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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 | ||
24 | #include <asm/irq_regs.h> | |
25 | #include <linux/kvm_para.h> | |
26 | #include <linux/perf_event.h> | |
27 | #include <linux/kthread.h> | |
28 | ||
29 | /* | |
30 | * The run state of the lockup detectors is controlled by the content of the | |
31 | * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit - | |
32 | * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector. | |
33 | * | |
34 | * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled' | |
35 | * are variables that are only used as an 'interface' between the parameters | |
36 | * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The | |
37 | * 'watchdog_thresh' variable is handled differently because its value is not | |
38 | * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh' | |
39 | * is equal zero. | |
40 | */ | |
41 | #define NMI_WATCHDOG_ENABLED_BIT 0 | |
42 | #define SOFT_WATCHDOG_ENABLED_BIT 1 | |
43 | #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT) | |
44 | #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT) | |
45 | ||
46 | static DEFINE_MUTEX(watchdog_proc_mutex); | |
47 | ||
48 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
49 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED; | |
50 | #else | |
51 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; | |
52 | #endif | |
53 | int __read_mostly nmi_watchdog_enabled; | |
54 | int __read_mostly soft_watchdog_enabled; | |
55 | int __read_mostly watchdog_user_enabled; | |
56 | int __read_mostly watchdog_thresh = 10; | |
57 | ||
58 | #ifdef CONFIG_SMP | |
59 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
60 | int __read_mostly sysctl_hardlockup_all_cpu_backtrace; | |
61 | #else | |
62 | #define sysctl_softlockup_all_cpu_backtrace 0 | |
63 | #define sysctl_hardlockup_all_cpu_backtrace 0 | |
64 | #endif | |
65 | static struct cpumask watchdog_cpumask __read_mostly; | |
66 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); | |
67 | ||
68 | /* Helper for online, unparked cpus. */ | |
69 | #define for_each_watchdog_cpu(cpu) \ | |
70 | for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask) | |
71 | ||
72 | /* | |
73 | * The 'watchdog_running' variable is set to 1 when the watchdog threads | |
74 | * are registered/started and is set to 0 when the watchdog threads are | |
75 | * unregistered/stopped, so it is an indicator whether the threads exist. | |
76 | */ | |
77 | static int __read_mostly watchdog_running; | |
78 | /* | |
79 | * If a subsystem has a need to deactivate the watchdog temporarily, it | |
80 | * can use the suspend/resume interface to achieve this. The content of | |
81 | * the 'watchdog_suspended' variable reflects this state. Existing threads | |
82 | * are parked/unparked by the lockup_detector_{suspend|resume} functions | |
83 | * (see comment blocks pertaining to those functions for further details). | |
84 | * | |
85 | * 'watchdog_suspended' also prevents threads from being registered/started | |
86 | * or unregistered/stopped via parameters in /proc/sys/kernel, so the state | |
87 | * of 'watchdog_running' cannot change while the watchdog is deactivated | |
88 | * temporarily (see related code in 'proc' handlers). | |
89 | */ | |
90 | static int __read_mostly watchdog_suspended; | |
91 | ||
92 | static u64 __read_mostly sample_period; | |
93 | ||
94 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
95 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
96 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
97 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
98 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); | |
99 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); | |
100 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
101 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); | |
102 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
103 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); | |
104 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
105 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); | |
106 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
107 | #endif | |
108 | static unsigned long soft_lockup_nmi_warn; | |
109 | ||
110 | /* boot commands */ | |
111 | /* | |
112 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
113 | */ | |
114 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
115 | unsigned int __read_mostly hardlockup_panic = | |
116 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
117 | static unsigned long hardlockup_allcpu_dumped; | |
118 | /* | |
