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Commit | Line | Data |
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58687acb DZ |
1 | /* |
2 | * Detect hard and soft lockups on a system | |
3 | * | |
4 | * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. | |
5 | * | |
86f5e6a7 FLVC |
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 | |
58687acb DZ |
9 | * to those contributors as well. |
10 | */ | |
11 | ||
4501980a AM |
12 | #define pr_fmt(fmt) "NMI watchdog: " fmt |
13 | ||
58687acb DZ |
14 | #include <linux/mm.h> |
15 | #include <linux/cpu.h> | |
16 | #include <linux/nmi.h> | |
17 | #include <linux/init.h> | |
58687acb DZ |
18 | #include <linux/module.h> |
19 | #include <linux/sysctl.h> | |
bcd951cf | 20 | #include <linux/smpboot.h> |
8bd75c77 | 21 | #include <linux/sched/rt.h> |
58687acb DZ |
22 | |
23 | #include <asm/irq_regs.h> | |
5d1c0f4a | 24 | #include <linux/kvm_para.h> |
58687acb DZ |
25 | #include <linux/perf_event.h> |
26 | ||
84d56e66 UO |
27 | /* |
28 | * The run state of the lockup detectors is controlled by the content of the | |
29 | * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit - | |
30 | * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector. | |
31 | * | |
32 | * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled' | |
33 | * are variables that are only used as an 'interface' between the parameters | |
34 | * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The | |
35 | * 'watchdog_thresh' variable is handled differently because its value is not | |
36 | * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh' | |
37 | * is equal zero. | |
38 | */ | |
39 | #define NMI_WATCHDOG_ENABLED_BIT 0 | |
40 | #define SOFT_WATCHDOG_ENABLED_BIT 1 | |
41 | #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT) | |
42 | #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT) | |
43 | ||
ab992dc3 PZ |
44 | static DEFINE_MUTEX(watchdog_proc_mutex); |
45 | ||
84d56e66 UO |
46 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
47 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED; | |
48 | #else | |
49 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; | |
50 | #endif | |
51 | int __read_mostly nmi_watchdog_enabled; | |
52 | int __read_mostly soft_watchdog_enabled; | |
53 | int __read_mostly watchdog_user_enabled; | |
4eec42f3 | 54 | int __read_mostly watchdog_thresh = 10; |
84d56e66 | 55 | |
ed235875 AT |
56 | #ifdef CONFIG_SMP |
57 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
58 | #else | |
59 | #define sysctl_softlockup_all_cpu_backtrace 0 | |
60 | #endif | |
61 | ||
3c00ea82 | 62 | static int __read_mostly watchdog_running; |
0f34c400 | 63 | static u64 __read_mostly sample_period; |
58687acb DZ |
64 | |
65 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
66 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
67 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
68 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 69 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
bcd951cf TG |
70 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
71 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
b1a8de1f | 72 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); |
23637d47 | 73 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
cafcd80d DZ |
74 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); |
75 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
58687acb DZ |
76 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); |
77 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
78 | #endif | |
ed235875 | 79 | static unsigned long soft_lockup_nmi_warn; |
58687acb | 80 | |
58687acb DZ |
81 | /* boot commands */ |
82 | /* | |
83 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
84 | */ | |
23637d47 | 85 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
fef2c9bc DZ |
86 | static int hardlockup_panic = |
87 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
6e7458a6 UO |
88 | /* |
89 | * We may not want to enable hard lockup detection by default in all cases, | |
90 | * for example when running the kernel as a guest on a hypervisor. In these | |
91 | * cases this function can be called to disable hard lockup detection. This | |
92 | * function should only be executed once by the boot processor before the | |
