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  * allotted 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 <linux/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(struct timer_list *);
 126
 127 static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire);
 128
 129 static void hangcheck_fire(struct timer_list *unused)
 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);