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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> |
fe4ba3c3 | 22 | #include <linux/tick.h> |
58687acb DZ |
23 | |
24 | #include <asm/irq_regs.h> | |
5d1c0f4a | 25 | #include <linux/kvm_para.h> |
58687acb | 26 | #include <linux/perf_event.h> |
81a4beef | 27 | #include <linux/kthread.h> |
58687acb | 28 | |
84d56e66 UO |
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 | ||
ab992dc3 PZ |
46 | static DEFINE_MUTEX(watchdog_proc_mutex); |
47 | ||
84d56e66 UO |
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; | |
4eec42f3 | 56 | int __read_mostly watchdog_thresh = 10; |
84d56e66 | 57 | |
ed235875 AT |
58 | #ifdef CONFIG_SMP |
59 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
60 | #else | |
61 | #define sysctl_softlockup_all_cpu_backtrace 0 | |
62 | #endif | |
fe4ba3c3 CM |
63 | static struct cpumask watchdog_cpumask __read_mostly; |
64 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); | |
65 | ||
66 | /* Helper for online, unparked cpus. */ | |
67 | #define for_each_watchdog_cpu(cpu) \ | |
68 | for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask) | |
ed235875 | 69 | |
ec6a9066 UO |
70 | /* |
71 | * The 'watchdog_running' variable is set to 1 when the watchdog threads | |
72 | * are registered/started and is set to 0 when the watchdog threads are | |
73 | * unregistered/stopped, so it is an indicator whether the threads exist. | |
74 | */ | |
3c00ea82 | 75 | static int __read_mostly watchdog_running; |
ec6a9066 UO |
76 | /* |
77 | * If a subsystem has a need to deactivate the watchdog temporarily, it | |
78 | * can use the suspend/resume interface to achieve this. The content of | |
79 | * the 'watchdog_suspended' variable reflects this state. Existing threads | |
80 | * are parked/unparked by the lockup_detector_{suspend|resume} functions | |
81 | * (see comment blocks pertaining to those functions for further details). | |
82 | * | |
83 | * 'watchdog_suspended' also prevents threads from being registered/started | |
84 | * or unregistered/stopped via parameters in /proc/sys/kernel, so the state | |
85 | * of 'watchdog_running' cannot change while the watchdog is deactivated | |
86 | * temporarily (see related code in 'proc' handlers). | |
87 | */ | |
88 | static int __read_mostly watchdog_suspended; | |
89 | ||
0f34c400 | 90 | static u64 __read_mostly sample_period; |
58687acb DZ |
91 | |
92 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
93 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
94 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
95 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 96 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
bcd951cf TG |
97 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
98 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
b1a8de1f | 99 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); |
23637d47 | 100 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
cafcd80d DZ |
101 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); |
102 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
58687acb DZ |
103 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); |
104 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
105 | #endif | |
ed235875 | 106 | static unsigned long soft_lockup_nmi_warn; |
58687acb | 107 | |
58687acb DZ |
108 | /* boot commands */ |
109 | /* | |
110 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
111 | */ | |
23637d47 | 112 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
fef2c9bc DZ |
113 | static int hardlockup_panic = |
114 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
6e7458a6 UO |
115 | /* |
116 | * We may not want to enable hard lockup detection by default in all cases, | |
117 | * for example when running the kernel as a guest on a hypervisor. In these | |
118 | * cases this function can be called to disable hard lockup detection. This | |
119 | * function should only be executed once by the boot processor before the | |
120 | * kernel command line parameters are parsed, because otherwise it is not | |
121 | * possible to override this in hardlockup_panic_setup(). | |
122 | */ | |
692297d8 | 123 | void hardlockup_detector_disable(void) |
6e7458a6 | 124 | { |
692297d8 | 125 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; |
6e7458a6 UO |
126 | } |
127 | ||
58687acb DZ |
128 | static int __init hardlockup_panic_setup(char *str) |
129 | { | |
130 | if (!strncmp(str, "panic", 5)) | |
131 | hardlockup_panic = 1; | |
fef2c9bc DZ |
132 | else if (!strncmp(str, "nopanic", 7)) |
133 | hardlockup_panic = 0; | |
