Commit | Line | Data |
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58687acb DZ |
1 | /* |
2 | * Detect hard and soft lockups on a system | |
3 | * | |
4 | * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. | |
5 | * | |
6 | * this code detects hard lockups: incidents in where on a CPU | |
7 | * the kernel does not respond to anything except NMI. | |
8 | * | |
9 | * Note: Most of this code is borrowed heavily from softlockup.c, | |
10 | * so thanks to Ingo for the initial implementation. | |
11 | * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks | |
12 | * to those contributors as well. | |
13 | */ | |
14 | ||
15 | #include <linux/mm.h> | |
16 | #include <linux/cpu.h> | |
17 | #include <linux/nmi.h> | |
18 | #include <linux/init.h> | |
19 | #include <linux/delay.h> | |
20 | #include <linux/freezer.h> | |
21 | #include <linux/kthread.h> | |
22 | #include <linux/lockdep.h> | |
23 | #include <linux/notifier.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/sysctl.h> | |
26 | ||
27 | #include <asm/irq_regs.h> | |
28 | #include <linux/perf_event.h> | |
29 | ||
30 | int watchdog_enabled; | |
31 | int __read_mostly softlockup_thresh = 60; | |
32 | ||
33 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
34 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
35 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
36 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 37 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
23637d47 | 38 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
cafcd80d DZ |
39 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); |
40 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
58687acb DZ |
41 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
42 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); | |
43 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
44 | #endif | |
45 | ||
46 | static int __read_mostly did_panic; | |
47 | static int __initdata no_watchdog; | |
48 | ||
49 | ||
50 | /* boot commands */ | |
51 | /* | |
52 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
53 | */ | |
23637d47 | 54 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
55 | static int hardlockup_panic; |
56 | ||
57 | static int __init hardlockup_panic_setup(char *str) | |
58 | { | |
59 | if (!strncmp(str, "panic", 5)) | |
60 | hardlockup_panic = 1; | |
61 | return 1; | |
62 | } | |
63 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
64 | #endif | |
65 | ||
66 | unsigned int __read_mostly softlockup_panic = | |
67 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
68 | ||
69 | static int __init softlockup_panic_setup(char *str) | |
70 | { | |
71 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
72 | ||
73 | return 1; | |
74 | } | |
75 | __setup("softlockup_panic=", softlockup_panic_setup); | |
76 | ||
77 | static int __init nowatchdog_setup(char *str) | |
78 | { | |
79 | no_watchdog = 1; | |
80 | return 1; | |
81 | } | |
82 | __setup("nowatchdog", nowatchdog_setup); | |
83 | ||
84 | /* deprecated */ | |
85 | static int __init nosoftlockup_setup(char *str) | |
86 | { | |
87 | no_watchdog = 1; | |
88 | return 1; | |
89 | } | |
90 | __setup("nosoftlockup", nosoftlockup_setup); | |
91 | /* */ | |
92 | ||
93 | ||
94 | /* | |
95 | * Returns seconds, approximately. We don't need nanosecond | |
96 | * resolution, and we don't need to waste time with a big divide when | |
97 | * 2^30ns == 1.074s. | |
98 | */ | |
99 | static unsigned long get_timestamp(int this_cpu) | |
100 | { | |
101 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ | |
102 | } | |
103 | ||
104 | static unsigned long get_sample_period(void) | |
105 | { | |
106 | /* | |
107 | * convert softlockup_thresh from seconds to ns | |
108 | * the divide by 5 is to give hrtimer 5 chances to | |
109 | * increment before the hardlockup detector generates | |
110 | * a warning | |
