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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 | ||
44 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
45 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED; | |
46 | #else | |
47 | static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; | |
48 | #endif | |
49 | int __read_mostly nmi_watchdog_enabled; | |
50 | int __read_mostly soft_watchdog_enabled; | |
51 | int __read_mostly watchdog_user_enabled; | |
4eec42f3 | 52 | int __read_mostly watchdog_thresh = 10; |
84d56e66 | 53 | |
ed235875 AT |
54 | #ifdef CONFIG_SMP |
55 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
56 | #else | |
57 | #define sysctl_softlockup_all_cpu_backtrace 0 | |
58 | #endif | |
59 | ||
3c00ea82 | 60 | static int __read_mostly watchdog_running; |
0f34c400 | 61 | static u64 __read_mostly sample_period; |
58687acb DZ |
62 | |
63 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
64 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
65 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
66 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 67 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
bcd951cf TG |
68 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
69 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
b1a8de1f | 70 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); |
23637d47 | 71 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
cafcd80d DZ |
72 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); |
73 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
58687acb DZ |
74 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); |
75 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
76 | #endif | |
ed235875 | 77 | static unsigned long soft_lockup_nmi_warn; |
58687acb | 78 | |
58687acb DZ |
79 | /* boot commands */ |
80 | /* | |
81 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
82 | */ | |
23637d47 | 83 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
fef2c9bc DZ |
84 | static int hardlockup_panic = |
85 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
58687acb | 86 | |
6e7458a6 UO |
87 | static bool hardlockup_detector_enabled = true; |
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 | */ | |
96 | void watchdog_enable_hardlockup_detector(bool val) | |
97 | { | |
98 | hardlockup_detector_enabled = val; | |
99 | } | |
100 | ||
101 | bool watchdog_hardlockup_detector_is_enabled(void) | |
102 | { | |
103 | return hardlockup_detector_enabled; | |
104 | } | |
105 | ||
58687acb DZ |
106 | static int __init hardlockup_panic_setup(char *str) |
107 | { | |
108 | if (!strncmp(str, "panic", 5)) | |
109 | hardlockup_panic = 1; | |
fef2c9bc DZ |
110 | else if (!strncmp(str, "nopanic", 7)) |
111 | hardlockup_panic = 0; | |
5dc30558 | 112 | else if (!strncmp(str, "0", 1)) |
195daf66 UO |
113 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; |
114 | else if (!strncmp(str, "1", 1)) | |
115 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
58687acb DZ |
116 | return 1; |
117 | } | |
118 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
119 | #endif | |
120 | ||
121 | unsigned int __read_mostly softlockup_panic = | |
122 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
123 | ||
124 | static int __init softlockup_panic_setup(char *str) | |
125 | { | |
126 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
127 | ||
128 | return 1; | |
129 | } | |
130 | __setup("softlockup_panic=", softlockup_panic_setup); | |
131 | ||
132 | static int __init nowatchdog_setup(char *str) | |
133 | { | |
195daf66 | 134 | watchdog_enabled = 0; |
58687acb DZ |
135 | return 1; |
136 | } | |
137 | __setup("nowatchdog", nowatchdog_setup); | |
138 | ||
58687acb DZ |
139 | static int __init nosoftlockup_setup(char *str) |
140 | { | |
195daf66 | 141 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; |
58687acb DZ |
142 | return 1; |
143 | } | |
