linux/drivers/watchdog/softdog.c
Anithra P Janakiraman 7fff4beb31 watchdog: softdog.c: enhancement to optionally invoke panic instead of reboot on timer expiry
This is needed for determining the reason for failure when a softdog
timeout occurs.

We use softdog to watch for critical application failures and at the
minimum a snapshot of the system would help to determine the cause.  In
such a scenario the application could fail but there isn't a softlockup as
such, hence the detect softlockup feature does not help.

The patch adds a module parameter soft_panic which when set to 1 causes
softdog to invoke panic instead of reboot when the softdog timer expires. 
By invoking panic we execute kdump if it is configured and the vmcore
generated by kdump should provide atleast a minimal idea of the reason for
failure.

Based on an original patch by Ken Sugawara <sugaken.r3@gmail.com>
Signed-off-by: Anithra P J <anithra@linux.vnet.ibm.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2011-03-29 11:56:22 +00:00

329 lines
7.5 KiB
C

/*
* SoftDog 0.07: A Software Watchdog Device
*
* (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
* warranty for any of this software. This material is provided
* "AS-IS" and at no charge.
*
* (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk>
*
* Software only watchdog driver. Unlike its big brother the WDT501P
* driver this won't always recover a failed machine.
*
* 03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
* Modularised.
* Added soft_margin; use upon insmod to change the timer delay.
* NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
* minors.
*
* 19980911 Alan Cox
* Made SMP safe for 2.3.x
*
* 20011127 Joel Becker (jlbec@evilplan.org>
* Added soft_noboot; Allows testing the softdog trigger without
* requiring a recompile.
* Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
*
* 20020530 Joel Becker <joel.becker@oracle.com>
* Added Matt Domsch's nowayout module option.
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#define PFX "SoftDog: "
#define TIMER_MARGIN 60 /* Default is 60 seconds */
static int soft_margin = TIMER_MARGIN; /* in seconds */
module_param(soft_margin, int, 0);
MODULE_PARM_DESC(soft_margin,
"Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
__MODULE_STRING(TIMER_MARGIN) ")");
static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout,
"Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
#ifdef ONLY_TESTING
static int soft_noboot = 1;
#else
static int soft_noboot = 0;
#endif /* ONLY_TESTING */
module_param(soft_noboot, int, 0);
MODULE_PARM_DESC(soft_noboot,
"Softdog action, set to 1 to ignore reboots, 0 to reboot "
"(default depends on ONLY_TESTING)");
static int soft_panic;
module_param(soft_panic, int, 0);
MODULE_PARM_DESC(soft_panic,
"Softdog action, set to 1 to panic, 0 to reboot (default=0)");
/*
* Our timer
*/
static void watchdog_fire(unsigned long);
static struct timer_list watchdog_ticktock =
TIMER_INITIALIZER(watchdog_fire, 0, 0);
static unsigned long driver_open, orphan_timer;
static char expect_close;
/*
* If the timer expires..
*/
static void watchdog_fire(unsigned long data)
{
if (test_and_clear_bit(0, &orphan_timer))
module_put(THIS_MODULE);
if (soft_noboot)
printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
else if (soft_panic) {
printk(KERN_CRIT PFX "Initiating panic.\n");
panic("Software Watchdog Timer expired.");
} else {
printk(KERN_CRIT PFX "Initiating system reboot.\n");
emergency_restart();
printk(KERN_CRIT PFX "Reboot didn't ?????\n");
}
}
/*
* Softdog operations
*/
static int softdog_keepalive(void)
{
mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
return 0;
}
static int softdog_stop(void)
{
del_timer(&watchdog_ticktock);
return 0;
}
static int softdog_set_heartbeat(int t)
{
if ((t < 0x0001) || (t > 0xFFFF))
return -EINVAL;
soft_margin = t;
return 0;
}
/*
* /dev/watchdog handling
*/
static int softdog_open(struct inode *inode, struct file *file)
{
if (test_and_set_bit(0, &driver_open))
return -EBUSY;
if (!test_and_clear_bit(0, &orphan_timer))
__module_get(THIS_MODULE);
/*
* Activate timer
*/
softdog_keepalive();
return nonseekable_open(inode, file);
}
static int softdog_release(struct inode *inode, struct file *file)
{
/*
* Shut off the timer.
* Lock it in if it's a module and we set nowayout
*/
if (expect_close == 42) {
softdog_stop();
module_put(THIS_MODULE);
} else {
printk(KERN_CRIT PFX
"Unexpected close, not stopping watchdog!\n");
set_bit(0, &orphan_timer);
softdog_keepalive();
}
clear_bit(0, &driver_open);
expect_close = 0;
return 0;
}
static ssize_t softdog_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
/*
* Refresh the timer.
*/
if (len) {
if (!nowayout) {
size_t i;
/* In case it was set long ago */
expect_close = 0;
for (i = 0; i != len; i++) {
char c;
if (get_user(c, data + i))
return -EFAULT;
if (c == 'V')
expect_close = 42;
}
}
softdog_keepalive();
}
return len;
}
static long softdog_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
void __user *argp = (void __user *)arg;
int __user *p = argp;
int new_margin;
static const struct watchdog_info ident = {
.options = WDIOF_SETTIMEOUT |
WDIOF_KEEPALIVEPING |
WDIOF_MAGICCLOSE,
.firmware_version = 0,
.identity = "Software Watchdog",
};
switch (cmd) {
case WDIOC_GETSUPPORT:
return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
return put_user(0, p);
case WDIOC_KEEPALIVE:
softdog_keepalive();
return 0;
case WDIOC_SETTIMEOUT:
if (get_user(new_margin, p))
return -EFAULT;
if (softdog_set_heartbeat(new_margin))
return -EINVAL;
softdog_keepalive();
/* Fall */
case WDIOC_GETTIMEOUT:
return put_user(soft_margin, p);
default:
return -ENOTTY;
}
}
/*
* Notifier for system down
*/
static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
void *unused)
{
if (code == SYS_DOWN || code == SYS_HALT)
/* Turn the WDT off */
softdog_stop();
return NOTIFY_DONE;
}
/*
* Kernel Interfaces
*/
static const struct file_operations softdog_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.write = softdog_write,
.unlocked_ioctl = softdog_ioctl,
.open = softdog_open,
.release = softdog_release,
};
static struct miscdevice softdog_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &softdog_fops,
};
static struct notifier_block softdog_notifier = {
.notifier_call = softdog_notify_sys,
};
static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 "
"initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d "
"(nowayout= %d)\n";
static int __init watchdog_init(void)
{
int ret;
/* Check that the soft_margin value is within it's range;
if not reset to the default */
if (softdog_set_heartbeat(soft_margin)) {
softdog_set_heartbeat(TIMER_MARGIN);
printk(KERN_INFO PFX
"soft_margin must be 0 < soft_margin < 65536, using %d\n",
TIMER_MARGIN);
}
ret = register_reboot_notifier(&softdog_notifier);
if (ret) {
printk(KERN_ERR PFX
"cannot register reboot notifier (err=%d)\n", ret);
return ret;
}
ret = misc_register(&softdog_miscdev);
if (ret) {
printk(KERN_ERR PFX
"cannot register miscdev on minor=%d (err=%d)\n",
WATCHDOG_MINOR, ret);
unregister_reboot_notifier(&softdog_notifier);
return ret;
}
printk(banner, soft_noboot, soft_margin, soft_panic, nowayout);
return 0;
}
static void __exit watchdog_exit(void)
{
misc_deregister(&softdog_miscdev);
unregister_reboot_notifier(&softdog_notifier);
}
module_init(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Software Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);