linux/drivers/watchdog/softdog.c
Li RongQing 5889f06bd3 watchdog: refuse to unload softdog module when its timer is running
the softdog has static variables which are accessed if its timer is
still running after the driver is unloaded. and lead to crash:

   $modprobe softdog
   $echo 1 >/dev/watchdog
   $modprobe -r softdog

   CPU 20 Unable to handle kernel paging request at virtual address
   Oops[#1]:
   CPU: 20 PID: 0 Comm: swapper/20 Not tainted 4.1.13-WR8.0.0.0_standard
   ...
   Modules linked in: [last unloaded: softdog]
    ....
   Call Trace:
   [<ffffffff801e142c>] cascade+0x34/0xb0
   [<ffffffff801e1964>] run_timer_softirq+0x30c/0x368
   [<ffffffff80181044>] __do_softirq+0x1ec/0x418
   [<ffffffff801815d0>] irq_exit+0x90/0x98
   [<ffffffff8010749c>] plat_irq_dispatch+0xa4/0x140
   [<ffffffff80152740>] ret_from_irq+0x0/0x4
   [<ffffffff801529e0>] __r4k_wait+0x20/0x40
   [<ffffffff801c2278>] cpu_startup_entry+0x2a0/0x368
   [<ffffffff8015fa64>] start_secondary+0x444/0x4d8

add the module ref when timer is running to avoid to unload the softdog
module

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2015-12-27 21:02:21 +01:00

187 lines
4.7 KiB
C

/*
* SoftDog: 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.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#define TIMER_MARGIN 60 /* Default is 60 seconds */
static unsigned int soft_margin = TIMER_MARGIN; /* in seconds */
module_param(soft_margin, uint, 0);
MODULE_PARM_DESC(soft_margin,
"Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
__MODULE_STRING(TIMER_MARGIN) ")");
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
"Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
static int soft_noboot;
module_param(soft_noboot, int, 0);
MODULE_PARM_DESC(soft_noboot,
"Softdog action, set to 1 to ignore reboots, 0 to reboot (default=0)");
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);
/*
* If the timer expires..
*/
static void watchdog_fire(unsigned long data)
{
module_put(THIS_MODULE);
if (soft_noboot)
pr_crit("Triggered - Reboot ignored\n");
else if (soft_panic) {
pr_crit("Initiating panic\n");
panic("Software Watchdog Timer expired");
} else {
pr_crit("Initiating system reboot\n");
emergency_restart();
pr_crit("Reboot didn't ?????\n");
}
}
/*
* Softdog operations
*/
static int softdog_ping(struct watchdog_device *w)
{
if (!mod_timer(&watchdog_ticktock, jiffies+(w->timeout*HZ)))
__module_get(THIS_MODULE);
return 0;
}
static int softdog_stop(struct watchdog_device *w)
{
if (del_timer(&watchdog_ticktock))
module_put(THIS_MODULE);
return 0;
}
static int softdog_set_timeout(struct watchdog_device *w, unsigned int t)
{
w->timeout = t;
return 0;
}
/*
* Kernel Interfaces
*/
static struct watchdog_info softdog_info = {
.identity = "Software Watchdog",
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
};
static struct watchdog_ops softdog_ops = {
.owner = THIS_MODULE,
.start = softdog_ping,
.stop = softdog_stop,
.set_timeout = softdog_set_timeout,
};
static struct watchdog_device softdog_dev = {
.info = &softdog_info,
.ops = &softdog_ops,
.min_timeout = 1,
.max_timeout = 0xFFFF
};
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 (soft_margin < 1 || soft_margin > 65535) {
pr_info("soft_margin must be 0 < soft_margin < 65536, using %d\n",
TIMER_MARGIN);
return -EINVAL;
}
softdog_dev.timeout = soft_margin;
watchdog_set_nowayout(&softdog_dev, nowayout);
watchdog_stop_on_reboot(&softdog_dev);
ret = watchdog_register_device(&softdog_dev);
if (ret)
return ret;
pr_info("Software Watchdog Timer: 0.08 initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d (nowayout=%d)\n",
soft_noboot, soft_margin, soft_panic, nowayout);
return 0;
}
static void __exit watchdog_exit(void)
{
watchdog_unregister_device(&softdog_dev);
}
module_init(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Software Watchdog Device Driver");
MODULE_LICENSE("GPL");