144 | __setup("nosoftlockup", nosoftlockup_setup); | |
195daf66 | 145 | |
ed235875 AT |
146 | #ifdef CONFIG_SMP |
147 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
148 | { | |
149 | sysctl_softlockup_all_cpu_backtrace = | |
150 | !!simple_strtol(str, NULL, 0); | |
151 | return 1; | |
152 | } | |
153 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
154 | #endif | |
58687acb | 155 | |
4eec42f3 MSB |
156 | /* |
157 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
158 | * lockups can have false positives under extreme conditions. So we generally | |
159 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
160 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
161 | * time the hard threshold is. | |
162 | */ | |
6e9101ae | 163 | static int get_softlockup_thresh(void) |
4eec42f3 MSB |
164 | { |
165 | return watchdog_thresh * 2; | |
166 | } | |
58687acb DZ |
167 | |
168 | /* | |
169 | * Returns seconds, approximately. We don't need nanosecond | |
170 | * resolution, and we don't need to waste time with a big divide when | |
171 | * 2^30ns == 1.074s. | |
172 | */ | |
c06b4f19 | 173 | static unsigned long get_timestamp(void) |
58687acb | 174 | { |
545a2bf7 | 175 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ |
58687acb DZ |
176 | } |
177 | ||
0f34c400 | 178 | static void set_sample_period(void) |
58687acb DZ |
179 | { |
180 | /* | |
586692a5 | 181 | * convert watchdog_thresh from seconds to ns |
86f5e6a7 FLVC |
182 | * the divide by 5 is to give hrtimer several chances (two |
183 | * or three with the current relation between the soft | |
184 | * and hard thresholds) to increment before the | |
185 | * hardlockup detector generates a warning | |
58687acb | 186 | */ |
0f34c400 | 187 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); |
58687acb DZ |
188 | } |
189 | ||
190 | /* Commands for resetting the watchdog */ | |
191 | static void __touch_watchdog(void) | |
192 | { | |
c06b4f19 | 193 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); |
58687acb DZ |
194 | } |
195 | ||
332fbdbc | 196 | void touch_softlockup_watchdog(void) |
58687acb | 197 | { |
7861144b AM |
198 | /* |
199 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
200 | * gets zeroed here, so use the raw_ operation. | |
201 | */ | |
202 | raw_cpu_write(watchdog_touch_ts, 0); | |
58687acb | 203 | } |
0167c781 | 204 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 205 | |
332fbdbc | 206 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
207 | { |
208 | int cpu; | |
209 | ||
210 | /* | |
211 | * this is done lockless | |
212 | * do we care if a 0 races with a timestamp? | |
213 | * all it means is the softlock check starts one cycle later | |
214 | */ | |
215 | for_each_online_cpu(cpu) | |
216 | per_cpu(watchdog_touch_ts, cpu) = 0; | |
217 | } | |
218 | ||
cafcd80d | 219 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
220 | void touch_nmi_watchdog(void) |
221 | { | |
62572e29 BZ |
222 | /* |
223 | * Using __raw here because some code paths have | |
224 | * preemption enabled. If preemption is enabled | |
225 | * then interrupts should be enabled too, in which | |
226 | * case we shouldn't have to worry about the watchdog | |
227 | * going off. | |
228 | */ | |
f7f66b05 | 229 | raw_cpu_write(watchdog_nmi_touch, true); |
332fbdbc | 230 | touch_softlockup_watchdog(); |
58687acb DZ |
231 | } |
232 | EXPORT_SYMBOL(touch_nmi_watchdog); | |
233 | ||
cafcd80d DZ |
234 | #endif |
235 | ||
58687acb DZ |
236 | void touch_softlockup_watchdog_sync(void) |
237 | { | |
f7f66b05 CL |
238 | __this_cpu_write(softlockup_touch_sync, true); |
239 | __this_cpu_write(watchdog_touch_ts, 0); | |
58687acb DZ |
240 | } |
241 | ||
23637d47 | 242 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb | 243 | /* watchdog detector functions */ |
26e09c6e | 244 | static int is_hardlockup(void) |
58687acb | 245 | { |
909ea964 | 246 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