5dc30558 | 134 | else if (!strncmp(str, "0", 1)) |
195daf66 UO |
135 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; |
136 | else if (!strncmp(str, "1", 1)) | |
137 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
58687acb DZ |
138 | return 1; |
139 | } | |
140 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
141 | #endif | |
142 | ||
143 | unsigned int __read_mostly softlockup_panic = | |
144 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
145 | ||
146 | static int __init softlockup_panic_setup(char *str) | |
147 | { | |
148 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
149 | ||
150 | return 1; | |
151 | } | |
152 | __setup("softlockup_panic=", softlockup_panic_setup); | |
153 | ||
154 | static int __init nowatchdog_setup(char *str) | |
155 | { | |
195daf66 | 156 | watchdog_enabled = 0; |
58687acb DZ |
157 | return 1; |
158 | } | |
159 | __setup("nowatchdog", nowatchdog_setup); | |
160 | ||
58687acb DZ |
161 | static int __init nosoftlockup_setup(char *str) |
162 | { | |
195daf66 | 163 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; |
58687acb DZ |
164 | return 1; |
165 | } | |
166 | __setup("nosoftlockup", nosoftlockup_setup); | |
195daf66 | 167 | |
ed235875 AT |
168 | #ifdef CONFIG_SMP |
169 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
170 | { | |
171 | sysctl_softlockup_all_cpu_backtrace = | |
172 | !!simple_strtol(str, NULL, 0); | |
173 | return 1; | |
174 | } | |
175 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
176 | #endif | |
58687acb | 177 | |
4eec42f3 MSB |
178 | /* |
179 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
180 | * lockups can have false positives under extreme conditions. So we generally | |
181 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
182 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
183 | * time the hard threshold is. | |
184 | */ | |
6e9101ae | 185 | static int get_softlockup_thresh(void) |
4eec42f3 MSB |
186 | { |
187 | return watchdog_thresh * 2; | |
188 | } | |
58687acb DZ |
189 | |
190 | /* | |
191 | * Returns seconds, approximately. We don't need nanosecond | |
192 | * resolution, and we don't need to waste time with a big divide when | |
193 | * 2^30ns == 1.074s. | |
194 | */ | |
c06b4f19 | 195 | static unsigned long get_timestamp(void) |
58687acb | 196 | { |
545a2bf7 | 197 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ |
58687acb DZ |
198 | } |
199 | ||
0f34c400 | 200 | static void set_sample_period(void) |
58687acb DZ |
201 | { |
202 | /* | |
586692a5 | 203 | * convert watchdog_thresh from seconds to ns |
86f5e6a7 FLVC |
204 | * the divide by 5 is to give hrtimer several chances (two |
205 | * or three with the current relation between the soft | |
206 | * and hard thresholds) to increment before the | |
207 | * hardlockup detector generates a warning | |
58687acb | 208 | */ |
0f34c400 | 209 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); |
58687acb DZ |
210 | } |
211 | ||
212 | /* Commands for resetting the watchdog */ | |
213 | static void __touch_watchdog(void) | |
214 | { | |
c06b4f19 | 215 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); |
58687acb DZ |
216 | } |
217 | ||
332fbdbc | 218 | void touch_softlockup_watchdog(void) |
58687acb | 219 | { |
7861144b AM |
220 | /* |
221 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
222 | * gets zeroed here, so use the raw_ operation. | |
223 | */ | |
224 | raw_cpu_write(watchdog_touch_ts, 0); | |
58687acb | 225 | } |
0167c781 | 226 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 227 | |
332fbdbc | 228 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
229 | { |
230 | int cpu; | |
231 | ||
232 | /* | |
233 | * this is done lockless | |
234 | * do we care if a 0 races with a timestamp? | |
235 | * all it means is the softlock check starts one cycle later | |
236 | */ | |
fe4ba3c3 | 237 | for_each_watchdog_cpu(cpu) |
58687acb DZ |
238 | per_cpu(watchdog_touch_ts, cpu) = 0; |
239 | } | |
240 | ||
cafcd80d | 241 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb DZ |
242 | void touch_nmi_watchdog(void) |
243 | { | |
62572e29 BZ |
244 | /* |
245 | * Using __raw here because some code paths have | |
246 | * preemption enabled. If preemption is enabled | |
247 | * then interrupts should be enabled too, in which | |
248 | * case we shouldn't have to worry about the watchdog | |
249 | * going off. | |
250 | */ | |
f7f66b05 | 251 | raw_cpu_write(watchdog_nmi_touch, true); |
332fbdbc | 252 | touch_softlockup_watchdog(); |
58687acb DZ |
253 | } |
254 | EXPORT_SYMBOL(touch_nmi_watchdog); | |
255 | ||
cafcd80d DZ |
