linux/drivers/char/hangcheck-timer.c
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   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/time.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
  59static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
  60static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
  61static int hangcheck_reboot;  /* Defaults to not reboot */
  62static int hangcheck_dump_tasks;  /* Defaults to not dumping SysRQ T */
  63
  64/* options - modular */
  65module_param(hangcheck_tick, int, 0);
  66MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
  67module_param(hangcheck_margin, int, 0);
  68MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
  69module_param(hangcheck_reboot, int, 0);
  70MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
  71module_param(hangcheck_dump_tasks, int, 0);
  72MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");
  73
  74MODULE_AUTHOR("Oracle");
  75MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
  76MODULE_LICENSE("GPL");
  77MODULE_VERSION(VERSION_STR);
  78
  79/* options - nonmodular */
  80#ifndef MODULE
  81
  82static 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
  90static 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
  98static 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
 106static 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#if defined(CONFIG_S390)
 121# define HAVE_MONOTONIC
 122# define TIMER_FREQ 1000000000ULL
 123#else
 124# define TIMER_FREQ 1000000000ULL
 125#endif
 126
 127#ifdef HAVE_MONOTONIC
 128extern unsigned long long monotonic_clock(void);
 129#else
 130static inline unsigned long long monotonic_clock(void)
 131{
 132        struct timespec ts;
 133        getrawmonotonic(&ts);
 134        return timespec_to_ns(&ts);
 135}
 136#endif  /* HAVE_MONOTONIC */
 137
 138
 139/* Last time scheduled */
 140static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
 141
 142static void hangcheck_fire(unsigned long);
 143
 144static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire, 0, 0);
 145
 146
 147static void hangcheck_fire(unsigned long data)
 148{
 149        unsigned long long cur_tsc, tsc_diff;
 150
 151        cur_tsc = monotonic_clock();
 152
 153        if (cur_tsc > hangcheck_tsc)
 154                tsc_diff = cur_tsc - hangcheck_tsc;
 155        else
 156                tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
 157
 158        if (tsc_diff > hangcheck_tsc_margin) {
 159                if (hangcheck_dump_tasks) {
 160                        printk(KERN_CRIT "Hangcheck: Task state:\n");
 161#ifdef CONFIG_MAGIC_SYSRQ
 162                        handle_sysrq('t');
 163#endif  /* CONFIG_MAGIC_SYSRQ */
 164                }
 165                if (hangcheck_reboot) {
 166                        printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");
 167                        emergency_restart();
 168                } else {
 169                        printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");
 170                }
 171        }
 172#if 0
 173        /*
 174         * Enable to investigate delays in detail
 175         */
 176        printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n",
 177                        tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);
 178#endif
 179        mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 180        hangcheck_tsc = monotonic_clock();
 181}
 182
 183
 184static int __init hangcheck_init(void)
 185{
 186        printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
 187               VERSION_STR, hangcheck_tick, hangcheck_margin);
 188#if defined (HAVE_MONOTONIC)
 189        printk("Hangcheck: Using monotonic_clock().\n");
 190#else
 191        printk("Hangcheck: Using getrawmonotonic().\n");
 192#endif  /* HAVE_MONOTONIC */
 193        hangcheck_tsc_margin =
 194                (unsigned long long)(hangcheck_margin + hangcheck_tick);
 195        hangcheck_tsc_margin *= (unsigned long long)TIMER_FREQ;
 196
 197        hangcheck_tsc = monotonic_clock();
 198        mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 199
 200        return 0;
 201}
 202
 203
 204static void __exit hangcheck_exit(void)
 205{
 206        del_timer_sync(&hangcheck_ticktock);
 207        printk("Hangcheck: Stopped hangcheck timer.\n");
 208}
 209
 210module_init(hangcheck_init);
 211module_exit(hangcheck_exit);
 212
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