58687acb | 247 | |
909ea964 | 248 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
58687acb DZ |
249 | return 1; |
250 | ||
909ea964 | 251 | __this_cpu_write(hrtimer_interrupts_saved, hrint); |
58687acb DZ |
252 | return 0; |
253 | } | |
254 | #endif | |
255 | ||
26e09c6e | 256 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 257 | { |
c06b4f19 | 258 | unsigned long now = get_timestamp(); |
58687acb | 259 | |
195daf66 UO |
260 | if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) { |
261 | /* Warn about unreasonable delays. */ | |
262 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
263 | return now - touch_ts; | |
264 | } | |
58687acb DZ |
265 | return 0; |
266 | } | |
267 | ||
23637d47 | 268 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
1880c4ae | 269 | |
58687acb DZ |
270 | static struct perf_event_attr wd_hw_attr = { |
271 | .type = PERF_TYPE_HARDWARE, | |
272 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
273 | .size = sizeof(struct perf_event_attr), | |
274 | .pinned = 1, | |
275 | .disabled = 1, | |
276 | }; | |
277 | ||
278 | /* Callback function for perf event subsystem */ | |
a8b0ca17 | 279 | static void watchdog_overflow_callback(struct perf_event *event, |
58687acb DZ |
280 | struct perf_sample_data *data, |
281 | struct pt_regs *regs) | |
282 | { | |
c6db67cd PZ |
283 | /* Ensure the watchdog never gets throttled */ |
284 | event->hw.interrupts = 0; | |
285 | ||
909ea964 CL |
286 | if (__this_cpu_read(watchdog_nmi_touch) == true) { |
287 | __this_cpu_write(watchdog_nmi_touch, false); | |
58687acb DZ |
288 | return; |
289 | } | |
290 | ||
291 | /* check for a hardlockup | |
292 | * This is done by making sure our timer interrupt | |
293 | * is incrementing. The timer interrupt should have | |
294 | * fired multiple times before we overflow'd. If it hasn't | |
295 | * then this is a good indication the cpu is stuck | |
296 | */ | |
26e09c6e DZ |
297 | if (is_hardlockup()) { |
298 | int this_cpu = smp_processor_id(); | |
299 | ||
58687acb | 300 | /* only print hardlockups once */ |
909ea964 | 301 | if (__this_cpu_read(hard_watchdog_warn) == true) |
58687acb DZ |
302 | return; |
303 | ||
304 | if (hardlockup_panic) | |
656c3b79 FF |
305 | panic("Watchdog detected hard LOCKUP on cpu %d", |
306 | this_cpu); | |
58687acb | 307 | else |
656c3b79 FF |
308 | WARN(1, "Watchdog detected hard LOCKUP on cpu %d", |
309 | this_cpu); | |
58687acb | 310 | |
909ea964 | 311 | __this_cpu_write(hard_watchdog_warn, true); |
58687acb DZ |
312 | return; |
313 | } | |
314 | ||
909ea964 | 315 | __this_cpu_write(hard_watchdog_warn, false); |
58687acb DZ |
316 | return; |
317 | } | |
bcd951cf TG |
318 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
319 | ||
58687acb DZ |
320 | static void watchdog_interrupt_count(void) |
321 | { | |
909ea964 | 322 | __this_cpu_inc(hrtimer_interrupts); |
58687acb | 323 | } |
bcd951cf TG |
324 | |
325 | static int watchdog_nmi_enable(unsigned int cpu); | |
326 | static void watchdog_nmi_disable(unsigned int cpu); | |
58687acb DZ |
327 | |
328 | /* watchdog kicker functions */ | |
329 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
330 | { | |
909ea964 | 331 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
58687acb DZ |
332 | struct pt_regs *regs = get_irq_regs(); |
333 | int duration; | |
ed235875 | 334 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; |
58687acb DZ |
335 | |
336 | /* kick the hardlockup detector */ | |
337 | watchdog_interrupt_count(); | |
338 | ||
339 | /* kick the softlockup detector */ | |
909ea964 | 340 | wake_up_process(__this_cpu_read(softlockup_watchdog)); |
58687acb DZ |
341 | |
342 | /* .. and repeat */ | |
0f34c400 | 343 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); |
58687acb DZ |
344 | |
345 | if (touch_ts == 0) { | |
909ea964 | 346 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
58687acb DZ |
347 | /* |