93 | * kernel command line parameters are parsed, because otherwise it is not | |
94 | * possible to override this in hardlockup_panic_setup(). | |
95 | */ | |
692297d8 | 96 | void hardlockup_detector_disable(void) |
6e7458a6 | 97 | { |
692297d8 | 98 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; |
6e7458a6 UO |
99 | } |
100 | ||
58687acb DZ |
101 | static int __init hardlockup_panic_setup(char *str) |
102 | { | |
103 | if (!strncmp(str, "panic", 5)) | |
104 | hardlockup_panic = 1; | |
fef2c9bc DZ |
105 | else if (!strncmp(str, "nopanic", 7)) |
106 | hardlockup_panic = 0; | |
5dc30558 | 107 | else if (!strncmp(str, "0", 1)) |
195daf66 UO |
108 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; |
109 | else if (!strncmp(str, "1", 1)) | |
110 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
58687acb DZ |
111 | return 1; |
112 | } | |
113 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
114 | #endif | |
115 | ||
116 | unsigned int __read_mostly softlockup_panic = | |
117 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
118 | ||
119 | static int __init softlockup_panic_setup(char *str) | |
120 | { | |
121 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
122 | ||
123 | return 1; | |
124 | } | |
125 | __setup("softlockup_panic=", softlockup_panic_setup); | |
126 | ||
127 | static int __init nowatchdog_setup(char *str) | |
128 | { | |
195daf66 | 129 | watchdog_enabled = 0; |
58687acb DZ |
130 | return 1; |
131 | } | |
132 | __setup("nowatchdog", nowatchdog_setup); | |
133 | ||
58687acb DZ |
134 | static int __init nosoftlockup_setup(char *str) |
135 | { | |
195daf66 | 136 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; |
58687acb DZ |
137 | return 1; |
138 | } | |
139 | __setup("nosoftlockup", nosoftlockup_setup); | |
195daf66 | 140 | |
ed235875 AT |
141 | #ifdef CONFIG_SMP |
142 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
143 | { | |
144 | sysctl_softlockup_all_cpu_backtrace = | |
145 | !!simple_strtol(str, NULL, 0); | |
146 | return 1; | |
147 | } | |
148 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
149 | #endif | |
58687acb | 150 | |
4eec42f3 MSB |
151 | /* |
152 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
153 | * lockups can have false positives under extreme conditions. So we generally | |
154 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
155 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
156 | * time the hard threshold is. | |
157 | */ | |
6e9101ae | 158 | static int get_softlockup_thresh(void) |
4eec42f3 MSB |
159 | { |
160 | return watchdog_thresh * 2; | |
161 | } | |
58687acb DZ |
162 | |
163 | /* | |
164 | * Returns seconds, approximately. We don't need nanosecond | |
165 | * resolution, and we don't need to waste time with a big divide when | |
166 | * 2^30ns == 1.074s. | |
167 | */ | |
c06b4f19 | 168 | static unsigned long get_timestamp(void) |
58687acb | 169 | { |
545a2bf7 | 170 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ |
58687acb DZ |
171 | } |
172 | ||
0f34c400 | 173 | static void set_sample_period(void) |
58687acb DZ |
174 | { |
175 | /* | |
586692a5 | 176 | * convert watchdog_thresh from seconds to ns |
86f5e6a7 FLVC |
177 | * the divide by 5 is to give hrtimer several chances (two |
178 | * or three with the current relation between the soft | |
179 | * and hard thresholds) to increment before the | |
180 | * hardlockup detector generates a warning | |
58687acb | 181 | */ |
0f34c400 | 182 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); |
58687acb DZ |
183 | } |
184 | ||
185 | /* Commands for resetting the watchdog */ | |
186 | static void __touch_watchdog(void) | |
187 | { | |
c06b4f19 | 188 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); |
58687acb DZ |
189 | } |
190 | ||
332fbdbc | 191 | void touch_softlockup_watchdog(void) |
58687acb | 192 | { |
7861144b AM |
193 | /* |
194 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
195 | * gets zeroed here, so use the raw_ operation. | |
196 | */ | |
197 | raw_cpu_write(watchdog_touch_ts, 0); | |
58687acb | 198 | } |
0167c781 | 199 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 200 | |
332fbdbc | 201 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
202 | { |
203 | int cpu; | |
204 | ||
205 | /* | |
206 | * this is done lockless | |
207 | * do we care if a 0 races with a timestamp? | |
