drivers/char/hangcheck-timer.c

   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
  53 #define VERSION_STR "0.9.0"
  54
  55 #define DEFAULT_IOFENCE_MARGIN 60       /* Default fudge factor, in seconds */
  56 #define DEFAULT_IOFENCE_TICK 180        /* Default timer timeout, in seconds */
  57
  58 static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
  59 static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
  60 static int hangcheck_reboot;  /* Defaults to not reboot */
  61 static int hangcheck_dump_tasks;  /* Defaults to not dumping SysRQ T */
  62
  63 /* options - modular */
  64 module_param(hangcheck_tick, int, 0);
  65 MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
  66 module_param(hangcheck_margin, int, 0);
  67 MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
  68 module_param(hangcheck_reboot, int, 0);
  69 MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
  70 module_param(hangcheck_dump_tasks, int, 0);
  71 MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");
  72
  73 MODULE_AUTHOR("Oracle");
  74 MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
  75 MODULE_LICENSE("GPL");
  76 MODULE_VERSION(VERSION_STR);
  77
  78 /* options - nonmodular */
  79 #ifndef MODULE
  80
  81 static int __init hangcheck_parse_tick(char *str)
  82 {
  83         int par;
  84         if (get_option(&str,&par))
  85                 hangcheck_tick = par;
  86         return 1;
  87 }
  88
  89 static int __init hangcheck_parse_margin(char *str)
  90 {
  91         int par;
  92         if (get_option(&str,&par))
  93                 hangcheck_margin = par;
  94         return 1;
  95 }
  96
  97 static int __init hangcheck_parse_reboot(char *str)
  98 {
  99         int par;
 100         if (get_option(&str,&par))
 101                 hangcheck_reboot = par;
 102         return 1;
 103 }
 104
 105 static int __init hangcheck_parse_dump_tasks(char *str)
 106 {
 107         int par;
 108         if (get_option(&str,&par))
 109                 hangcheck_dump_tasks = par;
 110         return 1;
 111 }
 112
 113 __setup("hcheck_tick", hangcheck_parse_tick);
 114 __setup("hcheck_margin", hangcheck_parse_margin);
 115 __setup("hcheck_reboot", hangcheck_parse_reboot);
 116 __setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);
 117 #endif /* not MODULE */
 118
 119 #if defined(CONFIG_S390)
 120 # define HAVE_MONOTONIC
 121 # define TIMER_FREQ 1000000000ULL
 122 #elif defined(CONFIG_IA64)
 123 # define TIMER_FREQ ((unsigned long long)local_cpu_data->itc_freq)
 124 #else
 125 # define TIMER_FREQ (HZ*loops_per_jiffy)
 126 #endif
 127
 128 #ifdef HAVE_MONOTONIC
 129 extern unsigned long long monotonic_clock(void);
 130 #else
 131 static inline unsigned long long monotonic_clock(void)
 132 {
 133         return get_cycles();
 134 }
 135 #endif  /* HAVE_MONOTONIC */
 136
 137
 138 /* Last time scheduled */
 139 static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
 140
 141 static void hangcheck_fire(unsigned long);
 142
 143 static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire, 0, 0);
 144
 145
 146 static void hangcheck_fire(unsigned long data)
 147 {
 148         unsigned long long cur_tsc, tsc_diff;
 149
 150         cur_tsc = monotonic_clock();
 151
 152         if (cur_tsc > hangcheck_tsc)
 153                 tsc_diff = cur_tsc - hangcheck_tsc;
 154         else
 155                 tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
 156
 157         if (tsc_diff > hangcheck_tsc_margin) {
 158                 if (hangcheck_dump_tasks) {
 159                         printk(KERN_CRIT "Hangcheck: Task state:\n");
 160 #ifdef CONFIG_MAGIC_SYSRQ
 161                         handle_sysrq('t', NULL);
 162 #endif  /* CONFIG_MAGIC_SYSRQ */
 163                 }
 164                 if (hangcheck_reboot) {
 165                         printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");
 166                         emergency_restart();
 167                 } else {
 168                         printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");
 169                 }
 170         }
 171         mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 172         hangcheck_tsc = monotonic_clock();
 173 }
 174
 175
 176 static int __init hangcheck_init(void)
 177 {
 178         printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
 179                VERSION_STR, hangcheck_tick, hangcheck_margin);
 180 #if defined (HAVE_MONOTONIC)
 181         printk("Hangcheck: Using monotonic_clock().\n");
 182 #else
 183         printk("Hangcheck: Using get_cycles().\n");
 184 #endif  /* HAVE_MONOTONIC */
 185         hangcheck_tsc_margin =
 186                 (unsigned long long)(hangcheck_margin + hangcheck_tick);
 187         hangcheck_tsc_margin *= (unsigned long long)TIMER_FREQ;
 188
 189         hangcheck_tsc = monotonic_clock();
 190         mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 191
 192         return 0;
 193 }
 194
 195
 196 static void __exit hangcheck_exit(void)
 197 {
 198         del_timer_sync(&hangcheck_ticktock);
 199         printk("Hangcheck: Stopped hangcheck timer.\n");
 200 }
 201
 202 module_init(hangcheck_init);
 203 module_exit(hangcheck_exit);