348 | * If the time stamp was touched atomically | |
349 | * make sure the scheduler tick is up to date. | |
350 | */ | |
909ea964 | 351 | __this_cpu_write(softlockup_touch_sync, false); |
58687acb DZ |
352 | sched_clock_tick(); |
353 | } | |
5d1c0f4a EM |
354 | |
355 | /* Clear the guest paused flag on watchdog reset */ | |
356 | kvm_check_and_clear_guest_paused(); | |
58687acb DZ |
357 | __touch_watchdog(); |
358 | return HRTIMER_RESTART; | |
359 | } | |
360 | ||
361 | /* check for a softlockup | |
362 | * This is done by making sure a high priority task is | |
363 | * being scheduled. The task touches the watchdog to | |
364 | * indicate it is getting cpu time. If it hasn't then | |
365 | * this is a good indication some task is hogging the cpu | |
366 | */ | |
26e09c6e | 367 | duration = is_softlockup(touch_ts); |
58687acb | 368 | if (unlikely(duration)) { |
5d1c0f4a EM |
369 | /* |
370 | * If a virtual machine is stopped by the host it can look to | |
371 | * the watchdog like a soft lockup, check to see if the host | |
372 | * stopped the vm before we issue the warning | |
373 | */ | |
374 | if (kvm_check_and_clear_guest_paused()) | |
375 | return HRTIMER_RESTART; | |
376 | ||
58687acb | 377 | /* only warn once */ |
b1a8de1f | 378 | if (__this_cpu_read(soft_watchdog_warn) == true) { |
379 | /* | |
380 | * When multiple processes are causing softlockups the | |
381 | * softlockup detector only warns on the first one | |
382 | * because the code relies on a full quiet cycle to | |
383 | * re-arm. The second process prevents the quiet cycle | |
384 | * and never gets reported. Use task pointers to detect | |
385 | * this. | |
386 | */ | |
387 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
388 | current) { | |
389 | __this_cpu_write(soft_watchdog_warn, false); | |
390 | __touch_watchdog(); | |
391 | } | |
58687acb | 392 | return HRTIMER_RESTART; |
b1a8de1f | 393 | } |
58687acb | 394 | |
ed235875 AT |
395 | if (softlockup_all_cpu_backtrace) { |
396 | /* Prevent multiple soft-lockup reports if one cpu is already | |
397 | * engaged in dumping cpu back traces | |
398 | */ | |
399 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
400 | /* Someone else will report us. Let's give up */ | |
401 | __this_cpu_write(soft_watchdog_warn, true); | |
402 | return HRTIMER_RESTART; | |
403 | } | |
404 | } | |
405 | ||
656c3b79 | 406 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", |
26e09c6e | 407 | smp_processor_id(), duration, |
58687acb | 408 | current->comm, task_pid_nr(current)); |
b1a8de1f | 409 | __this_cpu_write(softlockup_task_ptr_saved, current); |
58687acb DZ |
410 | print_modules(); |
411 | print_irqtrace_events(current); | |
412 | if (regs) | |
413 | show_regs(regs); | |
414 | else | |
415 | dump_stack(); | |
416 | ||
ed235875 AT |
417 | if (softlockup_all_cpu_backtrace) { |
418 | /* Avoid generating two back traces for current | |
419 | * given that one is already made above | |
420 | */ | |
421 | trigger_allbutself_cpu_backtrace(); | |
422 | ||
423 | clear_bit(0, &soft_lockup_nmi_warn); | |
424 | /* Barrier to sync with other cpus */ | |
425 | smp_mb__after_atomic(); | |
426 | } | |
427 | ||
69361eef | 428 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |
58687acb DZ |
429 | if (softlockup_panic) |
430 | panic("softlockup: hung tasks"); | |
909ea964 | 431 | __this_cpu_write(soft_watchdog_warn, true); |
58687acb | 432 | } else |
909ea964 | 433 | __this_cpu_write(soft_watchdog_warn, false); |
58687acb DZ |
434 | |
435 | return HRTIMER_RESTART; | |
436 | } | |
437 | ||
bcd951cf TG |
438 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) |
439 | { | |
440 | struct sched_param param = { .sched_priority = prio }; | |
58687acb | 441 | |
bcd951cf TG |
442 | sched_setscheduler(current, policy, ¶m); |
443 | } | |
444 | ||
445 | static void watchdog_enable(unsigned int cpu) | |
58687acb | 446 | { |
