1 /* 2 * hangcheck-timer.c 3 * 4 * Driver for a little io fencing timer. 5 * 6 * Copyright (C) 2002, 2003 Oracle. All rights reserved. 7 * 8 * Author: Joel Becker <joel.becker@oracle.com> 9 * 10 * This program is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU General Public 12 * License version 2 as published by the Free Software Foundation. 13 * 14 * This program is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 17 * General Public License for more details. 18 * 19 * You should have received a copy of the GNU General Public 20 * License along with this program; if not, write to the 21 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, 22 * Boston, MA 021110-1307, USA. 23 */ 24 25 /* 26 * The hangcheck-timer driver uses the TSC to catch delays that 27 * jiffies does not notice. A timer is set. When the timer fires, it 28 * checks whether it was delayed and if that delay exceeds a given 29 * margin of error. The hangcheck_tick module parameter takes the timer 30 * duration in seconds. The hangcheck_margin parameter defines the 31 * margin of error, in seconds. The defaults are 60 seconds for the 32 * timer and 180 seconds for the margin of error. IOW, a timer is set 33 * for 60 seconds. When the timer fires, the callback checks the 34 * actual duration that the timer waited. If the duration exceeds the 35 * alloted time and margin (here 60 + 180, or 240 seconds), the machine 36 * is restarted. A healthy machine will have the duration match the 37 * expected timeout very closely. 38 */ 39 40 #include <linux/module.h> 41 #include <linux/moduleparam.h> 42 #include <linux/types.h> 43 #include <linux/kernel.h> 44 #include <linux/fs.h> 45 #include <linux/mm.h> 46 #include <linux/reboot.h> 47 #include <linux/init.h> 48 #include <linux/delay.h> 49 #include <asm/uaccess.h> 50 #include <linux/sysrq.h> 51 #include <linux/timer.h> 52 #include <linux/hrtimer.h> 53 54 #define VERSION_STR "0.9.1" 55 56 #define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */ 57 #define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */ 58 59 static int hangcheck_tick = DEFAULT_IOFENCE_TICK; 60 static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN; 61 static int hangcheck_reboot; /* Defaults to not reboot */ 62 static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */ 63 64 /* options - modular */ 65 module_param(hangcheck_tick, int, 0); 66 MODULE_PARM_DESC(hangcheck_tick, "Timer delay."); 67 module_param(hangcheck_margin, int, 0); 68 MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire."); 69 module_param(hangcheck_reboot, int, 0); 70 MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded."); 71 module_param(hangcheck_dump_tasks, int, 0); 72 MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded."); 73 74 MODULE_AUTHOR("Oracle"); 75 MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin."); 76 MODULE_LICENSE("GPL"); 77 MODULE_VERSION(VERSION_STR); 78 79 /* options - nonmodular */ 80 #ifndef MODULE 81 82 static int __init hangcheck_parse_tick(char *str) 83 { 84 int par; 85 if (get_option(&str,&par)) 86 hangcheck_tick = par; 87 return 1; 88 } 89 90 static int __init hangcheck_parse_margin(char *str) 91 { 92 int par; 93 if (get_option(&str,&par)) 94 hangcheck_margin = par; 95 return 1; 96 } 97 98 static int __init hangcheck_parse_reboot(char *str) 99 { 100 int par; 101 if (get_option(&str,&par)) 102 hangcheck_reboot = par; 103 return 1; 104 } 105 106 static int __init hangcheck_parse_dump_tasks(char *str) 107 { 108 int par; 109 if (get_option(&str,&par)) 110 hangcheck_dump_tasks = par; 111 return 1; 112 } 113 114 __setup("hcheck_tick", hangcheck_parse_tick); 115 __setup("hcheck_margin", hangcheck_parse_margin); 116 __setup("hcheck_reboot", hangcheck_parse_reboot); 117 __setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks); 118 #endif /* not MODULE */ 119 120 #define TIMER_FREQ 1000000000ULL 121 122 /* Last time scheduled */ 123 static unsigned long long hangcheck_tsc, hangcheck_tsc_margin; 124 125 static void hangcheck_fire(unsigned long); 126 127 static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire, 0, 0); 128 129 static void hangcheck_fire(unsigned long data) 130 { 131 unsigned long long cur_tsc, tsc_diff; 132 133 cur_tsc = ktime_get_ns(); 134 135 if (cur_tsc > hangcheck_tsc) 136 tsc_diff = cur_tsc - hangcheck_tsc; 137 else 138 tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */ 139 140 if (tsc_diff > hangcheck_tsc_margin) { 141 if (hangcheck_dump_tasks) { 142 printk(KERN_CRIT "Hangcheck: Task state:\n"); 143 #ifdef CONFIG_MAGIC_SYSRQ 144 handle_sysrq('t'); 145 #endif /* CONFIG_MAGIC_SYSRQ */ 146 } 147 if (hangcheck_reboot) { 148 printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n"); 149 emergency_restart(); 150 } else { 151 printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n"); 152 } 153 } 154 #if 0 155 /* 156 * Enable to investigate delays in detail 157 */ 158 printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n", 159 tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ); 160 #endif 161 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); 162 hangcheck_tsc = ktime_get_ns(); 163 } 164 165 166 static int __init hangcheck_init(void) 167 { 168 printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n", 169 VERSION_STR, hangcheck_tick, hangcheck_margin); 170 hangcheck_tsc_margin = 171 (unsigned long long)hangcheck_margin + hangcheck_tick; 172 hangcheck_tsc_margin *= TIMER_FREQ; 173 174 hangcheck_tsc = ktime_get_ns(); 175 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); 176 177 return 0; 178 } 179 180 181 static void __exit hangcheck_exit(void) 182 { 183 del_timer_sync(&hangcheck_ticktock); 184 printk("Hangcheck: Stopped hangcheck timer.\n"); 185 } 186 187 module_init(hangcheck_init); 188 module_exit(hangcheck_exit); 189