119 | * We may not want to enable hard lockup detection by default in all cases, | |
120 | * for example when running the kernel as a guest on a hypervisor. In these | |
121 | * cases this function can be called to disable hard lockup detection. This | |
122 | * function should only be executed once by the boot processor before the | |
123 | * kernel command line parameters are parsed, because otherwise it is not | |
124 | * possible to override this in hardlockup_panic_setup(). | |
125 | */ | |
126 | void hardlockup_detector_disable(void) | |
127 | { | |
128 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
129 | } | |
130 | ||
131 | static int __init hardlockup_panic_setup(char *str) | |
132 | { | |
133 | if (!strncmp(str, "panic", 5)) | |
134 | hardlockup_panic = 1; | |
135 | else if (!strncmp(str, "nopanic", 7)) | |
136 | hardlockup_panic = 0; | |
137 | else if (!strncmp(str, "0", 1)) | |
138 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
139 | else if (!strncmp(str, "1", 1)) | |
140 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
141 | return 1; | |
142 | } | |
143 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
144 | #endif | |
145 | ||
146 | unsigned int __read_mostly softlockup_panic = | |
147 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
148 | ||
149 | static int __init softlockup_panic_setup(char *str) | |
150 | { | |
151 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
152 | ||
153 | return 1; | |
154 | } | |
155 | __setup("softlockup_panic=", softlockup_panic_setup); | |
156 | ||
157 | static int __init nowatchdog_setup(char *str) | |
158 | { | |
159 | watchdog_enabled = 0; | |
160 | return 1; | |
161 | } | |
162 | __setup("nowatchdog", nowatchdog_setup); | |
163 | ||
164 | static int __init nosoftlockup_setup(char *str) | |
165 | { | |
166 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; | |
167 | return 1; | |
168 | } | |
169 | __setup("nosoftlockup", nosoftlockup_setup); | |
170 | ||
171 | #ifdef CONFIG_SMP | |
172 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
173 | { | |
174 | sysctl_softlockup_all_cpu_backtrace = | |
175 | !!simple_strtol(str, NULL, 0); | |
176 | return 1; | |
177 | } | |
178 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
179 | static int __init hardlockup_all_cpu_backtrace_setup(char *str) | |
180 | { | |
181 | sysctl_hardlockup_all_cpu_backtrace = | |
182 | !!simple_strtol(str, NULL, 0); | |
183 | return 1; | |
184 | } | |
185 | __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup); | |
186 | #endif | |
187 | ||
188 | /* | |
189 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
190 | * lockups can have false positives under extreme conditions. So we generally | |
191 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
192 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
193 | * time the hard threshold is. | |
194 | */ | |
195 | static int get_softlockup_thresh(void) | |
196 | { | |
197 | return watchdog_thresh * 2; | |
198 | } | |
199 | ||
200 | /* | |
201 | * Returns seconds, approximately. We don't need nanosecond | |
202 | * resolution, and we don't need to waste time with a big divide when | |
203 | * 2^30ns == 1.074s. | |
204 | */ | |
205 | static unsigned long get_timestamp(void) | |
206 | { | |
207 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ | |
208 | } | |
209 | ||
210 | static void set_sample_period(void) | |
211 | { | |
212 | /* | |
213 | * convert watchdog_thresh from seconds to ns | |
214 | * the divide by 5 is to give hrtimer several chances (two | |
215 | * or three with the current relation between the soft | |
216 | * and hard thresholds) to increment before the | |
217 | * hardlockup detector generates a warning | |
218 | */ | |
219 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); | |
220 | } | |
221 | ||
222 | /* Commands for resetting the watchdog */ | |
223 | static void __touch_watchdog(void) | |
224 | { | |
225 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); | |
226 | } | |
227 | ||
228 | void touch_softlockup_watchdog(void) | |
229 | { | |
230 | /* | |
231 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
232 | * gets zeroed here, so use the raw_ operation. | |
233 | */ | |
234 | raw_cpu_write(watchdog_touch_ts, 0); | |
235 | } | |
236 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
237 | ||
238 | void touch_all_softlockup_watchdogs(void) | |
239 | { | |
240 | int cpu; | |
241 | ||
242 | /* | |
243 | * this is done lockless | |
244 | * do we care if a 0 races with a timestamp? | |
245 | * all it means is the softlock check starts one cycle later | |
246 | */ | |
