Re: [PATCH 4/6] Watchdog: introdouce "pretimeout" into framework

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On 05/15/2015 04:24 AM, fu.wei@xxxxxxxxxx wrote:
From: Fu Wei <fu.wei@xxxxxxxxxx>

Reasons:
(1)kernel already has two watchdog drivers are using "pretimeout":
	drivers/char/ipmi/ipmi_watchdog.c
	drivers/watchdog/kempld_wdt.c(but the definition is different)
(2)some other dirvers are going to use this: ARM SBSA Generic Watchdog

Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
---
  drivers/watchdog/watchdog_core.c | 66 ++++++++++++++++++++++++++++++++++++++++
  drivers/watchdog/watchdog_dev.c  | 48 +++++++++++++++++++++++++++++
  include/linux/watchdog.h         | 19 ++++++++++++
  3 files changed, 133 insertions(+)

diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index cec9b55..6ca9578 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -54,6 +54,14 @@ static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  		wdd->min_timeout = 0;
  		wdd->max_timeout = 0;
  	}
+	if (wdd->min_pretimeout && wdd->min_timeout < wdd->min_pretimeout) {
+		pr_info("Invalid min timeout, resetting to min pretimeout!\n");
+		wdd->min_timeout = wdd->min_pretimeout;
+	}
+	if (wdd->max_pretimeout && wdd->max_timeout < wdd->max_pretimeout) {
+		pr_info("Invalid max timeout, resetting to max pretimeout!\n");
+		wdd->max_timeout = wdd->max_pretimeout;
+	}

I am a bit concerned about the context dependency introduced here. If someone calls
_init_pretimeout after calling init_timeout, this may result in still invalid timeout
values.

  }

  /**
@@ -98,6 +106,63 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
  }
  EXPORT_SYMBOL_GPL(watchdog_init_timeout);

+static void watchdog_check_min_max_pretimeout(struct watchdog_device *wdd)
+{
+	/*
+	 * Check that we have valid min and max pretimeout values, if
+	 * not reset them both to 0 (=not used or unknown)
+	 */
+	if (wdd->min_pretimeout > wdd->max_pretimeout) {
+		pr_info("Invalid min and max pretimeout, resetting to 0!\n");
+		wdd->min_pretimeout = 0;
+		wdd->max_pretimeout = 0;
+	}
+}
+
+/**
+ * watchdog_init_pretimeout() - initialize the pretimeout field
+ * @pretimeout_parm: pretimeout module parameter
+ * @dev: Device that stores the timeout-sec property
+ *
+ * Initialize the pretimeout field of the watchdog_device struct with either
+ * the pretimeout module parameter (if it is valid value) or the timeout-sec
+ * property (only if it is a valid value and the timeout_parm is out of bounds).
+ * If none of them are valid then we keep the old value (which should normally
+ * be the default pretimeout value.
+ *
+ * A zero is returned on success and -EINVAL for failure.
+ */

The new API function also needs to be documented in
Documentation/watchdog/watchdog-kernel-api.txt.

+int watchdog_init_pretimeout(struct watchdog_device *wdd,
+			     unsigned int pretimeout_parm, struct device *dev)
+{
+	int ret = 0;
+	u32 timeouts[2];
+
+	watchdog_check_min_max_pretimeout(wdd);
+
+	/* try to get the timeout module parameter first */
+	if (!watchdog_pretimeout_invalid(wdd, pretimeout_parm) &&
+	    pretimeout_parm) {
+		wdd->pretimeout = pretimeout_parm;
+		return ret;
+	}
+	if (pretimeout_parm)
+		ret = -EINVAL;
+
+	/* try to get the timeout_sec property */
+	if (!dev || !dev->of_node)
+		return ret;
+	ret = of_property_read_u32_array(dev->of_node,
+					 "timeout-sec", timeouts, 2);
+	if (!watchdog_pretimeout_invalid(wdd, timeouts[1]) && timeouts[1])

Guess we are still waiting for feedback from the devicetree maintainers on this.

Both the above synchronization concern and this makes me wonder if we should introduce
watchdog_init_timeouts() instead, which would take pretimeout as additional parameter.
What do you think about that ?

+		wdd->pretimeout = timeouts[1];
+	else
+		ret = -EINVAL;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(watchdog_init_pretimeout);
+
  /**
   * watchdog_register_device() - register a watchdog device
   * @wdd: watchdog device
@@ -119,6 +184,7 @@ int watchdog_register_device(struct watchdog_device *wdd)
  	if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
  		return -EINVAL;

+	watchdog_check_min_max_pretimeout(wdd);
  	watchdog_check_min_max_timeout(wdd);

  	/*
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 6aaefba..b519257 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -218,6 +218,38 @@ out_timeout:
  }