256 | #endif |
257 | ||
58687acb DZ |
258 | void touch_softlockup_watchdog_sync(void) |
259 | { | |
f7f66b05 CL |
260 | __this_cpu_write(softlockup_touch_sync, true); |
261 | __this_cpu_write(watchdog_touch_ts, 0); | |
58687acb DZ |
262 | } |
263 | ||
23637d47 | 264 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
58687acb | 265 | /* watchdog detector functions */ |
451637e4 | 266 | static bool is_hardlockup(void) |
58687acb | 267 | { |
909ea964 | 268 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
58687acb | 269 | |
909ea964 | 270 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
451637e4 | 271 | return true; |
58687acb | 272 | |
909ea964 | 273 | __this_cpu_write(hrtimer_interrupts_saved, hrint); |
451637e4 | 274 | return false; |
58687acb DZ |
275 | } |
276 | #endif | |
277 | ||
26e09c6e | 278 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 279 | { |
c06b4f19 | 280 | unsigned long now = get_timestamp(); |
58687acb | 281 | |
195daf66 UO |
282 | if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) { |
283 | /* Warn about unreasonable delays. */ | |
284 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
285 | return now - touch_ts; | |
286 | } | |
58687acb DZ |
287 | return 0; |
288 | } | |
289 | ||
23637d47 | 290 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
1880c4ae | 291 | |
58687acb DZ |
292 | static struct perf_event_attr wd_hw_attr = { |
293 | .type = PERF_TYPE_HARDWARE, | |
294 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
295 | .size = sizeof(struct perf_event_attr), | |
296 | .pinned = 1, | |
297 | .disabled = 1, | |
298 | }; | |
299 | ||
300 | /* Callback function for perf event subsystem */ | |
a8b0ca17 | 301 | static void watchdog_overflow_callback(struct perf_event *event, |
58687acb DZ |
302 | struct perf_sample_data *data, |
303 | struct pt_regs *regs) | |
304 | { | |
c6db67cd PZ |
305 | /* Ensure the watchdog never gets throttled */ |
306 | event->hw.interrupts = 0; | |
307 | ||
909ea964 CL |
308 | if (__this_cpu_read(watchdog_nmi_touch) == true) { |
309 | __this_cpu_write(watchdog_nmi_touch, false); | |
58687acb DZ |
310 | return; |
311 | } | |
312 | ||
313 | /* check for a hardlockup | |
314 | * This is done by making sure our timer interrupt | |
315 | * is incrementing. The timer interrupt should have | |
316 | * fired multiple times before we overflow'd. If it hasn't | |
317 | * then this is a good indication the cpu is stuck | |
318 | */ | |
26e09c6e DZ |
319 | if (is_hardlockup()) { |
320 | int this_cpu = smp_processor_id(); | |
321 | ||
58687acb | 322 | /* only print hardlockups once */ |
909ea964 | 323 | if (__this_cpu_read(hard_watchdog_warn) == true) |
58687acb DZ |
324 | return; |
325 | ||
326 | if (hardlockup_panic) | |
656c3b79 FF |
327 | panic("Watchdog detected hard LOCKUP on cpu %d", |
328 | this_cpu); | |
58687acb | 329 | else |
656c3b79 FF |
330 | WARN(1, "Watchdog detected hard LOCKUP on cpu %d", |
331 | this_cpu); | |
58687acb | 332 | |
909ea964 | 333 | __this_cpu_write(hard_watchdog_warn, true); |
58687acb DZ |
334 | return; |
335 | } | |
336 | ||
909ea964 | 337 | __this_cpu_write(hard_watchdog_warn, false); |
58687acb DZ |
338 | return; |
339 | } | |
bcd951cf TG |
340 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
341 | ||
58687acb DZ |
342 | static void watchdog_interrupt_count(void) |
343 | { | |
909ea964 | 344 | __this_cpu_inc(hrtimer_interrupts); |
58687acb | 345 | } |
bcd951cf TG |
346 | |
347 | static int watchdog_nmi_enable(unsigned int cpu); | |
348 | static void watchdog_nmi_disable(unsigned int cpu); | |
58687acb | 349 | |
58cf690a UO |
350 | static int watchdog_enable_all_cpus(void); |
351 | static void watchdog_disable_all_cpus(void); | |
352 | ||
58687acb DZ |
353 | /* watchdog kicker functions */ |
354 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
355 | { | |
909ea964 | 356 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
58687acb DZ |
357 | struct pt_regs *regs = get_irq_regs(); |
358 | int duration; | |
ed235875 | 359 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; |
58687acb DZ |
360 | |
361 | /* kick the hardlockup detector */ | |
362 | watchdog_interrupt_count(); | |
363 | ||
364 | /* kick the softlockup detector */ | |
909ea964 | 365 | wake_up_process(__this_cpu_read(softlockup_watchdog)); |
58687acb DZ |
366 | |
367 | /* .. and repeat */ | |
0f34c400 | 368 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); |
58687acb DZ |
369 | |
370 | if (touch_ts == 0) { | |
909ea964 | 371 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
58687acb DZ |
372 | /* |
373 | * If the time stamp was touched atomically | |