247 | for_each_watchdog_cpu(cpu) | |
248 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
249 | } | |
250 | ||
251 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
252 | void touch_nmi_watchdog(void) | |
253 | { | |
254 | /* | |
255 | * Using __raw here because some code paths have | |
256 | * preemption enabled. If preemption is enabled | |
257 | * then interrupts should be enabled too, in which | |
258 | * case we shouldn't have to worry about the watchdog | |
259 | * going off. | |
260 | */ | |
261 | raw_cpu_write(watchdog_nmi_touch, true); | |
262 | touch_softlockup_watchdog(); | |
263 | } | |
264 | EXPORT_SYMBOL(touch_nmi_watchdog); | |
265 | ||
266 | #endif | |
267 | ||
268 | void touch_softlockup_watchdog_sync(void) | |
269 | { | |
270 | __this_cpu_write(softlockup_touch_sync, true); | |
271 | __this_cpu_write(watchdog_touch_ts, 0); | |
272 | } | |
273 | ||
274 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
275 | /* watchdog detector functions */ | |
276 | static bool is_hardlockup(void) | |
277 | { | |
278 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); | |
279 | ||
280 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) | |
281 | return true; | |
282 | ||
283 | __this_cpu_write(hrtimer_interrupts_saved, hrint); | |
284 | return false; | |
285 | } | |
286 | #endif | |
287 | ||
288 | static int is_softlockup(unsigned long touch_ts) | |
289 | { | |
290 | unsigned long now = get_timestamp(); | |
291 | ||
292 | if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ | |
293 | /* Warn about unreasonable delays. */ | |
294 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
295 | return now - touch_ts; | |
296 | } | |
297 | return 0; | |
298 | } | |
299 | ||
300 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
301 | ||
302 | static struct perf_event_attr wd_hw_attr = { | |
303 | .type = PERF_TYPE_HARDWARE, | |
304 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
305 | .size = sizeof(struct perf_event_attr), | |
306 | .pinned = 1, | |
307 | .disabled = 1, | |
308 | }; | |
309 | ||
310 | /* Callback function for perf event subsystem */ | |
311 | static void watchdog_overflow_callback(struct perf_event *event, | |
312 | struct perf_sample_data *data, | |
313 | struct pt_regs *regs) | |
314 | { | |
315 | /* Ensure the watchdog never gets throttled */ | |
316 | event->hw.interrupts = 0; | |
317 | ||
318 | if (__this_cpu_read(watchdog_nmi_touch) == true) { | |
319 | __this_cpu_write(watchdog_nmi_touch, false); | |
320 | return; | |
321 | } | |
322 | ||
323 | /* check for a hardlockup | |
324 | * This is done by making sure our timer interrupt | |
325 | * is incrementing. The timer interrupt should have | |
326 | * fired multiple times before we overflow'd. If it hasn't | |
327 | * then this is a good indication the cpu is stuck | |
328 | */ | |
329 | if (is_hardlockup()) { | |
330 | int this_cpu = smp_processor_id(); | |
331 | struct pt_regs *regs = get_irq_regs(); | |
332 | ||
333 | /* only print hardlockups once */ | |
334 | if (__this_cpu_read(hard_watchdog_warn) == true) | |
335 | return; | |
336 | ||
337 | pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu); | |
338 | print_modules(); | |
339 | print_irqtrace_events(current); | |
340 | if (regs) | |
341 | show_regs(regs); | |
342 | else | |
343 | dump_stack(); | |
344 | ||
345 | /* | |
346 | * Perform all-CPU dump only once to avoid multiple hardlockups | |
347 | * generating interleaving traces | |
348 | */ | |
349 | if (sysctl_hardlockup_all_cpu_backtrace && | |
350 | !test_and_set_bit(0, &hardlockup_allcpu_dumped)) | |
351 | trigger_allbutself_cpu_backtrace(); | |
352 | ||
353 | if (hardlockup_panic) | |
354 | panic("Hard LOCKUP"); | |
355 | ||
356 | __this_cpu_write(hard_watchdog_warn, true); | |
357 | return; | |
358 | } | |
359 | ||
360 | __this_cpu_write(hard_watchdog_warn, false); | |
361 | return; | |
362 | } | |
363 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ | |
364 | ||
365 | static void watchdog_interrupt_count(void) | |
366 | { | |
367 | __this_cpu_inc(hrtimer_interrupts); | |
368 | } | |
369 | ||
370 | static int watchdog_nmi_enable(unsigned int cpu); | |
371 | static void watchdog_nmi_disable(unsigned int cpu); | |
372 | ||
373 | static int watchdog_enable_all_cpus(void); | |
374 | static void watchdog_disable_all_cpus(void); | |
375 | ||
376 | /* watchdog kicker functions */ | |
377 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
378 | { | |
379 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); | |
380 | struct pt_regs *regs = get_irq_regs(); | |
381 | int duration; | |
382 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; | |
