linux/drivers/watchdog/softdog.c
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   1/*
   2 *      SoftDog:        A Software Watchdog Device
   3 *
   4 *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5 *                                                      All Rights Reserved.
   6 *
   7 *      This program is free software; you can redistribute it and/or
   8 *      modify it under the terms of the GNU General Public License
   9 *      as published by the Free Software Foundation; either version
  10 *      2 of the License, or (at your option) any later version.
  11 *
  12 *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
  13 *      warranty for any of this software. This material is provided
  14 *      "AS-IS" and at no charge.
  15 *
  16 *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  17 *
  18 *      Software only watchdog driver. Unlike its big brother the WDT501P
  19 *      driver this won't always recover a failed machine.
  20 *
  21 *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
  22 *      Modularised.
  23 *      Added soft_margin; use upon insmod to change the timer delay.
  24 *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
  25 *          minors.
  26 *
  27 *  19980911 Alan Cox
  28 *      Made SMP safe for 2.3.x
  29 *
  30 *  20011127 Joel Becker (jlbec@evilplan.org>
  31 *      Added soft_noboot; Allows testing the softdog trigger without
  32 *      requiring a recompile.
  33 *      Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
  34 *
  35 *  20020530 Joel Becker <joel.becker@oracle.com>
  36 *      Added Matt Domsch's nowayout module option.
  37 */
  38
  39#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  40
  41#include <linux/module.h>
  42#include <linux/moduleparam.h>
  43#include <linux/types.h>
  44#include <linux/timer.h>
  45#include <linux/miscdevice.h>
  46#include <linux/watchdog.h>
  47#include <linux/notifier.h>
  48#include <linux/reboot.h>
  49#include <linux/init.h>
  50#include <linux/jiffies.h>
  51#include <linux/kernel.h>
  52
  53#define TIMER_MARGIN    60              /* Default is 60 seconds */
  54static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
  55module_param(soft_margin, uint, 0);
  56MODULE_PARM_DESC(soft_margin,
  57        "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  58                                        __MODULE_STRING(TIMER_MARGIN) ")");
  59
  60static bool nowayout = WATCHDOG_NOWAYOUT;
  61module_param(nowayout, bool, 0);
  62MODULE_PARM_DESC(nowayout,
  63                "Watchdog cannot be stopped once started (default="
  64                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  65
  66static int soft_noboot = 0;
  67module_param(soft_noboot, int, 0);
  68MODULE_PARM_DESC(soft_noboot,
  69        "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
  70
  71static int soft_panic;
  72module_param(soft_panic, int, 0);
  73MODULE_PARM_DESC(soft_panic,
  74        "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
  75
  76/*
  77 *      Our timer
  78 */
  79
  80static void watchdog_fire(unsigned long);
  81
  82static struct timer_list watchdog_ticktock =
  83                TIMER_INITIALIZER(watchdog_fire, 0, 0);
  84
  85/*
  86 *      If the timer expires..
  87 */
  88
  89static void watchdog_fire(unsigned long data)
  90{
  91        if (soft_noboot)
  92                pr_crit("Triggered - Reboot ignored\n");
  93        else if (soft_panic) {
  94                pr_crit("Initiating panic\n");
  95                panic("Software Watchdog Timer expired");
  96        } else {
  97                pr_crit("Initiating system reboot\n");
  98                emergency_restart();
  99                pr_crit("Reboot didn't ?????\n");
 100        }
 101}
 102
 103/*
 104 *      Softdog operations
 105 */
 106
 107static int softdog_ping(struct watchdog_device *w)
 108{
 109        mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ));
 110        return 0;
 111}
 112
 113static int softdog_stop(struct watchdog_device *w)
 114{
 115        del_timer(&watchdog_ticktock);
 116        return 0;
 117}
 118
 119static int softdog_set_timeout(struct watchdog_device *w, unsigned int t)
 120{
 121        w->timeout = t;
 122        return 0;
 123}
 124
 125/*
 126 *      Notifier for system down
 127 */
 128
 129static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
 130        void *unused)
 131{
 132        if (code == SYS_DOWN || code == SYS_HALT)
 133                /* Turn the WDT off */
 134                softdog_stop(NULL);
 135        return NOTIFY_DONE;
 136}
 137
 138/*
 139 *      Kernel Interfaces
 140 */
 141
 142static struct notifier_block softdog_notifier = {
 143        .notifier_call  = softdog_notify_sys,
 144};
 145
 146static struct watchdog_info softdog_info = {
 147        .identity = "Software Watchdog",
 148        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 149};
 150
 151static struct watchdog_ops softdog_ops = {
 152        .owner = THIS_MODULE,
 153        .start = softdog_ping,
 154        .stop = softdog_stop,
 155        .set_timeout = softdog_set_timeout,
 156};
 157
 158static struct watchdog_device softdog_dev = {
 159        .info = &softdog_info,
 160        .ops = &softdog_ops,
 161        .min_timeout = 1,
 162        .max_timeout = 0xFFFF
 163};
 164
 165static int __init watchdog_init(void)
 166{
 167        int ret;
 168
 169        /* Check that the soft_margin value is within it's range;
 170           if not reset to the default */
 171        if (soft_margin < 1 || soft_margin > 65535) {
 172                pr_info("soft_margin must be 0 < soft_margin < 65536, using %d\n",
 173                        TIMER_MARGIN);
 174                return -EINVAL;
 175        }
 176        softdog_dev.timeout = soft_margin;
 177
 178        watchdog_set_nowayout(&softdog_dev, nowayout);
 179
 180        ret = register_reboot_notifier(&softdog_notifier);
 181        if (ret) {
 182                pr_err("cannot register reboot notifier (err=%d)\n", ret);
 183                return ret;
 184        }
 185
 186        ret = watchdog_register_device(&softdog_dev);
 187        if (ret) {
 188                unregister_reboot_notifier(&softdog_notifier);
 189                return ret;
 190        }
 191
 192        pr_info("Software Watchdog Timer: 0.08 initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
 193                soft_noboot, soft_margin, soft_panic, nowayout);
 194
 195        return 0;
 196}
 197
 198static void __exit watchdog_exit(void)
 199{
 200        watchdog_unregister_device(&softdog_dev);
 201        unregister_reboot_notifier(&softdog_notifier);
 202}
 203
 204module_init(watchdog_init);
 205module_exit(watchdog_exit);
 206
 207MODULE_AUTHOR("Alan Cox");
 208MODULE_DESCRIPTION("Software Watchdog Device Driver");
 209MODULE_LICENSE("GPL");
 210MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 211
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