drivers/watchdog/softdog.c

/*
 *	SoftDog:	A Software Watchdog Device
 *
 *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *							All Rights Reserved.
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *	warranty for any of this software. This material is provided
 *	"AS-IS" and at no charge.
 *
 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *	Software only watchdog driver. Unlike its big brother the WDT501P
 *	driver this won't always recover a failed machine.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>

#define TIMER_MARGIN	60		/* Default is 60 seconds */
static unsigned int soft_margin = TIMER_MARGIN;	/* in seconds */
module_param(soft_margin, uint, 0);
MODULE_PARM_DESC(soft_margin,
	"Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
					__MODULE_STRING(TIMER_MARGIN) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
		"Watchdog cannot be stopped once started (default="
				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static int soft_noboot;
module_param(soft_noboot, int, 0);
MODULE_PARM_DESC(soft_noboot,
	"Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");

static int soft_panic;
module_param(soft_panic, int, 0);
MODULE_PARM_DESC(soft_panic,
	"Softdog action, set to 1 to panic, 0 to reboot (default=0)");

static void watchdog_fire(unsigned long);

static struct timer_list watchdog_ticktock =
		TIMER_INITIALIZER(watchdog_fire, 0, 0);

static void watchdog_fire(unsigned long data)
{
	module_put(THIS_MODULE);
	if (soft_noboot)
		pr_crit("Triggered - Reboot ignored\n");
	else if (soft_panic) {
		pr_crit("Initiating panic\n");
		panic("Software Watchdog Timer expired");
	} else {
		pr_crit("Initiating system reboot\n");
		emergency_restart();
		pr_crit("Reboot didn't ?????\n");
	}
}

static int softdog_ping(struct watchdog_device *w)
{
	if (!mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ)))
		__module_get(THIS_MODULE);
	return 0;
}

static int softdog_stop(struct watchdog_device *w)
{
	if (del_timer(&watchdog_ticktock))
		module_put(THIS_MODULE);

	return 0;
}

static int softdog_set_timeout(struct watchdog_device *w, unsigned int t)
{
	w->timeout = t;
	return 0;
}

static struct watchdog_info softdog_info = {
	.identity = "Software Watchdog",
	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
};

static struct watchdog_ops softdog_ops = {
	.owner = THIS_MODULE,
	.start = softdog_ping,
	.stop = softdog_stop,
	.set_timeout = softdog_set_timeout,
};

static struct watchdog_device softdog_dev = {
	.info = &softdog_info,
	.ops = &softdog_ops,
	.min_timeout = 1,
	.max_timeout = 65535,
	.timeout = TIMER_MARGIN,
};

static int __init watchdog_init(void)
{
	int ret;

	watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
	watchdog_set_nowayout(&softdog_dev, nowayout);
	watchdog_stop_on_reboot(&softdog_dev);

	ret = watchdog_register_device(&softdog_dev);
	if (ret)
		return ret;

	pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
		soft_noboot, softdog_dev.timeout, soft_panic, nowayout);

	return 0;
}

static void __exit watchdog_exit(void)
{
	watchdog_unregister_device(&softdog_dev);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Software Watchdog Device Driver");
MODULE_LICENSE("GPL");