383 | ||
384 | /* kick the hardlockup detector */ | |
385 | watchdog_interrupt_count(); | |
386 | ||
387 | /* kick the softlockup detector */ | |
388 | wake_up_process(__this_cpu_read(softlockup_watchdog)); | |
389 | ||
390 | /* .. and repeat */ | |
391 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); | |
392 | ||
393 | if (touch_ts == 0) { | |
394 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { | |
395 | /* | |
396 | * If the time stamp was touched atomically | |
397 | * make sure the scheduler tick is up to date. | |
398 | */ | |
399 | __this_cpu_write(softlockup_touch_sync, false); | |
400 | sched_clock_tick(); | |
401 | } | |
402 | ||
403 | /* Clear the guest paused flag on watchdog reset */ | |
404 | kvm_check_and_clear_guest_paused(); | |
405 | __touch_watchdog(); | |
406 | return HRTIMER_RESTART; | |
407 | } | |
408 | ||
409 | /* check for a softlockup | |
410 | * This is done by making sure a high priority task is | |
411 | * being scheduled. The task touches the watchdog to | |
412 | * indicate it is getting cpu time. If it hasn't then | |
413 | * this is a good indication some task is hogging the cpu | |
414 | */ | |
415 | duration = is_softlockup(touch_ts); | |
416 | if (unlikely(duration)) { | |
417 | /* | |
418 | * If a virtual machine is stopped by the host it can look to | |
419 | * the watchdog like a soft lockup, check to see if the host | |
420 | * stopped the vm before we issue the warning | |
421 | */ | |
422 | if (kvm_check_and_clear_guest_paused()) | |
423 | return HRTIMER_RESTART; | |
424 | ||
425 | /* only warn once */ | |
426 | if (__this_cpu_read(soft_watchdog_warn) == true) { | |
427 | /* | |
428 | * When multiple processes are causing softlockups the | |
429 | * softlockup detector only warns on the first one | |
430 | * because the code relies on a full quiet cycle to | |
431 | * re-arm. The second process prevents the quiet cycle | |
432 | * and never gets reported. Use task pointers to detect | |
433 | * this. | |
434 | */ | |
435 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
436 | current) { | |
437 | __this_cpu_write(soft_watchdog_warn, false); | |
438 | __touch_watchdog(); | |
439 | } | |
440 | return HRTIMER_RESTART; | |
441 | } | |
442 | ||
443 | if (softlockup_all_cpu_backtrace) { | |
444 | /* Prevent multiple soft-lockup reports if one cpu is already | |
445 | * engaged in dumping cpu back traces | |
446 | */ | |
447 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
448 | /* Someone else will report us. Let's give up */ | |
449 | __this_cpu_write(soft_watchdog_warn, true); | |
450 | return HRTIMER_RESTART; | |
451 | } | |
452 | } | |
453 | ||
454 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", | |
455 | smp_processor_id(), duration, | |
456 | current->comm, task_pid_nr(current)); | |
457 | __this_cpu_write(softlockup_task_ptr_saved, current); | |
458 | print_modules(); | |
459 | print_irqtrace_events(current); | |
460 | if (regs) | |
461 | show_regs(regs); | |
462 | else | |
463 | dump_stack(); | |
464 | ||
465 | if (softlockup_all_cpu_backtrace) { | |
466 | /* Avoid generating two back traces for current | |
467 | * given that one is already made above | |
468 | */ | |
469 | trigger_allbutself_cpu_backtrace(); | |
470 | ||
471 | clear_bit(0, &soft_lockup_nmi_warn); | |
472 | /* Barrier to sync with other cpus */ | |
473 | smp_mb__after_atomic(); | |
474 | } | |
475 | ||
476 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); | |
477 | if (softlockup_panic) | |
478 | panic("softlockup: hung tasks"); | |
479 | __this_cpu_write(soft_watchdog_warn, true); | |
480 | } else | |
481 | __this_cpu_write(soft_watchdog_warn, false); | |
482 | ||
483 | return HRTIMER_RESTART; | |
484 | } | |
485 | ||
486 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) | |
487 | { | |
488 | struct sched_param param = { .sched_priority = prio }; | |
489 | ||
490 | sched_setscheduler(current, policy, ¶m); | |
491 | } | |
492 | ||
493 | static void watchdog_enable(unsigned int cpu) | |
494 | { | |
495 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); | |
496 | ||
497 | /* kick off the timer for the hardlockup detector */ | |
498 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
499 | hrtimer->function = watchdog_timer_fn; | |
500 | ||
501 | /* Enable the perf event */ | |
502 | watchdog_nmi_enable(cpu); | |
503 | ||
504 | /* done here because hrtimer_start can only pin to smp_processor_id() */ | |
505 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), | |
506 | HRTIMER_MODE_REL_PINNED); | |
507 | ||
508 | /* initialize timestamp */ | |
