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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 | ||
5f92a7b0 | 12 | #define pr_fmt(fmt) "watchdog: " fmt |
4501980a | 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> |
ae7e81c0 | 22 | #include <uapi/linux/sched/types.h> |
fe4ba3c3 | 23 | #include <linux/tick.h> |
82607adc | 24 | #include <linux/workqueue.h> |
e6017571 | 25 | #include <linux/sched/clock.h> |
b17b0153 | 26 | #include <linux/sched/debug.h> |
58687acb DZ |
27 | |
28 | #include <asm/irq_regs.h> | |
5d1c0f4a | 29 | #include <linux/kvm_para.h> |
81a4beef | 30 | #include <linux/kthread.h> |
58687acb | 31 | |
05a4a952 | 32 | /* Watchdog configuration */ |
ab992dc3 PZ |
33 | static DEFINE_MUTEX(watchdog_proc_mutex); |
34 | ||
05a4a952 NP |
35 | int __read_mostly nmi_watchdog_enabled; |
36 | ||
37 | #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG) | |
38 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED | | |
39 | NMI_WATCHDOG_ENABLED; | |
84d56e66 | 40 | #else |
249e52e3 | 41 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; |
84d56e66 | 42 | #endif |
05a4a952 NP |
43 | |
44 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
45 | /* boot commands */ | |
46 | /* | |
47 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
48 | */ | |
49 | unsigned int __read_mostly hardlockup_panic = | |
50 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
51 | /* | |
52 | * We may not want to enable hard lockup detection by default in all cases, | |
53 | * for example when running the kernel as a guest on a hypervisor. In these | |
54 | * cases this function can be called to disable hard lockup detection. This | |
55 | * function should only be executed once by the boot processor before the | |
56 | * kernel command line parameters are parsed, because otherwise it is not | |
57 | * possible to override this in hardlockup_panic_setup(). | |
58 | */ | |
59 | void hardlockup_detector_disable(void) | |
60 | { | |
61 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
62 | } | |
63 | ||
64 | static int __init hardlockup_panic_setup(char *str) | |
65 | { | |
66 | if (!strncmp(str, "panic", 5)) | |
67 | hardlockup_panic = 1; | |
68 | else if (!strncmp(str, "nopanic", 7)) | |
69 | hardlockup_panic = 0; | |
70 | else if (!strncmp(str, "0", 1)) | |
71 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
72 | else if (!strncmp(str, "1", 1)) | |
73 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
74 | return 1; | |
75 | } | |
76 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
77 | ||
78 | #endif | |
79 | ||
80 | #ifdef CONFIG_SOFTLOCKUP_DETECTOR | |
84d56e66 | 81 | int __read_mostly soft_watchdog_enabled; |
05a4a952 NP |
82 | #endif |
83 | ||
84d56e66 | 84 | int __read_mostly watchdog_user_enabled; |
4eec42f3 | 85 | int __read_mostly watchdog_thresh = 10; |
84d56e66 | 86 | |
ed235875 AT |
87 | #ifdef CONFIG_SMP |
88 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
55537871 | 89 | int __read_mostly sysctl_hardlockup_all_cpu_backtrace; |
ed235875 | 90 | #endif |
05a4a952 | 91 | struct cpumask watchdog_cpumask __read_mostly; |
fe4ba3c3 CM |
92 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); |
93 | ||
ec6a9066 UO |
94 | /* |
95 | * The 'watchdog_running' variable is set to 1 when the watchdog threads | |
96 | * are registered/started and is set to 0 when the watchdog threads are | |
97 | * unregistered/stopped, so it is an indicator whether the threads exist. | |
98 | */ | |
3c00ea82 | 99 | static int __read_mostly watchdog_running; |
05a4a952 NP |
100 | |
101 | /* | |
102 | * These functions can be overridden if an architecture implements its | |
103 | * own hardlockup detector. | |
a10a842f NP |
104 | * |
105 | * watchdog_nmi_enable/disable can be implemented to start and stop when | |
106 | * softlockup watchdog threads start and stop. The arch must select the | |
107 | * SOFTLOCKUP_DETECTOR Kconfig. | |
05a4a952 NP |
108 | */ |
109 | int __weak watchdog_nmi_enable(unsigned int cpu) | |
110 | { | |
111 | return 0; | |
112 | } | |
113 | void __weak watchdog_nmi_disable(unsigned int cpu) | |
