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1 | /* | |
2 | * Detect hard and soft lockups on a system | |
3 | * | |
4 | * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. | |
5 | * | |
6 | * Note: Most of this code is borrowed heavily from the original softlockup | |
7 | * detector, so thanks to Ingo for the initial implementation. | |
8 | * Some chunks also taken from the old x86-specific nmi watchdog code, thanks | |
9 | * to those contributors as well. | |
10 | */ | |
11 | ||
12 | #define pr_fmt(fmt) "watchdog: " fmt | |
13 | ||
14 | #include <linux/mm.h> | |
15 | #include <linux/cpu.h> | |
16 | #include <linux/nmi.h> | |
17 | #include <linux/init.h> | |
18 | #include <linux/module.h> | |
19 | #include <linux/sysctl.h> | |
20 | #include <linux/smpboot.h> | |
21 | #include <linux/sched/rt.h> | |
22 | #include <uapi/linux/sched/types.h> | |
23 | #include <linux/tick.h> | |
24 | #include <linux/workqueue.h> | |
25 | #include <linux/sched/clock.h> | |
26 | #include <linux/sched/debug.h> | |
27 | ||
28 | #include <asm/irq_regs.h> | |
29 | #include <linux/kvm_para.h> | |
30 | #include <linux/kthread.h> | |
31 | ||
32 | static DEFINE_MUTEX(watchdog_mutex); | |
33 | ||
34 | #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG) | |
35 | # define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED) | |
36 | # define NMI_WATCHDOG_DEFAULT 1 | |
37 | #else | |
38 | # define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED) | |
39 | # define NMI_WATCHDOG_DEFAULT 0 | |
40 | #endif | |
41 | ||
42 | unsigned long __read_mostly watchdog_enabled; | |
43 | int __read_mostly watchdog_user_enabled = 1; | |
44 | int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT; | |
45 | int __read_mostly soft_watchdog_user_enabled = 1; | |
46 | int __read_mostly watchdog_thresh = 10; | |
47 | int __read_mostly nmi_watchdog_available; | |
48 | ||
49 | struct cpumask watchdog_allowed_mask __read_mostly; | |
50 | ||
51 | struct cpumask watchdog_cpumask __read_mostly; | |
52 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); | |
53 | ||
54 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
55 | /* | |
56 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
57 | */ | |
58 | unsigned int __read_mostly hardlockup_panic = | |
59 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
60 | /* | |
61 | * We may not want to enable hard lockup detection by default in all cases, | |
62 | * for example when running the kernel as a guest on a hypervisor. In these | |
63 | * cases this function can be called to disable hard lockup detection. This | |
64 | * function should only be executed once by the boot processor before the | |
65 | * kernel command line parameters are parsed, because otherwise it is not | |
66 | * possible to override this in hardlockup_panic_setup(). | |
67 | */ | |
68 | void __init hardlockup_detector_disable(void) | |
69 | { | |
70 | nmi_watchdog_user_enabled = 0; | |
71 | } | |
72 | ||
73 | static int __init hardlockup_panic_setup(char *str) | |
74 | { | |
75 | if (!strncmp(str, "panic", 5)) | |
76 | hardlockup_panic = 1; | |
77 | else if (!strncmp(str, "nopanic", 7)) | |
78 | hardlockup_panic = 0; | |
79 | else if (!strncmp(str, "0", 1)) | |
80 | nmi_watchdog_user_enabled = 0; | |
81 | else if (!strncmp(str, "1", 1)) | |
82 | nmi_watchdog_user_enabled = 1; | |
83 | return 1; | |
84 | } | |
85 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
86 | ||
87 | # ifdef CONFIG_SMP | |
88 | int __read_mostly sysctl_hardlockup_all_cpu_backtrace; | |
89 | ||
90 | static int __init hardlockup_all_cpu_backtrace_setup(char *str) | |
91 | { | |
92 | sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0); | |
93 | return 1; | |
94 | } | |
95 | __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup); | |
96 | # endif /* CONFIG_SMP */ | |
97 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ | |
98 | ||
99 | /* | |
100 | * These functions can be overridden if an architecture implements its | |
101 | * own hardlockup detector. | |
102 | * | |