208 | * all it means is the softlock check starts one cycle later | |
209 | */ | |
210 | for_each_online_cpu(cpu) | |
211 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
212 | } | |
213 | ||
cafcd80d | 214 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
215 | void touch_nmi_watchdog(void) |
216 | { | |
62572e29 BZ |
217 | /* |
218 | * Using __raw here because some code paths have | |
219 | * preemption enabled. If preemption is enabled | |
220 | * then interrupts should be enabled too, in which | |
221 | * case we shouldn't have to worry about the watchdog | |
222 | * going off. | |
223 | */ | |
f7f66b05 | 224 | raw_cpu_write(watchdog_nmi_touch, true); |
332fbdbc | 225 | touch_softlockup_watchdog(); |
58687acb DZ |
226 | } |
227 | EXPORT_SYMBOL(touch_nmi_watchdog); | |
228 | ||
cafcd80d DZ |
229 | #endif |
230 | ||
58687acb DZ |
231 | void touch_softlockup_watchdog_sync(void) |
232 | { | |
f7f66b05 CL |
233 | __this_cpu_write(softlockup_touch_sync, true); |
234 | __this_cpu_write(watchdog_touch_ts, 0); | |
58687acb DZ |
235 | } |
236 | ||
23637d47 | 237 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb | 238 | /* watchdog detector functions */ |
26e09c6e | 239 | static int is_hardlockup(void) |
58687acb | 240 | { |
909ea964 | 241 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
58687acb | 242 | |
909ea964 | 243 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
58687acb DZ |
244 | return 1; |
245 | ||
909ea964 | 246 | __this_cpu_write(hrtimer_interrupts_saved, hrint); |
58687acb DZ |
247 | return 0; |
248 | } | |
249 | #endif | |
250 | ||
26e09c6e | 251 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 252 | { |
c06b4f19 | 253 | unsigned long now = get_timestamp(); |
58687acb | 254 | |
195daf66 UO |
255 | if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) { |
256 | /* Warn about unreasonable delays. */ | |
257 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
258 | return now - touch_ts; | |
259 | } | |
58687acb DZ |
260 | return 0; |
261 | } | |
262 | ||
23637d47 | 263 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
1880c4ae | 264 | |
58687acb DZ |
265 | static struct perf_event_attr wd_hw_attr = { |
266 | .type = PERF_TYPE_HARDWARE, | |
267 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
268 | .size = sizeof(struct perf_event_attr), | |
269 | .pinned = 1, | |
270 | .disabled = 1, | |
271 | }; | |
272 | ||
273 | /* Callback function for perf event subsystem */ | |
a8b0ca17 | 274 | static void watchdog_overflow_callback(struct perf_event *event, |
58687acb DZ |
275 | struct perf_sample_data *data, |
276 | struct pt_regs *regs) | |
277 | { | |
c6db67cd PZ |
278 | /* Ensure the watchdog never gets throttled */ |
279 | event->hw.interrupts = 0; | |
280 | ||
909ea964 CL |
281 | if (__this_cpu_read(watchdog_nmi_touch) == true) { |
282 | __this_cpu_write(watchdog_nmi_touch, false); | |
58687acb DZ |
283 | return; |
284 | } | |
285 | ||
286 | /* check for a hardlockup | |
287 | * This is done by making sure our timer interrupt | |
288 | * is incrementing. The timer interrupt should have | |
289 | * fired multiple times before we overflow'd. If it hasn't | |
290 | * then this is a good indication the cpu is stuck | |
291 | */ | |
26e09c6e DZ |
292 | if (is_hardlockup()) { |
293 | int this_cpu = smp_processor_id(); | |
294 | ||
58687acb | 295 | /* only print hardlockups once */ |
909ea964 | 296 | if (__this_cpu_read(hard_watchdog_warn) == true) |
58687acb DZ |
297 | return; |
298 | ||
299 | if (hardlockup_panic) | |
656c3b79 FF |
300 | panic("Watchdog detected hard LOCKUP on cpu %d", |
301 | this_cpu); | |
58687acb | 302 | else |
656c3b79 FF |
303 | WARN(1, "Watchdog detected hard LOCKUP on cpu %d", |
304 | this_cpu); | |
58687acb | 305 | |
909ea964 | 306 | __this_cpu_write(hard_watchdog_warn, true); |
58687acb DZ |
307 | return; |
308 | } | |
309 | ||
909ea964 | 310 | __this_cpu_write(hard_watchdog_warn, false); |
58687acb DZ |
311 | return; |
312 | } | |
bcd951cf TG |
313 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
314 | ||
58687acb DZ |
315 | static void watchdog_interrupt_count(void) |
316 | { | |
909ea964 | 317 | __this_cpu_inc(hrtimer_interrupts); |
58687acb | 318 | } |
bcd951cf TG |
319 | |
320 | static int watchdog_nmi_enable(unsigned int cpu); | |