f7f66b05 | 447 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 448 | |
3935e895 BM |
449 | /* kick off the timer for the hardlockup detector */ |
450 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
451 | hrtimer->function = watchdog_timer_fn; | |
452 | ||
bcd951cf TG |
453 | /* Enable the perf event */ |
454 | watchdog_nmi_enable(cpu); | |
58687acb | 455 | |
58687acb | 456 | /* done here because hrtimer_start can only pin to smp_processor_id() */ |
0f34c400 | 457 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), |
58687acb DZ |
458 | HRTIMER_MODE_REL_PINNED); |
459 | ||
bcd951cf TG |
460 | /* initialize timestamp */ |
461 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
462 | __touch_watchdog(); | |
463 | } | |
58687acb | 464 | |
bcd951cf TG |
465 | static void watchdog_disable(unsigned int cpu) |
466 | { | |
f7f66b05 | 467 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 468 | |
bcd951cf TG |
469 | watchdog_set_prio(SCHED_NORMAL, 0); |
470 | hrtimer_cancel(hrtimer); | |
471 | /* disable the perf event */ | |
472 | watchdog_nmi_disable(cpu); | |
58687acb DZ |
473 | } |
474 | ||
b8900bc0 FW |
475 | static void watchdog_cleanup(unsigned int cpu, bool online) |
476 | { | |
477 | watchdog_disable(cpu); | |
478 | } | |
479 | ||
bcd951cf TG |
480 | static int watchdog_should_run(unsigned int cpu) |
481 | { | |
482 | return __this_cpu_read(hrtimer_interrupts) != | |
483 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
484 | } | |
485 | ||
486 | /* | |
487 | * The watchdog thread function - touches the timestamp. | |
488 | * | |
0f34c400 | 489 | * It only runs once every sample_period seconds (4 seconds by |
bcd951cf TG |
490 | * default) to reset the softlockup timestamp. If this gets delayed |
491 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
492 | * triggers in watchdog_timer_fn(). | |
493 | */ | |
494 | static void watchdog(unsigned int cpu) | |
495 | { | |
496 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
497 | __this_cpu_read(hrtimer_interrupts)); | |
498 | __touch_watchdog(); | |
bcfba4f4 UO |
499 | |
500 | /* | |
501 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
502 | * failure path. Check for failures that can occur asynchronously - | |
503 | * for example, when CPUs are on-lined - and shut down the hardware | |
504 | * perf event on each CPU accordingly. | |
505 | * | |
506 | * The only non-obvious place this bit can be cleared is through | |
507 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
508 | * pr_info here would be too noisy as it would result in a message | |
509 | * every few seconds if the hardlockup was disabled but the softlockup | |
510 | * enabled. | |
511 | */ | |
512 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
513 | watchdog_nmi_disable(cpu); | |
bcd951cf | 514 | } |
58687acb | 515 | |
23637d47 | 516 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
a7027046 DZ |
517 | /* |
518 | * People like the simple clean cpu node info on boot. | |
519 | * Reduce the watchdog noise by only printing messages | |
520 | * that are different from what cpu0 displayed. | |
521 | */ | |
522 | static unsigned long cpu0_err; | |
523 | ||
bcd951cf | 524 | static int watchdog_nmi_enable(unsigned int cpu) |
58687acb DZ |
525 | { |
526 | struct perf_event_attr *wd_attr; | |
527 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
528 | ||
195daf66 UO |
529 | /* nothing to do if the hard lockup detector is disabled */ |
530 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
531 | goto out; | |
532 | ||
6e7458a6 UO |
533 | /* |
534 | * Some kernels need to default hard lockup detection to | |
535 | * 'disabled', for example a guest on a hypervisor. | |
536 | */ | |
537 | if (!watchdog_hardlockup_detector_is_enabled()) { | |
538 | event = ERR_PTR(-ENOENT); | |
539 | goto handle_err; | |
540 | } | |
541 | ||
58687acb DZ |
542 | /* is it already setup and enabled? */ |
543 | if (event && event->state > PERF_EVENT_STATE_OFF) | |