103 | * watchdog_nmi_enable/disable can be implemented to start and stop when | |
104 | * softlockup watchdog threads start and stop. The arch must select the | |
105 | * SOFTLOCKUP_DETECTOR Kconfig. | |
106 | */ | |
107 | int __weak watchdog_nmi_enable(unsigned int cpu) | |
108 | { | |
109 | hardlockup_detector_perf_enable(); | |
110 | return 0; | |
111 | } | |
112 | ||
113 | void __weak watchdog_nmi_disable(unsigned int cpu) | |
114 | { | |
115 | hardlockup_detector_perf_disable(); | |
116 | } | |
117 | ||
118 | /* Return 0, if a NMI watchdog is available. Error code otherwise */ | |
119 | int __weak __init watchdog_nmi_probe(void) | |
120 | { | |
121 | return hardlockup_detector_perf_init(); | |
122 | } | |
123 | ||
124 | /** | |
125 | * watchdog_nmi_stop - Stop the watchdog for reconfiguration | |
126 | * | |
127 | * The reconfiguration steps are: | |
128 | * watchdog_nmi_stop(); | |
129 | * update_variables(); | |
130 | * watchdog_nmi_start(); | |
131 | */ | |
132 | void __weak watchdog_nmi_stop(void) { } | |
133 | ||
134 | /** | |
135 | * watchdog_nmi_start - Start the watchdog after reconfiguration | |
136 | * | |
137 | * Counterpart to watchdog_nmi_stop(). | |
138 | * | |
139 | * The following variables have been updated in update_variables() and | |
140 | * contain the currently valid configuration: | |
141 | * - watchdog_enabled | |
142 | * - watchdog_thresh | |
143 | * - watchdog_cpumask | |
144 | */ | |
145 | void __weak watchdog_nmi_start(void) { } | |
146 | ||
147 | /** | |
148 | * lockup_detector_update_enable - Update the sysctl enable bit | |
149 | * | |
150 | * Caller needs to make sure that the NMI/perf watchdogs are off, so this | |
151 | * can't race with watchdog_nmi_disable(). | |
152 | */ | |
153 | static void lockup_detector_update_enable(void) | |
154 | { | |
155 | watchdog_enabled = 0; | |
156 | if (!watchdog_user_enabled) | |
157 | return; | |
158 | if (nmi_watchdog_available && nmi_watchdog_user_enabled) | |
159 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
160 | if (soft_watchdog_user_enabled) | |
161 | watchdog_enabled |= SOFT_WATCHDOG_ENABLED; | |
162 | } | |
163 | ||
164 | #ifdef CONFIG_SOFTLOCKUP_DETECTOR | |
165 | ||
166 | /* Global variables, exported for sysctl */ | |
167 | unsigned int __read_mostly softlockup_panic = | |
168 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
169 | ||
170 | static bool softlockup_threads_initialized __read_mostly; | |
171 | static u64 __read_mostly sample_period; | |
172 | ||
173 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
174 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
175 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
176 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
177 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); | |
178 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); | |
179 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
180 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); | |
181 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); | |
182 | static unsigned long soft_lockup_nmi_warn; | |
183 | ||
184 | static int __init softlockup_panic_setup(char *str) | |
185 | { | |
186 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
187 | return 1; | |
188 | } | |
189 | __setup("softlockup_panic=", softlockup_panic_setup); | |
190 | ||
191 | static int __init nowatchdog_setup(char *str) | |
192 | { | |
193 | watchdog_user_enabled = 0; | |
194 | return 1; | |
195 | } | |
196 | __setup("nowatchdog", nowatchdog_setup); | |
197 | ||
198 | static int __init nosoftlockup_setup(char *str) | |
199 | { | |
200 | soft_watchdog_user_enabled = 0; | |
201 | return 1; | |
202 | } | |
203 | __setup("nosoftlockup", nosoftlockup_setup); | |
204 | ||
205 | #ifdef CONFIG_SMP | |
206 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
207 | ||
208 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
209 | { | |
210 | sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0); | |
211 | return 1; | |
212 | } | |
213 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
214 | #endif | |
