// SPDX-License-Identifier: GPL-2.0-only /* * hangcheck-timer.c * * Driver for a little io fencing timer. * * Copyright (C) 2002, 2003 Oracle. All rights reserved. * * Author: Joel Becker <joel.becker@oracle.com> */ /* * The hangcheck-timer driver uses the TSC to catch delays that * jiffies does not notice. A timer is set. When the timer fires, it * checks whether it was delayed and if that delay exceeds a given * margin of error. The hangcheck_tick module parameter takes the timer * duration in seconds. The hangcheck_margin parameter defines the * margin of error, in seconds. The defaults are 60 seconds for the * timer and 180 seconds for the margin of error. IOW, a timer is set * for 60 seconds. When the timer fires, the callback checks the * actual duration that the timer waited. If the duration exceeds the * allotted time and margin (here 60 + 180, or 240 seconds), the machine * is restarted. A healthy machine will have the duration match the * expected timeout very closely. */ #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/types.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/reboot.h> #include <linux/init.h> #include <linux/delay.h> #include <linux/uaccess.h> #include <linux/sysrq.h> #include <linux/timer.h> #include <linux/hrtimer.h> #define VERSION_STR "0.9.1" #define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */ #define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */ static int hangcheck_tick = DEFAULT_IOFENCE_TICK; static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN; static int hangcheck_reboot; /* Defaults to not reboot */ static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */ /* options - modular */ module_param(hangcheck_tick, int, 0); MODULE_PARM_DESC(hangcheck_tick, "Timer delay."); module_param(hangcheck_margin, int, 0); MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire."); module_param(hangcheck_reboot, int, 0); MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded."); module_param(hangcheck_dump_tasks, int, 0); MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded."); MODULE_AUTHOR("Oracle"); MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin."); MODULE_LICENSE("GPL"); MODULE_VERSION(VERSION_STR); /* options - nonmodular */ #ifndef MODULE static int __init hangcheck_parse_tick(char *str) { int par; if (get_option(&str,&par)) hangcheck_tick = par; return 1; } static int __init hangcheck_parse_margin(char *str) { int par; if (get_option(&str,&par)) hangcheck_margin = par; return 1; } static int __init hangcheck_parse_reboot(char *str) { int par; if (get_option(&str,&par)) hangcheck_reboot = par; return 1; } static int __init hangcheck_parse_dump_tasks(char *str) { int par; if (get_option(&str,&par)) hangcheck_dump_tasks = par; return 1; } __setup("hcheck_tick", hangcheck_parse_tick); __setup("hcheck_margin", hangcheck_parse_margin); __setup("hcheck_reboot", hangcheck_parse_reboot); __setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks); #endif /* not MODULE */ #define TIMER_FREQ 1000000000ULL /* Last time scheduled */ static unsigned long long hangcheck_tsc, hangcheck_tsc_margin; static void hangcheck_fire(struct timer_list *); static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire); static void hangcheck_fire(struct timer_list *unused) { unsigned long long cur_tsc, tsc_diff; cur_tsc = ktime_get_ns(); if (cur_tsc > hangcheck_tsc) tsc_diff = cur_tsc - hangcheck_tsc; else tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */ if (tsc_diff > hangcheck_tsc_margin) { if (hangcheck_dump_tasks) { printk(KERN_CRIT "Hangcheck: Task state:\n"); #ifdef CONFIG_MAGIC_SYSRQ handle_sysrq('t'); #endif /* CONFIG_MAGIC_SYSRQ */ } if (hangcheck_reboot) { printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n"); emergency_restart(); } else { printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n"); } } #if 0 /* * Enable to investigate delays in detail */ printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n", tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ); #endif mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); hangcheck_tsc = ktime_get_ns(); } static int __init hangcheck_init(void) { printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n", VERSION_STR, hangcheck_tick, hangcheck_margin); hangcheck_tsc_margin = (unsigned long long)hangcheck_margin + hangcheck_tick; hangcheck_tsc_margin *= TIMER_FREQ; hangcheck_tsc = ktime_get_ns(); mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); return 0; } static void __exit hangcheck_exit(void) { del_timer_sync(&hangcheck_ticktock); printk("Hangcheck: Stopped hangcheck timer.\n"); } module_init(hangcheck_init); module_exit(hangcheck_exit);