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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
46static int hangcheck_tick = DEFAULT_IOFENCE_TICK;
47static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;
48static int hangcheck_reboot; /* Defaults to not reboot */
49static int hangcheck_dump_tasks; /* Defaults to not dumping SysRQ T */
50
51/* options - modular */
52module_param(hangcheck_tick, int, 0);
53MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");
54module_param(hangcheck_margin, int, 0);
55MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");
56module_param(hangcheck_reboot, int, 0);
57MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");
58module_param(hangcheck_dump_tasks, int, 0);
59MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded.");
60
61MODULE_AUTHOR("Oracle");
62MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");
63MODULE_LICENSE("GPL");
64MODULE_VERSION(VERSION_STR);
65
66/* options - nonmodular */
67#ifndef MODULE
68
69static int __init hangcheck_parse_tick(char *str)
70{
71 int par;
72
73 if (get_option(&str, &par))
74 hangcheck_tick = par;
75 return 1;
76}
77
78static int __init hangcheck_parse_margin(char *str)
79{
80 int par;
81
82 if (get_option(&str, &par))
83 hangcheck_margin = par;
84 return 1;
85}
86
87static int __init hangcheck_parse_reboot(char *str)
88{
89 int par;
90
91 if (get_option(&str, &par))
92 hangcheck_reboot = par;
93 return 1;
94}
95
96static int __init hangcheck_parse_dump_tasks(char *str)
97{
98 int par;
99
100 if (get_option(&str, &par))
101 hangcheck_dump_tasks = par;
102 return 1;
103}
104
105__setup("hcheck_tick", hangcheck_parse_tick);
106__setup("hcheck_margin", hangcheck_parse_margin);
107__setup("hcheck_reboot", hangcheck_parse_reboot);
108__setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);
109#endif /* not MODULE */
110
111#define TIMER_FREQ 1000000000ULL
112
113/* Last time scheduled */
114static unsigned long long hangcheck_tsc, hangcheck_tsc_margin;
115
116static void hangcheck_fire(struct timer_list *);
117
118static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire);
119
120static void hangcheck_fire(struct timer_list *unused)
121{
122 unsigned long long cur_tsc, tsc_diff;
123
124 cur_tsc = ktime_get_ns();
125
126 if (cur_tsc > hangcheck_tsc)
127 tsc_diff = cur_tsc - hangcheck_tsc;
128 else
129 tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */
130
131 if (tsc_diff > hangcheck_tsc_margin) {
132 if (hangcheck_dump_tasks) {
133 pr_crit("Hangcheck: Task state:\n");
134#ifdef CONFIG_MAGIC_SYSRQ
135 handle_sysrq('t');
136#endif /* CONFIG_MAGIC_SYSRQ */
137 }
138 if (hangcheck_reboot) {
139 pr_crit("Hangcheck: hangcheck is restarting the machine.\n");
140 emergency_restart();
141 } else {
142 pr_crit("Hangcheck: hangcheck value past margin!\n");
143 }
144 }
145#if 0
146 /*
147 * Enable to investigate delays in detail
148 */
149 pr_debug("Hangcheck: called %lld ns since last time (%lld ns overshoot)\n",
150 tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);
151#endif
152 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
153 hangcheck_tsc = ktime_get_ns();
154}
155
156
157static int __init hangcheck_init(void)
158{
159 pr_debug("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",
160 VERSION_STR, hangcheck_tick, hangcheck_margin);
161 hangcheck_tsc_margin =
162 (unsigned long long)hangcheck_margin + hangcheck_tick;
163 hangcheck_tsc_margin *= TIMER_FREQ;
164
165 hangcheck_tsc = ktime_get_ns();
166 mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));
167
168 return 0;
169}
170
171
172static void __exit hangcheck_exit(void)
173{
174 timer_delete_sync(&hangcheck_ticktock);
175 pr_debug("Hangcheck: Stopped hangcheck timer.\n");
176}
177
178module_init(hangcheck_init);
179module_exit(hangcheck_exit);