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7
8#include <linux/mm.h>
9#include <linux/cpu.h>
10#include <linux/nmi.h>
11#include <linux/init.h>
12#include <linux/delay.h>
13#include <linux/freezer.h>
14#include <linux/kthread.h>
15#include <linux/lockdep.h>
16#include <linux/module.h>
17#include <linux/sysctl.h>
18
19
20
21
22unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
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29
30
31#define HUNG_TASK_BATCHING 1024
32
33
34
35
36unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120;
37
38unsigned long __read_mostly sysctl_hung_task_warnings = 10;
39
40static int __read_mostly did_panic;
41
42static struct task_struct *watchdog_task;
43
44
45
46
47
48unsigned int __read_mostly sysctl_hung_task_panic =
49 CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
50
51static int __init hung_task_panic_setup(char *str)
52{
53 sysctl_hung_task_panic = simple_strtoul(str, NULL, 0);
54
55 return 1;
56}
57__setup("hung_task_panic=", hung_task_panic_setup);
58
59static int
60hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
61{
62 did_panic = 1;
63
64 return NOTIFY_DONE;
65}
66
67static struct notifier_block panic_block = {
68 .notifier_call = hung_task_panic,
69};
70
71static void check_hung_task(struct task_struct *t, unsigned long timeout)
72{
73 unsigned long switch_count = t->nvcsw + t->nivcsw;
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75
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78
79
80
81 if (unlikely(t->flags & PF_FROZEN || !switch_count))
82 return;
83
84 if (switch_count != t->last_switch_count) {
85 t->last_switch_count = switch_count;
86 return;
87 }
88 if (!sysctl_hung_task_warnings)
89 return;
90 sysctl_hung_task_warnings--;
91
92
93
94
95
96 printk(KERN_ERR "INFO: task %s:%d blocked for more than "
97 "%ld seconds.\n", t->comm, t->pid, timeout);
98 printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
99 " disables this message.\n");
100 sched_show_task(t);
101 debug_show_held_locks(t);
102
103 touch_nmi_watchdog();
104
105 if (sysctl_hung_task_panic)
106 panic("hung_task: blocked tasks");
107}
108
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112
113
114
115
116static void rcu_lock_break(struct task_struct *g, struct task_struct *t)
117{
118 get_task_struct(g);
119 get_task_struct(t);
120 rcu_read_unlock();
121 cond_resched();
122 rcu_read_lock();
123 put_task_struct(t);
124 put_task_struct(g);
125}
126
127
128
129
130
131
132static void check_hung_uninterruptible_tasks(unsigned long timeout)
133{
134 int max_count = sysctl_hung_task_check_count;
135 int batch_count = HUNG_TASK_BATCHING;
136 struct task_struct *g, *t;
137
138
139
140
141
142 if (test_taint(TAINT_DIE) || did_panic)
143 return;
144
145 rcu_read_lock();
146 do_each_thread(g, t) {
147 if (!max_count--)
148 goto unlock;
149 if (!--batch_count) {
150 batch_count = HUNG_TASK_BATCHING;
151 rcu_lock_break(g, t);
152
153 if (t->state == TASK_DEAD || g->state == TASK_DEAD)
154 goto unlock;
155 }
156
157 if (t->state == TASK_UNINTERRUPTIBLE)
158 check_hung_task(t, timeout);
159 } while_each_thread(g, t);
160 unlock:
161 rcu_read_unlock();
162}
163
164static unsigned long timeout_jiffies(unsigned long timeout)
165{
166
167 return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
168}
169
170
171
172
173int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
174 void __user *buffer,
175 size_t *lenp, loff_t *ppos)
176{
177 int ret;
178
179 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
180
181 if (ret || !write)
182 goto out;
183
184 wake_up_process(watchdog_task);
185
186 out:
187 return ret;
188}
189
190
191
192
193static int watchdog(void *dummy)
194{
195 set_user_nice(current, 0);
196
197 for ( ; ; ) {
198 unsigned long timeout = sysctl_hung_task_timeout_secs;
199
200 while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
201 timeout = sysctl_hung_task_timeout_secs;
202
203 check_hung_uninterruptible_tasks(timeout);
204 }
205
206 return 0;
207}
208
209static int __init hung_task_init(void)
210{
211 atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
212 watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
213
214 return 0;
215}
216
217module_init(hung_task_init);
218