114 | { | |
115 | } | |
116 | ||
a10a842f NP |
117 | /* |
118 | * watchdog_nmi_reconfigure can be implemented to be notified after any | |
119 | * watchdog configuration change. The arch hardlockup watchdog should | |
120 | * respond to the following variables: | |
121 | * - nmi_watchdog_enabled | |
122 | * - watchdog_thresh | |
123 | * - watchdog_cpumask | |
124 | * - sysctl_hardlockup_all_cpu_backtrace | |
125 | * - hardlockup_panic | |
a10a842f NP |
126 | */ |
127 | void __weak watchdog_nmi_reconfigure(void) | |
128 | { | |
129 | } | |
130 | ||
131 | ||
05a4a952 NP |
132 | #ifdef CONFIG_SOFTLOCKUP_DETECTOR |
133 | ||
134 | /* Helper for online, unparked cpus. */ | |
135 | #define for_each_watchdog_cpu(cpu) \ | |
136 | for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask) | |
137 | ||
138 | atomic_t watchdog_park_in_progress = ATOMIC_INIT(0); | |
ec6a9066 | 139 | |
0f34c400 | 140 | static u64 __read_mostly sample_period; |
58687acb DZ |
141 | |
142 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
143 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
144 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
145 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 146 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
bcd951cf TG |
147 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
148 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
b1a8de1f | 149 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); |
58687acb | 150 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); |
ed235875 | 151 | static unsigned long soft_lockup_nmi_warn; |
58687acb | 152 | |
58687acb DZ |
153 | unsigned int __read_mostly softlockup_panic = |
154 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
155 | ||
156 | static int __init softlockup_panic_setup(char *str) | |
157 | { | |
158 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
159 | ||
160 | return 1; | |
161 | } | |
162 | __setup("softlockup_panic=", softlockup_panic_setup); | |
163 | ||
164 | static int __init nowatchdog_setup(char *str) | |
165 | { | |
195daf66 | 166 | watchdog_enabled = 0; |
58687acb DZ |
167 | return 1; |
168 | } | |
169 | __setup("nowatchdog", nowatchdog_setup); | |
170 | ||
58687acb DZ |
171 | static int __init nosoftlockup_setup(char *str) |
172 | { | |
195daf66 | 173 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; |
58687acb DZ |
174 | return 1; |
175 | } | |
176 | __setup("nosoftlockup", nosoftlockup_setup); | |
195daf66 | 177 | |
ed235875 AT |
178 | #ifdef CONFIG_SMP |
179 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
180 | { | |
181 | sysctl_softlockup_all_cpu_backtrace = | |
182 | !!simple_strtol(str, NULL, 0); | |
183 | return 1; | |
184 | } | |
185 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
05a4a952 | 186 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
55537871 JK |
187 | static int __init hardlockup_all_cpu_backtrace_setup(char *str) |
188 | { | |
189 | sysctl_hardlockup_all_cpu_backtrace = | |
190 | !!simple_strtol(str, NULL, 0); | |
191 | return 1; | |
192 | } | |
193 | __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup); | |
ed235875 | 194 | #endif |
05a4a952 | 195 | #endif |
58687acb | 196 | |
4eec42f3 MSB |
197 | /* |
198 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
199 | * lockups can have false positives under extreme conditions. So we generally | |
200 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
201 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
202 | * time the hard threshold is. | |
203 | */ | |
6e9101ae | 204 | static int get_softlockup_thresh(void) |
4eec42f3 MSB |
205 | { |
206 | return watchdog_thresh * 2; | |
207 | } | |
58687acb DZ |
208 | |
209 | /* | |
210 | * Returns seconds, approximately. We don't need nanosecond | |
211 | * resolution, and we don't need to waste time with a big divide when | |
212 | * 2^30ns == 1.074s. | |
213 | */ | |
c06b4f19 | 214 | static unsigned long get_timestamp(void) |
58687acb | 215 | { |
545a2bf7 | 216 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ |
58687acb DZ |
217 | } |
218 | ||
0f34c400 | 219 | static void set_sample_period(void) |
