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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) "NMI 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 <linux/tick.h> | |
23 | #include <linux/workqueue.h> | |
24 | ||
25 | #include <asm/irq_regs.h> | |
26 | #include <linux/kvm_para.h> | |
27 | #include <linux/kthread.h> | |
28 | ||
29 | static DEFINE_MUTEX(watchdog_proc_mutex); | |
30 | ||
31 | #if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR) | |
32 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED; | |
33 | #else | |
34 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; | |
35 | #endif | |
36 | int __read_mostly nmi_watchdog_enabled; | |
37 | int __read_mostly soft_watchdog_enabled; | |
38 | int __read_mostly watchdog_user_enabled; | |
39 | int __read_mostly watchdog_thresh = 10; | |
40 | ||
41 | #ifdef CONFIG_SMP | |
42 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
43 | int __read_mostly sysctl_hardlockup_all_cpu_backtrace; | |
44 | #endif | |
45 | static struct cpumask watchdog_cpumask __read_mostly; | |
46 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); | |
47 | ||
48 | /* Helper for online, unparked cpus. */ | |
49 | #define for_each_watchdog_cpu(cpu) \ | |
50 | for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask) | |
51 | ||
52 | atomic_t watchdog_park_in_progress = ATOMIC_INIT(0); | |
53 | ||
54 | /* | |
55 | * The 'watchdog_running' variable is set to 1 when the watchdog threads | |
56 | * are registered/started and is set to 0 when the watchdog threads are | |
57 | * unregistered/stopped, so it is an indicator whether the threads exist. | |
58 | */ | |
59 | static int __read_mostly watchdog_running; | |
60 | /* | |
61 | * If a subsystem has a need to deactivate the watchdog temporarily, it | |
62 | * can use the suspend/resume interface to achieve this. The content of | |
63 | * the 'watchdog_suspended' variable reflects this state. Existing threads | |
64 | * are parked/unparked by the lockup_detector_{suspend|resume} functions | |
65 | * (see comment blocks pertaining to those functions for further details). | |
66 | * | |
67 | * 'watchdog_suspended' also prevents threads from being registered/started | |
68 | * or unregistered/stopped via parameters in /proc/sys/kernel, so the state | |
69 | * of 'watchdog_running' cannot change while the watchdog is deactivated | |
70 | * temporarily (see related code in 'proc' handlers). | |
71 | */ | |
72 | static int __read_mostly watchdog_suspended; | |
73 | ||
74 | static u64 __read_mostly sample_period; | |
75 | ||
76 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
77 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
78 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
79 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
80 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); | |
81 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); | |
82 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
83 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); | |
84 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); | |
85 | static unsigned long soft_lockup_nmi_warn; | |
86 | ||
87 | unsigned int __read_mostly softlockup_panic = | |
88 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
89 | ||
90 | static int __init softlockup_panic_setup(char *str) | |
91 | { | |
92 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
93 | ||
94 | return 1; | |
95 | } | |
96 | __setup("softlockup_panic=", softlockup_panic_setup); | |
97 | ||
98 | static int __init nowatchdog_setup(char *str) | |
99 | { | |
100 | watchdog_enabled = 0; | |
101 | return 1; | |
102 | } | |
103 | __setup("nowatchdog", nowatchdog_setup); | |
104 | ||
105 | static int __init nosoftlockup_setup(char *str) | |
106 | { | |
107 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; | |
108 | return 1; | |
109 | } | |
110 | __setup("nosoftlockup", nosoftlockup_setup); | |
111 | ||
112 | #ifdef CONFIG_SMP | |
113 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
114 | { | |
115 | sysctl_softlockup_all_cpu_backtrace = | |
116 | !!simple_strtol(str, NULL, 0); | |