321 | static void watchdog_nmi_disable(unsigned int cpu); | |
58687acb DZ |
322 | |
323 | /* watchdog kicker functions */ | |
324 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
325 | { | |
909ea964 | 326 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
58687acb DZ |
327 | struct pt_regs *regs = get_irq_regs(); |
328 | int duration; | |
ed235875 | 329 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; |
58687acb DZ |
330 | |
331 | /* kick the hardlockup detector */ | |
332 | watchdog_interrupt_count(); | |
333 | ||
334 | /* kick the softlockup detector */ | |
909ea964 | 335 | wake_up_process(__this_cpu_read(softlockup_watchdog)); |
58687acb DZ |
336 | |
337 | /* .. and repeat */ | |
0f34c400 | 338 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); |
58687acb DZ |
339 | |
340 | if (touch_ts == 0) { | |
909ea964 | 341 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
58687acb DZ |
342 | /* |
343 | * If the time stamp was touched atomically | |
344 | * make sure the scheduler tick is up to date. | |
345 | */ | |
909ea964 | 346 | __this_cpu_write(softlockup_touch_sync, false); |
58687acb DZ |
347 | sched_clock_tick(); |
348 | } | |
5d1c0f4a EM |
349 | |
350 | /* Clear the guest paused flag on watchdog reset */ | |
351 | kvm_check_and_clear_guest_paused(); | |
58687acb DZ |
352 | __touch_watchdog(); |
353 | return HRTIMER_RESTART; | |
354 | } | |
355 | ||
356 | /* check for a softlockup | |
357 | * This is done by making sure a high priority task is | |
358 | * being scheduled. The task touches the watchdog to | |
359 | * indicate it is getting cpu time. If it hasn't then | |
360 | * this is a good indication some task is hogging the cpu | |
361 | */ | |
26e09c6e | 362 | duration = is_softlockup(touch_ts); |
58687acb | 363 | if (unlikely(duration)) { |
5d1c0f4a EM |
364 | /* |
365 | * If a virtual machine is stopped by the host it can look to | |
366 | * the watchdog like a soft lockup, check to see if the host | |
367 | * stopped the vm before we issue the warning | |
368 | */ | |
369 | if (kvm_check_and_clear_guest_paused()) | |
370 | return HRTIMER_RESTART; | |
371 | ||
58687acb | 372 | /* only warn once */ |
b1a8de1f | 373 | if (__this_cpu_read(soft_watchdog_warn) == true) { |
374 | /* | |
375 | * When multiple processes are causing softlockups the | |
376 | * softlockup detector only warns on the first one | |
377 | * because the code relies on a full quiet cycle to | |
378 | * re-arm. The second process prevents the quiet cycle | |
379 | * and never gets reported. Use task pointers to detect | |
380 | * this. | |
381 | */ | |
382 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
383 | current) { | |
384 | __this_cpu_write(soft_watchdog_warn, false); | |
385 | __touch_watchdog(); | |
386 | } | |
58687acb | 387 | return HRTIMER_RESTART; |
b1a8de1f | 388 | } |
58687acb | 389 | |
ed235875 AT |
390 | if (softlockup_all_cpu_backtrace) { |
391 | /* Prevent multiple soft-lockup reports if one cpu is already | |
392 | * engaged in dumping cpu back traces | |
393 | */ | |
394 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
395 | /* Someone else will report us. Let's give up */ | |
396 | __this_cpu_write(soft_watchdog_warn, true); | |
397 | return HRTIMER_RESTART; | |
398 | } | |
399 | } | |
400 | ||
656c3b79 | 401 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", |
26e09c6e | 402 | smp_processor_id(), duration, |
58687acb | 403 | current->comm, task_pid_nr(current)); |
b1a8de1f | 404 | __this_cpu_write(softlockup_task_ptr_saved, current); |
58687acb DZ |
405 | print_modules(); |
406 | print_irqtrace_events(current); | |
407 | if (regs) | |
408 | show_regs(regs); | |
409 | else | |
410 | dump_stack(); | |
411 | ||
ed235875 AT |
412 | if (softlockup_all_cpu_backtrace) { |
413 | /* Avoid generating two back traces for current | |
414 | * given that one is already made above | |
415 | */ | |
416 | trigger_allbutself_cpu_backtrace(); | |
417 | ||
418 | clear_bit(0, &soft_lockup_nmi_warn); | |
419 | /* Barrier to sync with other cpus */ | |
420 | smp_mb__after_atomic(); | |
421 | } | |
422 | ||
69361eef | 423 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |
58687acb DZ |
424 | if (softlockup_panic) |
425 | panic("softlockup: hung tasks"); | |
909ea964 | 426 | __this_cpu_write(soft_watchdog_warn, true); |
58687acb | 427 | } else |
