Commit | Line | Data |
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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
e162b39a MSB |
2 | /* |
3 | * Detect Hung Task | |
4 | * | |
5 | * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state | |
6 | * | |
7 | */ | |
8 | ||
9 | #include <linux/mm.h> | |
10 | #include <linux/cpu.h> | |
11 | #include <linux/nmi.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/delay.h> | |
14 | #include <linux/freezer.h> | |
15 | #include <linux/kthread.h> | |
16 | #include <linux/lockdep.h> | |
9984de1a | 17 | #include <linux/export.h> |
f39650de | 18 | #include <linux/panic_notifier.h> |
e162b39a | 19 | #include <linux/sysctl.h> |
a1c6ca3c | 20 | #include <linux/suspend.h> |
41e85ce8 | 21 | #include <linux/utsname.h> |
3f07c014 | 22 | #include <linux/sched/signal.h> |
b17b0153 | 23 | #include <linux/sched/debug.h> |
a98eb6f1 | 24 | #include <linux/sched/sysctl.h> |
3f07c014 | 25 | |
6a716c90 | 26 | #include <trace/events/sched.h> |
e162b39a MSB |
27 | |
28 | /* | |
ce9dbe24 | 29 | * The number of tasks checked: |
e162b39a | 30 | */ |
882c5b26 | 31 | static int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; |
ce9dbe24 MSB |
32 | |
33 | /* | |
34 | * Limit number of tasks checked in a batch. | |
35 | * | |
36 | * This value controls the preemptibility of khungtaskd since preemption | |
37 | * is disabled during the critical section. It also controls the size of | |
38 | * the RCU grace period. So it needs to be upper-bound. | |
39 | */ | |
304ae427 | 40 | #define HUNG_TASK_LOCK_BREAK (HZ / 10) |
e162b39a MSB |
41 | |
42 | /* | |
43 | * Zero means infinite timeout - no checking done: | |
44 | */ | |
e11feaa1 | 45 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT; |
5c3273ec | 46 | EXPORT_SYMBOL_GPL(sysctl_hung_task_timeout_secs); |
e162b39a | 47 | |
a2e51445 DV |
48 | /* |
49 | * Zero (default value) means use sysctl_hung_task_timeout_secs: | |
50 | */ | |
882c5b26 | 51 | static unsigned long __read_mostly sysctl_hung_task_check_interval_secs; |
a2e51445 | 52 | |
882c5b26 | 53 | static int __read_mostly sysctl_hung_task_warnings = 10; |
e162b39a MSB |
54 | |
55 | static int __read_mostly did_panic; | |
780cbcf2 | 56 | static bool hung_task_show_lock; |
401c636a | 57 | static bool hung_task_call_panic; |
0ec9dc9b | 58 | static bool hung_task_show_all_bt; |
e162b39a MSB |
59 | |
60 | static struct task_struct *watchdog_task; | |
61 | ||
0ec9dc9b GP |
62 | #ifdef CONFIG_SMP |
63 | /* | |
64 | * Should we dump all CPUs backtraces in a hung task event? | |
65 | * Defaults to 0, can be changed via sysctl. | |
66 | */ | |
bbe7a10e XN |
67 | static unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace; |
68 | #else | |
69 | #define sysctl_hung_task_all_cpu_backtrace 0 | |
0ec9dc9b GP |
70 | #endif /* CONFIG_SMP */ |
71 | ||
e162b39a MSB |
72 | /* |
73 | * Should we panic (and reboot, if panic_timeout= is set) when a | |
74 | * hung task is detected: | |
75 | */ | |
882c5b26 TR |
76 | static unsigned int __read_mostly sysctl_hung_task_panic = |
77 | IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC); | |
e162b39a | 78 | |
e162b39a MSB |
79 | static int |
80 | hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
81 | { | |
82 | did_panic = 1; | |
83 | ||
84 | return NOTIFY_DONE; | |
85 | } | |
86 | ||
87 | static struct notifier_block panic_block = { | |
88 | .notifier_call = hung_task_panic, | |
89 | }; | |
90 | ||
17406b82 | 91 | static void check_hung_task(struct task_struct *t, unsigned long timeout) |
e162b39a MSB |
92 | { |
93 | unsigned long switch_count = t->nvcsw + t->nivcsw; | |
94 | ||
cf2592f5 FW |
95 | /* |
96 | * Ensure the task is not frozen. | |