215 | ||
216 | static void __lockup_detector_cleanup(void); | |
217 | ||
218 | /* | |
219 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
220 | * lockups can have false positives under extreme conditions. So we generally | |
221 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
222 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
223 | * time the hard threshold is. | |
224 | */ | |
225 | static int get_softlockup_thresh(void) | |
226 | { | |
227 | return watchdog_thresh * 2; | |
228 | } | |
229 | ||
230 | /* | |
231 | * Returns seconds, approximately. We don't need nanosecond | |
232 | * resolution, and we don't need to waste time with a big divide when | |
233 | * 2^30ns == 1.074s. | |
234 | */ | |
235 | static unsigned long get_timestamp(void) | |
236 | { | |
237 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ | |
238 | } | |
239 | ||
240 | static void set_sample_period(void) | |
241 | { | |
242 | /* | |
243 | * convert watchdog_thresh from seconds to ns | |
244 | * the divide by 5 is to give hrtimer several chances (two | |
245 | * or three with the current relation between the soft | |
246 | * and hard thresholds) to increment before the | |
247 | * hardlockup detector generates a warning | |
248 | */ | |
249 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); | |
250 | watchdog_update_hrtimer_threshold(sample_period); | |
251 | } | |
252 | ||
253 | /* Commands for resetting the watchdog */ | |
254 | static void __touch_watchdog(void) | |
255 | { | |
256 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); | |
257 | } | |
258 | ||
259 | /** | |
260 | * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls | |
261 | * | |
262 | * Call when the scheduler may have stalled for legitimate reasons | |
263 | * preventing the watchdog task from executing - e.g. the scheduler | |
264 | * entering idle state. This should only be used for scheduler events. | |
265 | * Use touch_softlockup_watchdog() for everything else. | |
266 | */ | |
267 | void touch_softlockup_watchdog_sched(void) | |
268 | { | |
269 | /* | |
270 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
271 | * gets zeroed here, so use the raw_ operation. | |
272 | */ | |
273 | raw_cpu_write(watchdog_touch_ts, 0); | |
274 | } | |
275 | ||
276 | void touch_softlockup_watchdog(void) | |
277 | { | |
278 | touch_softlockup_watchdog_sched(); | |
279 | wq_watchdog_touch(raw_smp_processor_id()); | |
280 | } | |
281 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
282 | ||
283 | void touch_all_softlockup_watchdogs(void) | |
284 | { | |
285 | int cpu; | |
286 | ||
287 | /* | |
288 | * watchdog_mutex cannpt be taken here, as this might be called | |
289 | * from (soft)interrupt context, so the access to | |
290 | * watchdog_allowed_cpumask might race with a concurrent update. | |
291 | * | |
292 | * The watchdog time stamp can race against a concurrent real | |
293 | * update as well, the only side effect might be a cycle delay for | |
294 | * the softlockup check. | |
295 | */ | |
296 | for_each_cpu(cpu, &watchdog_allowed_mask) | |
297 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
298 | wq_watchdog_touch(-1); | |
299 | } | |
300 | ||
301 | void touch_softlockup_watchdog_sync(void) | |
302 | { | |
303 | __this_cpu_write(softlockup_touch_sync, true); | |
304 | __this_cpu_write(watchdog_touch_ts, 0); | |
305 | } | |
306 | ||
307 | static int is_softlockup(unsigned long touch_ts) | |
308 | { | |
309 | unsigned long now = get_timestamp(); | |
310 | ||
311 | if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ | |
312 | /* Warn about unreasonable delays. */ | |
313 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
314 | return now - touch_ts; | |
315 | } | |
316 | return 0; | |
317 | } | |
318 | ||
319 | /* watchdog detector functions */ | |
320 | bool is_hardlockup(void) | |
321 | { | |
322 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); | |
323 | ||
324 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) | |
325 | return true; | |
326 | ||
327 | __this_cpu_write(hrtimer_interrupts_saved, hrint); | |
