drivers/watchdog/softdog.c

   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
  22 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  23
  24 #include <linux/init.h>
  25 #include <linux/jiffies.h>
  26 #include <linux/kernel.h>
  27 #include <linux/module.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/reboot.h>
  30 #include <linux/timer.h>
  31 #include <linux/types.h>
  32 #include <linux/watchdog.h>
  33
  34 #define TIMER_MARGIN    60              /* Default is 60 seconds */
  35 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
  36 module_param(soft_margin, uint, 0);
  37 MODULE_PARM_DESC(soft_margin,
  38         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  39                                         __MODULE_STRING(TIMER_MARGIN) ")");
  40
  41 static bool nowayout = WATCHDOG_NOWAYOUT;
  42 module_param(nowayout, bool, 0);
  43 MODULE_PARM_DESC(nowayout,
  44                 "Watchdog cannot be stopped once started (default="
  45                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  46
  47 static int soft_noboot;
  48 module_param(soft_noboot, int, 0);
  49 MODULE_PARM_DESC(soft_noboot,
  50         "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
  51
  52 static int soft_panic;
  53 module_param(soft_panic, int, 0);
  54 MODULE_PARM_DESC(soft_panic,
  55         "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
  56
  57 static void softdog_fire(unsigned long data)
  58 {
  59         module_put(THIS_MODULE);
  60         if (soft_noboot) {
  61                 pr_crit("Triggered - Reboot ignored\n");
  62         } else if (soft_panic) {
  63                 pr_crit("Initiating panic\n");
  64                 panic("Software Watchdog Timer expired");
  65         } else {
  66                 pr_crit("Initiating system reboot\n");
  67                 emergency_restart();
  68                 pr_crit("Reboot didn't ?????\n");
  69         }
  70 }
  71
  72 static struct timer_list softdog_ticktock =
  73                 TIMER_INITIALIZER(softdog_fire, 0, 0);
  74
  75 static struct watchdog_device softdog_dev;
  76
  77 static void softdog_pretimeout(unsigned long data)
  78 {
  79         watchdog_notify_pretimeout(&softdog_dev);
  80 }
  81
  82 static struct timer_list softdog_preticktock =
  83                 TIMER_INITIALIZER(softdog_pretimeout, 0, 0);
  84
  85 static int softdog_ping(struct watchdog_device *w)
  86 {
  87         if (!mod_timer(&softdog_ticktock, jiffies + (w->timeout * HZ)))
  88                 __module_get(THIS_MODULE);
  89
  90         if (w->pretimeout)
  91                 mod_timer(&softdog_preticktock, jiffies +
  92                           (w->timeout - w->pretimeout) * HZ);
  93         else
  94                 del_timer(&softdog_preticktock);
  95
  96         return 0;
  97 }
  98
  99 static int softdog_stop(struct watchdog_device *w)
 100 {
 101         if (del_timer(&softdog_ticktock))
 102                 module_put(THIS_MODULE);
 103
 104         del_timer(&softdog_preticktock);
 105
 106         return 0;
 107 }
 108
 109 static struct watchdog_info softdog_info = {
 110         .identity = "Software Watchdog",
 111         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE |
 112                    WDIOF_PRETIMEOUT,
 113 };
 114
 115 static const struct watchdog_ops softdog_ops = {
 116         .owner = THIS_MODULE,
 117         .start = softdog_ping,
 118         .stop = softdog_stop,
 119 };
 120
 121 static struct watchdog_device softdog_dev = {
 122         .info = &softdog_info,
 123         .ops = &softdog_ops,
 124         .min_timeout = 1,
 125         .max_timeout = 65535,
 126         .timeout = TIMER_MARGIN,
 127 };
 128
 129 static int __init softdog_init(void)
 130 {
 131         int ret;
 132
 133         watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
 134         watchdog_set_nowayout(&softdog_dev, nowayout);
 135         watchdog_stop_on_reboot(&softdog_dev);
 136
 137         ret = watchdog_register_device(&softdog_dev);
 138         if (ret)
 139                 return ret;
 140
 141         pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
 142                 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
 143
 144         return 0;
 145 }
 146 module_init(softdog_init);
 147
 148 static void __exit softdog_exit(void)
 149 {
 150         watchdog_unregister_device(&softdog_dev);
 151 }
 152 module_exit(softdog_exit);
 153
 154 MODULE_AUTHOR("Alan Cox");
 155 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 156 MODULE_LICENSE("GPL");