225 lines · c
1// SPDX-License-Identifier: GPL-2.0+2/*3 * SoftDog: A Software Watchdog Device4 *5 * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,6 * All Rights Reserved.7 *8 * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide9 * warranty for any of this software. This material is provided10 * "AS-IS" and at no charge.11 *12 * (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk>13 *14 * Software only watchdog driver. Unlike its big brother the WDT501P15 * driver this won't always recover a failed machine.16 */17 18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt19 20#include <linux/hrtimer.h>21#include <linux/init.h>22#include <linux/kernel.h>23#include <linux/kthread.h>24#include <linux/module.h>25#include <linux/moduleparam.h>26#include <linux/reboot.h>27#include <linux/types.h>28#include <linux/watchdog.h>29#include <linux/workqueue.h>30 31#define TIMER_MARGIN 60 /* Default is 60 seconds */32static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */33module_param(soft_margin, uint, 0);34MODULE_PARM_DESC(soft_margin,35 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="36 __MODULE_STRING(TIMER_MARGIN) ")");37 38static bool nowayout = WATCHDOG_NOWAYOUT;39module_param(nowayout, bool, 0);40MODULE_PARM_DESC(nowayout,41 "Watchdog cannot be stopped once started (default="42 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");43 44static int soft_noboot;45module_param(soft_noboot, int, 0);46MODULE_PARM_DESC(soft_noboot,47 "Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");48 49static int soft_panic;50module_param(soft_panic, int, 0);51MODULE_PARM_DESC(soft_panic,52 "Softdog action, set to 1 to panic, 0 to reboot (default=0)");53 54static char *soft_reboot_cmd;55module_param(soft_reboot_cmd, charp, 0000);56MODULE_PARM_DESC(soft_reboot_cmd,57 "Set reboot command. Emergency reboot takes place if unset");58 59static bool soft_active_on_boot;60module_param(soft_active_on_boot, bool, 0000);61MODULE_PARM_DESC(soft_active_on_boot,62 "Set to true to active Softdog on boot (default=false)");63 64static struct hrtimer softdog_ticktock;65static struct hrtimer softdog_preticktock;66 67static int reboot_kthread_fn(void *data)68{69 kernel_restart(soft_reboot_cmd);70 return -EPERM; /* Should not reach here */71}72 73static void reboot_work_fn(struct work_struct *unused)74{75 kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");76}77 78static enum hrtimer_restart softdog_fire(struct hrtimer *timer)79{80 static bool soft_reboot_fired;81 82 module_put(THIS_MODULE);83 if (soft_noboot) {84 pr_crit("Triggered - Reboot ignored\n");85 } else if (soft_panic) {86 pr_crit("Initiating panic\n");87 panic("Software Watchdog Timer expired");88 } else {89 pr_crit("Initiating system reboot\n");90 if (!soft_reboot_fired && soft_reboot_cmd != NULL) {91 static DECLARE_WORK(reboot_work, reboot_work_fn);92 /*93 * The 'kernel_restart' is a 'might-sleep' operation.94 * Also, executing it in system-wide workqueues blocks95 * any driver from using the same workqueue in its96 * shutdown callback function. Thus, we should execute97 * the 'kernel_restart' in a standalone kernel thread.98 * But since starting a kernel thread is also a99 * 'might-sleep' operation, so the 'reboot_work' is100 * required as a launcher of the kernel thread.101 *102 * After request the reboot, restart the timer to103 * schedule an 'emergency_restart' reboot after104 * 'TIMER_MARGIN' seconds. It's because if the softdog105 * hangs, it might be because of scheduling issues. And106 * if that is the case, both 'schedule_work' and107 * 'kernel_restart' may possibly be malfunctional at the108 * same time.109 */110 soft_reboot_fired = true;111 schedule_work(&reboot_work);112 hrtimer_add_expires_ns(timer,113 (u64)TIMER_MARGIN * NSEC_PER_SEC);114 115 return HRTIMER_RESTART;116 }117 emergency_restart();118 pr_crit("Reboot didn't ?????\n");119 }120 121 return HRTIMER_NORESTART;122}123 124static struct watchdog_device softdog_dev;125 126static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)127{128 watchdog_notify_pretimeout(&softdog_dev);129 130 return HRTIMER_NORESTART;131}132 133static int softdog_ping(struct watchdog_device *w)134{135 if (!hrtimer_active(&softdog_ticktock))136 __module_get(THIS_MODULE);137 hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),138 HRTIMER_MODE_REL);139 140 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {141 if (w->pretimeout)142 hrtimer_start(&softdog_preticktock,143 ktime_set(w->timeout - w->pretimeout, 0),144 HRTIMER_MODE_REL);145 else146 hrtimer_cancel(&softdog_preticktock);147 }148 149 return 0;150}151 152static int softdog_stop(struct watchdog_device *w)153{154 if (hrtimer_cancel(&softdog_ticktock))155 module_put(THIS_MODULE);156 157 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))158 hrtimer_cancel(&softdog_preticktock);159 160 return 0;161}162 163static struct watchdog_info softdog_info = {164 .identity = "Software Watchdog",165 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,166};167 168static const struct watchdog_ops softdog_ops = {169 .owner = THIS_MODULE,170 .start = softdog_ping,171 .stop = softdog_stop,172};173 174static struct watchdog_device softdog_dev = {175 .info = &softdog_info,176 .ops = &softdog_ops,177 .min_timeout = 1,178 .max_timeout = 65535,179 .timeout = TIMER_MARGIN,180};181 182static int __init softdog_init(void)183{184 int ret;185 186 watchdog_init_timeout(&softdog_dev, soft_margin, NULL);187 watchdog_set_nowayout(&softdog_dev, nowayout);188 watchdog_stop_on_reboot(&softdog_dev);189 190 hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);191 softdog_ticktock.function = softdog_fire;192 193 if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {194 softdog_info.options |= WDIOF_PRETIMEOUT;195 hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,196 HRTIMER_MODE_REL);197 softdog_preticktock.function = softdog_pretimeout;198 }199 200 if (soft_active_on_boot)201 softdog_ping(&softdog_dev);202 203 ret = watchdog_register_device(&softdog_dev);204 if (ret)205 return ret;206 207 pr_info("initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",208 soft_noboot, softdog_dev.timeout, soft_panic, nowayout);209 pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n",210 soft_reboot_cmd ?: "<not set>", soft_active_on_boot);211 212 return 0;213}214module_init(softdog_init);215 216static void __exit softdog_exit(void)217{218 watchdog_unregister_device(&softdog_dev);219}220module_exit(softdog_exit);221 222MODULE_AUTHOR("Alan Cox");223MODULE_DESCRIPTION("Software Watchdog Device Driver");224MODULE_LICENSE("GPL");225