909ea964 | 428 | __this_cpu_write(soft_watchdog_warn, false); |
58687acb DZ |
429 | |
430 | return HRTIMER_RESTART; | |
431 | } | |
432 | ||
bcd951cf TG |
433 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) |
434 | { | |
435 | struct sched_param param = { .sched_priority = prio }; | |
58687acb | 436 | |
bcd951cf TG |
437 | sched_setscheduler(current, policy, ¶m); |
438 | } | |
439 | ||
440 | static void watchdog_enable(unsigned int cpu) | |
58687acb | 441 | { |
f7f66b05 | 442 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 443 | |
3935e895 BM |
444 | /* kick off the timer for the hardlockup detector */ |
445 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
446 | hrtimer->function = watchdog_timer_fn; | |
447 | ||
bcd951cf TG |
448 | /* Enable the perf event */ |
449 | watchdog_nmi_enable(cpu); | |
58687acb | 450 | |
58687acb | 451 | /* done here because hrtimer_start can only pin to smp_processor_id() */ |
0f34c400 | 452 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), |
58687acb DZ |
453 | HRTIMER_MODE_REL_PINNED); |
454 | ||
bcd951cf TG |
455 | /* initialize timestamp */ |
456 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
457 | __touch_watchdog(); | |
458 | } | |
58687acb | 459 | |
bcd951cf TG |
460 | static void watchdog_disable(unsigned int cpu) |
461 | { | |
f7f66b05 | 462 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 463 | |
bcd951cf TG |
464 | watchdog_set_prio(SCHED_NORMAL, 0); |
465 | hrtimer_cancel(hrtimer); | |
466 | /* disable the perf event */ | |
467 | watchdog_nmi_disable(cpu); | |
58687acb DZ |
468 | } |
469 | ||
b8900bc0 FW |
470 | static void watchdog_cleanup(unsigned int cpu, bool online) |
471 | { | |
472 | watchdog_disable(cpu); | |
473 | } | |
474 | ||
bcd951cf TG |
475 | static int watchdog_should_run(unsigned int cpu) |
476 | { | |
477 | return __this_cpu_read(hrtimer_interrupts) != | |
478 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
479 | } | |
480 | ||
481 | /* | |
482 | * The watchdog thread function - touches the timestamp. | |
483 | * | |
0f34c400 | 484 | * It only runs once every sample_period seconds (4 seconds by |
bcd951cf TG |
485 | * default) to reset the softlockup timestamp. If this gets delayed |
486 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
487 | * triggers in watchdog_timer_fn(). | |
488 | */ | |
489 | static void watchdog(unsigned int cpu) | |
490 | { | |
491 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
492 | __this_cpu_read(hrtimer_interrupts)); | |
493 | __touch_watchdog(); | |
bcfba4f4 UO |
494 | |
495 | /* | |
496 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
497 | * failure path. Check for failures that can occur asynchronously - | |
498 | * for example, when CPUs are on-lined - and shut down the hardware | |
499 | * perf event on each CPU accordingly. | |
500 | * | |
501 | * The only non-obvious place this bit can be cleared is through | |
502 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
503 | * pr_info here would be too noisy as it would result in a message | |
504 | * every few seconds if the hardlockup was disabled but the softlockup | |
505 | * enabled. | |
506 | */ | |
507 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
508 | watchdog_nmi_disable(cpu); | |
bcd951cf | 509 | } |
58687acb | 510 | |
23637d47 | 511 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
a7027046 DZ |
512 | /* |
513 | * People like the simple clean cpu node info on boot. | |
514 | * Reduce the watchdog noise by only printing messages | |
515 | * that are different from what cpu0 displayed. | |
516 | */ | |
517 | static unsigned long cpu0_err; | |
518 | ||
bcd951cf | 519 | static int watchdog_nmi_enable(unsigned int cpu) |
58687acb DZ |
520 | { |
521 | struct perf_event_attr *wd_attr; | |
522 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
523 | ||
195daf66 UO |
524 | /* nothing to do if the hard lockup detector is disabled */ |
525 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
526 | goto out; | |
6e7458a6 | 527 | |
58687acb DZ |
528 | /* is it already setup and enabled? */ |
529 | if (event && event->state > PERF_EVENT_STATE_OFF) | |
530 | goto out; | |
531 | ||
532 | /* it is setup but not enabled */ | |
533 | if (event != NULL) | |
534 | goto out_enable; | |
535 | ||
58687acb | 536 | wd_attr = &wd_hw_attr; |