374 | * make sure the scheduler tick is up to date. | |
375 | */ | |
909ea964 | 376 | __this_cpu_write(softlockup_touch_sync, false); |
58687acb DZ |
377 | sched_clock_tick(); |
378 | } | |
5d1c0f4a EM |
379 | |
380 | /* Clear the guest paused flag on watchdog reset */ | |
381 | kvm_check_and_clear_guest_paused(); | |
58687acb DZ |
382 | __touch_watchdog(); |
383 | return HRTIMER_RESTART; | |
384 | } | |
385 | ||
386 | /* check for a softlockup | |
387 | * This is done by making sure a high priority task is | |
388 | * being scheduled. The task touches the watchdog to | |
389 | * indicate it is getting cpu time. If it hasn't then | |
390 | * this is a good indication some task is hogging the cpu | |
391 | */ | |
26e09c6e | 392 | duration = is_softlockup(touch_ts); |
58687acb | 393 | if (unlikely(duration)) { |
5d1c0f4a EM |
394 | /* |
395 | * If a virtual machine is stopped by the host it can look to | |
396 | * the watchdog like a soft lockup, check to see if the host | |
397 | * stopped the vm before we issue the warning | |
398 | */ | |
399 | if (kvm_check_and_clear_guest_paused()) | |
400 | return HRTIMER_RESTART; | |
401 | ||
58687acb | 402 | /* only warn once */ |
b1a8de1f | 403 | if (__this_cpu_read(soft_watchdog_warn) == true) { |
404 | /* | |
405 | * When multiple processes are causing softlockups the | |
406 | * softlockup detector only warns on the first one | |
407 | * because the code relies on a full quiet cycle to | |
408 | * re-arm. The second process prevents the quiet cycle | |
409 | * and never gets reported. Use task pointers to detect | |
410 | * this. | |
411 | */ | |
412 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
413 | current) { | |
414 | __this_cpu_write(soft_watchdog_warn, false); | |
415 | __touch_watchdog(); | |
416 | } | |
58687acb | 417 | return HRTIMER_RESTART; |
b1a8de1f | 418 | } |
58687acb | 419 | |
ed235875 AT |
420 | if (softlockup_all_cpu_backtrace) { |
421 | /* Prevent multiple soft-lockup reports if one cpu is already | |
422 | * engaged in dumping cpu back traces | |
423 | */ | |
424 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
425 | /* Someone else will report us. Let's give up */ | |
426 | __this_cpu_write(soft_watchdog_warn, true); | |
427 | return HRTIMER_RESTART; | |
428 | } | |
429 | } | |
430 | ||
656c3b79 | 431 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", |
26e09c6e | 432 | smp_processor_id(), duration, |
58687acb | 433 | current->comm, task_pid_nr(current)); |
b1a8de1f | 434 | __this_cpu_write(softlockup_task_ptr_saved, current); |
58687acb DZ |
435 | print_modules(); |
436 | print_irqtrace_events(current); | |
437 | if (regs) | |
438 | show_regs(regs); | |
439 | else | |
440 | dump_stack(); | |
441 | ||
ed235875 AT |
442 | if (softlockup_all_cpu_backtrace) { |
443 | /* Avoid generating two back traces for current | |
444 | * given that one is already made above | |
445 | */ | |
446 | trigger_allbutself_cpu_backtrace(); | |
447 | ||
448 | clear_bit(0, &soft_lockup_nmi_warn); | |
449 | /* Barrier to sync with other cpus */ | |
450 | smp_mb__after_atomic(); | |
451 | } | |
452 | ||
69361eef | 453 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |
58687acb DZ |
454 | if (softlockup_panic) |
455 | panic("softlockup: hung tasks"); | |
909ea964 | 456 | __this_cpu_write(soft_watchdog_warn, true); |
58687acb | 457 | } else |
909ea964 | 458 | __this_cpu_write(soft_watchdog_warn, false); |
58687acb DZ |
459 | |
460 | return HRTIMER_RESTART; | |
461 | } | |
462 | ||
bcd951cf TG |
463 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) |
464 | { | |
465 | struct sched_param param = { .sched_priority = prio }; | |
58687acb | 466 | |
bcd951cf TG |
467 | sched_setscheduler(current, policy, ¶m); |
468 | } | |
469 | ||
470 | static void watchdog_enable(unsigned int cpu) | |
58687acb | 471 | { |
f7f66b05 | 472 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 473 | |
3935e895 BM |
474 | /* kick off the timer for the hardlockup detector */ |
475 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
476 | hrtimer->function = watchdog_timer_fn; | |
477 | ||
bcd951cf TG |
478 | /* Enable the perf event */ |
479 | watchdog_nmi_enable(cpu); | |
58687acb | 480 | |
58687acb | 481 | /* done here because hrtimer_start can only pin to smp_processor_id() */ |
0f34c400 | 482 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), |
58687acb DZ |
483 | HRTIMER_MODE_REL_PINNED); |
484 | ||
bcd951cf TG |
485 | /* initialize timestamp */ |
486 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
487 | __touch_watchdog(); | |