509 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
510 | __touch_watchdog(); | |
511 | } | |
512 | ||
513 | static void watchdog_disable(unsigned int cpu) | |
514 | { | |
515 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); | |
516 | ||
517 | watchdog_set_prio(SCHED_NORMAL, 0); | |
518 | hrtimer_cancel(hrtimer); | |
519 | /* disable the perf event */ | |
520 | watchdog_nmi_disable(cpu); | |
521 | } | |
522 | ||
523 | static void watchdog_cleanup(unsigned int cpu, bool online) | |
524 | { | |
525 | watchdog_disable(cpu); | |
526 | } | |
527 | ||
528 | static int watchdog_should_run(unsigned int cpu) | |
529 | { | |
530 | return __this_cpu_read(hrtimer_interrupts) != | |
531 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
532 | } | |
533 | ||
534 | /* | |
535 | * The watchdog thread function - touches the timestamp. | |
536 | * | |
537 | * It only runs once every sample_period seconds (4 seconds by | |
538 | * default) to reset the softlockup timestamp. If this gets delayed | |
539 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
540 | * triggers in watchdog_timer_fn(). | |
541 | */ | |
542 | static void watchdog(unsigned int cpu) | |
543 | { | |
544 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
545 | __this_cpu_read(hrtimer_interrupts)); | |
546 | __touch_watchdog(); | |
547 | ||
548 | /* | |
549 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
550 | * failure path. Check for failures that can occur asynchronously - | |
551 | * for example, when CPUs are on-lined - and shut down the hardware | |
552 | * perf event on each CPU accordingly. | |
553 | * | |
554 | * The only non-obvious place this bit can be cleared is through | |
555 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
556 | * pr_info here would be too noisy as it would result in a message | |
557 | * every few seconds if the hardlockup was disabled but the softlockup | |
558 | * enabled. | |
559 | */ | |
560 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
561 | watchdog_nmi_disable(cpu); | |
562 | } | |
563 | ||
564 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
565 | /* | |
566 | * People like the simple clean cpu node info on boot. | |
567 | * Reduce the watchdog noise by only printing messages | |
568 | * that are different from what cpu0 displayed. | |
569 | */ | |
570 | static unsigned long cpu0_err; | |
571 | ||
572 | static int watchdog_nmi_enable(unsigned int cpu) | |
573 | { | |
574 | struct perf_event_attr *wd_attr; | |
575 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
576 | ||
577 | /* nothing to do if the hard lockup detector is disabled */ | |
578 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
579 | goto out; | |
580 | ||
581 | /* is it already setup and enabled? */ | |
582 | if (event && event->state > PERF_EVENT_STATE_OFF) | |
583 | goto out; | |
584 | ||
585 | /* it is setup but not enabled */ | |
586 | if (event != NULL) | |
587 | goto out_enable; | |
588 | ||
589 | wd_attr = &wd_hw_attr; | |
590 | wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); | |
591 | ||
592 | /* Try to register using hardware perf events */ | |
593 | event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); | |
594 | ||
595 | /* save cpu0 error for future comparision */ | |
596 | if (cpu == 0 && IS_ERR(event)) | |
597 | cpu0_err = PTR_ERR(event); | |
598 | ||
599 | if (!IS_ERR(event)) { | |
600 | /* only print for cpu0 or different than cpu0 */ | |
601 | if (cpu == 0 || cpu0_err) | |
602 | pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n"); | |
603 | goto out_save; | |
604 | } | |
605 | ||
606 | /* | |
607 | * Disable the hard lockup detector if _any_ CPU fails to set up | |
608 | * set up the hardware perf event. The watchdog() function checks | |
609 | * the NMI_WATCHDOG_ENABLED bit periodically. | |
610 | * | |
611 | * The barriers are for syncing up watchdog_enabled across all the | |
612 | * cpus, as clear_bit() does not use barriers. | |
613 | */ | |
614 | smp_mb__before_atomic(); | |
615 | clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); | |
616 | smp_mb__after_atomic(); | |
617 | ||
618 | /* skip displaying the same error again */ | |
619 | if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) | |
620 | return PTR_ERR(event); | |
621 | ||
622 | /* vary the KERN level based on the returned errno */ | |
623 | if (PTR_ERR(event) == -EOPNOTSUPP) | |
624 | pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu); | |
625 | else if (PTR_ERR(event) == -ENOENT) | |
626 | pr_warn("disabled (cpu%i): hardware events not enabled\n", | |
627 | cpu); | |
628 | else | |
629 | pr_err("disabled (cpu%i): unable to create perf event: %ld\n", | |