544 | goto out; | |
545 | ||
546 | /* it is setup but not enabled */ | |
547 | if (event != NULL) | |
548 | goto out_enable; | |
549 | ||
58687acb | 550 | wd_attr = &wd_hw_attr; |
4eec42f3 | 551 | wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); |
1880c4ae CG |
552 | |
553 | /* Try to register using hardware perf events */ | |
4dc0da86 | 554 | event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); |
a7027046 | 555 | |
6e7458a6 | 556 | handle_err: |
a7027046 DZ |
557 | /* save cpu0 error for future comparision */ |
558 | if (cpu == 0 && IS_ERR(event)) | |
559 | cpu0_err = PTR_ERR(event); | |
560 | ||
58687acb | 561 | if (!IS_ERR(event)) { |
a7027046 DZ |
562 | /* only print for cpu0 or different than cpu0 */ |
563 | if (cpu == 0 || cpu0_err) | |
564 | pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n"); | |
58687acb DZ |
565 | goto out_save; |
566 | } | |
567 | ||
bcfba4f4 UO |
568 | /* |
569 | * Disable the hard lockup detector if _any_ CPU fails to set up | |
570 | * set up the hardware perf event. The watchdog() function checks | |
571 | * the NMI_WATCHDOG_ENABLED bit periodically. | |
572 | * | |
573 | * The barriers are for syncing up watchdog_enabled across all the | |
574 | * cpus, as clear_bit() does not use barriers. | |
575 | */ | |
576 | smp_mb__before_atomic(); | |
577 | clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); | |
578 | smp_mb__after_atomic(); | |
579 | ||
a7027046 DZ |
580 | /* skip displaying the same error again */ |
581 | if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) | |
582 | return PTR_ERR(event); | |
5651f7f4 DZ |
583 | |
584 | /* vary the KERN level based on the returned errno */ | |
585 | if (PTR_ERR(event) == -EOPNOTSUPP) | |
4501980a | 586 | pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu); |
5651f7f4 | 587 | else if (PTR_ERR(event) == -ENOENT) |
656c3b79 | 588 | pr_warn("disabled (cpu%i): hardware events not enabled\n", |
4501980a | 589 | cpu); |
5651f7f4 | 590 | else |
4501980a AM |
591 | pr_err("disabled (cpu%i): unable to create perf event: %ld\n", |
592 | cpu, PTR_ERR(event)); | |
bcfba4f4 UO |
593 | |
594 | pr_info("Shutting down hard lockup detector on all cpus\n"); | |
595 | ||
eac24335 | 596 | return PTR_ERR(event); |
58687acb DZ |
597 | |
598 | /* success path */ | |
599 | out_save: | |
600 | per_cpu(watchdog_ev, cpu) = event; | |
601 | out_enable: | |
602 | perf_event_enable(per_cpu(watchdog_ev, cpu)); | |
603 | out: | |
604 | return 0; | |
605 | } | |
606 | ||
bcd951cf | 607 | static void watchdog_nmi_disable(unsigned int cpu) |
58687acb DZ |
608 | { |
609 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
610 | ||
611 | if (event) { | |
612 | perf_event_disable(event); | |
613 | per_cpu(watchdog_ev, cpu) = NULL; | |
614 | ||
615 | /* should be in cleanup, but blocks oprofile */ | |
616 | perf_event_release_kernel(event); | |
617 | } | |
df577149 UO |
618 | if (cpu == 0) { |
619 | /* watchdog_nmi_enable() expects this to be zero initially. */ | |
620 | cpu0_err = 0; | |
621 | } | |
58687acb DZ |
622 | } |
623 | #else | |
bcd951cf TG |
624 | static int watchdog_nmi_enable(unsigned int cpu) { return 0; } |
625 | static void watchdog_nmi_disable(unsigned int cpu) { return; } | |
23637d47 | 626 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
58687acb | 627 | |
b8900bc0 FW |
628 | static struct smp_hotplug_thread watchdog_threads = { |
629 | .store = &softlockup_watchdog, | |
630 | .thread_should_run = watchdog_should_run, | |
631 | .thread_fn = watchdog, | |
632 | .thread_comm = "watchdog/%u", | |
633 | .setup = watchdog_enable, | |
634 | .cleanup = watchdog_cleanup, | |
635 | .park = watchdog_disable, | |
636 | .unpark = watchdog_enable, | |
637 | }; | |
638 | ||
9809b18f MH |
639 | static void restart_watchdog_hrtimer(void *info) |
640 | { | |
f7f66b05 | 641 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
9809b18f MH |