488 | } | |
58687acb | 489 | |
bcd951cf TG |
490 | static void watchdog_disable(unsigned int cpu) |
491 | { | |
f7f66b05 | 492 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 493 | |
bcd951cf TG |
494 | watchdog_set_prio(SCHED_NORMAL, 0); |
495 | hrtimer_cancel(hrtimer); | |
496 | /* disable the perf event */ | |
497 | watchdog_nmi_disable(cpu); | |
58687acb DZ |
498 | } |
499 | ||
b8900bc0 FW |
500 | static void watchdog_cleanup(unsigned int cpu, bool online) |
501 | { | |
502 | watchdog_disable(cpu); | |
503 | } | |
504 | ||
bcd951cf TG |
505 | static int watchdog_should_run(unsigned int cpu) |
506 | { | |
507 | return __this_cpu_read(hrtimer_interrupts) != | |
508 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
509 | } | |
510 | ||
511 | /* | |
512 | * The watchdog thread function - touches the timestamp. | |
513 | * | |
0f34c400 | 514 | * It only runs once every sample_period seconds (4 seconds by |
bcd951cf TG |
515 | * default) to reset the softlockup timestamp. If this gets delayed |
516 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
517 | * triggers in watchdog_timer_fn(). | |
518 | */ | |
519 | static void watchdog(unsigned int cpu) | |
520 | { | |
521 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
522 | __this_cpu_read(hrtimer_interrupts)); | |
523 | __touch_watchdog(); | |
bcfba4f4 UO |
524 | |
525 | /* | |
526 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
527 | * failure path. Check for failures that can occur asynchronously - | |
528 | * for example, when CPUs are on-lined - and shut down the hardware | |
529 | * perf event on each CPU accordingly. | |
530 | * | |
531 | * The only non-obvious place this bit can be cleared is through | |
532 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
533 | * pr_info here would be too noisy as it would result in a message | |
534 | * every few seconds if the hardlockup was disabled but the softlockup | |
535 | * enabled. | |
536 | */ | |
537 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
538 | watchdog_nmi_disable(cpu); | |
bcd951cf | 539 | } |
58687acb | 540 | |
23637d47 | 541 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
a7027046 DZ |
542 | /* |
543 | * People like the simple clean cpu node info on boot. | |
544 | * Reduce the watchdog noise by only printing messages | |
545 | * that are different from what cpu0 displayed. | |
546 | */ | |
547 | static unsigned long cpu0_err; | |
548 | ||
bcd951cf | 549 | static int watchdog_nmi_enable(unsigned int cpu) |
58687acb DZ |
550 | { |
551 | struct perf_event_attr *wd_attr; | |
552 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
553 | ||
195daf66 UO |
554 | /* nothing to do if the hard lockup detector is disabled */ |
555 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
556 | goto out; | |
6e7458a6 | 557 | |
58687acb DZ |
558 | /* is it already setup and enabled? */ |
559 | if (event && event->state > PERF_EVENT_STATE_OFF) | |
560 | goto out; | |
561 | ||
562 | /* it is setup but not enabled */ | |
563 | if (event != NULL) | |
564 | goto out_enable; | |
565 | ||
58687acb | 566 | wd_attr = &wd_hw_attr; |
4eec42f3 | 567 | wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); |
1880c4ae CG |
568 | |
569 | /* Try to register using hardware perf events */ | |
4dc0da86 | 570 | event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); |
a7027046 DZ |
571 | |
572 | /* save cpu0 error for future comparision */ | |
573 | if (cpu == 0 && IS_ERR(event)) | |
574 | cpu0_err = PTR_ERR(event); | |
575 | ||
58687acb | 576 | if (!IS_ERR(event)) { |
a7027046 DZ |
577 | /* only print for cpu0 or different than cpu0 */ |
578 | if (cpu == 0 || cpu0_err) | |
579 | pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n"); | |
58687acb DZ |
580 | goto out_save; |
581 | } | |
582 | ||
bcfba4f4 UO |
583 | /* |
584 | * Disable the hard lockup detector if _any_ CPU fails to set up | |
585 | * set up the hardware perf event. The watchdog() function checks | |
586 | * the NMI_WATCHDOG_ENABLED bit periodically. | |
587 | * | |
588 | * The barriers are for syncing up watchdog_enabled across all the | |
589 | * cpus, as clear_bit() does not use barriers. | |
590 | */ | |
591 | smp_mb__before_atomic(); | |
592 | clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); | |
593 | smp_mb__after_atomic(); | |
594 | ||
a7027046 DZ |
595 | /* skip displaying the same error again */ |
596 | if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) | |
597 | return PTR_ERR(event); | |
5651f7f4 DZ |
598 | |
599 | /* vary the KERN level based on the returned errno */ | |
600 | if (PTR_ERR(event) == -EOPNOTSUPP) | |