630 | cpu, PTR_ERR(event)); | |
631 | ||
632 | pr_info("Shutting down hard lockup detector on all cpus\n"); | |
633 | ||
634 | return PTR_ERR(event); | |
635 | ||
636 | /* success path */ | |
637 | out_save: | |
638 | per_cpu(watchdog_ev, cpu) = event; | |
639 | out_enable: | |
640 | perf_event_enable(per_cpu(watchdog_ev, cpu)); | |
641 | out: | |
642 | return 0; | |
643 | } | |
644 | ||
645 | static void watchdog_nmi_disable(unsigned int cpu) | |
646 | { | |
647 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
648 | ||
649 | if (event) { | |
650 | perf_event_disable(event); | |
651 | per_cpu(watchdog_ev, cpu) = NULL; | |
652 | ||
653 | /* should be in cleanup, but blocks oprofile */ | |
654 | perf_event_release_kernel(event); | |
655 | } | |
656 | if (cpu == 0) { | |
657 | /* watchdog_nmi_enable() expects this to be zero initially. */ | |
658 | cpu0_err = 0; | |
659 | } | |
660 | } | |
661 | ||
662 | #else | |
663 | static int watchdog_nmi_enable(unsigned int cpu) { return 0; } | |
664 | static void watchdog_nmi_disable(unsigned int cpu) { return; } | |
665 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ | |
666 | ||
667 | static struct smp_hotplug_thread watchdog_threads = { | |
668 | .store = &softlockup_watchdog, | |
669 | .thread_should_run = watchdog_should_run, | |
670 | .thread_fn = watchdog, | |
671 | .thread_comm = "watchdog/%u", | |
672 | .setup = watchdog_enable, | |
673 | .cleanup = watchdog_cleanup, | |
674 | .park = watchdog_disable, | |
675 | .unpark = watchdog_enable, | |
676 | }; | |
677 | ||
678 | /* | |
679 | * park all watchdog threads that are specified in 'watchdog_cpumask' | |
680 | * | |
681 | * This function returns an error if kthread_park() of a watchdog thread | |
682 | * fails. In this situation, the watchdog threads of some CPUs can already | |
683 | * be parked and the watchdog threads of other CPUs can still be runnable. | |
684 | * Callers are expected to handle this special condition as appropriate in | |
685 | * their context. | |
686 | * | |
687 | * This function may only be called in a context that is protected against | |
688 | * races with CPU hotplug - for example, via get_online_cpus(). | |
689 | */ | |
690 | static int watchdog_park_threads(void) | |
691 | { | |
692 | int cpu, ret = 0; | |
693 | ||
694 | for_each_watchdog_cpu(cpu) { | |
695 | ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); | |
696 | if (ret) | |
697 | break; | |
698 | } | |
699 | ||
700 | return ret; | |
701 | } | |
702 | ||
703 | /* | |
704 | * unpark all watchdog threads that are specified in 'watchdog_cpumask' | |
705 | * | |
706 | * This function may only be called in a context that is protected against | |
707 | * races with CPU hotplug - for example, via get_online_cpus(). | |
708 | */ | |
709 | static void watchdog_unpark_threads(void) | |
710 | { | |
711 | int cpu; | |
712 | ||
713 | for_each_watchdog_cpu(cpu) | |
714 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
715 | } | |
716 | ||
717 | /* | |
718 | * Suspend the hard and soft lockup detector by parking the watchdog threads. | |
719 | */ | |
720 | int lockup_detector_suspend(void) | |
721 | { | |
722 | int ret = 0; | |
723 | ||
724 | get_online_cpus(); | |
725 | mutex_lock(&watchdog_proc_mutex); | |
726 | /* | |
727 | * Multiple suspend requests can be active in parallel (counted by | |
728 | * the 'watchdog_suspended' variable). If the watchdog threads are | |
729 | * running, the first caller takes care that they will be parked. | |
730 | * The state of 'watchdog_running' cannot change while a suspend | |
731 | * request is active (see related code in 'proc' handlers). | |
732 | */ | |
733 | if (watchdog_running && !watchdog_suspended) | |
734 | ret = watchdog_park_threads(); | |
735 | ||
736 | if (ret == 0) | |
737 | watchdog_suspended++; | |
738 | else { | |
739 | watchdog_disable_all_cpus(); | |
740 | pr_err("Failed to suspend lockup detectors, disabled\n"); | |
741 | watchdog_enabled = 0; | |
742 | } | |
743 | ||
744 | mutex_unlock(&watchdog_proc_mutex); | |
745 | ||
746 | return ret; | |
747 | } | |
748 | ||
749 | /* | |
750 | * Resume the hard and soft lockup detector by unparking the watchdog threads. | |
751 | */ | |
752 | void lockup_detector_resume(void) | |
753 | { | |
754 | mutex_lock(&watchdog_proc_mutex); | |
755 | ||
756 | watchdog_suspended--; | |
757 | /* | |
758 | * The watchdog threads are unparked if they were previously running | |
759 | * and if there is no more active suspend request. | |
760 | */ | |
761 | if (watchdog_running && !watchdog_suspended) | |
762 | watchdog_unpark_threads(); | |