58687acb DZ |
220 | { |
221 | /* | |
586692a5 | 222 | * convert watchdog_thresh from seconds to ns |
86f5e6a7 FLVC |
223 | * the divide by 5 is to give hrtimer several chances (two |
224 | * or three with the current relation between the soft | |
225 | * and hard thresholds) to increment before the | |
226 | * hardlockup detector generates a warning | |
58687acb | 227 | */ |
0f34c400 | 228 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); |
7edaeb68 | 229 | watchdog_update_hrtimer_threshold(sample_period); |
58687acb DZ |
230 | } |
231 | ||
232 | /* Commands for resetting the watchdog */ | |
233 | static void __touch_watchdog(void) | |
234 | { | |
c06b4f19 | 235 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); |
58687acb DZ |
236 | } |
237 | ||
03e0d461 TH |
238 | /** |
239 | * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls | |
240 | * | |
241 | * Call when the scheduler may have stalled for legitimate reasons | |
242 | * preventing the watchdog task from executing - e.g. the scheduler | |
243 | * entering idle state. This should only be used for scheduler events. | |
244 | * Use touch_softlockup_watchdog() for everything else. | |
245 | */ | |
246 | void touch_softlockup_watchdog_sched(void) | |
58687acb | 247 | { |
7861144b AM |
248 | /* |
249 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
250 | * gets zeroed here, so use the raw_ operation. | |
251 | */ | |
252 | raw_cpu_write(watchdog_touch_ts, 0); | |
58687acb | 253 | } |
03e0d461 TH |
254 | |
255 | void touch_softlockup_watchdog(void) | |
256 | { | |
257 | touch_softlockup_watchdog_sched(); | |
82607adc | 258 | wq_watchdog_touch(raw_smp_processor_id()); |
03e0d461 | 259 | } |
0167c781 | 260 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 261 | |
332fbdbc | 262 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
263 | { |
264 | int cpu; | |
265 | ||
266 | /* | |
267 | * this is done lockless | |
268 | * do we care if a 0 races with a timestamp? | |
269 | * all it means is the softlock check starts one cycle later | |
270 | */ | |
fe4ba3c3 | 271 | for_each_watchdog_cpu(cpu) |
58687acb | 272 | per_cpu(watchdog_touch_ts, cpu) = 0; |
82607adc | 273 | wq_watchdog_touch(-1); |
58687acb DZ |
274 | } |
275 | ||
58687acb DZ |
276 | void touch_softlockup_watchdog_sync(void) |
277 | { | |
f7f66b05 CL |
278 | __this_cpu_write(softlockup_touch_sync, true); |
279 | __this_cpu_write(watchdog_touch_ts, 0); | |
58687acb DZ |
280 | } |
281 | ||
26e09c6e | 282 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 283 | { |
c06b4f19 | 284 | unsigned long now = get_timestamp(); |
58687acb | 285 | |
39d2da21 | 286 | if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ |
195daf66 UO |
287 | /* Warn about unreasonable delays. */ |
288 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
289 | return now - touch_ts; | |
290 | } | |
58687acb DZ |
291 | return 0; |
292 | } | |
293 | ||
05a4a952 NP |
294 | /* watchdog detector functions */ |
295 | bool is_hardlockup(void) | |
58687acb | 296 | { |
05a4a952 | 297 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
bcd951cf | 298 | |
05a4a952 NP |
299 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
300 | return true; | |
301 | ||
302 | __this_cpu_write(hrtimer_interrupts_saved, hrint); | |
303 | return false; | |
73ce0511 | 304 | } |
05a4a952 NP |
305 | |
306 | static void watchdog_interrupt_count(void) | |
73ce0511 | 307 | { |
05a4a952 | 308 | __this_cpu_inc(hrtimer_interrupts); |
73ce0511 | 309 | } |
58687acb | 310 | |
58cf690a UO |
311 | static int watchdog_enable_all_cpus(void); |
312 | static void watchdog_disable_all_cpus(void); | |
313 | ||
58687acb DZ |
314 | /* watchdog kicker functions */ |
315 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
316 | { | |
909ea964 | 317 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
58687acb DZ |
318 | struct pt_regs *regs = get_irq_regs(); |
319 | int duration; | |
ed235875 | 320 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; |
58687acb | 321 | |
6554fd8c TG |
322 | if (!watchdog_enabled || |
323 | atomic_read(&watchdog_park_in_progress) != 0) | |
