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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * hangcheck-timer.c4 *5 * Driver for a little io fencing timer.6 *7 * Copyright (C) 2002, 2003 Oracle. All rights reserved.8 *9 * Author: Joel Becker <joel.becker@oracle.com>10 */11 12/*13 * The hangcheck-timer driver uses the TSC to catch delays that14 * jiffies does not notice. A timer is set. When the timer fires, it15 * checks whether it was delayed and if that delay exceeds a given16 * margin of error. The hangcheck_tick module parameter takes the timer17 * duration in seconds. The hangcheck_margin parameter defines the18 * margin of error, in seconds. The defaults are 60 seconds for the19 * timer and 180 seconds for the margin of error. IOW, a timer is set20 * for 60 seconds. When the timer fires, the callback checks the21 * actual duration that the timer waited. If the duration exceeds the22 * allotted time and margin (here 60 + 180, or 240 seconds), the machine23 * is restarted. A healthy machine will have the duration match the24 * expected timeout very closely.25 */26 27#include <linux/module.h>28#include <linux/moduleparam.h>29#include <linux/types.h>30#include <linux/kernel.h>31#include <linux/fs.h>32#include <linux/mm.h>33#include <linux/reboot.h>34#include <linux/init.h>35#include <linux/delay.h>36#include <linux/uaccess.h>37#include <linux/sysrq.h>38#include <linux/timer.h>39#include <linux/hrtimer.h>40 41#define VERSION_STR "0.9.1"42 43#define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */44#define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */45 46static int hangcheck_tick = DEFAULT_IOFENCE_TICK;47static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;48static int hangcheck_reboot; /* Defaults to not reboot */49static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */50 51/* options - modular */52module_param(hangcheck_tick, int, 0);53MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");54module_param(hangcheck_margin, int, 0);55MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");56module_param(hangcheck_reboot, int, 0);57MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");58module_param(hangcheck_dump_tasks, int, 0);59MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");60 61MODULE_AUTHOR("Oracle");62MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");63MODULE_LICENSE("GPL");64MODULE_VERSION(VERSION_STR);65 66/* options - nonmodular */67#ifndef MODULE68 69static int __init hangcheck_parse_tick(char *str)70{71 int par;72 if (get_option(&str,&par))73 hangcheck_tick = par;74 return 1;75}76 77static int __init hangcheck_parse_margin(char *str)78{79 int par;80 if (get_option(&str,&par))81 hangcheck_margin = par;82 return 1;83}84 85static int __init hangcheck_parse_reboot(char *str)86{87 int par;88 if (get_option(&str,&par))89 hangcheck_reboot = par;90 return 1;91}92 93static int __init hangcheck_parse_dump_tasks(char *str)94{95 int par;96 if (get_option(&str,&par))97 hangcheck_dump_tasks = par;98 return 1;99}100 101__setup("hcheck_tick", hangcheck_parse_tick);102__setup("hcheck_margin", hangcheck_parse_margin);103__setup("hcheck_reboot", hangcheck_parse_reboot);104__setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);105#endif /* not MODULE */106 107#define TIMER_FREQ 1000000000ULL108 109/* Last time scheduled */110static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;111 112static void hangcheck_fire(struct timer_list *);113 114static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire);115 116static void hangcheck_fire(struct timer_list *unused)117{118 unsigned long long cur_tsc, tsc_diff;119 120 cur_tsc = ktime_get_ns();121 122 if (cur_tsc > hangcheck_tsc)123 tsc_diff = cur_tsc - hangcheck_tsc;124 else125 tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */126 127 if (tsc_diff > hangcheck_tsc_margin) {128 if (hangcheck_dump_tasks) {129 printk(KERN_CRIT "Hangcheck: Task state:\n");130#ifdef CONFIG_MAGIC_SYSRQ131 handle_sysrq('t');132#endif /* CONFIG_MAGIC_SYSRQ */133 }134 if (hangcheck_reboot) {135 printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");136 emergency_restart();137 } else {138 printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");139 }140 }141#if 0142 /*143 * Enable to investigate delays in detail144 */145 printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n",146 tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);147#endif148 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));149 hangcheck_tsc = ktime_get_ns();150}151 152 153static int __init hangcheck_init(void)154{155 printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",156 VERSION_STR, hangcheck_tick, hangcheck_margin);157 hangcheck_tsc_margin =158 (unsigned long long)hangcheck_margin + hangcheck_tick;159 hangcheck_tsc_margin *= TIMER_FREQ;160 161 hangcheck_tsc = ktime_get_ns();162 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));163 164 return 0;165}166 167 168static void __exit hangcheck_exit(void)169{170 del_timer_sync(&hangcheck_ticktock);171 printk("Hangcheck: Stopped hangcheck timer.\n");172}173 174module_init(hangcheck_init);175module_exit(hangcheck_exit);176