763 | ||
764 | mutex_unlock(&watchdog_proc_mutex); | |
765 | put_online_cpus(); | |
766 | } | |
767 | ||
768 | static int update_watchdog_all_cpus(void) | |
769 | { | |
770 | int ret; | |
771 | ||
772 | ret = watchdog_park_threads(); | |
773 | if (ret) | |
774 | return ret; | |
775 | ||
776 | watchdog_unpark_threads(); | |
777 | ||
778 | return 0; | |
779 | } | |
780 | ||
781 | static int watchdog_enable_all_cpus(void) | |
782 | { | |
783 | int err = 0; | |
784 | ||
785 | if (!watchdog_running) { | |
786 | err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, | |
787 | &watchdog_cpumask); | |
788 | if (err) | |
789 | pr_err("Failed to create watchdog threads, disabled\n"); | |
790 | else | |
791 | watchdog_running = 1; | |
792 | } else { | |
793 | /* | |
794 | * Enable/disable the lockup detectors or | |
795 | * change the sample period 'on the fly'. | |
796 | */ | |
797 | err = update_watchdog_all_cpus(); | |
798 | ||
799 | if (err) { | |
800 | watchdog_disable_all_cpus(); | |
801 | pr_err("Failed to update lockup detectors, disabled\n"); | |
802 | } | |
803 | } | |
804 | ||
805 | if (err) | |
806 | watchdog_enabled = 0; | |
807 | ||
808 | return err; | |
809 | } | |
810 | ||
811 | static void watchdog_disable_all_cpus(void) | |
812 | { | |
813 | if (watchdog_running) { | |
814 | watchdog_running = 0; | |
815 | smpboot_unregister_percpu_thread(&watchdog_threads); | |
816 | } | |
817 | } | |
818 | ||
819 | #ifdef CONFIG_SYSCTL | |
820 | ||
821 | /* | |
822 | * Update the run state of the lockup detectors. | |
823 | */ | |
824 | static int proc_watchdog_update(void) | |
825 | { | |
826 | int err = 0; | |
827 | ||
828 | /* | |
829 | * Watchdog threads won't be started if they are already active. | |
830 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
831 | * care of this. If those threads are already active, the sample | |
832 | * period will be updated and the lockup detectors will be enabled | |
833 | * or disabled 'on the fly'. | |
834 | */ | |
835 | if (watchdog_enabled && watchdog_thresh) | |
836 | err = watchdog_enable_all_cpus(); | |
837 | else | |
838 | watchdog_disable_all_cpus(); | |
839 | ||
840 | return err; | |
841 | ||
842 | } | |
843 | ||
844 | /* | |
845 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
846 | * | |
847 | * caller | table->data points to | 'which' contains the flag(s) | |
848 | * -------------------|-----------------------|----------------------------- | |
849 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
850 | * | | with SOFT_WATCHDOG_ENABLED | |
851 | * -------------------|-----------------------|----------------------------- | |
852 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
853 | * -------------------|-----------------------|----------------------------- | |
854 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
855 | */ | |
856 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
857 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
858 | { | |
859 | int err, old, new; | |
860 | int *watchdog_param = (int *)table->data; | |
861 | ||
862 | get_online_cpus(); | |
863 | mutex_lock(&watchdog_proc_mutex); | |
864 | ||
865 | if (watchdog_suspended) { | |
866 | /* no parameter changes allowed while watchdog is suspended */ | |
867 | err = -EAGAIN; | |
868 | goto out; | |
869 | } | |
870 | ||
871 | /* | |
872 | * If the parameter is being read return the state of the corresponding | |
873 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
874 | * run state of the lockup detectors. | |
875 | */ | |
876 | if (!write) { | |
877 | *watchdog_param = (watchdog_enabled & which) != 0; | |
878 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
879 | } else { | |
880 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
881 | if (err) | |
882 | goto out; | |
883 | ||
884 | /* | |
885 | * There is a race window between fetching the current value | |
886 | * from 'watchdog_enabled' and storing the new value. During | |
887 | * this race window, watchdog_nmi_enable() can sneak in and | |
888 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
889 | * The 'cmpxchg' detects this race and the loop retries. | |
890 | */ | |
891 | do { | |
892 | old = watchdog_enabled; | |
893 | /* | |
894 | * If the parameter value is not zero set the | |
895 | * corresponding bit(s), else clear it(them). | |
896 | */ | |
897 | if (*watchdog_param) | |
898 | new = old | which; | |
899 | else | |
900 | new = old & ~which; | |
901 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
902 | ||
903 | /* | |
904 | * Update the run state of the lockup detectors. There is _no_ | |