b94f5118 DZ |
324 | return HRTIMER_NORESTART; |
325 | ||
58687acb DZ |
326 | /* kick the hardlockup detector */ |
327 | watchdog_interrupt_count(); | |
328 | ||
329 | /* kick the softlockup detector */ | |
909ea964 | 330 | wake_up_process(__this_cpu_read(softlockup_watchdog)); |
58687acb DZ |
331 | |
332 | /* .. and repeat */ | |
0f34c400 | 333 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); |
58687acb DZ |
334 | |
335 | if (touch_ts == 0) { | |
909ea964 | 336 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
58687acb DZ |
337 | /* |
338 | * If the time stamp was touched atomically | |
339 | * make sure the scheduler tick is up to date. | |
340 | */ | |
909ea964 | 341 | __this_cpu_write(softlockup_touch_sync, false); |
58687acb DZ |
342 | sched_clock_tick(); |
343 | } | |
5d1c0f4a EM |
344 | |
345 | /* Clear the guest paused flag on watchdog reset */ | |
346 | kvm_check_and_clear_guest_paused(); | |
58687acb DZ |
347 | __touch_watchdog(); |
348 | return HRTIMER_RESTART; | |
349 | } | |
350 | ||
351 | /* check for a softlockup | |
352 | * This is done by making sure a high priority task is | |
353 | * being scheduled. The task touches the watchdog to | |
354 | * indicate it is getting cpu time. If it hasn't then | |
355 | * this is a good indication some task is hogging the cpu | |
356 | */ | |
26e09c6e | 357 | duration = is_softlockup(touch_ts); |
58687acb | 358 | if (unlikely(duration)) { |
5d1c0f4a EM |
359 | /* |
360 | * If a virtual machine is stopped by the host it can look to | |
361 | * the watchdog like a soft lockup, check to see if the host | |
362 | * stopped the vm before we issue the warning | |
363 | */ | |
364 | if (kvm_check_and_clear_guest_paused()) | |
365 | return HRTIMER_RESTART; | |
366 | ||
58687acb | 367 | /* only warn once */ |
b1a8de1f | 368 | if (__this_cpu_read(soft_watchdog_warn) == true) { |
369 | /* | |
370 | * When multiple processes are causing softlockups the | |
371 | * softlockup detector only warns on the first one | |
372 | * because the code relies on a full quiet cycle to | |
373 | * re-arm. The second process prevents the quiet cycle | |
374 | * and never gets reported. Use task pointers to detect | |
375 | * this. | |
376 | */ | |
377 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
378 | current) { | |
379 | __this_cpu_write(soft_watchdog_warn, false); | |
380 | __touch_watchdog(); | |
381 | } | |
58687acb | 382 | return HRTIMER_RESTART; |
b1a8de1f | 383 | } |
58687acb | 384 | |
ed235875 AT |
385 | if (softlockup_all_cpu_backtrace) { |
386 | /* Prevent multiple soft-lockup reports if one cpu is already | |
387 | * engaged in dumping cpu back traces | |
388 | */ | |
389 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
390 | /* Someone else will report us. Let's give up */ | |
391 | __this_cpu_write(soft_watchdog_warn, true); | |
392 | return HRTIMER_RESTART; | |
393 | } | |
394 | } | |
395 | ||
656c3b79 | 396 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", |
26e09c6e | 397 | smp_processor_id(), duration, |
58687acb | 398 | current->comm, task_pid_nr(current)); |
b1a8de1f | 399 | __this_cpu_write(softlockup_task_ptr_saved, current); |
58687acb DZ |
400 | print_modules(); |
401 | print_irqtrace_events(current); | |
402 | if (regs) | |
403 | show_regs(regs); | |
404 | else | |
405 | dump_stack(); | |
406 | ||
ed235875 AT |
407 | if (softlockup_all_cpu_backtrace) { |
408 | /* Avoid generating two back traces for current | |
409 | * given that one is already made above | |
410 | */ | |
411 | trigger_allbutself_cpu_backtrace(); | |
412 | ||
413 | clear_bit(0, &soft_lockup_nmi_warn); | |
414 | /* Barrier to sync with other cpus */ | |
415 | smp_mb__after_atomic(); | |
416 | } | |
417 | ||
69361eef | 418 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |
58687acb DZ |
419 | if (softlockup_panic) |
420 | panic("softlockup: hung tasks"); | |
909ea964 | 421 | __this_cpu_write(soft_watchdog_warn, true); |
58687acb | 422 | } else |
909ea964 | 423 | __this_cpu_write(soft_watchdog_warn, false); |
58687acb DZ |
424 | |
425 | return HRTIMER_RESTART; | |
426 | } | |
427 | ||