f9fab10b | 97 | * Also, skip vfork and any other user process that freezer should skip. |
cf2592f5 | 98 | */ |
fdf756f7 | 99 | if (unlikely(READ_ONCE(t->__state) & TASK_FROZEN)) |
f5d39b02 | 100 | return; |
f9fab10b MSB |
101 | |
102 | /* | |
103 | * When a freshly created task is scheduled once, changes its state to | |
104 | * TASK_UNINTERRUPTIBLE without having ever been switched out once, it | |
105 | * musn't be checked. | |
106 | */ | |
107 | if (unlikely(!switch_count)) | |
e162b39a MSB |
108 | return; |
109 | ||
17406b82 | 110 | if (switch_count != t->last_switch_count) { |
e162b39a | 111 | t->last_switch_count = switch_count; |
a2e51445 | 112 | t->last_switch_time = jiffies; |
e162b39a MSB |
113 | return; |
114 | } | |
a2e51445 DV |
115 | if (time_is_after_jiffies(t->last_switch_time + timeout * HZ)) |
116 | return; | |
6a716c90 ON |
117 | |
118 | trace_sched_process_hang(t); | |
119 | ||
168e06f7 LC |
120 | if (sysctl_hung_task_panic) { |
121 | console_verbose(); | |
122 | hung_task_show_lock = true; | |
123 | hung_task_call_panic = true; | |
124 | } | |
270750db | 125 | |
e162b39a MSB |
126 | /* |
127 | * Ok, the task did not get scheduled for more than 2 minutes, | |
128 | * complain: | |
129 | */ | |
48a6d64e | 130 | if (sysctl_hung_task_warnings) { |
4ca5ede0 TH |
131 | if (sysctl_hung_task_warnings > 0) |
132 | sysctl_hung_task_warnings--; | |
48a6d64e | 133 | pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", |
b014beba | 134 | t->comm, t->pid, (jiffies - t->last_switch_time) / HZ); |
48a6d64e JS |
135 | pr_err(" %s %s %.*s\n", |
136 | print_tainted(), init_utsname()->release, | |
137 | (int)strcspn(init_utsname()->version, " "), | |
138 | init_utsname()->version); | |
139 | pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" | |
140 | " disables this message.\n"); | |
141 | sched_show_task(t); | |
780cbcf2 | 142 | hung_task_show_lock = true; |
0ec9dc9b GP |
143 | |
144 | if (sysctl_hung_task_all_cpu_backtrace) | |
145 | hung_task_show_all_bt = true; | |
b1f712b3 | 146 | if (!sysctl_hung_task_warnings) |
147 | pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n"); | |
48a6d64e | 148 | } |
e162b39a | 149 | |
e162b39a | 150 | touch_nmi_watchdog(); |
e162b39a MSB |
151 | } |
152 | ||
ce9dbe24 MSB |
153 | /* |
154 | * To avoid extending the RCU grace period for an unbounded amount of time, | |
155 | * periodically exit the critical section and enter a new one. | |
156 | * | |
157 | * For preemptible RCU it is sufficient to call rcu_read_unlock in order | |
6a103b0d | 158 | * to exit the grace period. For classic RCU, a reschedule is required. |
ce9dbe24 | 159 | */ |
6027ce49 | 160 | static bool rcu_lock_break(struct task_struct *g, struct task_struct *t) |
ce9dbe24 | 161 | { |
6027ce49 ON |
162 | bool can_cont; |
163 | ||
ce9dbe24 MSB |
164 | get_task_struct(g); |
165 | get_task_struct(t); | |
166 | rcu_read_unlock(); | |
167 | cond_resched(); | |
168 | rcu_read_lock(); | |
6027ce49 | 169 | can_cont = pid_alive(g) && pid_alive(t); |
ce9dbe24 MSB |
170 | put_task_struct(t); |
171 | put_task_struct(g); | |
6027ce49 ON |
172 | |
173 | return can_cont; | |
ce9dbe24 MSB |
174 | } |
175 | ||
e162b39a MSB |
176 | /* |
177 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for | |
178 | * a really long time (120 seconds). If that happens, print out | |
179 | * a warning. | |
180 | */ | |
603a148f | 181 | static void check_hung_uninterruptible_tasks(unsigned long timeout) |
e162b39a MSB |
182 | { |
183 | int max_count = sysctl_hung_task_check_count; | |
304ae427 | 184 | unsigned long last_break = jiffies; |
e162b39a MSB |
185 | struct task_struct *g, *t; |
186 | ||
187 | /* | |