117 | return 1; | |
118 | } | |
119 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
120 | static int __init hardlockup_all_cpu_backtrace_setup(char *str) | |
121 | { | |
122 | sysctl_hardlockup_all_cpu_backtrace = | |
123 | !!simple_strtol(str, NULL, 0); | |
124 | return 1; | |
125 | } | |
126 | __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup); | |
127 | #endif | |
128 | ||
129 | /* | |
130 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
131 | * lockups can have false positives under extreme conditions. So we generally | |
132 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
133 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
134 | * time the hard threshold is. | |
135 | */ | |
136 | static int get_softlockup_thresh(void) | |
137 | { | |
138 | return watchdog_thresh * 2; | |
139 | } | |
140 | ||
141 | /* | |
142 | * Returns seconds, approximately. We don't need nanosecond | |
143 | * resolution, and we don't need to waste time with a big divide when | |
144 | * 2^30ns == 1.074s. | |
145 | */ | |
146 | static unsigned long get_timestamp(void) | |
147 | { | |
148 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ | |
149 | } | |
150 | ||
151 | static void set_sample_period(void) | |
152 | { | |
153 | /* | |
154 | * convert watchdog_thresh from seconds to ns | |
155 | * the divide by 5 is to give hrtimer several chances (two | |
156 | * or three with the current relation between the soft | |
157 | * and hard thresholds) to increment before the | |
158 | * hardlockup detector generates a warning | |
159 | */ | |
160 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); | |
161 | } | |
162 | ||
163 | /* Commands for resetting the watchdog */ | |
164 | static void __touch_watchdog(void) | |
165 | { | |
166 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); | |
167 | } | |
168 | ||
169 | /** | |
170 | * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls | |
171 | * | |
172 | * Call when the scheduler may have stalled for legitimate reasons | |
173 | * preventing the watchdog task from executing - e.g. the scheduler | |
174 | * entering idle state. This should only be used for scheduler events. | |
175 | * Use touch_softlockup_watchdog() for everything else. | |
176 | */ | |
177 | void touch_softlockup_watchdog_sched(void) | |
178 | { | |
179 | /* | |
180 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
181 | * gets zeroed here, so use the raw_ operation. | |
182 | */ | |
183 | raw_cpu_write(watchdog_touch_ts, 0); | |
184 | } | |
185 | ||
186 | void touch_softlockup_watchdog(void) | |
187 | { | |
188 | touch_softlockup_watchdog_sched(); | |
189 | wq_watchdog_touch(raw_smp_processor_id()); | |
190 | } | |
191 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
192 | ||
193 | void touch_all_softlockup_watchdogs(void) | |
194 | { | |
195 | int cpu; | |
196 | ||
197 | /* | |
198 | * this is done lockless | |
199 | * do we care if a 0 races with a timestamp? | |
200 | * all it means is the softlock check starts one cycle later | |
201 | */ | |
202 | for_each_watchdog_cpu(cpu) | |
203 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
204 | wq_watchdog_touch(-1); | |
205 | } | |
206 | ||
207 | void touch_softlockup_watchdog_sync(void) | |
208 | { | |
209 | __this_cpu_write(softlockup_touch_sync, true); | |
210 | __this_cpu_write(watchdog_touch_ts, 0); | |
211 | } | |
212 | ||
213 | /* watchdog detector functions */ | |
214 | bool is_hardlockup(void) | |
215 | { | |
216 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); | |
217 | ||
218 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) | |
219 | return true; | |
220 | ||
221 | __this_cpu_write(hrtimer_interrupts_saved, hrint); | |
222 | return false; | |
223 | } | |
224 | ||
225 | static int is_softlockup(unsigned long touch_ts) | |
226 | { | |
227 | unsigned long now = get_timestamp(); | |
228 | ||
229 | if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ | |
230 | /* Warn about unreasonable delays. */ | |
231 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
232 | return now - touch_ts; | |
233 | } | |
234 | return 0; | |
