1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * hangcheck-timer.c |
4 | * |
5 | * Driver for a little io fencing timer. |
6 | * |
7 | * Copyright (C) 2002, 2003 Oracle. All rights reserved. |
8 | * |
9 | * Author: Joel Becker <joel.becker@oracle.com> |
10 | */ |
11 | |
12 | /* |
13 | * The hangcheck-timer driver uses the TSC to catch delays that |
14 | * jiffies does not notice. A timer is set. When the timer fires, it |
15 | * checks whether it was delayed and if that delay exceeds a given |
16 | * margin of error. The hangcheck_tick module parameter takes the timer |
17 | * duration in seconds. The hangcheck_margin parameter defines the |
18 | * margin of error, in seconds. The defaults are 60 seconds for the |
19 | * timer and 180 seconds for the margin of error. IOW, a timer is set |
20 | * for 60 seconds. When the timer fires, the callback checks the |
21 | * actual duration that the timer waited. If the duration exceeds the |
22 | * allotted time and margin (here 60 + 180, or 240 seconds), the machine |
23 | * is restarted. A healthy machine will have the duration match the |
24 | * expected timeout very closely. |
25 | */ |
26 | |
27 | #include <linux/module.h> |
28 | #include <linux/moduleparam.h> |
29 | #include <linux/types.h> |
30 | #include <linux/kernel.h> |
31 | #include <linux/fs.h> |
32 | #include <linux/mm.h> |
33 | #include <linux/reboot.h> |
34 | #include <linux/init.h> |
35 | #include <linux/delay.h> |
36 | #include <linux/uaccess.h> |
37 | #include <linux/sysrq.h> |
38 | #include <linux/timer.h> |
39 | #include <linux/hrtimer.h> |
40 | |
41 | #define VERSION_STR "0.9.1" |
42 | |
43 | #define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */ |
44 | #define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */ |
45 | |
46 | static int hangcheck_tick = DEFAULT_IOFENCE_TICK; |
47 | static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN; |
48 | static int hangcheck_reboot; /* Defaults to not reboot */ |
49 | static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */ |
50 | |
51 | /* options - modular */ |
52 | module_param(hangcheck_tick, int, 0); |
53 | MODULE_PARM_DESC(hangcheck_tick, "Timer delay." ); |
54 | module_param(hangcheck_margin, int, 0); |
55 | MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire." ); |
56 | module_param(hangcheck_reboot, int, 0); |
57 | MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded." ); |
58 | module_param(hangcheck_dump_tasks, int, 0); |
59 | MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded." ); |
60 | |
61 | MODULE_AUTHOR("Oracle" ); |
62 | MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin." ); |
63 | MODULE_LICENSE("GPL" ); |
64 | MODULE_VERSION(VERSION_STR); |
65 | |
66 | /* options - nonmodular */ |
67 | #ifndef MODULE |
68 | |
69 | static int __init hangcheck_parse_tick(char *str) |
70 | { |
71 | int par; |
72 | if (get_option(str: &str,pint: &par)) |
73 | hangcheck_tick = par; |
74 | return 1; |
75 | } |
76 | |
77 | static int __init hangcheck_parse_margin(char *str) |
78 | { |
79 | int par; |
80 | if (get_option(str: &str,pint: &par)) |
81 | hangcheck_margin = par; |
82 | return 1; |
83 | } |
84 | |
85 | static int __init hangcheck_parse_reboot(char *str) |
86 | { |
87 | int par; |
88 | if (get_option(str: &str,pint: &par)) |
89 | hangcheck_reboot = par; |
90 | return 1; |
91 | } |
92 | |
93 | static int __init hangcheck_parse_dump_tasks(char *str) |
94 | { |
95 | int par; |
96 | if (get_option(str: &str,pint: &par)) |
97 | hangcheck_dump_tasks = par; |
98 | return 1; |
99 | } |
100 | |
101 | __setup("hcheck_tick" , hangcheck_parse_tick); |
102 | __setup("hcheck_margin" , hangcheck_parse_margin); |
103 | __setup("hcheck_reboot" , hangcheck_parse_reboot); |
104 | __setup("hcheck_dump_tasks" , hangcheck_parse_dump_tasks); |
105 | #endif /* not MODULE */ |
106 | |
107 | #define TIMER_FREQ 1000000000ULL |
108 | |
109 | /* Last time scheduled */ |
110 | static unsigned long long hangcheck_tsc, hangcheck_tsc_margin; |
111 | |
112 | static void hangcheck_fire(struct timer_list *); |
113 | |
114 | static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire); |
115 | |
116 | static void hangcheck_fire(struct timer_list *unused) |
117 | { |
118 | unsigned long long cur_tsc, tsc_diff; |
119 | |
120 | cur_tsc = ktime_get_ns(); |
121 | |
122 | if (cur_tsc > hangcheck_tsc) |
123 | tsc_diff = cur_tsc - hangcheck_tsc; |
124 | else |
125 | tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */ |
126 | |
127 | if (tsc_diff > hangcheck_tsc_margin) { |
128 | if (hangcheck_dump_tasks) { |
129 | printk(KERN_CRIT "Hangcheck: Task state:\n" ); |
130 | #ifdef CONFIG_MAGIC_SYSRQ |
131 | handle_sysrq(key: 't'); |
132 | #endif /* CONFIG_MAGIC_SYSRQ */ |
133 | } |
134 | if (hangcheck_reboot) { |
135 | printk(KERN_CRIT "Hangcheck: hangcheck is restarting the machine.\n" ); |
136 | emergency_restart(); |
137 | } else { |
138 | printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n" ); |
139 | } |
140 | } |
141 | #if 0 |
142 | /* |
143 | * Enable to investigate delays in detail |
144 | */ |
145 | printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n" , |
146 | tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ); |
147 | #endif |
148 | mod_timer(timer: &hangcheck_ticktock, expires: jiffies + (hangcheck_tick*HZ)); |
149 | hangcheck_tsc = ktime_get_ns(); |
150 | } |
151 | |
152 | |
153 | static int __init hangcheck_init(void) |
154 | { |
155 | printk("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n" , |
156 | VERSION_STR, hangcheck_tick, hangcheck_margin); |
157 | hangcheck_tsc_margin = |
158 | (unsigned long long)hangcheck_margin + hangcheck_tick; |
159 | hangcheck_tsc_margin *= TIMER_FREQ; |
160 | |
161 | hangcheck_tsc = ktime_get_ns(); |
162 | mod_timer(timer: &hangcheck_ticktock, expires: jiffies + (hangcheck_tick*HZ)); |
163 | |
164 | return 0; |
165 | } |
166 | |
167 | |
168 | static void __exit hangcheck_exit(void) |
169 | { |
170 | del_timer_sync(timer: &hangcheck_ticktock); |
171 | printk("Hangcheck: Stopped hangcheck timer.\n" ); |
172 | } |
173 | |
174 | module_init(hangcheck_init); |
175 | module_exit(hangcheck_exit); |
176 | |