4eec42f3 | 537 | wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); |
1880c4ae CG |
538 | |
539 | /* Try to register using hardware perf events */ | |
4dc0da86 | 540 | event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); |
a7027046 DZ |
541 | |
542 | /* save cpu0 error for future comparision */ | |
543 | if (cpu == 0 && IS_ERR(event)) | |
544 | cpu0_err = PTR_ERR(event); | |
545 | ||
58687acb | 546 | if (!IS_ERR(event)) { |
a7027046 DZ |
547 | /* only print for cpu0 or different than cpu0 */ |
548 | if (cpu == 0 || cpu0_err) | |
549 | pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n"); | |
58687acb DZ |
550 | goto out_save; |
551 | } | |
552 | ||
bcfba4f4 UO |
553 | /* |
554 | * Disable the hard lockup detector if _any_ CPU fails to set up | |
555 | * set up the hardware perf event. The watchdog() function checks | |
556 | * the NMI_WATCHDOG_ENABLED bit periodically. | |
557 | * | |
558 | * The barriers are for syncing up watchdog_enabled across all the | |
559 | * cpus, as clear_bit() does not use barriers. | |
560 | */ | |
561 | smp_mb__before_atomic(); | |
562 | clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); | |
563 | smp_mb__after_atomic(); | |
564 | ||
a7027046 DZ |
565 | /* skip displaying the same error again */ |
566 | if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) | |
567 | return PTR_ERR(event); | |
5651f7f4 DZ |
568 | |
569 | /* vary the KERN level based on the returned errno */ | |
570 | if (PTR_ERR(event) == -EOPNOTSUPP) | |
4501980a | 571 | pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu); |
5651f7f4 | 572 | else if (PTR_ERR(event) == -ENOENT) |
656c3b79 | 573 | pr_warn("disabled (cpu%i): hardware events not enabled\n", |
4501980a | 574 | cpu); |
5651f7f4 | 575 | else |
4501980a AM |
576 | pr_err("disabled (cpu%i): unable to create perf event: %ld\n", |
577 | cpu, PTR_ERR(event)); | |
bcfba4f4 UO |
578 | |
579 | pr_info("Shutting down hard lockup detector on all cpus\n"); | |
580 | ||
eac24335 | 581 | return PTR_ERR(event); |
58687acb DZ |
582 | |
583 | /* success path */ | |
584 | out_save: | |
585 | per_cpu(watchdog_ev, cpu) = event; | |
586 | out_enable: | |
587 | perf_event_enable(per_cpu(watchdog_ev, cpu)); | |
588 | out: | |
589 | return 0; | |
590 | } | |
591 | ||
bcd951cf | 592 | static void watchdog_nmi_disable(unsigned int cpu) |
58687acb DZ |
593 | { |
594 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
595 | ||
596 | if (event) { | |
597 | perf_event_disable(event); | |
598 | per_cpu(watchdog_ev, cpu) = NULL; | |
599 | ||
600 | /* should be in cleanup, but blocks oprofile */ | |
601 | perf_event_release_kernel(event); | |
602 | } | |
df577149 UO |
603 | if (cpu == 0) { |
604 | /* watchdog_nmi_enable() expects this to be zero initially. */ | |
605 | cpu0_err = 0; | |
606 | } | |
58687acb | 607 | } |
b3738d29 SE |
608 | |
609 | void watchdog_nmi_enable_all(void) | |
610 | { | |
611 | int cpu; | |
612 | ||
ab992dc3 PZ |
613 | mutex_lock(&watchdog_proc_mutex); |
614 | ||
615 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
616 | goto unlock; | |
b3738d29 SE |
617 | |
618 | get_online_cpus(); | |
619 | for_each_online_cpu(cpu) | |
620 | watchdog_nmi_enable(cpu); | |
621 | put_online_cpus(); | |
ab992dc3 PZ |
622 | |
623 | unlock: | |
1173ff09 | 624 | mutex_unlock(&watchdog_proc_mutex); |
b3738d29 SE |
625 | } |
626 | ||
627 | void watchdog_nmi_disable_all(void) | |
628 | { | |
629 | int cpu; | |
630 | ||
ab992dc3 PZ |
631 | mutex_lock(&watchdog_proc_mutex); |
632 | ||
b3738d29 | 633 | if (!watchdog_running) |
ab992dc3 | 634 | goto unlock; |
b3738d29 SE |
635 | |
636 | get_online_cpus(); | |
637 | for_each_online_cpu(cpu) | |
638 | watchdog_nmi_disable(cpu); | |
639 | put_online_cpus(); | |
ab992dc3 PZ |
640 | |
641 | unlock: | |
642 | mutex_unlock(&watchdog_proc_mutex); | |
b3738d29 | 643 | } |
58687acb | 644 | #else |
bcd951cf TG |
645 | static int watchdog_nmi_enable(unsigned int cpu) { return 0; } |
646 | static void watchdog_nmi_disable(unsigned int cpu) { return; } | |
b3738d29 SE |
647 | void watchdog_nmi_enable_all(void) {} |
648 | void watchdog_nmi_disable_all(void) {} | |
23637d47 | 649 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
58687acb | 650 | |
b8900bc0 FW |
651 | static struct smp_hotplug_thread watchdog_threads = { |