235 | } | |
236 | ||
237 | static void watchdog_interrupt_count(void) | |
238 | { | |
239 | __this_cpu_inc(hrtimer_interrupts); | |
240 | } | |
241 | ||
242 | /* | |
243 | * These two functions are mostly architecture specific | |
244 | * defining them as weak here. | |
245 | */ | |
246 | int __weak watchdog_nmi_enable(unsigned int cpu) | |
247 | { | |
248 | return 0; | |
249 | } | |
250 | void __weak watchdog_nmi_disable(unsigned int cpu) | |
251 | { | |
252 | } | |
253 | ||
254 | static int watchdog_enable_all_cpus(void); | |
255 | static void watchdog_disable_all_cpus(void); | |
256 | ||
257 | /* watchdog kicker functions */ | |
258 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
259 | { | |
260 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); | |
261 | struct pt_regs *regs = get_irq_regs(); | |
262 | int duration; | |
263 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; | |
264 | ||
265 | if (atomic_read(&watchdog_park_in_progress) != 0) | |
266 | return HRTIMER_NORESTART; | |
267 | ||
268 | /* kick the hardlockup detector */ | |
269 | watchdog_interrupt_count(); | |
270 | ||
271 | /* kick the softlockup detector */ | |
272 | wake_up_process(__this_cpu_read(softlockup_watchdog)); | |
273 | ||
274 | /* .. and repeat */ | |
275 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); | |
276 | ||
277 | if (touch_ts == 0) { | |
278 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { | |
279 | /* | |
280 | * If the time stamp was touched atomically | |
281 | * make sure the scheduler tick is up to date. | |
282 | */ | |
283 | __this_cpu_write(softlockup_touch_sync, false); | |
284 | sched_clock_tick(); | |
285 | } | |
286 | ||
287 | /* Clear the guest paused flag on watchdog reset */ | |
288 | kvm_check_and_clear_guest_paused(); | |
289 | __touch_watchdog(); | |
290 | return HRTIMER_RESTART; | |
291 | } | |
292 | ||
293 | /* check for a softlockup | |
294 | * This is done by making sure a high priority task is | |
295 | * being scheduled. The task touches the watchdog to | |
296 | * indicate it is getting cpu time. If it hasn't then | |
297 | * this is a good indication some task is hogging the cpu | |
298 | */ | |
299 | duration = is_softlockup(touch_ts); | |
300 | if (unlikely(duration)) { | |
301 | /* | |
302 | * If a virtual machine is stopped by the host it can look to | |
303 | * the watchdog like a soft lockup, check to see if the host | |
304 | * stopped the vm before we issue the warning | |
305 | */ | |
306 | if (kvm_check_and_clear_guest_paused()) | |
307 | return HRTIMER_RESTART; | |
308 | ||
309 | /* only warn once */ | |
310 | if (__this_cpu_read(soft_watchdog_warn) == true) { | |
311 | /* | |
312 | * When multiple processes are causing softlockups the | |
313 | * softlockup detector only warns on the first one | |
314 | * because the code relies on a full quiet cycle to | |
315 | * re-arm. The second process prevents the quiet cycle | |
316 | * and never gets reported. Use task pointers to detect | |
317 | * this. | |
318 | */ | |
319 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
320 | current) { | |
321 | __this_cpu_write(soft_watchdog_warn, false); | |
322 | __touch_watchdog(); | |
323 | } | |
324 | return HRTIMER_RESTART; | |
325 | } | |
326 | ||
327 | if (softlockup_all_cpu_backtrace) { | |
328 | /* Prevent multiple soft-lockup reports if one cpu is already | |
329 | * engaged in dumping cpu back traces | |
330 | */ | |
331 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
332 | /* Someone else will report us. Let's give up */ | |
333 | __this_cpu_write(soft_watchdog_warn, true); | |
334 | return HRTIMER_RESTART; | |
335 | } | |
336 | } | |
337 | ||
338 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", | |
339 | smp_processor_id(), duration, | |
340 | current->comm, task_pid_nr(current)); | |
341 | __this_cpu_write(softlockup_task_ptr_saved, current); | |
342 | print_modules(); | |
343 | print_irqtrace_events(current); | |
344 | if (regs) | |
345 | show_regs(regs); | |
346 | else | |
347 | dump_stack(); | |
348 | ||
349 | if (softlockup_all_cpu_backtrace) { | |
