diff options
Diffstat (limited to 'drivers/watchdog/softdog.c')
| -rw-r--r-- | drivers/watchdog/softdog.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c new file mode 100644 index 000000000..7a1096265 --- /dev/null +++ b/drivers/watchdog/softdog.c @@ -0,0 +1,224 @@ +// 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"); + 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"); |