4501980a | 601 | pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu); |
5651f7f4 | 602 | else if (PTR_ERR(event) == -ENOENT) |
656c3b79 | 603 | pr_warn("disabled (cpu%i): hardware events not enabled\n", |
4501980a | 604 | cpu); |
5651f7f4 | 605 | else |
4501980a AM |
606 | pr_err("disabled (cpu%i): unable to create perf event: %ld\n", |
607 | cpu, PTR_ERR(event)); | |
bcfba4f4 UO |
608 | |
609 | pr_info("Shutting down hard lockup detector on all cpus\n"); | |
610 | ||
eac24335 | 611 | return PTR_ERR(event); |
58687acb DZ |
612 | |
613 | /* success path */ | |
614 | out_save: | |
615 | per_cpu(watchdog_ev, cpu) = event; | |
616 | out_enable: | |
617 | perf_event_enable(per_cpu(watchdog_ev, cpu)); | |
618 | out: | |
619 | return 0; | |
620 | } | |
621 | ||
bcd951cf | 622 | static void watchdog_nmi_disable(unsigned int cpu) |
58687acb DZ |
623 | { |
624 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
625 | ||
626 | if (event) { | |
627 | perf_event_disable(event); | |
628 | per_cpu(watchdog_ev, cpu) = NULL; | |
629 | ||
630 | /* should be in cleanup, but blocks oprofile */ | |
631 | perf_event_release_kernel(event); | |
632 | } | |
df577149 UO |
633 | if (cpu == 0) { |
634 | /* watchdog_nmi_enable() expects this to be zero initially. */ | |
635 | cpu0_err = 0; | |
636 | } | |
58687acb | 637 | } |
b3738d29 | 638 | |
58687acb | 639 | #else |
bcd951cf TG |
640 | static int watchdog_nmi_enable(unsigned int cpu) { return 0; } |
641 | static void watchdog_nmi_disable(unsigned int cpu) { return; } | |
23637d47 | 642 | #endif /* CONFIG_HARDLOCKUP_DETECTOR */ |
58687acb | 643 | |
b8900bc0 FW |
644 | static struct smp_hotplug_thread watchdog_threads = { |
645 | .store = &softlockup_watchdog, | |
646 | .thread_should_run = watchdog_should_run, | |
647 | .thread_fn = watchdog, | |
648 | .thread_comm = "watchdog/%u", | |
649 | .setup = watchdog_enable, | |
650 | .cleanup = watchdog_cleanup, | |
651 | .park = watchdog_disable, | |
652 | .unpark = watchdog_enable, | |
653 | }; | |
654 | ||
81a4beef UO |
655 | /* |
656 | * park all watchdog threads that are specified in 'watchdog_cpumask' | |
657 | */ | |
658 | static int watchdog_park_threads(void) | |
659 | { | |
660 | int cpu, ret = 0; | |
661 | ||
662 | get_online_cpus(); | |
663 | for_each_watchdog_cpu(cpu) { | |
664 | ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); | |
665 | if (ret) | |
666 | break; | |
667 | } | |
668 | if (ret) { | |
669 | for_each_watchdog_cpu(cpu) | |
670 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
671 | } | |
672 | put_online_cpus(); | |
673 | ||
674 | return ret; | |
675 | } | |
676 | ||
677 | /* | |
678 | * unpark all watchdog threads that are specified in 'watchdog_cpumask' | |
679 | */ | |
680 | static void watchdog_unpark_threads(void) | |
681 | { | |
682 | int cpu; | |
683 | ||
684 | get_online_cpus(); | |
685 | for_each_watchdog_cpu(cpu) | |
686 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
687 | put_online_cpus(); | |
688 | } | |
689 | ||
8c073d27 UO |
690 | /* |
691 | * Suspend the hard and soft lockup detector by parking the watchdog threads. | |
692 | */ | |
ec6a9066 | 693 | int lockup_detector_suspend(void) |
8c073d27 UO |
694 | { |
695 | int ret = 0; | |
696 | ||
697 | mutex_lock(&watchdog_proc_mutex); | |
698 | /* | |
699 | * Multiple suspend requests can be active in parallel (counted by | |
700 | * the 'watchdog_suspended' variable). If the watchdog threads are | |
701 | * running, the first caller takes care that they will be parked. | |
702 | * The state of 'watchdog_running' cannot change while a suspend | |
ec6a9066 | 703 | * request is active (see related code in 'proc' handlers). |
8c073d27 UO |
704 | */ |
705 | if (watchdog_running && !watchdog_suspended) | |
706 | ret = watchdog_park_threads(); | |
707 | ||
708 | if (ret == 0) | |
709 | watchdog_suspended++; | |
710 | ||
711 | mutex_unlock(&watchdog_proc_mutex); | |
712 | ||
713 | return ret; | |
714 | } | |
715 | ||
716 | /* | |
717 | * Resume the hard and soft lockup detector by unparking the watchdog threads. | |
718 | */ | |
ec6a9066 | 719 | void lockup_detector_resume(void) |
8c073d27 UO |
720 | { |
721 | mutex_lock(&watchdog_proc_mutex); | |
722 | ||
723 | watchdog_suspended--; | |
724 | /* | |
725 | * The watchdog threads are unparked if they were previously running | |
726 | * and if there is no more active suspend request. | |
727 | */ | |
728 | if (watchdog_running && !watchdog_suspended) | |
729 | watchdog_unpark_threads(); | |
730 | ||
731 | mutex_unlock(&watchdog_proc_mutex); | |
732 | } | |
733 | ||