350 | /* Avoid generating two back traces for current | |
351 | * given that one is already made above | |
352 | */ | |
353 | trigger_allbutself_cpu_backtrace(); | |
354 | ||
355 | clear_bit(0, &soft_lockup_nmi_warn); | |
356 | /* Barrier to sync with other cpus */ | |
357 | smp_mb__after_atomic(); | |
358 | } | |
359 | ||
360 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); | |
361 | if (softlockup_panic) | |
362 | panic("softlockup: hung tasks"); | |
363 | __this_cpu_write(soft_watchdog_warn, true); | |
364 | } else | |
365 | __this_cpu_write(soft_watchdog_warn, false); | |
366 | ||
367 | return HRTIMER_RESTART; | |
368 | } | |
369 | ||
370 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) | |
371 | { | |
372 | struct sched_param param = { .sched_priority = prio }; | |
373 | ||
374 | sched_setscheduler(current, policy, ¶m); | |
375 | } | |
376 | ||
377 | static void watchdog_enable(unsigned int cpu) | |
378 | { | |
379 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); | |
380 | ||
381 | /* kick off the timer for the hardlockup detector */ | |
382 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
383 | hrtimer->function = watchdog_timer_fn; | |
384 | ||
385 | /* Enable the perf event */ | |
386 | watchdog_nmi_enable(cpu); | |
387 | ||
388 | /* done here because hrtimer_start can only pin to smp_processor_id() */ | |
389 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), | |
390 | HRTIMER_MODE_REL_PINNED); | |
391 | ||
392 | /* initialize timestamp */ | |
393 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
394 | __touch_watchdog(); | |
395 | } | |
396 | ||
397 | static void watchdog_disable(unsigned int cpu) | |
398 | { | |
399 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); | |
400 | ||
401 | watchdog_set_prio(SCHED_NORMAL, 0); | |
402 | hrtimer_cancel(hrtimer); | |
403 | /* disable the perf event */ | |
404 | watchdog_nmi_disable(cpu); | |
405 | } | |
406 | ||
407 | static void watchdog_cleanup(unsigned int cpu, bool online) | |
408 | { | |
409 | watchdog_disable(cpu); | |
410 | } | |
411 | ||
412 | static int watchdog_should_run(unsigned int cpu) | |
413 | { | |
414 | return __this_cpu_read(hrtimer_interrupts) != | |
415 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
416 | } | |
417 | ||
418 | /* | |
419 | * The watchdog thread function - touches the timestamp. | |
420 | * | |
421 | * It only runs once every sample_period seconds (4 seconds by | |
422 | * default) to reset the softlockup timestamp. If this gets delayed | |
423 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
424 | * triggers in watchdog_timer_fn(). | |
425 | */ | |
426 | static void watchdog(unsigned int cpu) | |
427 | { | |
428 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
429 | __this_cpu_read(hrtimer_interrupts)); | |
430 | __touch_watchdog(); | |
431 | ||
432 | /* | |
433 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
434 | * failure path. Check for failures that can occur asynchronously - | |
435 | * for example, when CPUs are on-lined - and shut down the hardware | |
436 | * perf event on each CPU accordingly. | |
437 | * | |
438 | * The only non-obvious place this bit can be cleared is through | |
439 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
440 | * pr_info here would be too noisy as it would result in a message | |
441 | * every few seconds if the hardlockup was disabled but the softlockup | |
442 | * enabled. | |
443 | */ | |
444 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
445 | watchdog_nmi_disable(cpu); | |
446 | } | |
447 | ||
448 | static struct smp_hotplug_thread watchdog_threads = { | |
449 | .store = &softlockup_watchdog, | |
450 | .thread_should_run = watchdog_should_run, | |
451 | .thread_fn = watchdog, | |
452 | .thread_comm = "watchdog/%u", | |
453 | .setup = watchdog_enable, | |
454 | .cleanup = watchdog_cleanup, | |
455 | .park = watchdog_disable, | |
456 | .unpark = watchdog_enable, | |
457 | }; | |
458 | ||
459 | /* | |
460 | * park all watchdog threads that are specified in 'watchdog_cpumask' | |
461 | * | |
462 | * This function returns an error if kthread_park() of a watchdog thread | |