111 | */ | |
112 | return softlockup_thresh / 5 * NSEC_PER_SEC; | |
113 | } | |
114 | ||
115 | /* Commands for resetting the watchdog */ | |
116 | static void __touch_watchdog(void) | |
117 | { | |
26e09c6e | 118 | int this_cpu = smp_processor_id(); |
58687acb DZ |
119 | |
120 | __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu); | |
121 | } | |
122 | ||
332fbdbc | 123 | void touch_softlockup_watchdog(void) |
58687acb | 124 | { |
68d3f1d8 | 125 | __raw_get_cpu_var(watchdog_touch_ts) = 0; |
58687acb | 126 | } |
0167c781 | 127 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 128 | |
332fbdbc | 129 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
130 | { |
131 | int cpu; | |
132 | ||
133 | /* | |
134 | * this is done lockless | |
135 | * do we care if a 0 races with a timestamp? | |
136 | * all it means is the softlock check starts one cycle later | |
137 | */ | |
138 | for_each_online_cpu(cpu) | |
139 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
140 | } | |
141 | ||
cafcd80d | 142 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
143 | void touch_nmi_watchdog(void) |
144 | { | |
68d3f1d8 DZ |
145 | if (watchdog_enabled) { |
146 | unsigned cpu; | |
147 | ||
148 | for_each_present_cpu(cpu) { | |
149 | if (per_cpu(watchdog_nmi_touch, cpu) != true) | |
150 | per_cpu(watchdog_nmi_touch, cpu) = true; | |
151 | } | |
152 | } | |
332fbdbc | 153 | touch_softlockup_watchdog(); |
58687acb DZ |
154 | } |
155 | EXPORT_SYMBOL(touch_nmi_watchdog); | |
156 | ||
cafcd80d DZ |
157 | #endif |
158 | ||
58687acb DZ |
159 | void touch_softlockup_watchdog_sync(void) |
160 | { | |
161 | __raw_get_cpu_var(softlockup_touch_sync) = true; | |
162 | __raw_get_cpu_var(watchdog_touch_ts) = 0; | |
163 | } | |
164 | ||
23637d47 | 165 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb | 166 | /* watchdog detector functions */ |
26e09c6e | 167 | static int is_hardlockup(void) |
58687acb | 168 | { |
26e09c6e | 169 | unsigned long hrint = __get_cpu_var(hrtimer_interrupts); |
58687acb | 170 | |
26e09c6e | 171 | if (__get_cpu_var(hrtimer_interrupts_saved) == hrint) |
58687acb DZ |
172 | return 1; |
173 | ||
26e09c6e | 174 | __get_cpu_var(hrtimer_interrupts_saved) = hrint; |
58687acb DZ |
175 | return 0; |
176 | } | |
177 | #endif | |
178 | ||
26e09c6e | 179 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 180 | { |
26e09c6e | 181 | unsigned long now = get_timestamp(smp_processor_id()); |
58687acb DZ |
182 | |
183 | /* Warn about unreasonable delays: */ | |
184 | if (time_after(now, touch_ts + softlockup_thresh)) | |
185 | return now - touch_ts; | |
186 | ||
187 | return 0; | |
188 | } | |
189 | ||
190 | static int | |
191 | watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
192 | { | |
193 | did_panic = 1; | |
194 | ||
195 | return NOTIFY_DONE; | |
196 | } | |
197 | ||
198 | static struct notifier_block panic_block = { | |
199 | .notifier_call = watchdog_panic, | |
200 | }; | |
201 | ||
23637d47 | 202 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
203 | static struct perf_event_attr wd_hw_attr = { |
204 | .type = PERF_TYPE_HARDWARE, | |
205 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
206 | .size = sizeof(struct perf_event_attr), | |
207 | .pinned = 1, | |
208 | .disabled = 1, | |
209 | }; | |
210 | ||
211 | /* Callback function for perf event subsystem */ | |
212 | void watchdog_overflow_callback(struct perf_event *event, int nmi, | |
213 | struct perf_sample_data *data, | |
214 | struct pt_regs *regs) | |
215 | { | |
c6db67cd PZ |
216 | /* Ensure the watchdog never gets throttled */ |
217 | event->hw.interrupts = 0; | |
218 | ||
d7c54733 DZ |
219 | if (__get_cpu_var(watchdog_nmi_touch) == true) { |
220 | __get_cpu_var(watchdog_nmi_touch) = false; | |
58687acb DZ |
221 | return; |
222 | } | |
223 | ||
224 | /* check for a hardlockup | |
225 | * This is done by making sure our timer interrupt | |
