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