642 | int ret; |
643 | ||
644 | /* | |
645 | * No need to cancel and restart hrtimer if it is currently executing | |
646 | * because it will reprogram itself with the new period now. | |
647 | * We should never see it unqueued here because we are running per-cpu | |
648 | * with interrupts disabled. | |
649 | */ | |
650 | ret = hrtimer_try_to_cancel(hrtimer); | |
651 | if (ret == 1) | |
652 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), | |
653 | HRTIMER_MODE_REL_PINNED); | |
654 | } | |
655 | ||
656 | static void update_timers(int cpu) | |
657 | { | |
9809b18f MH |
658 | /* |
659 | * Make sure that perf event counter will adopt to a new | |
660 | * sampling period. Updating the sampling period directly would | |
661 | * be much nicer but we do not have an API for that now so | |
662 | * let's use a big hammer. | |
663 | * Hrtimer will adopt the new period on the next tick but this | |
664 | * might be late already so we have to restart the timer as well. | |
665 | */ | |
666 | watchdog_nmi_disable(cpu); | |
e0a23b06 | 667 | smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1); |
9809b18f MH |
668 | watchdog_nmi_enable(cpu); |
669 | } | |
670 | ||
671 | static void update_timers_all_cpus(void) | |
672 | { | |
673 | int cpu; | |
674 | ||
675 | get_online_cpus(); | |
9809b18f MH |
676 | for_each_online_cpu(cpu) |
677 | update_timers(cpu); | |
9809b18f MH |
678 | put_online_cpus(); |
679 | } | |
680 | ||
681 | static int watchdog_enable_all_cpus(bool sample_period_changed) | |
58687acb | 682 | { |
b8900bc0 | 683 | int err = 0; |
58687acb | 684 | |
3c00ea82 | 685 | if (!watchdog_running) { |
b8900bc0 FW |
686 | err = smpboot_register_percpu_thread(&watchdog_threads); |
687 | if (err) | |
688 | pr_err("Failed to create watchdog threads, disabled\n"); | |
689 | else | |
3c00ea82 | 690 | watchdog_running = 1; |
9809b18f MH |
691 | } else if (sample_period_changed) { |
692 | update_timers_all_cpus(); | |
bcd951cf | 693 | } |
b8900bc0 FW |
694 | |
695 | return err; | |
58687acb DZ |
696 | } |
697 | ||
b8900bc0 FW |
698 | /* prepare/enable/disable routines */ |
699 | /* sysctl functions */ | |
700 | #ifdef CONFIG_SYSCTL | |
58687acb DZ |
701 | static void watchdog_disable_all_cpus(void) |
702 | { | |
3c00ea82 FW |
703 | if (watchdog_running) { |
704 | watchdog_running = 0; | |
b8900bc0 | 705 | smpboot_unregister_percpu_thread(&watchdog_threads); |
bcd951cf | 706 | } |
58687acb DZ |
707 | } |
708 | ||
a0c9cbb9 UO |
709 | /* |
710 | * Update the run state of the lockup detectors. | |
711 | */ | |
712 | static int proc_watchdog_update(void) | |
713 | { | |
714 | int err = 0; | |
715 | ||
716 | /* | |
717 | * Watchdog threads won't be started if they are already active. | |
718 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
719 | * care of this. If those threads are already active, the sample | |
720 | * period will be updated and the lockup detectors will be enabled | |
721 | * or disabled 'on the fly'. | |
722 | */ | |
723 | if (watchdog_enabled && watchdog_thresh) | |
724 | err = watchdog_enable_all_cpus(true); | |
725 | else | |
726 | watchdog_disable_all_cpus(); | |
727 | ||
728 | return err; | |
729 | ||
730 | } | |
731 | ||
f54c2274 UO |
732 | static DEFINE_MUTEX(watchdog_proc_mutex); |
733 | ||
ef246a21 UO |
734 | /* |
735 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
736 | * | |
737 | * caller | table->data points to | 'which' contains the flag(s) | |
738 | * -------------------|-----------------------|----------------------------- | |
739 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
740 | * | | with SOFT_WATCHDOG_ENABLED | |
741 | * -------------------|-----------------------|----------------------------- | |
742 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
743 | * -------------------|-----------------------|----------------------------- | |
744 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
