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// SPDX-License-Identifier: GPL-2.0+
/*
* SoftDog: A Software Watchdog Device
*
* (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* 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/hrtimer.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/reboot.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/workqueue.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 char *soft_reboot_cmd;
module_param(soft_reboot_cmd, charp, 0000);
MODULE_PARM_DESC(soft_reboot_cmd,
"Set reboot command. Emergency reboot takes place if unset");
static bool soft_active_on_boot;
module_param(soft_active_on_boot, bool, 0000);
MODULE_PARM_DESC(soft_active_on_boot,
"Set to true to active Softdog on boot (default=false)");
static struct hrtimer softdog_ticktock;
static struct hrtimer softdog_preticktock;
static int reboot_kthread_fn(void *data)
{
kernel_restart(soft_reboot_cmd);
return -EPERM; /* Should not reach here */
}
static void reboot_work_fn(struct work_struct *unused)
{
kthread_run(reboot_kthread_fn, NULL, "softdog_reboot");
}
static enum hrtimer_restart softdog_fire(struct hrtimer *timer)
{
static bool soft_reboot_fired;
module_put(THIS_MODULE);
if (soft_noboot) {
pr_crit("Triggered - Reboot ignored\n");
} else if (soft_panic) {
pr_crit("Initiating panic\n");
if (sysctl_hardlockup_all_cpu_backtrace && 1)
trigger_allbutself_cpu_backtrace();
panic("Software Watchdog Timer expired");
} else {
pr_crit("Initiating system reboot\n");
if (!soft_reboot_fired && soft_reboot_cmd != NULL) {
static DECLARE_WORK(reboot_work, reboot_work_fn);
/*
* The 'kernel_restart' is a 'might-sleep' operation.
* Also, executing it in system-wide workqueues blocks
* any driver from using the same workqueue in its
* shutdown callback function. Thus, we should execute
* the 'kernel_restart' in a standalone kernel thread.
* But since starting a kernel thread is also a
* 'might-sleep' operation, so the 'reboot_work' is
* required as a launcher of the kernel thread.
*
* After request the reboot, restart the timer to
* schedule an 'emergency_restart' reboot after
* 'TIMER_MARGIN' seconds. It's because if the softdog
* hangs, it might be because of scheduling issues. And
* if that is the case, both 'schedule_work' and
* 'kernel_restart' may possibly be malfunctional at the
* same time.
*/
soft_reboot_fired = true;
schedule_work(&reboot_work);
hrtimer_add_expires_ns(timer,
(u64)TIMER_MARGIN * NSEC_PER_SEC);
return HRTIMER_RESTART;
}
emergency_restart();
pr_crit("Reboot didn't ?????\n");
}
return HRTIMER_NORESTART;
}
static struct watchdog_device softdog_dev;
static enum hrtimer_restart softdog_pretimeout(struct hrtimer *timer)
{
watchdog_notify_pretimeout(&softdog_dev);
return HRTIMER_NORESTART;
}
static int softdog_ping(struct watchdog_device *w)
{
if (!hrtimer_active(&softdog_ticktock))
__module_get(THIS_MODULE);
hrtimer_start(&softdog_ticktock, ktime_set(w->timeout, 0),
HRTIMER_MODE_REL);
if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
if (w->pretimeout)
hrtimer_start(&softdog_preticktock,
ktime_set(w->timeout - w->pretimeout, 0),
HRTIMER_MODE_REL);
else
hrtimer_cancel(&softdog_preticktock);
}
return 0;
}
static int softdog_stop(struct watchdog_device *w)
{
if (hrtimer_cancel(&softdog_ticktock))
module_put(THIS_MODULE);
if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT))
hrtimer_cancel(&softdog_preticktock);
return 0;
}
static struct watchdog_info softdog_info = {
.identity = "Software Watchdog",
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
};
static const struct watchdog_ops softdog_ops = {
.owner = THIS_MODULE,
.start = softdog_ping,
.stop = softdog_stop,
};
static struct watchdog_device softdog_dev = {
.info = &softdog_info,
.ops = &softdog_ops,
.min_timeout = 1,
.max_timeout = 65535,
.timeout = TIMER_MARGIN,
};
static int __init softdog_init(void)
{
int ret;
watchdog_init_timeout(&softdog_dev, soft_margin, NULL);
watchdog_set_nowayout(&softdog_dev, nowayout);
watchdog_stop_on_reboot(&softdog_dev);
hrtimer_init(&softdog_ticktock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
softdog_ticktock.function = softdog_fire;
if (IS_ENABLED(CONFIG_SOFT_WATCHDOG_PRETIMEOUT)) {
softdog_info.options |= WDIOF_PRETIMEOUT;
hrtimer_init(&softdog_preticktock, CLOCK_MONOTONIC,
HRTIMER_MODE_REL);
softdog_preticktock.function = softdog_pretimeout;
}
if (soft_active_on_boot)
softdog_ping(&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);
pr_info(" soft_reboot_cmd=%s soft_active_on_boot=%d\n",
soft_reboot_cmd ?: "<not set>", soft_active_on_boot);
return 0;
}
module_init(softdog_init);
static void __exit softdog_exit(void)
{
watchdog_unregister_device(&softdog_dev);
}
module_exit(softdog_exit);
MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Software Watchdog Device Driver");
MODULE_LICENSE("GPL");
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