_hw_running(wdd)) {
		__module_get(wdd->ops->owner);
		kref_get(&wd_data->kref);
		queue_delayed_work(watchdog_wq, &wd_data->work, 0);
		}

		return 0;
		}

		/*
		* watchdog_cdev_unregister: unregister watchdog character device
		* @watchdog: watchdog device

include/linux/watchdog.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -105,6 +105,7 @@ struct watchdog_device {
		#define WDOG_ACTIVE 0 /* Is the watchdog running/active */
		#define WDOG_NO_WAY_OUT 1 /* Is 'nowayout' feature set ? */
		#define WDOG_STOP_ON_REBOOT 2 /* Should be stopped on reboot */
		#define WDOG_HW_RUNNING 3 /* True if HW watchdog running */
		struct list_head deferred;
		};

		@@ -117,6 +118,15 @@ static inline bool watchdog_active(struct watchdog_device *wdd)
		return test_bit(WDOG_ACTIVE, &wdd->status);
		}

		/*
		* Use the following function to check whether or not the hardware watchdog
		* is running
		*/
		static inline bool watchdog_hw_running(struct watchdog_device *wdd)
		{
		return test_bit(WDOG_HW_RUNNING, &wdd->status);
		}

		/* Use the following function to set the nowayout feature */
		static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool nowayout)
		{

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