463 | * fails. In this situation, the watchdog threads of some CPUs can already | |
464 | * be parked and the watchdog threads of other CPUs can still be runnable. | |
465 | * Callers are expected to handle this special condition as appropriate in | |
466 | * their context. | |
467 | * | |
468 | * This function may only be called in a context that is protected against | |
469 | * races with CPU hotplug - for example, via get_online_cpus(). | |
470 | */ | |
471 | static int watchdog_park_threads(void) | |
472 | { | |
473 | int cpu, ret = 0; | |
474 | ||
475 | atomic_set(&watchdog_park_in_progress, 1); | |
476 | ||
477 | for_each_watchdog_cpu(cpu) { | |
478 | ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); | |
479 | if (ret) | |
480 | break; | |
481 | } | |
482 | ||
483 | atomic_set(&watchdog_park_in_progress, 0); | |
484 | ||
485 | return ret; | |
486 | } | |
487 | ||
488 | /* | |
489 | * unpark all watchdog threads that are specified in 'watchdog_cpumask' | |
490 | * | |
491 | * This function may only be called in a context that is protected against | |
492 | * races with CPU hotplug - for example, via get_online_cpus(). | |
493 | */ | |
494 | static void watchdog_unpark_threads(void) | |
495 | { | |
496 | int cpu; | |
497 | ||
498 | for_each_watchdog_cpu(cpu) | |
499 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
500 | } | |
501 | ||
502 | /* | |
503 | * Suspend the hard and soft lockup detector by parking the watchdog threads. | |
504 | */ | |
505 | int lockup_detector_suspend(void) | |
506 | { | |
507 | int ret = 0; | |
508 | ||
509 | get_online_cpus(); | |
510 | mutex_lock(&watchdog_proc_mutex); | |
511 | /* | |
512 | * Multiple suspend requests can be active in parallel (counted by | |
513 | * the 'watchdog_suspended' variable). If the watchdog threads are | |
514 | * running, the first caller takes care that they will be parked. | |
515 | * The state of 'watchdog_running' cannot change while a suspend | |
516 | * request is active (see related code in 'proc' handlers). | |
517 | */ | |
518 | if (watchdog_running && !watchdog_suspended) | |
519 | ret = watchdog_park_threads(); | |
520 | ||
521 | if (ret == 0) | |
522 | watchdog_suspended++; | |
523 | else { | |
524 | watchdog_disable_all_cpus(); | |
525 | pr_err("Failed to suspend lockup detectors, disabled\n"); | |
526 | watchdog_enabled = 0; | |
527 | } | |
528 | ||
529 | mutex_unlock(&watchdog_proc_mutex); | |
530 | ||
531 | return ret; | |
532 | } | |
533 | ||
534 | /* | |
535 | * Resume the hard and soft lockup detector by unparking the watchdog threads. | |
536 | */ | |
537 | void lockup_detector_resume(void) | |
538 | { | |
539 | mutex_lock(&watchdog_proc_mutex); | |
540 | ||
541 | watchdog_suspended--; | |
542 | /* | |
543 | * The watchdog threads are unparked if they were previously running | |
544 | * and if there is no more active suspend request. | |
545 | */ | |
546 | if (watchdog_running && !watchdog_suspended) | |
547 | watchdog_unpark_threads(); | |
548 | ||
549 | mutex_unlock(&watchdog_proc_mutex); | |
550 | put_online_cpus(); | |
551 | } | |
552 | ||
553 | static int update_watchdog_all_cpus(void) | |
554 | { | |
555 | int ret; | |
556 | ||
557 | ret = watchdog_park_threads(); | |
558 | if (ret) | |
559 | return ret; | |
560 | ||
561 | watchdog_unpark_threads(); | |
562 | ||
563 | return 0; | |
564 | } | |
565 | ||
566 | static int watchdog_enable_all_cpus(void) | |
567 | { | |
568 | int err = 0; | |
569 | ||
570 | if (!watchdog_running) { | |
571 | err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, | |
572 | &watchdog_cpumask); | |
573 | if (err) | |
574 | pr_err("Failed to create watchdog threads, disabled\n"); | |
575 | else | |
576 | watchdog_running = 1; | |
577 | } else { | |
578 | /* | |
579 | * Enable/disable the lockup detectors or | |
580 | * change the sample period 'on the fly'. | |
581 | */ | |
582 | err = update_watchdog_all_cpus(); | |
583 | ||
584 | if (err) { | |
585 | watchdog_disable_all_cpus(); | |
586 | pr_err("Failed to update lockup detectors, disabled\n"); | |
587 | } | |
588 | } | |
589 | ||
590 | if (err) | |