bcd951cf TG |
428 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) |
429 | { | |
430 | struct sched_param param = { .sched_priority = prio }; | |
58687acb | 431 | |
bcd951cf TG |
432 | sched_setscheduler(current, policy, ¶m); |
433 | } | |
434 | ||
435 | static void watchdog_enable(unsigned int cpu) | |
58687acb | 436 | { |
f7f66b05 | 437 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 438 | |
3935e895 BM |
439 | /* kick off the timer for the hardlockup detector */ |
440 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
441 | hrtimer->function = watchdog_timer_fn; | |
442 | ||
bcd951cf TG |
443 | /* Enable the perf event */ |
444 | watchdog_nmi_enable(cpu); | |
58687acb | 445 | |
58687acb | 446 | /* done here because hrtimer_start can only pin to smp_processor_id() */ |
0f34c400 | 447 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), |
58687acb DZ |
448 | HRTIMER_MODE_REL_PINNED); |
449 | ||
bcd951cf TG |
450 | /* initialize timestamp */ |
451 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); | |
452 | __touch_watchdog(); | |
453 | } | |
58687acb | 454 | |
bcd951cf TG |
455 | static void watchdog_disable(unsigned int cpu) |
456 | { | |
f7f66b05 | 457 | struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer); |
58687acb | 458 | |
bcd951cf TG |
459 | watchdog_set_prio(SCHED_NORMAL, 0); |
460 | hrtimer_cancel(hrtimer); | |
461 | /* disable the perf event */ | |
462 | watchdog_nmi_disable(cpu); | |
58687acb DZ |
463 | } |
464 | ||
b8900bc0 FW |
465 | static void watchdog_cleanup(unsigned int cpu, bool online) |
466 | { | |
467 | watchdog_disable(cpu); | |
468 | } | |
469 | ||
bcd951cf TG |
470 | static int watchdog_should_run(unsigned int cpu) |
471 | { | |
472 | return __this_cpu_read(hrtimer_interrupts) != | |
473 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
474 | } | |
475 | ||
476 | /* | |
477 | * The watchdog thread function - touches the timestamp. | |
478 | * | |
0f34c400 | 479 | * It only runs once every sample_period seconds (4 seconds by |
bcd951cf TG |
480 | * default) to reset the softlockup timestamp. If this gets delayed |
481 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
482 | * triggers in watchdog_timer_fn(). | |
483 | */ | |
484 | static void watchdog(unsigned int cpu) | |
485 | { | |
486 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
487 | __this_cpu_read(hrtimer_interrupts)); | |
488 | __touch_watchdog(); | |
bcfba4f4 UO |
489 | |
490 | /* | |
491 | * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the | |
492 | * failure path. Check for failures that can occur asynchronously - | |
493 | * for example, when CPUs are on-lined - and shut down the hardware | |
494 | * perf event on each CPU accordingly. | |
495 | * | |
496 | * The only non-obvious place this bit can be cleared is through | |
497 | * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a | |
498 | * pr_info here would be too noisy as it would result in a message | |
499 | * every few seconds if the hardlockup was disabled but the softlockup | |
500 | * enabled. | |
501 | */ | |
502 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
503 | watchdog_nmi_disable(cpu); | |
bcd951cf | 504 | } |
58687acb | 505 | |
b8900bc0 FW |
506 | static struct smp_hotplug_thread watchdog_threads = { |
507 | .store = &softlockup_watchdog, | |
508 | .thread_should_run = watchdog_should_run, | |
509 | .thread_fn = watchdog, | |
510 | .thread_comm = "watchdog/%u", | |
511 | .setup = watchdog_enable, | |
512 | .cleanup = watchdog_cleanup, | |
513 | .park = watchdog_disable, | |
514 | .unpark = watchdog_enable, | |
515 | }; | |
516 | ||
81a4beef UO |
517 | /* |
518 | * park all watchdog threads that are specified in 'watchdog_cpumask' | |
ee7fed54 UO |
519 | * |
520 | * This function returns an error if kthread_park() of a watchdog thread | |
521 | * fails. In this situation, the watchdog threads of some CPUs can already | |
522 | * be parked and the watchdog threads of other CPUs can still be runnable. | |
523 | * Callers are expected to handle this special condition as appropriate in | |
524 | * their context. | |
a2a45b85 UO |