  /*
+ *	watchdog_set_pretimeout: set the watchdog timer pretimeout
+ *	@wddev: the watchdog device to set the timeout for
+ *	@pretimeout: pretimeout to set in seconds
+ */
+
+static int watchdog_set_pretimeout(struct watchdog_device *wddev,
+				   unsigned int pretimeout)
+{
+	int err;
+
+	if (!wddev->ops->set_pretimeout ||
+	    !(wddev->info->options & WDIOF_PRETIMEOUT))
+		return -EOPNOTSUPP;
+
+	if (watchdog_pretimeout_invalid(wddev, pretimeout))
+		return -EINVAL;
+
+	mutex_lock(&wddev->lock);
+
+	if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
+		err = -ENODEV;
+		goto out_pretimeout;
+	}
+
+	err = wddev->ops->set_pretimeout(wddev, pretimeout);
+
+out_pretimeout:
+	mutex_unlock(&wddev->lock);
+	return err;
+}
+
+/*
   *	watchdog_get_timeleft: wrapper to get the time left before a reboot
   *	@wddev: the watchdog device to get the remaining time from
   *	@timeleft: the time that's left
@@ -388,6 +420,22 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
  		if (wdd->timeout == 0)
  			return -EOPNOTSUPP;
  		return put_user(wdd->timeout, p);
+	case WDIOC_SETPRETIMEOUT:
+		if (get_user(val, p))
+			return -EFAULT;
+		err = watchdog_set_pretimeout(wdd, val);
+		if (err < 0)
+			return err;
+		/* If the watchdog is active then we send a keepalive ping
+		 * to make sure that the watchdog keep's running (and if

s/keep's/keeps/

+		 * possible that it takes the new timeout) */

Please use the common multi-line comment style (that it isn't used above is not
an argument).

+		watchdog_ping(wdd);
+		/* Fall */
+	case WDIOC_GETPRETIMEOUT:
+		/* timeout == 0 means that we don't use the pretimeout */
+		if (wdd->pretimeout == 0)
+			return -EOPNOTSUPP;
+		return put_user(wdd->pretimeout, p);
  	case WDIOC_GETTIMELEFT:
  		err = watchdog_get_timeleft(wdd, &val);
  		if (err)
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index a746bf5..f0a3c5b 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -25,6 +25,7 @@ struct watchdog_device;
   * @ping:	The routine that sends a keepalive ping to the watchdog device.
   * @status:	The routine that shows the status of the watchdog device.
   * @set_timeout:The routine for setting the watchdog devices timeout value.
+ * @set_pretimeout:The routine for setting the watchdog devices pretimeout value
   * @get_timeleft:The routine that get's the time that's left before a reset.
   * @ref:	The ref operation for dyn. allocated watchdog_device structs
   * @unref:	The unref operation for dyn. allocated watchdog_device structs
@@ -44,6 +45,7 @@ struct watchdog_ops {
  	int (*ping)(struct watchdog_device *);
  	unsigned int (*status)(struct watchdog_device *);
  	int (*set_timeout)(struct watchdog_device *, unsigned int);
+	int (*set_pretimeout)(struct watchdog_device *, unsigned int);
  	unsigned int (*get_timeleft)(struct watchdog_device *);
  	void (*ref)(struct watchdog_device *);
  	void (*unref)(struct watchdog_device *);
@@ -62,6 +64,9 @@ struct watchdog_ops {
   * @timeout:	The watchdog devices timeout value.
   * @min_timeout:The watchdog devices minimum timeout value.
   * @max_timeout:The watchdog devices maximum timeout value.
+ * @pretimeout:	The watchdog devices pretimeout value.
+ * @min_pretimeout:The watchdog devices minimum pretimeout value.
+ * @max_pretimeout:The watchdog devices maximum pretimeout value.
   * @driver-data:Pointer to the drivers private data.
   * @lock:	Lock for watchdog core internal use only.
   * @status:	Field that contains the devices internal status bits.
@@ -86,6 +91,9 @@ struct watchdog_device {
  	unsigned int timeout;
  	unsigned int min_timeout;
  	unsigned int max_timeout;
+	unsigned int pretimeout;
+	unsigned int min_pretimeout;
+	unsigned int max_pretimeout;
  	void *driver_data;
  	struct mutex lock;
  	unsigned long status;
@@ -120,6 +128,14 @@ static inline bool watchdog_timeout_invalid(struct watchdog_device *wdd, unsigne
  		(t < wdd->min_timeout || t > wdd->max_timeout));
  }

+/* Use the following function to check if a pretimeout value is invalid */
+static inline bool watchdog_pretimeout_invalid(struct watchdog_device *wdd,
+					       unsigned int t)
+{
+	return ((wdd->max_pretimeout != 0) &&
+		(t < wdd->min_pretimeout || t > wdd->max_pretimeout));
+}
+
  /* Use the following functions to manipulate watchdog driver specific data */
  static inline void watchdog_set_drvdata(struct watchdog_device *wdd, void *data)
  {
@@ -134,6 +150,9 @@ static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
  /* drivers/watchdog/watchdog_core.c */
  extern int watchdog_init_timeout(struct watchdog_device *wdd,
  				  unsigned int timeout_parm, struct device *dev);
+extern int watchdog_init_pretimeout(struct watchdog_device *wdd,
+				    unsigned int pretimeout_parm,
+				    struct device *dev);

Please drop the 'extern'. Guess it may be time to clean up the watchdog core code ;-).

Thanks,
Guenter

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