226 | * is incrementing. The timer interrupt should have | |
227 | * fired multiple times before we overflow'd. If it hasn't | |
228 | * then this is a good indication the cpu is stuck | |
229 | */ | |
26e09c6e DZ |
230 | if (is_hardlockup()) { |
231 | int this_cpu = smp_processor_id(); | |
232 | ||
58687acb DZ |
233 | /* only print hardlockups once */ |
234 | if (__get_cpu_var(hard_watchdog_warn) == true) | |
235 | return; | |
236 | ||
237 | if (hardlockup_panic) | |
238 | panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu); | |
239 | else | |
240 | WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu); | |
241 | ||
242 | __get_cpu_var(hard_watchdog_warn) = true; | |
243 | return; | |
244 | } | |
245 | ||
246 | __get_cpu_var(hard_watchdog_warn) = false; | |
247 | return; | |
248 | } | |
249 | static void watchdog_interrupt_count(void) | |
250 | { | |
251 | __get_cpu_var(hrtimer_interrupts)++; | |
252 | } | |
253 | #else | |
254 | static inline void watchdog_interrupt_count(void) { return; } | |
23637d47 | 255 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
58687acb DZ |
256 | |
257 | /* watchdog kicker functions */ | |
258 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
259 | { | |
58687acb DZ |
260 | unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts); |
261 | struct pt_regs *regs = get_irq_regs(); | |
262 | int duration; | |
263 | ||
264 | /* kick the hardlockup detector */ | |
265 | watchdog_interrupt_count(); | |
266 | ||
267 | /* kick the softlockup detector */ | |
268 | wake_up_process(__get_cpu_var(softlockup_watchdog)); | |
269 | ||
270 | /* .. and repeat */ | |
271 | hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period())); | |
272 | ||
273 | if (touch_ts == 0) { | |
26e09c6e | 274 | if (unlikely(__get_cpu_var(softlockup_touch_sync))) { |
58687acb DZ |
275 | /* |
276 | * If the time stamp was touched atomically | |
277 | * make sure the scheduler tick is up to date. | |
278 | */ | |
26e09c6e | 279 | __get_cpu_var(softlockup_touch_sync) = false; |
58687acb DZ |
280 | sched_clock_tick(); |
281 | } | |
282 | __touch_watchdog(); | |
283 | return HRTIMER_RESTART; | |
284 | } | |
285 | ||
286 | /* check for a softlockup | |
287 | * This is done by making sure a high priority task is | |
288 | * being scheduled. The task touches the watchdog to | |
289 | * indicate it is getting cpu time. If it hasn't then | |
290 | * this is a good indication some task is hogging the cpu | |
291 | */ | |
26e09c6e | 292 | duration = is_softlockup(touch_ts); |
58687acb DZ |
293 | if (unlikely(duration)) { |
294 | /* only warn once */ | |
295 | if (__get_cpu_var(soft_watchdog_warn) == true) | |
296 | return HRTIMER_RESTART; | |
297 | ||
298 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", | |
26e09c6e | 299 | smp_processor_id(), duration, |
58687acb DZ |
300 | current->comm, task_pid_nr(current)); |
301 | print_modules(); | |
302 | print_irqtrace_events(current); | |
303 | if (regs) | |
304 | show_regs(regs); | |
305 | else | |
306 | dump_stack(); | |
307 | ||
308 | if (softlockup_panic) | |
309 | panic("softlockup: hung tasks"); | |
310 | __get_cpu_var(soft_watchdog_warn) = true; | |
311 | } else | |
312 | __get_cpu_var(soft_watchdog_warn) = false; | |
313 | ||
314 | return HRTIMER_RESTART; | |
315 | } | |
316 | ||
317 | ||
318 | /* | |
319 | * The watchdog thread - touches the timestamp. | |
320 | */ | |
26e09c6e | 321 | static int watchdog(void *unused) |
58687acb DZ |
322 | { |
323 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; | |
26e09c6e | 324 | struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); |
58687acb DZ |
325 | |
326 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
327 | ||
328 | /* initialize timestamp */ | |
329 | __touch_watchdog(); | |
330 | ||
331 | /* kick off the timer for the hardlockup detector */ | |