905 | * need to check the value returned by proc_watchdog_update() | |
906 | * and to restore the previous value of 'watchdog_enabled' as | |
907 | * both lockup detectors are disabled if proc_watchdog_update() | |
908 | * returns an error. | |
909 | */ | |
910 | err = proc_watchdog_update(); | |
911 | } | |
912 | out: | |
913 | mutex_unlock(&watchdog_proc_mutex); | |
914 | put_online_cpus(); | |
915 | return err; | |
916 | } | |
917 | ||
918 | /* | |
919 | * /proc/sys/kernel/watchdog | |
920 | */ | |
921 | int proc_watchdog(struct ctl_table *table, int write, | |
922 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
923 | { | |
924 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
925 | table, write, buffer, lenp, ppos); | |
926 | } | |
927 | ||
928 | /* | |
929 | * /proc/sys/kernel/nmi_watchdog | |
930 | */ | |
931 | int proc_nmi_watchdog(struct ctl_table *table, int write, | |
932 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
933 | { | |
934 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
935 | table, write, buffer, lenp, ppos); | |
936 | } | |
937 | ||
938 | /* | |
939 | * /proc/sys/kernel/soft_watchdog | |
940 | */ | |
941 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
942 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
943 | { | |
944 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
945 | table, write, buffer, lenp, ppos); | |
946 | } | |
947 | ||
948 | /* | |
949 | * /proc/sys/kernel/watchdog_thresh | |
950 | */ | |
951 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
952 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
953 | { | |
954 | int err, old; | |
955 | ||
956 | get_online_cpus(); | |
957 | mutex_lock(&watchdog_proc_mutex); | |
958 | ||
959 | if (watchdog_suspended) { | |
960 | /* no parameter changes allowed while watchdog is suspended */ | |
961 | err = -EAGAIN; | |
962 | goto out; | |
963 | } | |
964 | ||
965 | old = ACCESS_ONCE(watchdog_thresh); | |
966 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
967 | ||
968 | if (err || !write) | |
969 | goto out; | |
970 | ||
971 | /* | |
972 | * Update the sample period. Restore on failure. | |
973 | */ | |
974 | set_sample_period(); | |
975 | err = proc_watchdog_update(); | |
976 | if (err) { | |
977 | watchdog_thresh = old; | |
978 | set_sample_period(); | |
979 | } | |
980 | out: | |
981 | mutex_unlock(&watchdog_proc_mutex); | |
982 | put_online_cpus(); | |
983 | return err; | |
984 | } | |
985 | ||
986 | /* | |
987 | * The cpumask is the mask of possible cpus that the watchdog can run | |
988 | * on, not the mask of cpus it is actually running on. This allows the | |
989 | * user to specify a mask that will include cpus that have not yet | |
990 | * been brought online, if desired. | |
991 | */ | |
992 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
993 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
994 | { | |
995 | int err; | |
996 | ||
997 | get_online_cpus(); | |
998 | mutex_lock(&watchdog_proc_mutex); | |
999 | ||
1000 | if (watchdog_suspended) { | |
1001 | /* no parameter changes allowed while watchdog is suspended */ | |
1002 | err = -EAGAIN; | |
1003 | goto out; | |
1004 | } | |
1005 | ||
1006 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); | |
1007 | if (!err && write) { | |
1008 | /* Remove impossible cpus to keep sysctl output cleaner. */ | |
1009 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, | |
1010 | cpu_possible_mask); | |
1011 | ||
1012 | if (watchdog_running) { | |
1013 | /* | |
1014 | * Failure would be due to being unable to allocate | |
1015 | * a temporary cpumask, so we are likely not in a | |
1016 | * position to do much else to make things better. | |
1017 | */ | |
1018 | if (smpboot_update_cpumask_percpu_thread( | |
1019 | &watchdog_threads, &watchdog_cpumask) != 0) | |
1020 | pr_err("cpumask update failed\n"); | |
1021 | } | |
1022 | } | |
1023 | out: | |
1024 | mutex_unlock(&watchdog_proc_mutex); | |
1025 | put_online_cpus(); | |
1026 | return err; | |
1027 | } | |
1028 | ||
1029 | #endif /* CONFIG_SYSCTL */ | |
1030 | ||
1031 | void __init lockup_detector_init(void) | |
1032 | { | |
1033 | set_sample_period(); | |
1034 | ||
1035 | #ifdef CONFIG_NO_HZ_FULL | |
1036 | if (tick_nohz_full_enabled()) { | |
1037 | pr_info("Disabling watchdog on nohz_full cores by default\n"); | |
1038 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
1039 | } else | |
1040 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
1041 | #else | |
1042 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
1043 | #endif | |
1044 | ||
1045 | if (watchdog_enabled) | |
1046 | watchdog_enable_all_cpus(); | |
1047 | } |