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Commit 53f96cee authored by Vladimir Zapolskiy's avatar Vladimir Zapolskiy Committed by Wim Van Sebroeck
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watchdog: pretimeout: add option to select a pretimeout governor in runtime 



The change converts watchdog device attribute "pretimeout_governor" from
read-only to read-write type to allow users to select a desirable
watchdog pretimeout governor in runtime, e.g.

  % echo -n panic > /sys/..../watchdog/watchdog0/pretimeout

To get this working a list of registered pretimeout governors is created
and a new helper function watchdog_pretimeout_governor_set() is exported
to watchdog_dev.c.

If a selected governor is gone, a watchdog device pretimeout notification
is delegated to a default built-in pretimeout governor.

Signed-off-by: default avatarVladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Reviewed-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent da0d12ff

drivers/watchdog/watchdog_dev.c

+14 −1
Original line number Diff line number Diff line
@@ -497,7 +497,20 @@ static ssize_t pretimeout_governor_show(struct device *dev, 


	return watchdog_pretimeout_governor_get(wdd, buf);

}

static DEVICE_ATTR_RO(pretimeout_governor);



static ssize_t pretimeout_governor_store(struct device *dev,

					 struct device_attribute *attr,

					 const char *buf, size_t count)

{

	struct watchdog_device *wdd = dev_get_drvdata(dev);

	int ret = watchdog_pretimeout_governor_set(wdd, buf);



	if (!ret)

		ret = count;



	return ret;

}

static DEVICE_ATTR_RW(pretimeout_governor);



static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,

				int n)

drivers/watchdog/watchdog_pretimeout.c

+76 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/list.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/string.h>

#include <linux/watchdog.h>



#include "watchdog_pretimeout.h"
@@ -29,6 +30,28 @@ struct watchdog_pretimeout { 
	struct list_head		entry;

};



/* The mutex protects governor list and serializes external interfaces */

static DEFINE_MUTEX(governor_lock);



/* List of the registered watchdog pretimeout governors */

static LIST_HEAD(governor_list);



struct governor_priv {

	struct watchdog_governor	*gov;

	struct list_head		entry;

};



static struct governor_priv *find_governor_by_name(const char *gov_name)

{

	struct governor_priv *priv;



	list_for_each_entry(priv, &governor_list, entry)

		if (sysfs_streq(gov_name, priv->gov->name))

			return priv;



	return NULL;

}



int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)

{

	int count = 0;
@@ -41,6 +64,28 @@ int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf) 
	return count;

}



int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,

				     const char *buf)

{

	struct governor_priv *priv;



	mutex_lock(&governor_lock);



	priv = find_governor_by_name(buf);

	if (!priv) {

		mutex_unlock(&governor_lock);

		return -EINVAL;

	}



	spin_lock_irq(&pretimeout_lock);

	wdd->gov = priv->gov;

	spin_unlock_irq(&pretimeout_lock);



	mutex_unlock(&governor_lock);



	return 0;

}



void watchdog_notify_pretimeout(struct watchdog_device *wdd)

{

	unsigned long flags;
@@ -59,6 +104,22 @@ EXPORT_SYMBOL_GPL(watchdog_notify_pretimeout); 
int watchdog_register_governor(struct watchdog_governor *gov)

{

	struct watchdog_pretimeout *p;

	struct governor_priv *priv;



	priv = kzalloc(sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;



	mutex_lock(&governor_lock);



	if (find_governor_by_name(gov->name)) {

		mutex_unlock(&governor_lock);

		kfree(priv);

		return -EBUSY;

	}



	priv->gov = gov;

	list_add(&priv->entry, &governor_list);



	if (!strncmp(gov->name, WATCHDOG_PRETIMEOUT_DEFAULT_GOV,

		     WATCHDOG_GOV_NAME_MAXLEN)) {
@@ -71,6 +132,8 @@ int watchdog_register_governor(struct watchdog_governor *gov) 
		spin_unlock_irq(&pretimeout_lock);

	}



	mutex_unlock(&governor_lock);



	return 0;

}

EXPORT_SYMBOL(watchdog_register_governor);
@@ -78,12 +141,25 @@ EXPORT_SYMBOL(watchdog_register_governor); 
void watchdog_unregister_governor(struct watchdog_governor *gov)

{

	struct watchdog_pretimeout *p;

	struct governor_priv *priv, *t;



	mutex_lock(&governor_lock);



	list_for_each_entry_safe(priv, t, &governor_list, entry) {

		if (priv->gov == gov) {

			list_del(&priv->entry);

			kfree(priv);

			break;

		}

	}



	spin_lock_irq(&pretimeout_lock);

	list_for_each_entry(p, &pretimeout_list, entry)

		if (p->wdd->gov == gov)

			p->wdd->gov = default_gov;

	spin_unlock_irq(&pretimeout_lock);



	mutex_unlock(&governor_lock);

}

EXPORT_SYMBOL(watchdog_unregister_governor);

drivers/watchdog/watchdog_pretimeout.h

+8 −0
Original line number Diff line number Diff line
@@ -19,6 +19,8 @@ void watchdog_unregister_governor(struct watchdog_governor *gov); 
int watchdog_register_pretimeout(struct watchdog_device *wdd);

void watchdog_unregister_pretimeout(struct watchdog_device *wdd);

int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf);

int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,

				     const char *buf);



#if IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOOP)

#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV		"noop"
@@ -41,6 +43,12 @@ static inline int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, 
{

	return -EINVAL;

}



static inline int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,

						   const char *buf)

{

	return -EINVAL;

}

#endif



#endif