188 | * If the system crashed already then all bets are off, | |
189 | * do not report extra hung tasks: | |
190 | */ | |
191 | if (test_taint(TAINT_DIE) || did_panic) | |
192 | return; | |
193 | ||
780cbcf2 | 194 | hung_task_show_lock = false; |
94be52dc | 195 | rcu_read_lock(); |
972fae69 | 196 | for_each_process_thread(g, t) { |
5aec788a PZ |
197 | unsigned int state; |
198 | ||
e5af0226 | 199 | if (!max_count--) |
e162b39a | 200 | goto unlock; |
304ae427 | 201 | if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) { |
6027ce49 | 202 | if (!rcu_lock_break(g, t)) |
ce9dbe24 | 203 | goto unlock; |
304ae427 | 204 | last_break = jiffies; |
ce9dbe24 | 205 | } |
fdf756f7 PZ |
206 | /* |
207 | * skip the TASK_KILLABLE tasks -- these can be killed | |
208 | * skip the TASK_IDLE tasks -- those are genuinely idle | |
209 | */ | |
5aec788a PZ |
210 | state = READ_ONCE(t->__state); |
211 | if ((state & TASK_UNINTERRUPTIBLE) && | |
fdf756f7 PZ |
212 | !(state & TASK_WAKEKILL) && |
213 | !(state & TASK_NOLOAD)) | |
17406b82 | 214 | check_hung_task(t, timeout); |
972fae69 | 215 | } |
e162b39a | 216 | unlock: |
94be52dc | 217 | rcu_read_unlock(); |
07a22b61 | 218 | if (hung_task_show_lock) |
780cbcf2 | 219 | debug_show_all_locks(); |
0ec9dc9b GP |
220 | |
221 | if (hung_task_show_all_bt) { | |
222 | hung_task_show_all_bt = false; | |
401c636a | 223 | trigger_all_cpu_backtrace(); |
401c636a | 224 | } |
0ec9dc9b GP |
225 | |
226 | if (hung_task_call_panic) | |
227 | panic("hung_task: blocked tasks"); | |
e162b39a MSB |
228 | } |
229 | ||
b4aa14a6 TH |
230 | static long hung_timeout_jiffies(unsigned long last_checked, |
231 | unsigned long timeout) | |
e162b39a MSB |
232 | { |
233 | /* timeout of 0 will disable the watchdog */ | |
b4aa14a6 TH |
234 | return timeout ? last_checked - jiffies + timeout * HZ : |
235 | MAX_SCHEDULE_TIMEOUT; | |
e162b39a MSB |
236 | } |
237 | ||
bbe7a10e | 238 | #ifdef CONFIG_SYSCTL |
e162b39a MSB |
239 | /* |
240 | * Process updating of timeout sysctl | |
241 | */ | |
bbe7a10e | 242 | static int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, |
591c32bd | 243 | void *buffer, |
bbe7a10e | 244 | size_t *lenp, loff_t *ppos) |
e162b39a MSB |
245 | { |
246 | int ret; | |
247 | ||
8d65af78 | 248 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
e162b39a MSB |
249 | |
250 | if (ret || !write) | |
251 | goto out; | |
252 | ||
e162b39a MSB |
253 | wake_up_process(watchdog_task); |
254 | ||
255 | out: | |
256 | return ret; | |
257 | } | |
258 | ||
bbe7a10e XN |
259 | /* |
260 | * This is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs | |
261 | * and hung_task_check_interval_secs | |
262 | */ | |
263 | static const unsigned long hung_task_timeout_max = (LONG_MAX / HZ); | |
264 | static struct ctl_table hung_task_sysctls[] = { | |
265 | #ifdef CONFIG_SMP | |
266 | { | |
267 | .procname = "hung_task_all_cpu_backtrace", | |
268 | .data = &sysctl_hung_task_all_cpu_backtrace, | |
269 | .maxlen = sizeof(int), | |
270 | .mode = 0644, | |
271 | .proc_handler = proc_dointvec_minmax, | |
272 | .extra1 = SYSCTL_ZERO, | |
273 | .extra2 = SYSCTL_ONE, | |
274 | }, | |
275 | #endif /* CONFIG_SMP */ | |
276 | { | |
277 | .procname = "hung_task_panic", | |
278 | .data = &sysctl_hung_task_panic, | |
279 | .maxlen = sizeof(int), | |
280 | .mode = 0644, | |
281 | .proc_handler = proc_dointvec_minmax, | |
282 | .extra1 = SYSCTL_ZERO, | |
283 | .extra2 = SYSCTL_ONE, | |
284 | }, | |
285 | { | |
286 | .procname = "hung_task_check_count", | |
287 | .data = &sysctl_hung_task_check_count, | |
288 | .maxlen = sizeof(int), | |
289 | .mode = 0644, | |
290 | .proc_handler = proc_dointvec_minmax, | |
291 | .extra1 = SYSCTL_ZERO, | |
292 | }, | |