591 | watchdog_enabled = 0; | |
592 | ||
593 | return err; | |
594 | } | |
595 | ||
596 | static void watchdog_disable_all_cpus(void) | |
597 | { | |
598 | if (watchdog_running) { | |
599 | watchdog_running = 0; | |
600 | smpboot_unregister_percpu_thread(&watchdog_threads); | |
601 | } | |
602 | } | |
603 | ||
604 | #ifdef CONFIG_SYSCTL | |
605 | ||
606 | /* | |
607 | * Update the run state of the lockup detectors. | |
608 | */ | |
609 | static int proc_watchdog_update(void) | |
610 | { | |
611 | int err = 0; | |
612 | ||
613 | /* | |
614 | * Watchdog threads won't be started if they are already active. | |
615 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
616 | * care of this. If those threads are already active, the sample | |
617 | * period will be updated and the lockup detectors will be enabled | |
618 | * or disabled 'on the fly'. | |
619 | */ | |
620 | if (watchdog_enabled && watchdog_thresh) | |
621 | err = watchdog_enable_all_cpus(); | |
622 | else | |
623 | watchdog_disable_all_cpus(); | |
624 | ||
625 | return err; | |
626 | ||
627 | } | |
628 | ||
629 | /* | |
630 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
631 | * | |
632 | * caller | table->data points to | 'which' contains the flag(s) | |
633 | * -------------------|-----------------------|----------------------------- | |
634 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
635 | * | | with SOFT_WATCHDOG_ENABLED | |
636 | * -------------------|-----------------------|----------------------------- | |
637 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
638 | * -------------------|-----------------------|----------------------------- | |
639 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
640 | */ | |
641 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
642 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
643 | { | |
644 | int err, old, new; | |
645 | int *watchdog_param = (int *)table->data; | |
646 | ||
647 | get_online_cpus(); | |
648 | mutex_lock(&watchdog_proc_mutex); | |
649 | ||
650 | if (watchdog_suspended) { | |
651 | /* no parameter changes allowed while watchdog is suspended */ | |
652 | err = -EAGAIN; | |
653 | goto out; | |
654 | } | |
655 | ||
656 | /* | |
657 | * If the parameter is being read return the state of the corresponding | |
658 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
659 | * run state of the lockup detectors. | |
660 | */ | |
661 | if (!write) { | |
662 | *watchdog_param = (watchdog_enabled & which) != 0; | |
663 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
664 | } else { | |
665 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
666 | if (err) | |
667 | goto out; | |
668 | ||
669 | /* | |
670 | * There is a race window between fetching the current value | |
671 | * from 'watchdog_enabled' and storing the new value. During | |
672 | * this race window, watchdog_nmi_enable() can sneak in and | |
673 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
674 | * The 'cmpxchg' detects this race and the loop retries. | |
675 | */ | |
676 | do { | |
677 | old = watchdog_enabled; | |
678 | /* | |
679 | * If the parameter value is not zero set the | |
680 | * corresponding bit(s), else clear it(them). | |
681 | */ | |
682 | if (*watchdog_param) | |
683 | new = old | which; | |
684 | else | |
685 | new = old & ~which; | |
686 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
687 | ||
688 | /* | |
689 | * Update the run state of the lockup detectors. There is _no_ | |
690 | * need to check the value returned by proc_watchdog_update() | |
691 | * and to restore the previous value of 'watchdog_enabled' as | |
692 | * both lockup detectors are disabled if proc_watchdog_update() | |
693 | * returns an error. | |
694 | */ | |
695 | if (old == new) | |
696 | goto out; | |
697 | ||
698 | err = proc_watchdog_update(); | |
699 | } | |
700 | out: | |
701 | mutex_unlock(&watchdog_proc_mutex); | |
702 | put_online_cpus(); | |
703 | return err; | |
704 | } | |
705 | ||
706 | /* | |
707 | * /proc/sys/kernel/watchdog | |
708 | */ | |
709 | int proc_watchdog(struct ctl_table *table, int write, | |