b2f57c3a | 734 | static void update_watchdog_all_cpus(void) |
9809b18f | 735 | { |
d4bdd0b2 UO |
736 | watchdog_park_threads(); |
737 | watchdog_unpark_threads(); | |
9809b18f MH |
738 | } |
739 | ||
b2f57c3a | 740 | static int watchdog_enable_all_cpus(void) |
58687acb | 741 | { |
b8900bc0 | 742 | int err = 0; |
58687acb | 743 | |
3c00ea82 | 744 | if (!watchdog_running) { |
230ec939 FW |
745 | err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, |
746 | &watchdog_cpumask); | |
b8900bc0 FW |
747 | if (err) |
748 | pr_err("Failed to create watchdog threads, disabled\n"); | |
230ec939 | 749 | else |
3c00ea82 | 750 | watchdog_running = 1; |
b2f57c3a UO |
751 | } else { |
752 | /* | |
753 | * Enable/disable the lockup detectors or | |
754 | * change the sample period 'on the fly'. | |
755 | */ | |
756 | update_watchdog_all_cpus(); | |
bcd951cf | 757 | } |
b8900bc0 FW |
758 | |
759 | return err; | |
58687acb DZ |
760 | } |
761 | ||
762 | static void watchdog_disable_all_cpus(void) | |
763 | { | |
3c00ea82 FW |
764 | if (watchdog_running) { |
765 | watchdog_running = 0; | |
b8900bc0 | 766 | smpboot_unregister_percpu_thread(&watchdog_threads); |
bcd951cf | 767 | } |
58687acb DZ |
768 | } |
769 | ||
58cf690a UO |
770 | #ifdef CONFIG_SYSCTL |
771 | ||
58687acb | 772 | /* |
a0c9cbb9 UO |
773 | * Update the run state of the lockup detectors. |
774 | */ | |
775 | static int proc_watchdog_update(void) | |
776 | { | |
777 | int err = 0; | |
778 | ||
779 | /* | |
780 | * Watchdog threads won't be started if they are already active. | |
781 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
782 | * care of this. If those threads are already active, the sample | |
783 | * period will be updated and the lockup detectors will be enabled | |
784 | * or disabled 'on the fly'. | |
785 | */ | |
786 | if (watchdog_enabled && watchdog_thresh) | |
b2f57c3a | 787 | err = watchdog_enable_all_cpus(); |
a0c9cbb9 UO |
788 | else |
789 | watchdog_disable_all_cpus(); | |
790 | ||
791 | return err; | |
792 | ||
793 | } | |
794 | ||
ef246a21 UO |
795 | /* |
796 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
797 | * | |
798 | * caller | table->data points to | 'which' contains the flag(s) | |
799 | * -------------------|-----------------------|----------------------------- | |
800 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
801 | * | | with SOFT_WATCHDOG_ENABLED | |
802 | * -------------------|-----------------------|----------------------------- | |
803 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
804 | * -------------------|-----------------------|----------------------------- | |
805 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
806 | */ | |
807 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
808 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
809 | { | |
810 | int err, old, new; | |
811 | int *watchdog_param = (int *)table->data; | |
812 | ||
813 | mutex_lock(&watchdog_proc_mutex); | |
814 | ||
8c073d27 UO |
815 | if (watchdog_suspended) { |
816 | /* no parameter changes allowed while watchdog is suspended */ | |
817 | err = -EAGAIN; | |
818 | goto out; | |
819 | } | |
820 | ||
ef246a21 UO |
821 | /* |
822 | * If the parameter is being read return the state of the corresponding | |
823 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
824 | * run state of the lockup detectors. | |
825 | */ | |
826 | if (!write) { | |
827 | *watchdog_param = (watchdog_enabled & which) != 0; | |
828 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
829 | } else { | |
830 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
831 | if (err) | |
832 | goto out; | |
833 | ||
834 | /* | |
835 | * There is a race window between fetching the current value | |
836 | * from 'watchdog_enabled' and storing the new value. During | |
837 | * this race window, watchdog_nmi_enable() can sneak in and | |
838 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
839 | * The 'cmpxchg' detects this race and the loop retries. | |
840 | */ | |
841 | do { | |
842 | old = watchdog_enabled; | |
843 | /* | |
844 | * If the parameter value is not zero set the | |
845 | * corresponding bit(s), else clear it(them). | |
846 | */ | |
847 | if (*watchdog_param) | |
848 | new = old | which; | |
849 | else | |
850 | new = old & ~which; | |
851 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
852 | ||
853 | /* | |
854 | * Update the run state of the lockup detectors. | |
855 | * Restore 'watchdog_enabled' on failure. | |
856 | */ | |
857 | err = proc_watchdog_update(); | |
858 | if (err) | |
859 | watchdog_enabled = old; | |
860 | } | |
