drivers/char/hangcheck-timer.c

   1 /*
   2  * hangcheck-timer.c
   3  *
   4  * Driver for a little io fencing timer.
   5  *
   6  * Copyright (C) 2002 Oracle Corporation.  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 paramter 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 <asm/uaccess.h>
  49
  50
  51 #define VERSION_STR "0.5.0"
  52
  53 #define DEFAULT_IOFENCE_MARGIN 60       /* Default fudge factor, in seconds */
  54 #define DEFAULT_IOFENCE_TICK 180        /* Default timer timeout, in seconds */
  55
  56 static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
  57 static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
  58 static int hangcheck_reboot;  /* Defaults to not reboot */
  59
  60 /* Driver options */
  61 module_param(hangcheck_tick, int, 0);
  62 MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
  63 module_param(hangcheck_margin, int, 0);
  64 MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
  65 module_param(hangcheck_reboot, int, 0);
  66 MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
  67
  68 MODULE_AUTHOR("Joel Becker");
  69 MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
  70 MODULE_LICENSE("GPL");
  71
  72
  73 /* Last time scheduled */
  74 static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
  75
  76 static void hangcheck_fire(unsigned long);
  77
  78 static struct timer_list hangcheck_ticktock =
  79                 TIMER_INITIALIZER(hangcheck_fire, 0, 0);
  80
  81 extern unsigned long long monotonic_clock(void);
  82
  83 static void hangcheck_fire(unsigned long data)
  84 {
  85         unsigned long long cur_tsc, tsc_diff;
  86
  87         cur_tsc = monotonic_clock();
  88
  89         if (cur_tsc > hangcheck_tsc)
  90                 tsc_diff = cur_tsc - hangcheck_tsc;
  91         else
  92                 tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
  93
  94         if (tsc_diff > hangcheck_tsc_margin) {
  95                 if (hangcheck_reboot) {
  96                         printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");
  97                         machine_restart(NULL);
  98                 } else {
  99                         printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");
 100                 }
 101         }
 102         mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 103         hangcheck_tsc = monotonic_clock();
 104 }
 105
 106
 107 static int __init hangcheck_init(void)
 108 {
 109         printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
 110                VERSION_STR, hangcheck_tick, hangcheck_margin);
 111
 112         hangcheck_tsc_margin = hangcheck_margin + hangcheck_tick;
 113         hangcheck_tsc_margin *= 1000000000;
 114
 115
 116         hangcheck_tsc = monotonic_clock();
 117         mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
 118
 119         return 0;
 120 }
 121
 122
 123 static void __exit hangcheck_exit(void)
 124 {
 125         del_timer_sync(&hangcheck_ticktock);
 126 }
 127
 128 module_init(hangcheck_init);
 129 module_exit(hangcheck_exit);