525 | * |
526 | * This function may only be called in a context that is protected against | |
527 | * races with CPU hotplug - for example, via get_online_cpus(). | |
81a4beef UO |
528 | */ |
529 | static int watchdog_park_threads(void) | |
530 | { | |
531 | int cpu, ret = 0; | |
532 | ||
b94f5118 DZ |
533 | atomic_set(&watchdog_park_in_progress, 1); |
534 | ||
81a4beef UO |
535 | for_each_watchdog_cpu(cpu) { |
536 | ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); | |
537 | if (ret) | |
538 | break; | |
539 | } | |
81a4beef | 540 | |
b94f5118 DZ |
541 | atomic_set(&watchdog_park_in_progress, 0); |
542 | ||
81a4beef UO |
543 | return ret; |
544 | } | |
545 | ||
546 | /* | |
547 | * unpark all watchdog threads that are specified in 'watchdog_cpumask' | |
a2a45b85 UO |
548 | * |
549 | * This function may only be called in a context that is protected against | |
550 | * races with CPU hotplug - for example, via get_online_cpus(). | |
81a4beef UO |
551 | */ |
552 | static void watchdog_unpark_threads(void) | |
553 | { | |
554 | int cpu; | |
555 | ||
81a4beef UO |
556 | for_each_watchdog_cpu(cpu) |
557 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
81a4beef UO |
558 | } |
559 | ||
b43cb43c | 560 | static int update_watchdog_all_cpus(void) |
9809b18f | 561 | { |
b43cb43c UO |
562 | int ret; |
563 | ||
564 | ret = watchdog_park_threads(); | |
565 | if (ret) | |
566 | return ret; | |
567 | ||
d4bdd0b2 | 568 | watchdog_unpark_threads(); |
b43cb43c UO |
569 | |
570 | return 0; | |
9809b18f MH |
571 | } |
572 | ||
b2f57c3a | 573 | static int watchdog_enable_all_cpus(void) |
58687acb | 574 | { |
b8900bc0 | 575 | int err = 0; |
58687acb | 576 | |
3c00ea82 | 577 | if (!watchdog_running) { |
230ec939 FW |
578 | err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, |
579 | &watchdog_cpumask); | |
b8900bc0 FW |
580 | if (err) |
581 | pr_err("Failed to create watchdog threads, disabled\n"); | |
230ec939 | 582 | else |
3c00ea82 | 583 | watchdog_running = 1; |
b2f57c3a UO |
584 | } else { |
585 | /* | |
586 | * Enable/disable the lockup detectors or | |
587 | * change the sample period 'on the fly'. | |
588 | */ | |
b43cb43c UO |
589 | err = update_watchdog_all_cpus(); |
590 | ||
591 | if (err) { | |
592 | watchdog_disable_all_cpus(); | |
593 | pr_err("Failed to update lockup detectors, disabled\n"); | |
594 | } | |
bcd951cf | 595 | } |
b8900bc0 | 596 | |
b43cb43c UO |
597 | if (err) |
598 | watchdog_enabled = 0; | |
599 | ||
b8900bc0 | 600 | return err; |
58687acb DZ |
601 | } |
602 | ||
603 | static void watchdog_disable_all_cpus(void) | |
604 | { | |
3c00ea82 FW |
605 | if (watchdog_running) { |
606 | watchdog_running = 0; | |
b8900bc0 | 607 | smpboot_unregister_percpu_thread(&watchdog_threads); |
bcd951cf | 608 | } |
58687acb DZ |
609 | } |
610 | ||
a10a842f NP |
611 | #ifdef CONFIG_SYSCTL |
612 | static int watchdog_update_cpus(void) | |
613 | { | |
614 | return smpboot_update_cpumask_percpu_thread( | |
615 | &watchdog_threads, &watchdog_cpumask); | |
616 | } | |
617 | #endif | |
618 | ||
05a4a952 NP |
619 | #else /* SOFTLOCKUP */ |
620 | static int watchdog_park_threads(void) | |
621 | { | |
622 | return 0; | |
623 | } | |
624 | ||
625 | static void watchdog_unpark_threads(void) | |
626 | { | |
627 | } | |
628 | ||
629 | static int watchdog_enable_all_cpus(void) | |
630 | { | |
631 | return 0; | |
632 | } | |
633 | ||
634 | static void watchdog_disable_all_cpus(void) | |
635 | { | |
636 | } | |
637 | ||
a10a842f NP |
638 | #ifdef CONFIG_SYSCTL |
639 | static int watchdog_update_cpus(void) | |
640 | { | |
641 | return 0; | |
642 | } | |
643 | #endif | |
644 | ||
05a4a952 NP |
645 | static void set_sample_period(void) |
646 | { | |
647 | } | |
648 | #endif /* SOFTLOCKUP */ | |
649 | ||
6554fd8c TG |
650 | /** |
651 | * lockup_detector_soft_poweroff - Interface to stop lockup detector(s) | |
652 | * | |
653 | * Special interface for parisc. It prevents lockup detector warnings from | |
654 | * the default pm_poweroff() function which busy loops forever. | |
655 | */ | |
656 | void lockup_detector_soft_poweroff(void) | |
657 | { | |