745 | */ | |
746 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
747 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
748 | { | |
749 | int err, old, new; | |
750 | int *watchdog_param = (int *)table->data; | |
751 | ||
752 | mutex_lock(&watchdog_proc_mutex); | |
753 | ||
754 | /* | |
755 | * If the parameter is being read return the state of the corresponding | |
756 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
757 | * run state of the lockup detectors. | |
758 | */ | |
759 | if (!write) { | |
760 | *watchdog_param = (watchdog_enabled & which) != 0; | |
761 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
762 | } else { | |
763 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
764 | if (err) | |
765 | goto out; | |
766 | ||
767 | /* | |
768 | * There is a race window between fetching the current value | |
769 | * from 'watchdog_enabled' and storing the new value. During | |
770 | * this race window, watchdog_nmi_enable() can sneak in and | |
771 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
772 | * The 'cmpxchg' detects this race and the loop retries. | |
773 | */ | |
774 | do { | |
775 | old = watchdog_enabled; | |
776 | /* | |
777 | * If the parameter value is not zero set the | |
778 | * corresponding bit(s), else clear it(them). | |
779 | */ | |
780 | if (*watchdog_param) | |
781 | new = old | which; | |
782 | else | |
783 | new = old & ~which; | |
784 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
785 | ||
786 | /* | |
787 | * Update the run state of the lockup detectors. | |
788 | * Restore 'watchdog_enabled' on failure. | |
789 | */ | |
790 | err = proc_watchdog_update(); | |
791 | if (err) | |
792 | watchdog_enabled = old; | |
793 | } | |
794 | out: | |
795 | mutex_unlock(&watchdog_proc_mutex); | |
796 | return err; | |
797 | } | |
798 | ||
83a80a39 UO |
799 | /* |
800 | * /proc/sys/kernel/watchdog | |
801 | */ | |
802 | int proc_watchdog(struct ctl_table *table, int write, | |
803 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
804 | { | |
805 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
806 | table, write, buffer, lenp, ppos); | |
807 | } | |
808 | ||
809 | /* | |
810 | * /proc/sys/kernel/nmi_watchdog | |
811 | */ | |
812 | int proc_nmi_watchdog(struct ctl_table *table, int write, | |
813 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
814 | { | |
815 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
816 | table, write, buffer, lenp, ppos); | |
817 | } | |
818 | ||
819 | /* | |
820 | * /proc/sys/kernel/soft_watchdog | |
821 | */ | |
822 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
823 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
824 | { | |
825 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
826 | table, write, buffer, lenp, ppos); | |
827 | } | |
828 | ||
829 | /* | |
830 | * /proc/sys/kernel/watchdog_thresh | |
831 | */ | |
832 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
833 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
834 | { | |
835 | int err, old; | |
836 | ||
837 | mutex_lock(&watchdog_proc_mutex); | |
838 | ||
839 | old = ACCESS_ONCE(watchdog_thresh); | |
840 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
841 | ||
842 | if (err || !write) | |
843 | goto out; | |
844 | ||
845 | /* | |
846 | * Update the sample period. | |
847 | * Restore 'watchdog_thresh' on failure. | |
848 | */ | |
849 | set_sample_period(); | |
850 | err = proc_watchdog_update(); | |
851 | if (err) | |
852 | watchdog_thresh = old; | |
853 | out: | |
854 | mutex_unlock(&watchdog_proc_mutex); | |
855 | return err; | |
856 | } | |
58687acb DZ |
857 | #endif /* CONFIG_SYSCTL */ |
858 | ||
004417a6 | 859 | void __init lockup_detector_init(void) |
58687acb | 860 | { |
0f34c400 | 861 | set_sample_period(); |
b8900bc0 | 862 | |
195daf66 | 863 | if (watchdog_enabled) |
9809b18f | 864 | watchdog_enable_all_cpus(false); |
58687acb | 865 | } |