861 | out: | |
862 | mutex_unlock(&watchdog_proc_mutex); | |
863 | return err; | |
864 | } | |
865 | ||
83a80a39 UO |
866 | /* |
867 | * /proc/sys/kernel/watchdog | |
868 | */ | |
869 | int proc_watchdog(struct ctl_table *table, int write, | |
870 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
871 | { | |
872 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
873 | table, write, buffer, lenp, ppos); | |
874 | } | |
875 | ||
876 | /* | |
877 | * /proc/sys/kernel/nmi_watchdog | |
58687acb | 878 | */ |
83a80a39 UO |
879 | int proc_nmi_watchdog(struct ctl_table *table, int write, |
880 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
881 | { | |
882 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
883 | table, write, buffer, lenp, ppos); | |
884 | } | |
885 | ||
886 | /* | |
887 | * /proc/sys/kernel/soft_watchdog | |
888 | */ | |
889 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
890 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
891 | { | |
892 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
893 | table, write, buffer, lenp, ppos); | |
894 | } | |
58687acb | 895 | |
83a80a39 UO |
896 | /* |
897 | * /proc/sys/kernel/watchdog_thresh | |
898 | */ | |
899 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
900 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
58687acb | 901 | { |
83a80a39 | 902 | int err, old; |
58687acb | 903 | |
359e6fab | 904 | mutex_lock(&watchdog_proc_mutex); |
bcd951cf | 905 | |
8c073d27 UO |
906 | if (watchdog_suspended) { |
907 | /* no parameter changes allowed while watchdog is suspended */ | |
908 | err = -EAGAIN; | |
909 | goto out; | |
910 | } | |
911 | ||
83a80a39 | 912 | old = ACCESS_ONCE(watchdog_thresh); |
b8900bc0 | 913 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
83a80a39 | 914 | |
b8900bc0 | 915 | if (err || !write) |
359e6fab | 916 | goto out; |
e04ab2bc | 917 | |
b66a2356 | 918 | /* |
d283c640 | 919 | * Update the sample period. Restore on failure. |
b66a2356 | 920 | */ |
83a80a39 UO |
921 | set_sample_period(); |
922 | err = proc_watchdog_update(); | |
d283c640 | 923 | if (err) { |
83a80a39 | 924 | watchdog_thresh = old; |
d283c640 UO |
925 | set_sample_period(); |
926 | } | |
359e6fab MH |
927 | out: |
928 | mutex_unlock(&watchdog_proc_mutex); | |
b8900bc0 | 929 | return err; |
58687acb | 930 | } |
fe4ba3c3 CM |
931 | |
932 | /* | |
933 | * The cpumask is the mask of possible cpus that the watchdog can run | |
934 | * on, not the mask of cpus it is actually running on. This allows the | |
935 | * user to specify a mask that will include cpus that have not yet | |
936 | * been brought online, if desired. | |
937 | */ | |
938 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
939 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
940 | { | |
941 | int err; | |
942 | ||
943 | mutex_lock(&watchdog_proc_mutex); | |
8c073d27 UO |
944 | |
945 | if (watchdog_suspended) { | |
946 | /* no parameter changes allowed while watchdog is suspended */ | |
947 | err = -EAGAIN; | |
948 | goto out; | |
949 | } | |
950 | ||
fe4ba3c3 CM |
951 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); |
952 | if (!err && write) { | |
953 | /* Remove impossible cpus to keep sysctl output cleaner. */ | |
954 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, | |
955 | cpu_possible_mask); | |
956 | ||
957 | if (watchdog_running) { | |
958 | /* | |
959 | * Failure would be due to being unable to allocate | |
960 | * a temporary cpumask, so we are likely not in a | |
961 | * position to do much else to make things better. | |
962 | */ | |
963 | if (smpboot_update_cpumask_percpu_thread( | |
964 | &watchdog_threads, &watchdog_cpumask) != 0) | |
965 | pr_err("cpumask update failed\n"); | |
966 | } | |
967 | } | |
8c073d27 | 968 | out: |
fe4ba3c3 CM |
969 | mutex_unlock(&watchdog_proc_mutex); |
970 | return err; | |
971 | } | |
972 | ||
58687acb DZ |
973 | #endif /* CONFIG_SYSCTL */ |
974 | ||
004417a6 | 975 | void __init lockup_detector_init(void) |
58687acb | 976 | { |
0f34c400 | 977 | set_sample_period(); |
b8900bc0 | 978 | |
fe4ba3c3 CM |
979 | #ifdef CONFIG_NO_HZ_FULL |
980 | if (tick_nohz_full_enabled()) { | |
314b08ff FW |
981 | pr_info("Disabling watchdog on nohz_full cores by default\n"); |
982 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
fe4ba3c3 CM |
983 | } else |
984 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
985 | #else | |
986 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
987 | #endif | |
988 | ||
195daf66 | 989 | if (watchdog_enabled) |
b2f57c3a | 990 | watchdog_enable_all_cpus(); |
58687acb | 991 | } |