332 | /* done here because hrtimer_start can only pin to smp_processor_id() */ | |
333 | hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()), | |
334 | HRTIMER_MODE_REL_PINNED); | |
335 | ||
336 | set_current_state(TASK_INTERRUPTIBLE); | |
337 | /* | |
338 | * Run briefly once per second to reset the softlockup timestamp. | |
339 | * If this gets delayed for more than 60 seconds then the | |
26e09c6e | 340 | * debug-printout triggers in watchdog_timer_fn(). |
58687acb DZ |
341 | */ |
342 | while (!kthread_should_stop()) { | |
343 | __touch_watchdog(); | |
344 | schedule(); | |
345 | ||
346 | if (kthread_should_stop()) | |
347 | break; | |
348 | ||
349 | set_current_state(TASK_INTERRUPTIBLE); | |
350 | } | |
351 | __set_current_state(TASK_RUNNING); | |
352 | ||
353 | return 0; | |
354 | } | |
355 | ||
356 | ||
23637d47 | 357 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
358 | static int watchdog_nmi_enable(int cpu) |
359 | { | |
360 | struct perf_event_attr *wd_attr; | |
361 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
362 | ||
363 | /* is it already setup and enabled? */ | |
364 | if (event && event->state > PERF_EVENT_STATE_OFF) | |
365 | goto out; | |
366 | ||
367 | /* it is setup but not enabled */ | |
368 | if (event != NULL) | |
369 | goto out_enable; | |
370 | ||
371 | /* Try to register using hardware perf events */ | |
372 | wd_attr = &wd_hw_attr; | |
373 | wd_attr->sample_period = hw_nmi_get_sample_period(); | |
374 | event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback); | |
375 | if (!IS_ERR(event)) { | |
376 | printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n"); | |
377 | goto out_save; | |
378 | } | |
379 | ||
380 | printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event); | |
381 | return -1; | |
382 | ||
383 | /* success path */ | |
384 | out_save: | |
385 | per_cpu(watchdog_ev, cpu) = event; | |
386 | out_enable: | |
387 | perf_event_enable(per_cpu(watchdog_ev, cpu)); | |
388 | out: | |
389 | return 0; | |
390 | } | |
391 | ||
392 | static void watchdog_nmi_disable(int cpu) | |
393 | { | |
394 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
395 | ||
396 | if (event) { | |
397 | perf_event_disable(event); | |
398 | per_cpu(watchdog_ev, cpu) = NULL; | |
399 | ||
400 | /* should be in cleanup, but blocks oprofile */ | |
401 | perf_event_release_kernel(event); | |
402 | } | |
403 | return; | |
404 | } | |
405 | #else | |
406 | static int watchdog_nmi_enable(int cpu) { return 0; } | |
407 | static void watchdog_nmi_disable(int cpu) { return; } | |
23637d47 | 408 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
58687acb DZ |
409 | |
410 | /* prepare/enable/disable routines */ | |
411 | static int watchdog_prepare_cpu(int cpu) | |
412 | { | |
413 | struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); | |
414 | ||
415 | WARN_ON(per_cpu(softlockup_watchdog, cpu)); | |
416 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
417 | hrtimer->function = watchdog_timer_fn; | |
418 | ||
419 | return 0; | |
420 | } | |
421 | ||
422 | static int watchdog_enable(int cpu) | |
423 | { | |
424 | struct task_struct *p = per_cpu(softlockup_watchdog, cpu); | |
425 | ||
426 | /* enable the perf event */ | |
427 | if (watchdog_nmi_enable(cpu) != 0) | |
428 | return -1; | |
429 | ||
430 | /* create the watchdog thread */ | |
431 | if (!p) { | |
432 | p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu); | |
433 | if (IS_ERR(p)) { | |
434 | printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu); | |
435 | return -1; | |
436 | } | |
437 | kthread_bind(p, cpu); | |
438 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
439 | per_cpu(softlockup_watchdog, cpu) = p; | |
440 | wake_up_process(p); | |
441 | } | |
442 | ||
68d3f1d8 DZ |
443 | /* if any cpu succeeds, watchdog is considered enabled for the system */ |
444 | watchdog_enabled = 1; | |
445 | ||
58687acb DZ |