652 | .store = &softlockup_watchdog, | |
653 | .thread_should_run = watchdog_should_run, | |
654 | .thread_fn = watchdog, | |
655 | .thread_comm = "watchdog/%u", | |
656 | .setup = watchdog_enable, | |
657 | .cleanup = watchdog_cleanup, | |
658 | .park = watchdog_disable, | |
659 | .unpark = watchdog_enable, | |
660 | }; | |
661 | ||
9809b18f MH |
662 | static void restart_watchdog_hrtimer(void *info) |
663 | { | |
f7f66b05 | 664 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
9809b18f MH |
665 | int ret; |
666 | ||
667 | /* | |
668 | * No need to cancel and restart hrtimer if it is currently executing | |
669 | * because it will reprogram itself with the new period now. | |
670 | * We should never see it unqueued here because we are running per-cpu | |
671 | * with interrupts disabled. | |
672 | */ | |
673 | ret = hrtimer_try_to_cancel(hrtimer); | |
674 | if (ret == 1) | |
675 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), | |
676 | HRTIMER_MODE_REL_PINNED); | |
677 | } | |
678 | ||
b2f57c3a | 679 | static void update_watchdog(int cpu) |
9809b18f | 680 | { |
9809b18f MH |
681 | /* |
682 | * Make sure that perf event counter will adopt to a new | |
683 | * sampling period. Updating the sampling period directly would | |
684 | * be much nicer but we do not have an API for that now so | |
685 | * let's use a big hammer. | |
686 | * Hrtimer will adopt the new period on the next tick but this | |
687 | * might be late already so we have to restart the timer as well. | |
688 | */ | |
689 | watchdog_nmi_disable(cpu); | |
e0a23b06 | 690 | smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1); |
9809b18f MH |
691 | watchdog_nmi_enable(cpu); |
692 | } | |
693 | ||
b2f57c3a | 694 | static void update_watchdog_all_cpus(void) |
9809b18f MH |
695 | { |
696 | int cpu; | |
697 | ||
698 | get_online_cpus(); | |
9809b18f | 699 | for_each_online_cpu(cpu) |
b2f57c3a | 700 | update_watchdog(cpu); |
9809b18f MH |
701 | put_online_cpus(); |
702 | } | |
703 | ||
b2f57c3a | 704 | static int watchdog_enable_all_cpus(void) |
58687acb | 705 | { |
b8900bc0 | 706 | int err = 0; |
58687acb | 707 | |
3c00ea82 | 708 | if (!watchdog_running) { |
b8900bc0 FW |
709 | err = smpboot_register_percpu_thread(&watchdog_threads); |
710 | if (err) | |
711 | pr_err("Failed to create watchdog threads, disabled\n"); | |
712 | else | |
3c00ea82 | 713 | watchdog_running = 1; |
b2f57c3a UO |
714 | } else { |
715 | /* | |
716 | * Enable/disable the lockup detectors or | |
717 | * change the sample period 'on the fly'. | |
718 | */ | |
719 | update_watchdog_all_cpus(); | |
bcd951cf | 720 | } |
b8900bc0 FW |
721 | |
722 | return err; | |
58687acb DZ |
723 | } |
724 | ||
b8900bc0 FW |
725 | /* prepare/enable/disable routines */ |
726 | /* sysctl functions */ | |
727 | #ifdef CONFIG_SYSCTL | |
58687acb DZ |
728 | static void watchdog_disable_all_cpus(void) |
729 | { | |
3c00ea82 FW |
730 | if (watchdog_running) { |
731 | watchdog_running = 0; | |
b8900bc0 | 732 | smpboot_unregister_percpu_thread(&watchdog_threads); |
bcd951cf | 733 | } |
58687acb DZ |
734 | } |
735 | ||
58687acb | 736 | /* |
a0c9cbb9 UO |
737 | * Update the run state of the lockup detectors. |
738 | */ | |
739 | static int proc_watchdog_update(void) | |
740 | { | |
741 | int err = 0; | |
742 | ||
743 | /* | |
744 | * Watchdog threads won't be started if they are already active. | |
745 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
746 | * care of this. If those threads are already active, the sample | |
747 | * period will be updated and the lockup detectors will be enabled | |
748 | * or disabled 'on the fly'. | |
749 | */ | |
750 | if (watchdog_enabled && watchdog_thresh) | |
b2f57c3a | 751 | err = watchdog_enable_all_cpus(); |
a0c9cbb9 UO |
752 | else |
753 | watchdog_disable_all_cpus(); | |
754 | ||
755 | return err; | |
756 | ||
757 | } | |
758 | ||
ef246a21 UO |
759 | /* |
760 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
761 | * | |
762 | * caller | table->data points to | 'which' contains the flag(s) | |
763 | * -------------------|-----------------------|----------------------------- | |
764 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
765 | * | | with SOFT_WATCHDOG_ENABLED | |
766 | * -------------------|-----------------------|----------------------------- | |
