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/*

 * hangcheck-timer.c

 *

 * Driver for a little io fencing timer.

 *

 * Copyright (C) 2002, 2003 Oracle.  All rights reserved.

 *

 * Author: Joel Becker <joel.becker@oracle.com>

 *

 * 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

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * 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 paramter 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>

#define VERSION_STR "0.9.0"

#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_AUTHOR("Oracle");

MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");

MODULE_LICENSE("GPL");

MODULE_VERSION(VERSION_STR);

/* 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 */

#if defined(CONFIG_S390)

# define HAVE_MONOTONIC

# define TIMER_FREQ 1000000000ULL

#elif defined(CONFIG_IA64)

# define TIMER_FREQ ((unsigned long long)local_cpu_data->itc_freq)

#else

# define TIMER_FREQ (HZ*loops_per_jiffy)

#endif

#ifdef HAVE_MONOTONIC

extern unsigned long long monotonic_clock(void);

#else

static inline unsigned long long monotonic_clock(void)

{

        return get_cycles();

}

#endif  /* HAVE_MONOTONIC */

/* 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 = monotonic_clock();

        if (cur_tsc > hangcheck_tsc)

                tsc_diff = cur_tsc - hangcheck_tsc;

        else

                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");

#ifdef CONFIG_MAGIC_SYSRQ

                        handle_sysrq('t', NULL);

#endif  /* CONFIG_MAGIC_SYSRQ */

                }

                if (hangcheck_reboot) {

                        printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");

                        emergency_restart();

                } else {

                        printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");

                }

        }

        mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));

        hangcheck_tsc = monotonic_clock();

}

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);

#if defined (HAVE_MONOTONIC)

        printk("Hangcheck: Using monotonic_clock().\n");

#else

        printk("Hangcheck: Using get_cycles().\n");

#endif  /* HAVE_MONOTONIC */

        hangcheck_tsc_margin =

                (unsigned long long)(hangcheck_margin + hangcheck_tick);

        hangcheck_tsc_margin *= (unsigned long long)TIMER_FREQ;

        hangcheck_tsc = monotonic_clock();

        mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));

        return 0;

}

static void __exit hangcheck_exit(void)

{

        del_timer_sync(&hangcheck_ticktock);

        printk("Hangcheck: Stopped hangcheck timer.\n");

}

module_init(hangcheck_init);

module_exit(hangcheck_exit);