710 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
711 | { | |
712 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
713 | table, write, buffer, lenp, ppos); | |
714 | } | |
715 | ||
716 | /* | |
717 | * /proc/sys/kernel/nmi_watchdog | |
718 | */ | |
719 | int proc_nmi_watchdog(struct ctl_table *table, int write, | |
720 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
721 | { | |
722 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
723 | table, write, buffer, lenp, ppos); | |
724 | } | |
725 | ||
726 | /* | |
727 | * /proc/sys/kernel/soft_watchdog | |
728 | */ | |
729 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
730 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
731 | { | |
732 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
733 | table, write, buffer, lenp, ppos); | |
734 | } | |
735 | ||
736 | /* | |
737 | * /proc/sys/kernel/watchdog_thresh | |
738 | */ | |
739 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
740 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
741 | { | |
742 | int err, old, new; | |
743 | ||
744 | get_online_cpus(); | |
745 | mutex_lock(&watchdog_proc_mutex); | |
746 | ||
747 | if (watchdog_suspended) { | |
748 | /* no parameter changes allowed while watchdog is suspended */ | |
749 | err = -EAGAIN; | |
750 | goto out; | |
751 | } | |
752 | ||
753 | old = ACCESS_ONCE(watchdog_thresh); | |
754 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
755 | ||
756 | if (err || !write) | |
757 | goto out; | |
758 | ||
759 | /* | |
760 | * Update the sample period. Restore on failure. | |
761 | */ | |
762 | new = ACCESS_ONCE(watchdog_thresh); | |
763 | if (old == new) | |
764 | goto out; | |
765 | ||
766 | set_sample_period(); | |
767 | err = proc_watchdog_update(); | |
768 | if (err) { | |
769 | watchdog_thresh = old; | |
770 | set_sample_period(); | |
771 | } | |
772 | out: | |
773 | mutex_unlock(&watchdog_proc_mutex); | |
774 | put_online_cpus(); | |
775 | return err; | |
776 | } | |
777 | ||
778 | /* | |
779 | * The cpumask is the mask of possible cpus that the watchdog can run | |
780 | * on, not the mask of cpus it is actually running on. This allows the | |
781 | * user to specify a mask that will include cpus that have not yet | |
782 | * been brought online, if desired. | |
783 | */ | |
784 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
785 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
786 | { | |
787 | int err; | |
788 | ||
789 | get_online_cpus(); | |
790 | mutex_lock(&watchdog_proc_mutex); | |
791 | ||
792 | if (watchdog_suspended) { | |
793 | /* no parameter changes allowed while watchdog is suspended */ | |
794 | err = -EAGAIN; | |
795 | goto out; | |
796 | } | |
797 | ||
798 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); | |
799 | if (!err && write) { | |
800 | /* Remove impossible cpus to keep sysctl output cleaner. */ | |
801 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, | |
802 | cpu_possible_mask); | |
803 | ||
804 | if (watchdog_running) { | |
805 | /* | |
806 | * Failure would be due to being unable to allocate | |
807 | * a temporary cpumask, so we are likely not in a | |
808 | * position to do much else to make things better. | |
809 | */ | |
810 | if (smpboot_update_cpumask_percpu_thread( | |
811 | &watchdog_threads, &watchdog_cpumask) != 0) | |
812 | pr_err("cpumask update failed\n"); | |
813 | } | |
814 | } | |
815 | out: | |
816 | mutex_unlock(&watchdog_proc_mutex); | |
817 | put_online_cpus(); | |
818 | return err; | |
819 | } | |
820 | ||
821 | #endif /* CONFIG_SYSCTL */ | |
822 | ||
823 | void __init lockup_detector_init(void) | |
824 | { | |
825 | set_sample_period(); | |
826 | ||
827 | #ifdef CONFIG_NO_HZ_FULL | |
828 | if (tick_nohz_full_enabled()) { | |
829 | pr_info("Disabling watchdog on nohz_full cores by default\n"); | |
830 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
831 | } else | |
832 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
833 | #else | |
834 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
835 | #endif | |
836 | ||
837 | if (watchdog_enabled) | |
838 | watchdog_enable_all_cpus(); | |
839 | } |