blob: a7c5c59675f06944405e560cf54575fbe0f07e23 [file] [log] [blame]
* hangcheck-timer.c
* Driver for a little io fencing timer.
* Copyright (C) 2002, 2003 Oracle. All rights reserved.
* Author: Joel Becker <>
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License version 2 as published by the Free Software Foundation.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* General Public License for more details.
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
* The hangcheck-timer driver uses the TSC to catch delays that
* jiffies does not notice. A timer is set. When the timer fires, it
* checks whether it was delayed and if that delay exceeds a given
* margin of error. The hangcheck_tick module parameter takes the timer
* duration in seconds. The hangcheck_margin parameter defines the
* margin of error, in seconds. The defaults are 60 seconds for the
* timer and 180 seconds for the margin of error. IOW, a timer is set
* for 60 seconds. When the timer fires, the callback checks the
* actual duration that the timer waited. If the duration exceeds the
* alloted time and margin (here 60 + 180, or 240 seconds), the machine
* is restarted. A healthy machine will have the duration match the
* expected timeout very closely.
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <linux/sysrq.h>
#include <linux/timer.h>
#include <linux/hrtimer.h>
#define VERSION_STR "0.9.1"
#define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */
#define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */
static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
static int hangcheck_reboot; /* Defaults to not reboot */
static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */
/* options - modular */
module_param(hangcheck_tick, int, 0);
MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
module_param(hangcheck_margin, int, 0);
MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
module_param(hangcheck_reboot, int, 0);
MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
module_param(hangcheck_dump_tasks, int, 0);
MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");
MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
/* options - nonmodular */
#ifndef MODULE
static int __init hangcheck_parse_tick(char *str)
int par;
if (get_option(&str,&par))
hangcheck_tick = par;
return 1;
static int __init hangcheck_parse_margin(char *str)
int par;
if (get_option(&str,&par))
hangcheck_margin = par;
return 1;
static int __init hangcheck_parse_reboot(char *str)
int par;
if (get_option(&str,&par))
hangcheck_reboot = par;
return 1;
static int __init hangcheck_parse_dump_tasks(char *str)
int par;
if (get_option(&str,&par))
hangcheck_dump_tasks = par;
return 1;
__setup("hcheck_tick", hangcheck_parse_tick);
__setup("hcheck_margin", hangcheck_parse_margin);
__setup("hcheck_reboot", hangcheck_parse_reboot);
__setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);
#endif /* not MODULE */
#define TIMER_FREQ 1000000000ULL
/* Last time scheduled */
static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
static void hangcheck_fire(unsigned long);
static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire, 0, 0);
static void hangcheck_fire(unsigned long data)
unsigned long long cur_tsc, tsc_diff;
cur_tsc = ktime_get_ns();
if (cur_tsc > hangcheck_tsc)
tsc_diff = cur_tsc - hangcheck_tsc;
tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
if (tsc_diff > hangcheck_tsc_margin) {
if (hangcheck_dump_tasks) {
printk(KERN_CRIT "Hangcheck: Task state:\n");
if (hangcheck_reboot) {
printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");
} else {
printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");
#if 0
* Enable to investigate delays in detail
printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n",
tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);
mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
hangcheck_tsc = ktime_get_ns();
static int __init hangcheck_init(void)
printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
VERSION_STR, hangcheck_tick, hangcheck_margin);
hangcheck_tsc_margin =
(unsigned long long)hangcheck_margin + hangcheck_tick;
hangcheck_tsc_margin *= TIMER_FREQ;
hangcheck_tsc = ktime_get_ns();
mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
return 0;
static void __exit hangcheck_exit(void)
printk("Hangcheck: Stopped hangcheck timer.\n");