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/hrtimer.h>
  25 #include <linux/init.h>
  26 #include <linux/kernel.h>
  27 #include <linux/module.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/reboot.h>
  30 #include <linux/types.h>
  31 #include <linux/watchdog.h>
  32
  33 #define TIMER_MARGIN    60              /* Default is 60 seconds */
  34 static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
  35 module_param(soft_margin, uint, 0);
  36 MODULE_PARM_DESC(soft_margin,
  37         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
  38                                         __MODULE_STRING(TIMER_MARGIN) ")");
  39
  40 static bool nowayout = WATCHDOG_NOWAYOUT;
  41 module_param(nowayout, bool, 0);
  42 MODULE_PARM_DESC(nowayout,
  43                 "Watchdog cannot be stopped once started (default="
  44                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  45
  46 static int soft_noboot;
  47 module_param(soft_noboot, int, 0);
  48 MODULE_PARM_DESC(soft_noboot,
  49         "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
  50
  51 static int soft_panic;
  52 module_param(soft_panic, int, 0);
  53 MODULE_PARM_DESC(soft_panic,
  54         "Softdog action, set to 1 to panic, 0 to reboot (default=0)");
  55
  56 static struct hrtimer softdog_ticktock;
  57 static struct hrtimer softdog_preticktock;
  58
  59 static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
  60 {
  61         module_put(THIS_MODULE);
  62         if (soft_noboot) {
  63                 pr_crit("Triggered - Reboot ignored\n");
  64         } else if (soft_panic) {
  65                 pr_crit("Initiating panic\n");
  66                 panic("Software Watchdog Timer expired");
  67         } else {
  68                 pr_crit("Initiating system reboot\n");
  69                 emergency_restart();
  70                 pr_crit("Reboot didn't ?????\n");
  71         }
  72
  73         return HRTIMER_NORESTART;
  74 }
  75
  76 static struct watchdog_device softdog_dev;
  77
  78 static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
  79 {
  80         watchdog_notify_pretimeout(&softdog_dev);
  81
  82         return HRTIMER_NORESTART;
  83 }
  84
  85 static int softdog_ping(struct watchdog_device *w)
  86 {
  87         if (!hrtimer_active(&softdog_ticktock))
  88                 __module_get(THIS_MODULE);
  89         hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
  90                       HRTIMER_MODE_REL);
  91
  92         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
  93                 if (w->pretimeout)
  94                         hrtimer_start(&softdog_preticktock,
  95                                       ktime_set(w->timeout - w->pretimeout, 0),
  96                                       HRTIMER_MODE_REL);
  97                 else
  98                         hrtimer_cancel(&softdog_preticktock);
  99         }
 100
 101         return 0;
 102 }
 103
 104 static int softdog_stop(struct watchdog_device *w)
 105 {
 106         if (hrtimer_cancel(&softdog_ticktock))
 107                 module_put(THIS_MODULE);
 108
 109         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
 110                 hrtimer_cancel(&softdog_preticktock);
 111
 112         return 0;
 113 }
 114
 115 static struct watchdog_info softdog_info = {
 116         .identity = "Software Watchdog",
 117         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 118 };
 119
 120 static const struct watchdog_ops softdog_ops = {
 121         .owner = THIS_MODULE,
 122         .start = softdog_ping,
 123         .stop = softdog_stop,
 124 };
 125
 126 static struct watchdog_device softdog_dev = {
 127         .info = &softdog_info,
 128         .ops = &softdog_ops,
 129         .min_timeout = 1,
 130         .max_timeout = 65535,
 131         .timeout = TIMER_MARGIN,
 132 };
 133
 134 static int __init softdog_init(void)
 135 {
 136         int ret;
 137
 138         watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
 139         watchdog_set_nowayout(&softdog_dev, nowayout);
 140         watchdog_stop_on_reboot(&softdog_dev);
 141
 142         hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 143         softdog_ticktock.function = softdog_fire;
 144
 145         if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
 146                 softdog_info.options |= WDIOF_PRETIMEOUT;
 147                 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
 148                              HRTIMER_MODE_REL);
 149                 softdog_preticktock.function = softdog_pretimeout;
 150         }
 151
 152         ret = watchdog_register_device(&softdog_dev);
 153         if (ret)
 154                 return ret;
 155
 156         pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
 157                 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);
 158
 159         return 0;
 160 }
 161 module_init(softdog_init);
 162
 163 static void __exit softdog_exit(void)
 164 {
 165         watchdog_unregister_device(&softdog_dev);
 166 }
 167 module_exit(softdog_exit);
 168
 169 MODULE_AUTHOR("Alan Cox");
 170 MODULE_DESCRIPTION("Software Watchdog Device Driver");
 171 MODULE_LICENSE("GPL");