ACPI: Add the reference count to avoid unloading ACPI video bus twice
[linux-2.6.git] / drivers / watchdog / softdog.c
1 /*
2  *      SoftDog 0.07:   A Software Watchdog Device
3  *
4  *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
5  *                                                      All Rights Reserved.
6  *
7  *      This program is free software; you can redistribute it and/or
8  *      modify it under the terms of the GNU General Public License
9  *      as published by the Free Software Foundation; either version
10  *      2 of the License, or (at your option) any later version.
11  *
12  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
13  *      warranty for any of this software. This material is provided
14  *      "AS-IS" and at no charge.
15  *
16  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
17  *
18  *      Software only watchdog driver. Unlike its big brother the WDT501P
19  *      driver this won't always recover a failed machine.
20  *
21  *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
22  *      Modularised.
23  *      Added soft_margin; use upon insmod to change the timer delay.
24  *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
25  *          minors.
26  *
27  *  19980911 Alan Cox
28  *      Made SMP safe for 2.3.x
29  *
30  *  20011127 Joel Becker (jlbec@evilplan.org>
31  *      Added soft_noboot; Allows testing the softdog trigger without
32  *      requiring a recompile.
33  *      Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
34  *
35  *  20020530 Joel Becker <joel.becker@oracle.com>
36  *      Added Matt Domsch's nowayout module option.
37  */
38
39 #include <linux/module.h>
40 #include <linux/moduleparam.h>
41 #include <linux/types.h>
42 #include <linux/timer.h>
43 #include <linux/miscdevice.h>
44 #include <linux/watchdog.h>
45 #include <linux/fs.h>
46 #include <linux/notifier.h>
47 #include <linux/reboot.h>
48 #include <linux/init.h>
49 #include <linux/jiffies.h>
50 #include <linux/uaccess.h>
51
52 #define PFX "SoftDog: "
53
54 #define TIMER_MARGIN    60              /* Default is 60 seconds */
55 static int soft_margin = TIMER_MARGIN;  /* in seconds */
56 module_param(soft_margin, int, 0);
57 MODULE_PARM_DESC(soft_margin,
58         "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default="
59                                         __MODULE_STRING(TIMER_MARGIN) ")");
60
61 static int nowayout = WATCHDOG_NOWAYOUT;
62 module_param(nowayout, int, 0);
63 MODULE_PARM_DESC(nowayout,
64                 "Watchdog cannot be stopped once started (default="
65                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
66
67 #ifdef ONLY_TESTING
68 static int soft_noboot = 1;
69 #else
70 static int soft_noboot = 0;
71 #endif  /* ONLY_TESTING */
72
73 module_param(soft_noboot, int, 0);
74 MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)");
75
76 /*
77  *      Our timer
78  */
79
80 static void watchdog_fire(unsigned long);
81
82 static struct timer_list watchdog_ticktock =
83                 TIMER_INITIALIZER(watchdog_fire, 0, 0);
84 static unsigned long driver_open, orphan_timer;
85 static char expect_close;
86
87
88 /*
89  *      If the timer expires..
90  */
91
92 static void watchdog_fire(unsigned long data)
93 {
94         if (test_and_clear_bit(0, &orphan_timer))
95                 module_put(THIS_MODULE);
96
97         if (soft_noboot)
98                 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
99         else {
100                 printk(KERN_CRIT PFX "Initiating system reboot.\n");
101                 emergency_restart();
102                 printk(KERN_CRIT PFX "Reboot didn't ?????\n");
103         }
104 }
105
106 /*
107  *      Softdog operations
108  */
109
110 static int softdog_keepalive(void)
111 {
112         mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ));
113         return 0;
114 }
115
116 static int softdog_stop(void)
117 {
118         del_timer(&watchdog_ticktock);
119         return 0;
120 }
121
122 static int softdog_set_heartbeat(int t)
123 {
124         if ((t < 0x0001) || (t > 0xFFFF))
125                 return -EINVAL;
126
127         soft_margin = t;
128         return 0;
129 }
130
131 /*
132  *      /dev/watchdog handling
133  */
134
135 static int softdog_open(struct inode *inode, struct file *file)
136 {
137         if (test_and_set_bit(0, &driver_open))
138                 return -EBUSY;
139         if (!test_and_clear_bit(0, &orphan_timer))
140                 __module_get(THIS_MODULE);
141         /*
142          *      Activate timer
143          */
144         softdog_keepalive();
145         return nonseekable_open(inode, file);
146 }
147
148 static int softdog_release(struct inode *inode, struct file *file)
149 {
150         /*
151          *      Shut off the timer.