328 | return false; | |
329 | } | |
330 | ||
331 | static void watchdog_interrupt_count(void) | |
332 | { | |
333 | __this_cpu_inc(hrtimer_interrupts); | |
334 | } | |
335 | ||
336 | /* watchdog kicker functions */ | |
337 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
338 | { | |
339 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); | |
340 | struct pt_regs *regs = get_irq_regs(); | |
341 | int duration; | |
342 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; | |
343 | ||
344 | if (!watchdog_enabled) | |
345 | return HRTIMER_NORESTART; | |
346 | ||
347 | /* kick the hardlockup detector */ | |
348 | watchdog_interrupt_count(); | |
349 | ||
350 | /* kick the softlockup detector */ | |
351 | wake_up_process(__this_cpu_read(softlockup_watchdog)); | |
352 | ||
353 | /* .. and repeat */ | |
354 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); | |
355 | ||
356 | if (touch_ts == 0) { | |
357 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { | |
358 | /* | |
359 | * If the time stamp was touched atomically | |
360 | * make sure the scheduler tick is up to date. | |
361 | */ | |
362 | __this_cpu_write(softlockup_touch_sync, false); | |
363 | sched_clock_tick(); | |
364 | } | |
365 | ||
366 | /* Clear the guest paused flag on watchdog reset */ | |
367 | kvm_check_and_clear_guest_paused(); | |
368 | __touch_watchdog(); | |
369 | return HRTIMER_RESTART; | |
370 | } | |
371 | ||
372 | /* check for a softlockup | |
373 | * This is done by making sure a high priority task is | |
374 | * being scheduled. The task touches the watchdog to | |
375 | * indicate it is getting cpu time. If it hasn't then | |
376 | * this is a good indication some task is hogging the cpu | |
377 | */ | |
378 | duration = is_softlockup(touch_ts); | |
379 | if (unlikely(duration)) { | |
380 | /* | |
381 | * If a virtual machine is stopped by the host it can look to | |
382 | * the watchdog like a soft lockup, check to see if the host | |
383 | * stopped the vm before we issue the warning | |
384 | */ | |
385 | if (kvm_check_and_clear_guest_paused()) | |
386 | return HRTIMER_RESTART; | |
387 | ||
388 | /* only warn once */ | |
389 | if (__this_cpu_read(soft_watchdog_warn) == true) { | |
390 | /* | |
391 | * When multiple processes are causing softlockups the | |
392 | * softlockup detector only warns on the first one | |
393 | * because the code relies on a full quiet cycle to | |
394 | * re-arm. The second process prevents the quiet cycle | |
395 | * and never gets reported. Use task pointers to detect | |
396 | * this. | |
397 | */ | |
398 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
399 | current) { | |
400 | __this_cpu_write(soft_watchdog_warn, false); | |
401 | __touch_watchdog(); | |
402 | } | |
403 | return HRTIMER_RESTART; | |
404 | } | |
405 | ||
406 | if (softlockup_all_cpu_backtrace) { | |
407 | /* Prevent multiple soft-lockup reports if one cpu is already | |
408 | * engaged in dumping cpu back traces | |
409 | */ | |
410 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
411 | /* Someone else will report us. Let's give up */ | |
412 | __this_cpu_write(soft_watchdog_warn, true); | |
413 | return HRTIMER_RESTART; | |
414 | } | |
415 | } | |
416 | ||
417 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", | |
418 | smp_processor_id(), duration, | |
419 | current->comm, task_pid_nr(current)); | |
420 | __this_cpu_write(softlockup_task_ptr_saved, current); | |
421 | print_modules(); | |
422 | print_irqtrace_events(current); | |
423 | if (regs) | |
424 | show_regs(regs); | |
425 | else | |
426 | dump_stack(); | |
427 | ||
428 | if (softlockup_all_cpu_backtrace) { | |
429 | /* Avoid generating two back traces for current | |
430 | * given that one is already made above | |
431 | */ | |
432 | trigger_allbutself_cpu_backtrace(); | |
433 | ||
434 | clear_bit(0, &soft_lockup_nmi_warn); | |
435 | /* Barrier to sync with other cpus */ | |
436 | smp_mb__after_atomic(); | |
437 | } | |
438 | ||
439 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); | |
