Commit | Line | Data |
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e162b39a MSB |
1 | /* |
2 | * Detect Hung Task | |
3 | * | |
4 | * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state | |
5 | * | |
6 | */ | |
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 | * Have a reasonable limit on the number of tasks checked: | |
21 | */ | |
22 | unsigned long __read_mostly sysctl_hung_task_check_count = 1024; | |
23 | ||
24 | /* | |
25 | * Zero means infinite timeout - no checking done: | |
26 | */ | |
27 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; | |
28 | static unsigned long __read_mostly hung_task_poll_jiffies; | |
29 | ||
30 | unsigned long __read_mostly sysctl_hung_task_warnings = 10; | |
31 | ||
32 | static int __read_mostly did_panic; | |
33 | ||
34 | static struct task_struct *watchdog_task; | |
35 | ||
36 | /* | |
37 | * Should we panic (and reboot, if panic_timeout= is set) when a | |
38 | * hung task is detected: | |
39 | */ | |
40 | unsigned int __read_mostly sysctl_hung_task_panic = | |
41 | CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE; | |
42 | ||
43 | static int __init hung_task_panic_setup(char *str) | |
44 | { | |
45 | sysctl_hung_task_panic = simple_strtoul(str, NULL, 0); | |
46 | ||
47 | return 1; | |
48 | } | |
49 | __setup("hung_task_panic=", hung_task_panic_setup); | |
50 | ||
51 | static int | |
52 | hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
53 | { | |
54 | did_panic = 1; | |
55 | ||
56 | return NOTIFY_DONE; | |
57 | } | |
58 | ||
59 | static struct notifier_block panic_block = { | |
60 | .notifier_call = hung_task_panic, | |
61 | }; | |
62 | ||
63 | /* | |
64 | * Returns seconds, approximately. We don't need nanosecond | |
65 | * resolution, and we don't need to waste time with a big divide when | |
66 | * 2^30ns == 1.074s. | |
67 | */ | |
68 | static unsigned long get_timestamp(void) | |
69 | { | |
70 | int this_cpu = raw_smp_processor_id(); | |
71 | ||
72 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ | |
73 | } | |
74 | ||
75 | static void check_hung_task(struct task_struct *t, unsigned long now) | |
76 | { | |
77 | unsigned long switch_count = t->nvcsw + t->nivcsw; | |
78 | ||
79 | if (t->flags & PF_FROZEN) | |
80 | return; | |
81 | ||
82 | if (switch_count != t->last_switch_count || !t->last_switch_timestamp) { | |
83 | t->last_switch_count = switch_count; | |
84 | t->last_switch_timestamp = now; | |
85 | return; | |
86 | } | |
87 | if ((long)(now - t->last_switch_timestamp) < | |
88 | sysctl_hung_task_timeout_secs) | |
89 | return; | |
90 | if (!sysctl_hung_task_warnings) | |
91 | return; | |
92 | sysctl_hung_task_warnings--; | |
93 | ||
94 | /* | |
95 | * Ok, the task did not get scheduled for more than 2 minutes, | |
96 | * complain: | |
97 | */ | |
98 | printk(KERN_ERR "INFO: task %s:%d blocked for more than " | |
99 | "%ld seconds.\n", t->comm, t->pid, | |
100 | sysctl_hung_task_timeout_secs); | |
101 | printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" | |
102 | " disables this message.\n"); | |
103 | sched_show_task(t); | |
104 | __debug_show_held_locks(t); | |
105 | ||
106 | t->last_switch_timestamp = now; | |
107 | touch_nmi_watchdog(); | |
108 | ||
109 | if (sysctl_hung_task_panic) | |
110 | panic("hung_task: blocked tasks"); | |
111 | } | |
112 | ||
113 | /* | |
114 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for | |
115 | * a really long time (120 seconds). If that happens, print out | |
116 | * a warning. | |
117 | */ | |
118 | static void check_hung_uninterruptible_tasks(void) | |
119 | { | |
120 | int max_count = sysctl_hung_task_check_count; | |
121 | unsigned long now = get_timestamp(); | |
122 | struct task_struct *g, *t; | |
123 | ||
124 | /* | |
125 | * If the system crashed already then all bets are off, | |
126 | * do not report extra hung tasks: | |
127 | */ | |
128 | if (test_taint(TAINT_DIE) || did_panic) | |
129 | return; | |
130 | ||
131 | read_lock(&tasklist_lock); | |
132 | do_each_thread(g, t) { | |
133 | if (!--max_count) | |
134 | goto unlock; | |
135 | /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ | |
136 | if (t->state == TASK_UNINTERRUPTIBLE) | |
137 | check_hung_task(t, now); | |
138 | } while_each_thread(g, t); | |
139 | unlock: | |
140 | read_unlock(&tasklist_lock); | |
141 | } | |
142 | ||
143 | static void update_poll_jiffies(void) | |
144 | { | |
145 | /* timeout of 0 will disable the watchdog */ | |
146 | if (sysctl_hung_task_timeout_secs == 0) | |
147 | hung_task_poll_jiffies = MAX_SCHEDULE_TIMEOUT; | |
148 | else | |
149 | hung_task_poll_jiffies = sysctl_hung_task_timeout_secs * HZ / 2; | |
150 | } | |
151 | ||
152 | /* | |
153 | * Process updating of timeout sysctl | |
154 | */ | |
155 | int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, | |
156 | struct file *filp, void __user *buffer, | |
157 | size_t *lenp, loff_t *ppos) | |
158 | { | |
159 | int ret; | |
160 | ||
161 | ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos); | |
162 | ||
163 | if (ret || !write) | |
164 | goto out; | |
165 | ||
166 | update_poll_jiffies(); | |
167 | ||
168 | wake_up_process(watchdog_task); | |
169 | ||
170 | out: | |
171 | return ret; | |
172 | } | |
173 | ||
174 | /* | |
175 | * kthread which checks for tasks stuck in D state | |
176 | */ | |
177 | static int watchdog(void *dummy) | |
178 | { | |
179 | set_user_nice(current, 0); | |
180 | update_poll_jiffies(); | |
181 | ||
182 | for ( ; ; ) { | |
183 | while (schedule_timeout_interruptible(hung_task_poll_jiffies)); | |
184 | check_hung_uninterruptible_tasks(); | |
185 | } | |
186 | ||
187 | return 0; | |
188 | } | |
189 | ||
190 | static int __init hung_task_init(void) | |
191 | { | |
192 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); | |
193 | watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); | |
194 | ||
195 | return 0; | |
196 | } | |
197 | ||
198 | module_init(hung_task_init); |