658 | watchdog_enabled = 0; | |
659 | } | |
660 | ||
58cf690a UO |
661 | #ifdef CONFIG_SYSCTL |
662 | ||
58687acb | 663 | /* |
a0c9cbb9 UO |
664 | * Update the run state of the lockup detectors. |
665 | */ | |
666 | static int proc_watchdog_update(void) | |
667 | { | |
668 | int err = 0; | |
669 | ||
670 | /* | |
671 | * Watchdog threads won't be started if they are already active. | |
672 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
673 | * care of this. If those threads are already active, the sample | |
674 | * period will be updated and the lockup detectors will be enabled | |
675 | * or disabled 'on the fly'. | |
676 | */ | |
677 | if (watchdog_enabled && watchdog_thresh) | |
b2f57c3a | 678 | err = watchdog_enable_all_cpus(); |
a0c9cbb9 UO |
679 | else |
680 | watchdog_disable_all_cpus(); | |
681 | ||
a10a842f NP |
682 | watchdog_nmi_reconfigure(); |
683 | ||
a0c9cbb9 UO |
684 | return err; |
685 | ||
686 | } | |
687 | ||
ef246a21 UO |
688 | /* |
689 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
690 | * | |
691 | * caller | table->data points to | 'which' contains the flag(s) | |
692 | * -------------------|-----------------------|----------------------------- | |
693 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
694 | * | | with SOFT_WATCHDOG_ENABLED | |
695 | * -------------------|-----------------------|----------------------------- | |
696 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
697 | * -------------------|-----------------------|----------------------------- | |
698 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
699 | */ | |
700 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
701 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
702 | { | |
703 | int err, old, new; | |
704 | int *watchdog_param = (int *)table->data; | |
705 | ||
b7a34981 | 706 | cpu_hotplug_disable(); |
ef246a21 UO |
707 | mutex_lock(&watchdog_proc_mutex); |
708 | ||
709 | /* | |
710 | * If the parameter is being read return the state of the corresponding | |
711 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
712 | * run state of the lockup detectors. | |
713 | */ | |
714 | if (!write) { | |
715 | *watchdog_param = (watchdog_enabled & which) != 0; | |
716 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
717 | } else { | |
718 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
719 | if (err) | |
720 | goto out; | |
721 | ||
722 | /* | |
723 | * There is a race window between fetching the current value | |
724 | * from 'watchdog_enabled' and storing the new value. During | |
725 | * this race window, watchdog_nmi_enable() can sneak in and | |
726 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
727 | * The 'cmpxchg' detects this race and the loop retries. | |
728 | */ | |
729 | do { | |
730 | old = watchdog_enabled; | |
731 | /* | |
732 | * If the parameter value is not zero set the | |
733 | * corresponding bit(s), else clear it(them). | |
734 | */ | |
735 | if (*watchdog_param) | |
736 | new = old | which; | |
737 | else | |
738 | new = old & ~which; | |
739 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
740 | ||
741 | /* | |
b43cb43c UO |
742 | * Update the run state of the lockup detectors. There is _no_ |
743 | * need to check the value returned by proc_watchdog_update() | |
744 | * and to restore the previous value of 'watchdog_enabled' as | |
745 | * both lockup detectors are disabled if proc_watchdog_update() | |
746 | * returns an error. | |
ef246a21 | 747 | */ |
a1ee1932 JH |
748 | if (old == new) |
749 | goto out; | |
750 | ||
ef246a21 | 751 | err = proc_watchdog_update(); |
ef246a21 UO |
752 | } |
753 | out: | |
754 | mutex_unlock(&watchdog_proc_mutex); | |
b7a34981 | 755 | cpu_hotplug_enable(); |
ef246a21 UO |
756 | return err; |
757 | } | |
758 | ||
83a80a39 UO |
759 | /* |
760 | * /proc/sys/kernel/watchdog | |
761 | */ | |
762 | int proc_watchdog(struct ctl_table *table, int write, | |
763 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
764 | { | |
765 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
766 | table, write, buffer, lenp, ppos); | |
767 | } | |
768 | ||