440 | if (softlockup_panic) | |
441 | panic("softlockup: hung tasks"); | |
442 | __this_cpu_write(soft_watchdog_warn, true); | |
443 | } else | |
444 | __this_cpu_write(soft_watchdog_warn, false); | |
445 | ||
446 | return HRTIMER_RESTART; | |
447 | } | |
448 | ||
449 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) | |
450 | { | |
451 | struct sched_param param = { .sched_priority = prio }; | |
452 | ||
453 | sched_setscheduler(current, policy, ¶m); | |
454 | } | |
455 | ||
456 | static void watchdog_enable(unsigned int cpu) | |
457 | { | |
458 | struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); | |
459 | ||
460 | /* | |
461 | * Start the timer first to prevent the NMI watchdog triggering | |
462 | * before the timer has a chance to fire. | |
463 | */ | |
464 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
465 | hrtimer->function = watchdog_timer_fn; | |
466 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), | |
467 | HRTIMER_MODE_REL_PINNED); | |
468 | ||
469 | /* Initialize timestamp */ | |
470 | __touch_watchdog(); | |
471 | /* Enable the perf event */ | |
472 | if (watchdog_enabled & NMI_WATCHDOG_ENABLED) | |
473 | watchdog_nmi_enable(cpu); | |
474 | ||
475 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
476 | } | |
477 | ||
478 | static void watchdog_disable(unsigned int cpu) | |
479 | { | |
480 | struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); | |
481 | ||
482 | watchdog_set_prio(SCHED_NORMAL, 0); | |
483 | /* | |
484 | * Disable the perf event first. That prevents that a large delay | |
485 | * between disabling the timer and disabling the perf event causes | |
486 | * the perf NMI to detect a false positive. | |
487 | */ | |
488 | watchdog_nmi_disable(cpu); | |
489 | hrtimer_cancel(hrtimer); | |
490 | } | |
491 | ||
492 | static void watchdog_cleanup(unsigned int cpu, bool online) | |
493 | { | |
494 | watchdog_disable(cpu); | |
495 | } | |
496 | ||
497 | static int watchdog_should_run(unsigned int cpu) | |
498 | { | |
499 | return __this_cpu_read(hrtimer_interrupts) != | |
500 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
501 | } | |
502 | ||
503 | /* | |
504 | * The watchdog thread function - touches the timestamp. | |
505 | * | |
506 | * It only runs once every sample_period seconds (4 seconds by | |
507 | * default) to reset the softlockup timestamp. If this gets delayed | |
508 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
509 | * triggers in watchdog_timer_fn(). | |
510 | */ | |
511 | static void watchdog(unsigned int cpu) | |
512 | { | |
513 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
514 | __this_cpu_read(hrtimer_interrupts)); | |
515 | __touch_watchdog(); | |
516 | } | |
517 | ||
518 | static struct smp_hotplug_thread watchdog_threads = { | |
519 | .store = &softlockup_watchdog, | |
520 | .thread_should_run = watchdog_should_run, | |
521 | .thread_fn = watchdog, | |
522 | .thread_comm = "watchdog/%u", | |
523 | .setup = watchdog_enable, | |
524 | .cleanup = watchdog_cleanup, | |
525 | .park = watchdog_disable, | |
526 | .unpark = watchdog_enable, | |
527 | }; | |
528 | ||
529 | static void softlockup_update_smpboot_threads(void) | |
530 | { | |
531 | lockdep_assert_held(&watchdog_mutex); | |
532 | ||
533 | if (!softlockup_threads_initialized) | |
534 | return; | |
535 | ||
536 | smpboot_update_cpumask_percpu_thread(&watchdog_threads, | |
537 | &watchdog_allowed_mask); | |
538 | } | |
539 | ||
540 | /* Temporarily park all watchdog threads */ | |
541 | static void softlockup_park_all_threads(void) | |
542 | { | |
543 | cpumask_clear(&watchdog_allowed_mask); | |
544 | softlockup_update_smpboot_threads(); | |
545 | } | |
546 | ||
547 | /* Unpark enabled threads */ | |
548 | static void softlockup_unpark_threads(void) | |
549 | { | |
550 | cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask); | |
551 | softlockup_update_smpboot_threads(); | |
552 | } | |
553 | ||
554 | static void lockup_detector_reconfigure(void) | |
555 | { | |
556 | cpus_read_lock(); | |
557 | watchdog_nmi_stop(); | |
