1 /*
2  * hangcheck-timer.c
3  *
4  * Driver for a little io fencing timer.
5  *
6  * Copyright (C) 2002, 2003 Oracle.  All rights reserved.
7  *
8  * Author: Joel Becker <joel.becker@oracle.com>
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public
12  * License version 2 as published by the Free Software Foundation.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17  * General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public
20  * License along with this program; if not, write to the
21  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
22  * Boston, MA 021110-1307, USA.
23  */
24 
25 /*
26  * The hangcheck-timer driver uses the TSC to catch delays that
27  * jiffies does not notice.  A timer is set.  When the timer fires, it
28  * checks whether it was delayed and if that delay exceeds a given
29  * margin of error.  The hangcheck_tick module parameter takes the timer
30  * duration in seconds.  The hangcheck_margin parameter defines the
31  * margin of error, in seconds.  The defaults are 60 seconds for the
32  * timer and 180 seconds for the margin of error.  IOW, a timer is set
33  * for 60 seconds.  When the timer fires, the callback checks the
34  * actual duration that the timer waited.  If the duration exceeds the
35  * allotted time and margin (here 60 + 180, or 240 seconds), the machine
36  * is restarted.  A healthy machine will have the duration match the
37  * expected timeout very closely.
38  */
39 
40 #include <linux/module.h>
41 #include <linux/moduleparam.h>
42 #include <linux/types.h>
43 #include <linux/kernel.h>
44 #include <linux/fs.h>
45 #include <linux/mm.h>
46 #include <linux/reboot.h>
47 #include <linux/init.h>
48 #include <linux/delay.h>
49 #include <linux/uaccess.h>
50 #include <linux/sysrq.h>
51 #include <linux/timer.h>
52 #include <linux/hrtimer.h>
53 
54 #define VERSION_STR "0.9.1"
55 
56 #define DEFAULT_IOFENCE_MARGIN 60	/* Default fudge factor, in seconds */
57 #define DEFAULT_IOFENCE_TICK 180	/* Default timer timeout, in seconds */
58 
59 static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
60 static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
61 static int hangcheck_reboot;  /* Defaults to not reboot */
62 static int hangcheck_dump_tasks;  /* Defaults to not dumping SysRQ T */
63 
64 /* options - modular */
65 module_param(hangcheck_tick, int, 0);
66 MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
67 module_param(hangcheck_margin, int, 0);
68 MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
69 module_param(hangcheck_reboot, int, 0);
70 MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
71 module_param(hangcheck_dump_tasks, int, 0);
72 MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");
73 
74 MODULE_AUTHOR("Oracle");
75 MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
76 MODULE_LICENSE("GPL");
77 MODULE_VERSION(VERSION_STR);
78 
79 /* options - nonmodular */
80 #ifndef MODULE
81 
82 static int __init hangcheck_parse_tick(char *str)
83 {
84 	int par;
85 	if (get_option(&str,&par))
86 		hangcheck_tick = par;
87 	return 1;
88 }
89 
90 static int __init hangcheck_parse_margin(char *str)
91 {
92 	int par;
93 	if (get_option(&str,&par))
94 		hangcheck_margin = par;
95 	return 1;
96 }
97 
98 static int __init hangcheck_parse_reboot(char *str)
99 {
100 	int par;
101 	if (get_option(&str,&par))
102 		hangcheck_reboot = par;
103 	return 1;
104 }
105 
106 static int __init hangcheck_parse_dump_tasks(char *str)
107 {
108 	int par;
109 	if (get_option(&str,&par))
110 		hangcheck_dump_tasks = par;
111 	return 1;
112 }
113 
114 __setup("hcheck_tick", hangcheck_parse_tick);
115 __setup("hcheck_margin", hangcheck_parse_margin);
116 __setup("hcheck_reboot", hangcheck_parse_reboot);
117 __setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);
118 #endif /* not MODULE */
119 
120 #define TIMER_FREQ 1000000000ULL
121 
122 /* Last time scheduled */
123 static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
124 
125 static void hangcheck_fire(unsigned long);
126 
127 static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire, 0, 0);
128 
129 static void hangcheck_fire(unsigned long data)
130 {
131 	unsigned long long cur_tsc, tsc_diff;
132 
133 	cur_tsc = ktime_get_ns();
134 
135 	if (cur_tsc > hangcheck_tsc)
136 		tsc_diff = cur_tsc - hangcheck_tsc;
137 	else
138 		tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
139 
140 	if (tsc_diff > hangcheck_tsc_margin) {
141 		if (hangcheck_dump_tasks) {
142 			printk(KERN_CRIT "Hangcheck: Task state:\n");
143 #ifdef CONFIG_MAGIC_SYSRQ
144 			handle_sysrq('t');
145 #endif  /* CONFIG_MAGIC_SYSRQ */
146 		}
147 		if (hangcheck_reboot) {
148 			printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n");
149 			emergency_restart();
150 		} else {
151 			printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n");
152 		}
153 	}
154 #if 0
155 	/*
156 	 * Enable to investigate delays in detail
157 	 */
158 	printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n",
159 			tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);
160 #endif
161 	mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
162 	hangcheck_tsc = ktime_get_ns();
163 }
164 
165 
166 static int __init hangcheck_init(void)
167 {
168 	printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
169 	       VERSION_STR, hangcheck_tick, hangcheck_margin);
170 	hangcheck_tsc_margin =
171 		(unsigned long long)hangcheck_margin + hangcheck_tick;
172 	hangcheck_tsc_margin *= TIMER_FREQ;
173 
174 	hangcheck_tsc = ktime_get_ns();
175 	mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
176 
177 	return 0;
178 }
179 
180 
181 static void __exit hangcheck_exit(void)
182 {
183 	del_timer_sync(&hangcheck_ticktock);
184         printk("Hangcheck: Stopped hangcheck timer.\n");
185 }
186 
187 module_init(hangcheck_init);
188 module_exit(hangcheck_exit);
189