293 | { | |
294 | .procname = "hung_task_timeout_secs", | |
295 | .data = &sysctl_hung_task_timeout_secs, | |
296 | .maxlen = sizeof(unsigned long), | |
297 | .mode = 0644, | |
298 | .proc_handler = proc_dohung_task_timeout_secs, | |
299 | .extra2 = (void *)&hung_task_timeout_max, | |
300 | }, | |
301 | { | |
302 | .procname = "hung_task_check_interval_secs", | |
303 | .data = &sysctl_hung_task_check_interval_secs, | |
304 | .maxlen = sizeof(unsigned long), | |
305 | .mode = 0644, | |
306 | .proc_handler = proc_dohung_task_timeout_secs, | |
307 | .extra2 = (void *)&hung_task_timeout_max, | |
308 | }, | |
309 | { | |
310 | .procname = "hung_task_warnings", | |
311 | .data = &sysctl_hung_task_warnings, | |
312 | .maxlen = sizeof(int), | |
313 | .mode = 0644, | |
314 | .proc_handler = proc_dointvec_minmax, | |
315 | .extra1 = SYSCTL_NEG_ONE, | |
316 | }, | |
317 | {} | |
318 | }; | |
319 | ||
320 | static void __init hung_task_sysctl_init(void) | |
321 | { | |
322 | register_sysctl_init("kernel", hung_task_sysctls); | |
323 | } | |
324 | #else | |
325 | #define hung_task_sysctl_init() do { } while (0) | |
326 | #endif /* CONFIG_SYSCTL */ | |
327 | ||
328 | ||
8b414521 MT |
329 | static atomic_t reset_hung_task = ATOMIC_INIT(0); |
330 | ||
331 | void reset_hung_task_detector(void) | |
332 | { | |
333 | atomic_set(&reset_hung_task, 1); | |
334 | } | |
335 | EXPORT_SYMBOL_GPL(reset_hung_task_detector); | |
336 | ||
a1c6ca3c VK |
337 | static bool hung_detector_suspended; |
338 | ||
339 | static int hungtask_pm_notify(struct notifier_block *self, | |
340 | unsigned long action, void *hcpu) | |
341 | { | |
342 | switch (action) { | |
343 | case PM_SUSPEND_PREPARE: | |
344 | case PM_HIBERNATION_PREPARE: | |
345 | case PM_RESTORE_PREPARE: | |
346 | hung_detector_suspended = true; | |
347 | break; | |
348 | case PM_POST_SUSPEND: | |
349 | case PM_POST_HIBERNATION: | |
350 | case PM_POST_RESTORE: | |
351 | hung_detector_suspended = false; | |
352 | break; | |
353 | default: | |
354 | break; | |
355 | } | |
356 | return NOTIFY_OK; | |
357 | } | |
358 | ||
e162b39a MSB |
359 | /* |
360 | * kthread which checks for tasks stuck in D state | |
361 | */ | |
362 | static int watchdog(void *dummy) | |
363 | { | |
b4aa14a6 TH |
364 | unsigned long hung_last_checked = jiffies; |
365 | ||
e162b39a | 366 | set_user_nice(current, 0); |
e162b39a MSB |
367 | |
368 | for ( ; ; ) { | |
17406b82 | 369 | unsigned long timeout = sysctl_hung_task_timeout_secs; |
a2e51445 DV |
370 | unsigned long interval = sysctl_hung_task_check_interval_secs; |
371 | long t; | |
603a148f | 372 | |
a2e51445 DV |
373 | if (interval == 0) |
374 | interval = timeout; | |
375 | interval = min_t(unsigned long, interval, timeout); | |
376 | t = hung_timeout_jiffies(hung_last_checked, interval); | |
b4aa14a6 | 377 | if (t <= 0) { |
a1c6ca3c VK |
378 | if (!atomic_xchg(&reset_hung_task, 0) && |
379 | !hung_detector_suspended) | |
b4aa14a6 TH |
380 | check_hung_uninterruptible_tasks(timeout); |
381 | hung_last_checked = jiffies; | |
8b414521 | 382 | continue; |
b4aa14a6 TH |
383 | } |
384 | schedule_timeout_interruptible(t); | |
e162b39a MSB |
385 | } |
386 | ||
387 | return 0; | |
388 | } | |
389 | ||
390 | static int __init hung_task_init(void) | |
391 | { | |
392 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); | |
a1c6ca3c VK |
393 | |
394 | /* Disable hung task detector on suspend */ | |
395 | pm_notifier(hungtask_pm_notify, 0); | |
396 | ||
e162b39a | 397 | watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); |
bbe7a10e | 398 | hung_task_sysctl_init(); |
e162b39a MSB |
399 | |
400 | return 0; | |
401 | } | |
c96d6660 | 402 | subsys_initcall(hung_task_init); |