558 | softlockup_park_all_threads(); | |
559 | set_sample_period(); | |
560 | lockup_detector_update_enable(); | |
561 | if (watchdog_enabled && watchdog_thresh) | |
562 | softlockup_unpark_threads(); | |
563 | watchdog_nmi_start(); | |
564 | cpus_read_unlock(); | |
565 | /* | |
566 | * Must be called outside the cpus locked section to prevent | |
567 | * recursive locking in the perf code. | |
568 | */ | |
569 | __lockup_detector_cleanup(); | |
570 | } | |
571 | ||
572 | /* | |
573 | * Create the watchdog thread infrastructure and configure the detector(s). | |
574 | * | |
575 | * The threads are not unparked as watchdog_allowed_mask is empty. When | |
576 | * the threads are sucessfully initialized, take the proper locks and | |
577 | * unpark the threads in the watchdog_cpumask if the watchdog is enabled. | |
578 | */ | |
579 | static __init void lockup_detector_setup(void) | |
580 | { | |
581 | int ret; | |
582 | ||
583 | /* | |
584 | * If sysctl is off and watchdog got disabled on the command line, | |
585 | * nothing to do here. | |
586 | */ | |
587 | lockup_detector_update_enable(); | |
588 | ||
589 | if (!IS_ENABLED(CONFIG_SYSCTL) && | |
590 | !(watchdog_enabled && watchdog_thresh)) | |
591 | return; | |
592 | ||
593 | ret = smpboot_register_percpu_thread_cpumask(&watchdog_threads, | |
594 | &watchdog_allowed_mask); | |
595 | if (ret) { | |
596 | pr_err("Failed to initialize soft lockup detector threads\n"); | |
597 | return; | |
598 | } | |
599 | ||
600 | mutex_lock(&watchdog_mutex); | |
601 | softlockup_threads_initialized = true; | |
602 | lockup_detector_reconfigure(); | |
603 | mutex_unlock(&watchdog_mutex); | |
604 | } | |
605 | ||
606 | #else /* CONFIG_SOFTLOCKUP_DETECTOR */ | |
607 | static inline int watchdog_park_threads(void) { return 0; } | |
608 | static inline void watchdog_unpark_threads(void) { } | |
609 | static inline int watchdog_enable_all_cpus(void) { return 0; } | |
610 | static inline void watchdog_disable_all_cpus(void) { } | |
611 | static void lockup_detector_reconfigure(void) | |
612 | { | |
613 | cpus_read_lock(); | |
614 | watchdog_nmi_stop(); | |
615 | lockup_detector_update_enable(); | |
616 | watchdog_nmi_start(); | |
617 | cpus_read_unlock(); | |
618 | } | |
619 | static inline void lockup_detector_setup(void) | |
620 | { | |
621 | lockup_detector_reconfigure(); | |
622 | } | |
623 | #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ | |
624 | ||
625 | static void __lockup_detector_cleanup(void) | |
626 | { | |
627 | lockdep_assert_held(&watchdog_mutex); | |
628 | hardlockup_detector_perf_cleanup(); | |
629 | } | |
630 | ||
631 | /** | |
632 | * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes | |
633 | * | |
634 | * Caller must not hold the cpu hotplug rwsem. | |
635 | */ | |
636 | void lockup_detector_cleanup(void) | |
637 | { | |
638 | mutex_lock(&watchdog_mutex); | |
639 | __lockup_detector_cleanup(); | |
640 | mutex_unlock(&watchdog_mutex); | |
641 | } | |
642 | ||
643 | /** | |
644 | * lockup_detector_soft_poweroff - Interface to stop lockup detector(s) | |
645 | * | |
646 | * Special interface for parisc. It prevents lockup detector warnings from | |
647 | * the default pm_poweroff() function which busy loops forever. | |
648 | */ | |
649 | void lockup_detector_soft_poweroff(void) | |
650 | { | |
651 | watchdog_enabled = 0; | |
652 | } | |
653 | ||
654 | #ifdef CONFIG_SYSCTL | |
655 | ||
656 | /* Propagate any changes to the watchdog threads */ | |
657 | static void proc_watchdog_update(void) | |
658 | { | |
659 | /* Remove impossible cpus to keep sysctl output clean. */ | |
660 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); | |
661 | lockup_detector_reconfigure(); | |
662 | } | |
663 | ||
664 | /* | |
665 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
666 | * | |
667 | * caller | table->data points to | 'which' | |
668 | * -------------------|----------------------------|-------------------------- | |
669 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED | | |
670 | * | | SOFT_WATCHDOG_ENABLED | |