446 | return 0; |
447 | } | |
448 | ||
449 | static void watchdog_disable(int cpu) | |
450 | { | |
451 | struct task_struct *p = per_cpu(softlockup_watchdog, cpu); | |
452 | struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); | |
453 | ||
454 | /* | |
455 | * cancel the timer first to stop incrementing the stats | |
456 | * and waking up the kthread | |
457 | */ | |
458 | hrtimer_cancel(hrtimer); | |
459 | ||
460 | /* disable the perf event */ | |
461 | watchdog_nmi_disable(cpu); | |
462 | ||
463 | /* stop the watchdog thread */ | |
464 | if (p) { | |
465 | per_cpu(softlockup_watchdog, cpu) = NULL; | |
466 | kthread_stop(p); | |
467 | } | |
58687acb DZ |
468 | } |
469 | ||
470 | static void watchdog_enable_all_cpus(void) | |
471 | { | |
472 | int cpu; | |
eb703f98 | 473 | int result = 0; |
58687acb DZ |
474 | |
475 | for_each_online_cpu(cpu) | |
476 | result += watchdog_enable(cpu); | |
477 | ||
478 | if (result) | |
479 | printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n"); | |
480 | ||
481 | } | |
482 | ||
483 | static void watchdog_disable_all_cpus(void) | |
484 | { | |
485 | int cpu; | |
486 | ||
487 | for_each_online_cpu(cpu) | |
488 | watchdog_disable(cpu); | |
489 | ||
490 | /* if all watchdogs are disabled, then they are disabled for the system */ | |
491 | watchdog_enabled = 0; | |
492 | } | |
493 | ||
494 | ||
495 | /* sysctl functions */ | |
496 | #ifdef CONFIG_SYSCTL | |
497 | /* | |
498 | * proc handler for /proc/sys/kernel/nmi_watchdog | |
499 | */ | |
500 | ||
501 | int proc_dowatchdog_enabled(struct ctl_table *table, int write, | |
502 | void __user *buffer, size_t *length, loff_t *ppos) | |
503 | { | |
504 | proc_dointvec(table, write, buffer, length, ppos); | |
505 | ||
506 | if (watchdog_enabled) | |
507 | watchdog_enable_all_cpus(); | |
508 | else | |
509 | watchdog_disable_all_cpus(); | |
510 | return 0; | |
511 | } | |
512 | ||
513 | int proc_dowatchdog_thresh(struct ctl_table *table, int write, | |
514 | void __user *buffer, | |
515 | size_t *lenp, loff_t *ppos) | |
516 | { | |
517 | return proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
518 | } | |
58687acb DZ |
519 | #endif /* CONFIG_SYSCTL */ |
520 | ||
521 | ||
522 | /* | |
523 | * Create/destroy watchdog threads as CPUs come and go: | |
524 | */ | |
525 | static int __cpuinit | |
526 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) | |
527 | { | |
528 | int hotcpu = (unsigned long)hcpu; | |
529 | ||
530 | switch (action) { | |
531 | case CPU_UP_PREPARE: | |
532 | case CPU_UP_PREPARE_FROZEN: | |
533 | if (watchdog_prepare_cpu(hotcpu)) | |
534 | return NOTIFY_BAD; | |
535 | break; | |
536 | case CPU_ONLINE: | |
537 | case CPU_ONLINE_FROZEN: | |
538 | if (watchdog_enable(hotcpu)) | |
539 | return NOTIFY_BAD; | |
540 | break; | |
541 | #ifdef CONFIG_HOTPLUG_CPU | |
542 | case CPU_UP_CANCELED: | |
543 | case CPU_UP_CANCELED_FROZEN: | |
544 | watchdog_disable(hotcpu); | |
545 | break; | |
546 | case CPU_DEAD: | |
547 | case CPU_DEAD_FROZEN: | |
548 | watchdog_disable(hotcpu); | |
549 | break; | |
550 | #endif /* CONFIG_HOTPLUG_CPU */ | |
551 | } | |
552 | return NOTIFY_OK; | |
553 | } | |
554 | ||
555 | static struct notifier_block __cpuinitdata cpu_nfb = { | |
556 | .notifier_call = cpu_callback | |
557 | }; | |
558 | ||
559 | static int __init spawn_watchdog_task(void) | |
560 | { | |
561 | void *cpu = (void *)(long)smp_processor_id(); | |
562 | int err; | |
563 | ||
564 | if (no_watchdog) | |
565 | return 0; | |
566 | ||
567 | err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); | |
568 | WARN_ON(err == NOTIFY_BAD); | |
569 | ||
570 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); | |
571 | register_cpu_notifier(&cpu_nfb); | |
572 | ||
573 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); | |
574 | ||
575 | return 0; | |
576 | } | |
577 | early_initcall(spawn_watchdog_task); |