767 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
768 | * -------------------|-----------------------|----------------------------- | |
769 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
770 | */ | |
771 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
772 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
773 | { | |
774 | int err, old, new; | |
775 | int *watchdog_param = (int *)table->data; | |
776 | ||
777 | mutex_lock(&watchdog_proc_mutex); | |
778 | ||
779 | /* | |
780 | * If the parameter is being read return the state of the corresponding | |
781 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
782 | * run state of the lockup detectors. | |
783 | */ | |
784 | if (!write) { | |
785 | *watchdog_param = (watchdog_enabled & which) != 0; | |
786 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
787 | } else { | |
788 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
789 | if (err) | |
790 | goto out; | |
791 | ||
792 | /* | |
793 | * There is a race window between fetching the current value | |
794 | * from 'watchdog_enabled' and storing the new value. During | |
795 | * this race window, watchdog_nmi_enable() can sneak in and | |
796 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
797 | * The 'cmpxchg' detects this race and the loop retries. | |
798 | */ | |
799 | do { | |
800 | old = watchdog_enabled; | |
801 | /* | |
802 | * If the parameter value is not zero set the | |
803 | * corresponding bit(s), else clear it(them). | |
804 | */ | |
805 | if (*watchdog_param) | |
806 | new = old | which; | |
807 | else | |
808 | new = old & ~which; | |
809 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
810 | ||
811 | /* | |
812 | * Update the run state of the lockup detectors. | |
813 | * Restore 'watchdog_enabled' on failure. | |
814 | */ | |
815 | err = proc_watchdog_update(); | |
816 | if (err) | |
817 | watchdog_enabled = old; | |
818 | } | |
819 | out: | |
820 | mutex_unlock(&watchdog_proc_mutex); | |
821 | return err; | |
822 | } | |
823 | ||
83a80a39 UO |
824 | /* |
825 | * /proc/sys/kernel/watchdog | |
826 | */ | |
827 | int proc_watchdog(struct ctl_table *table, int write, | |
828 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
829 | { | |
830 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
831 | table, write, buffer, lenp, ppos); | |
832 | } | |
833 | ||
834 | /* | |
835 | * /proc/sys/kernel/nmi_watchdog | |
58687acb | 836 | */ |
83a80a39 UO |
837 | int proc_nmi_watchdog(struct ctl_table *table, int write, |
838 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
839 | { | |
840 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
841 | table, write, buffer, lenp, ppos); | |
842 | } | |
843 | ||
844 | /* | |
845 | * /proc/sys/kernel/soft_watchdog | |
846 | */ | |
847 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
848 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
849 | { | |
850 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
851 | table, write, buffer, lenp, ppos); | |
852 | } | |
58687acb | 853 | |
83a80a39 UO |
854 | /* |
855 | * /proc/sys/kernel/watchdog_thresh | |
856 | */ | |
857 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
858 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
58687acb | 859 | { |
83a80a39 | 860 | int err, old; |
58687acb | 861 | |
359e6fab | 862 | mutex_lock(&watchdog_proc_mutex); |
bcd951cf | 863 | |
83a80a39 | 864 | old = ACCESS_ONCE(watchdog_thresh); |
b8900bc0 | 865 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
83a80a39 | 866 | |
b8900bc0 | 867 | if (err || !write) |
359e6fab | 868 | goto out; |
e04ab2bc | 869 | |
b66a2356 | 870 | /* |
83a80a39 UO |
871 | * Update the sample period. |
872 | * Restore 'watchdog_thresh' on failure. | |
b66a2356 | 873 | */ |
83a80a39 UO |
874 | set_sample_period(); |
875 | err = proc_watchdog_update(); | |
876 | if (err) | |
877 | watchdog_thresh = old; | |
359e6fab MH |
878 | out: |
879 | mutex_unlock(&watchdog_proc_mutex); | |
b8900bc0 | 880 | return err; |
58687acb | 881 | } |
58687acb DZ |
882 | #endif /* CONFIG_SYSCTL */ |
883 | ||
004417a6 | 884 | void __init lockup_detector_init(void) |
58687acb | 885 | { |
0f34c400 | 886 | set_sample_period(); |
b8900bc0 | 887 | |
195daf66 | 888 | if (watchdog_enabled) |
b2f57c3a | 889 | watchdog_enable_all_cpus(); |
58687acb | 890 | } |