152          *      Lock it in if it's a module and we set nowayout
153          */
154         if (expect_close == 42) {
155                 softdog_stop();
156                 module_put(THIS_MODULE);
157         } else {
158                 printk(KERN_CRIT PFX
159                         "Unexpected close, not stopping watchdog!\n");
160                 set_bit(0, &orphan_timer);
161                 softdog_keepalive();
162         }
163         clear_bit(0, &driver_open);
164         expect_close = 0;
165         return 0;
166 }
167
168 static ssize_t softdog_write(struct file *file, const char __user *data,
169                                                 size_t len, loff_t *ppos)
170 {
171         /*
172          *      Refresh the timer.
173          */
174         if (len) {
175                 if (!nowayout) {
176                         size_t i;
177
178                         /* In case it was set long ago */
179                         expect_close = 0;
180
181                         for (i = 0; i != len; i++) {
182                                 char c;
183
184                                 if (get_user(c, data + i))
185                                         return -EFAULT;
186                                 if (c == 'V')
187                                         expect_close = 42;
188                         }
189                 }
190                 softdog_keepalive();
191         }
192         return len;
193 }
194
195 static long softdog_ioctl(struct file *file, unsigned int cmd,
196                                                         unsigned long arg)
197 {
198         void __user *argp = (void __user *)arg;
199         int __user *p = argp;
200         int new_margin;
201         static const struct watchdog_info ident = {
202                 .options =              WDIOF_SETTIMEOUT |
203                                         WDIOF_KEEPALIVEPING |
204                                         WDIOF_MAGICCLOSE,
205                 .firmware_version =     0,
206                 .identity =             "Software Watchdog",
207         };
208         switch (cmd) {
209         case WDIOC_GETSUPPORT:
210                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
211         case WDIOC_GETSTATUS:
212         case WDIOC_GETBOOTSTATUS:
213                 return put_user(0, p);
214         case WDIOC_KEEPALIVE:
215                 softdog_keepalive();
216                 return 0;
217         case WDIOC_SETTIMEOUT:
218                 if (get_user(new_margin, p))
219                         return -EFAULT;
220                 if (softdog_set_heartbeat(new_margin))
221                         return -EINVAL;
222                 softdog_keepalive();
223                 /* Fall */
224         case WDIOC_GETTIMEOUT:
225                 return put_user(soft_margin, p);
226         default:
227                 return -ENOTTY;
228         }
229 }
230
231 /*
232  *      Notifier for system down
233  */
234
235 static int softdog_notify_sys(struct notifier_block *this, unsigned long code,
236         void *unused)
237 {
238         if (code == SYS_DOWN || code == SYS_HALT)
239                 /* Turn the WDT off */
240                 softdog_stop();
241         return NOTIFY_DONE;
242 }
243
244 /*
245  *      Kernel Interfaces
246  */
247
248 static const struct file_operations softdog_fops = {
249         .owner          = THIS_MODULE,
250         .llseek         = no_llseek,
251         .write          = softdog_write,
252         .unlocked_ioctl = softdog_ioctl,
253         .open           = softdog_open,
254         .release        = softdog_release,
255 };
256
257 static struct miscdevice softdog_miscdev = {
258         .minor          = WATCHDOG_MINOR,
259         .name           = "watchdog",
260         .fops           = &softdog_fops,
261 };
262
263 static struct notifier_block softdog_notifier = {
264         .notifier_call  = softdog_notify_sys,
265 };
266
267 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
268
269 static int __init watchdog_init(void)
270 {
271         int ret;
272
273         /* Check that the soft_margin value is within it's range;
274            if not reset to the default */
275         if (softdog_set_heartbeat(soft_margin)) {
276                 softdog_set_heartbeat(TIMER_MARGIN);
277                 printk(KERN_INFO PFX
278                     "soft_margin must be 0 < soft_margin < 65536, using %d\n",
279                         TIMER_MARGIN);
280         }
281
282         ret = register_reboot_notifier(&softdog_notifier);
283         if (ret) {
284                 printk(KERN_ERR PFX
285                         "cannot register reboot notifier (err=%d)\n", ret);
286                 return ret;
287         }
288
289         ret = misc_register(&softdog_miscdev);
290         if (ret) {
291                 printk(KERN_ERR PFX
292                         "cannot register miscdev on minor=%d (err=%d)\n",
293                                                 WATCHDOG_MINOR, ret);
294                 unregister_reboot_notifier(&softdog_notifier);
295                 return ret;
296         }
297
298         printk(banner, soft_noboot, soft_margin, nowayout);
299
300         return 0;
301 }
302
303 static void __exit watchdog_exit(void)
304 {
305         misc_deregister(&softdog_miscdev);
306         unregister_reboot_notifier(&softdog_notifier);
307 }
308
309 module_init(watchdog_init);
310 module_exit(watchdog_exit);
311
312 MODULE_AUTHOR("Alan Cox");
313 MODULE_DESCRIPTION("Software Watchdog Device Driver");
314 MODULE_LICENSE("GPL");
315 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);