671 | * -------------------|----------------------------|-------------------------- | |
672 | * proc_nmi_watchdog | nmi_watchdog_user_enabled | NMI_WATCHDOG_ENABLED | |
673 | * -------------------|----------------------------|-------------------------- | |
674 | * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED | |
675 | */ | |
676 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
677 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
678 | { | |
679 | int err, old, *param = table->data; | |
680 | ||
681 | mutex_lock(&watchdog_mutex); | |
682 | ||
683 | if (!write) { | |
684 | /* | |
685 | * On read synchronize the userspace interface. This is a | |
686 | * racy snapshot. | |
687 | */ | |
688 | *param = (watchdog_enabled & which) != 0; | |
689 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
690 | } else { | |
691 | old = READ_ONCE(*param); | |
692 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
693 | if (!err && old != READ_ONCE(*param)) | |
694 | proc_watchdog_update(); | |
695 | } | |
696 | mutex_unlock(&watchdog_mutex); | |
697 | return err; | |
698 | } | |
699 | ||
700 | /* | |
701 | * /proc/sys/kernel/watchdog | |
702 | */ | |
703 | int proc_watchdog(struct ctl_table *table, int write, | |
704 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
705 | { | |
706 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
707 | table, write, buffer, lenp, ppos); | |
708 | } | |
709 | ||
710 | /* | |
711 | * /proc/sys/kernel/nmi_watchdog | |
712 | */ | |
713 | int proc_nmi_watchdog(struct ctl_table *table, int write, | |
714 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
715 | { | |
716 | if (!nmi_watchdog_available && write) | |
717 | return -ENOTSUPP; | |
718 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
719 | table, write, buffer, lenp, ppos); | |
720 | } | |
721 | ||
722 | /* | |
723 | * /proc/sys/kernel/soft_watchdog | |
724 | */ | |
725 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
726 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
727 | { | |
728 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
729 | table, write, buffer, lenp, ppos); | |
730 | } | |
731 | ||
732 | /* | |
733 | * /proc/sys/kernel/watchdog_thresh | |
734 | */ | |
735 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
736 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
737 | { | |
738 | int err, old; | |
739 | ||
740 | mutex_lock(&watchdog_mutex); | |
741 | ||
742 | old = READ_ONCE(watchdog_thresh); | |
743 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
744 | ||
745 | if (!err && write && old != READ_ONCE(watchdog_thresh)) | |
746 | proc_watchdog_update(); | |
747 | ||
748 | mutex_unlock(&watchdog_mutex); | |
749 | return err; | |
750 | } | |
751 | ||
752 | /* | |
753 | * The cpumask is the mask of possible cpus that the watchdog can run | |
754 | * on, not the mask of cpus it is actually running on. This allows the | |
755 | * user to specify a mask that will include cpus that have not yet | |
756 | * been brought online, if desired. | |
757 | */ | |
758 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
759 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
760 | { | |
761 | int err; | |
762 | ||
763 | mutex_lock(&watchdog_mutex); | |
764 | ||
765 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); | |
766 | if (!err && write) | |
767 | proc_watchdog_update(); | |
768 | ||
769 | mutex_unlock(&watchdog_mutex); | |
770 | return err; | |
771 | } | |
772 | #endif /* CONFIG_SYSCTL */ | |
773 | ||
774 | void __init lockup_detector_init(void) | |
775 | { | |
776 | #ifdef CONFIG_NO_HZ_FULL | |
777 | if (tick_nohz_full_enabled()) { | |
778 | pr_info("Disabling watchdog on nohz_full cores by default\n"); | |
779 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
780 | } else | |
781 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
782 | #else | |
783 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
784 | #endif | |
785 | ||
786 | if (!watchdog_nmi_probe()) | |
787 | nmi_watchdog_available = true; | |
788 | lockup_detector_setup(); | |
789 | } |