769 | /* | |
770 | * /proc/sys/kernel/nmi_watchdog | |
58687acb | 771 | */ |
83a80a39 UO |
772 | int proc_nmi_watchdog(struct ctl_table *table, int write, |
773 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
774 | { | |
775 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
776 | table, write, buffer, lenp, ppos); | |
777 | } | |
778 | ||
779 | /* | |
780 | * /proc/sys/kernel/soft_watchdog | |
781 | */ | |
782 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
783 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
784 | { | |
785 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
786 | table, write, buffer, lenp, ppos); | |
787 | } | |
58687acb | 788 | |
83a80a39 UO |
789 | /* |
790 | * /proc/sys/kernel/watchdog_thresh | |
791 | */ | |
792 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
793 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
58687acb | 794 | { |
a1ee1932 | 795 | int err, old, new; |
58687acb | 796 | |
b7a34981 | 797 | cpu_hotplug_disable(); |
359e6fab | 798 | mutex_lock(&watchdog_proc_mutex); |
bcd951cf | 799 | |
83a80a39 | 800 | old = ACCESS_ONCE(watchdog_thresh); |
b8900bc0 | 801 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
83a80a39 | 802 | |
b8900bc0 | 803 | if (err || !write) |
359e6fab | 804 | goto out; |
e04ab2bc | 805 | |
b66a2356 | 806 | /* |
d283c640 | 807 | * Update the sample period. Restore on failure. |
b66a2356 | 808 | */ |
a1ee1932 JH |
809 | new = ACCESS_ONCE(watchdog_thresh); |
810 | if (old == new) | |
811 | goto out; | |
812 | ||
83a80a39 UO |
813 | set_sample_period(); |
814 | err = proc_watchdog_update(); | |
d283c640 | 815 | if (err) { |
83a80a39 | 816 | watchdog_thresh = old; |
d283c640 UO |
817 | set_sample_period(); |
818 | } | |
359e6fab MH |
819 | out: |
820 | mutex_unlock(&watchdog_proc_mutex); | |
b7a34981 | 821 | cpu_hotplug_enable(); |
b8900bc0 | 822 | return err; |
58687acb | 823 | } |
fe4ba3c3 CM |
824 | |
825 | /* | |
826 | * The cpumask is the mask of possible cpus that the watchdog can run | |
827 | * on, not the mask of cpus it is actually running on. This allows the | |
828 | * user to specify a mask that will include cpus that have not yet | |
829 | * been brought online, if desired. | |
830 | */ | |
831 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
832 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
833 | { | |
834 | int err; | |
835 | ||
b7a34981 | 836 | cpu_hotplug_disable(); |
fe4ba3c3 | 837 | mutex_lock(&watchdog_proc_mutex); |
8c073d27 | 838 | |
fe4ba3c3 CM |
839 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); |
840 | if (!err && write) { | |
841 | /* Remove impossible cpus to keep sysctl output cleaner. */ | |
842 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, | |
843 | cpu_possible_mask); | |
844 | ||
845 | if (watchdog_running) { | |
846 | /* | |
847 | * Failure would be due to being unable to allocate | |
848 | * a temporary cpumask, so we are likely not in a | |
849 | * position to do much else to make things better. | |
850 | */ | |
a10a842f | 851 | if (watchdog_update_cpus() != 0) |
fe4ba3c3 CM |
852 | pr_err("cpumask update failed\n"); |
853 | } | |
a10a842f NP |
854 | |
855 | watchdog_nmi_reconfigure(); | |
fe4ba3c3 | 856 | } |
5490125d | 857 | |
fe4ba3c3 | 858 | mutex_unlock(&watchdog_proc_mutex); |
b7a34981 | 859 | cpu_hotplug_enable(); |
fe4ba3c3 CM |
860 | return err; |
861 | } | |
862 | ||
58687acb DZ |
863 | #endif /* CONFIG_SYSCTL */ |
864 | ||
004417a6 | 865 | void __init lockup_detector_init(void) |
58687acb | 866 | { |
0f34c400 | 867 | set_sample_period(); |
b8900bc0 | 868 | |
fe4ba3c3 CM |
869 | #ifdef CONFIG_NO_HZ_FULL |
870 | if (tick_nohz_full_enabled()) { | |
314b08ff FW |
871 | pr_info("Disabling watchdog on nohz_full cores by default\n"); |
872 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
fe4ba3c3 CM |
873 | } else |
874 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
875 | #else | |
876 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
877 | #endif | |
878 | ||
195daf66 | 879 | if (watchdog_enabled) |
b2f57c3a | 880 | watchdog_enable_all_cpus(); |
58687acb | 881 | } |