Commit | Line | Data |
---|---|---|
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 | |
946d1977 | 32 | static DEFINE_MUTEX(watchdog_mutex); |
ab992dc3 | 33 | |
05a4a952 NP |
34 | int __read_mostly nmi_watchdog_enabled; |
35 | ||
36 | #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG) | |
37 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED | | |
38 | NMI_WATCHDOG_ENABLED; | |
84d56e66 | 39 | #else |
249e52e3 | 40 | unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; |
84d56e66 | 41 | #endif |
05a4a952 NP |
42 | |
43 | #ifdef CONFIG_HARDLOCKUP_DETECTOR | |
44 | /* boot commands */ | |
45 | /* | |
46 | * Should we panic when a soft-lockup or hard-lockup occurs: | |
47 | */ | |
48 | unsigned int __read_mostly hardlockup_panic = | |
49 | CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; | |
50 | /* | |
51 | * We may not want to enable hard lockup detection by default in all cases, | |
52 | * for example when running the kernel as a guest on a hypervisor. In these | |
53 | * cases this function can be called to disable hard lockup detection. This | |
54 | * function should only be executed once by the boot processor before the | |
55 | * kernel command line parameters are parsed, because otherwise it is not | |
56 | * possible to override this in hardlockup_panic_setup(). | |
57 | */ | |
7a355820 | 58 | void __init hardlockup_detector_disable(void) |
05a4a952 NP |
59 | { |
60 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
61 | } | |
62 | ||
63 | static int __init hardlockup_panic_setup(char *str) | |
64 | { | |
65 | if (!strncmp(str, "panic", 5)) | |
66 | hardlockup_panic = 1; | |
67 | else if (!strncmp(str, "nopanic", 7)) | |
68 | hardlockup_panic = 0; | |
69 | else if (!strncmp(str, "0", 1)) | |
70 | watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; | |
71 | else if (!strncmp(str, "1", 1)) | |
72 | watchdog_enabled |= NMI_WATCHDOG_ENABLED; | |
73 | return 1; | |
74 | } | |
75 | __setup("nmi_watchdog=", hardlockup_panic_setup); | |
76 | ||
77 | #endif | |
78 | ||
79 | #ifdef CONFIG_SOFTLOCKUP_DETECTOR | |
84d56e66 | 80 | int __read_mostly soft_watchdog_enabled; |
05a4a952 NP |
81 | #endif |
82 | ||
84d56e66 | 83 | int __read_mostly watchdog_user_enabled; |
4eec42f3 | 84 | int __read_mostly watchdog_thresh = 10; |
84d56e66 | 85 | |
ed235875 AT |
86 | #ifdef CONFIG_SMP |
87 | int __read_mostly sysctl_softlockup_all_cpu_backtrace; | |
55537871 | 88 | int __read_mostly sysctl_hardlockup_all_cpu_backtrace; |
ed235875 | 89 | #endif |
05a4a952 | 90 | struct cpumask watchdog_cpumask __read_mostly; |
fe4ba3c3 CM |
91 | unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); |
92 | ||
ec6a9066 UO |
93 | /* |
94 | * The 'watchdog_running' variable is set to 1 when the watchdog threads | |
95 | * are registered/started and is set to 0 when the watchdog threads are | |
96 | * unregistered/stopped, so it is an indicator whether the threads exist. | |
97 | */ | |
3c00ea82 | 98 | static int __read_mostly watchdog_running; |
05a4a952 NP |
99 | |
100 | /* | |
101 | * These functions can be overridden if an architecture implements its | |
102 | * own hardlockup detector. | |
a10a842f NP |
103 | * |
104 | * watchdog_nmi_enable/disable can be implemented to start and stop when | |
105 | * softlockup watchdog threads start and stop. The arch must select the | |
106 | * SOFTLOCKUP_DETECTOR Kconfig. | |
05a4a952 NP |
107 | */ |
108 | int __weak watchdog_nmi_enable(unsigned int cpu) | |
109 | { | |
110 | return 0; | |
111 | } | |
941154bd | 112 | |
05a4a952 NP |
113 | void __weak watchdog_nmi_disable(unsigned int cpu) |
114 | { | |
941154bd | 115 | hardlockup_detector_perf_disable(); |
05a4a952 NP |
116 | } |
117 | ||
a10a842f NP |
118 | /* |
119 | * watchdog_nmi_reconfigure can be implemented to be notified after any | |
120 | * watchdog configuration change. The arch hardlockup watchdog should | |
121 | * respond to the following variables: | |
122 | * - nmi_watchdog_enabled | |
123 | * - watchdog_thresh | |
124 | * - watchdog_cpumask | |
125 | * - sysctl_hardlockup_all_cpu_backtrace | |
126 | * - hardlockup_panic | |
a10a842f | 127 | */ |
2b9d7f23 | 128 | void __weak watchdog_nmi_reconfigure(void) { } |
a10a842f | 129 | |
05a4a952 NP |
130 | #ifdef CONFIG_SOFTLOCKUP_DETECTOR |
131 | ||
132 | /* Helper for online, unparked cpus. */ | |
133 | #define for_each_watchdog_cpu(cpu) \ | |
134 | for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask) | |
135 | ||
2b9d7f23 TG |
136 | /* Global variables, exported for sysctl */ |
137 | unsigned int __read_mostly softlockup_panic = | |
138 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
139 | int __read_mostly soft_watchdog_enabled; | |
140 | ||
0f34c400 | 141 | static u64 __read_mostly sample_period; |
58687acb DZ |
142 | |
143 | static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); | |
144 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
145 | static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); | |
146 | static DEFINE_PER_CPU(bool, softlockup_touch_sync); | |
58687acb | 147 | static DEFINE_PER_CPU(bool, soft_watchdog_warn); |
bcd951cf TG |
148 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); |
149 | static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); | |
b1a8de1f | 150 | static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); |
58687acb | 151 | static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); |
ed235875 | 152 | static unsigned long soft_lockup_nmi_warn; |
58687acb | 153 | |
58687acb DZ |
154 | static int __init softlockup_panic_setup(char *str) |
155 | { | |
156 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
58687acb DZ |
157 | return 1; |
158 | } | |
159 | __setup("softlockup_panic=", softlockup_panic_setup); | |
160 | ||
161 | static int __init nowatchdog_setup(char *str) | |
162 | { | |
195daf66 | 163 | watchdog_enabled = 0; |
58687acb DZ |
164 | return 1; |
165 | } | |
166 | __setup("nowatchdog", nowatchdog_setup); | |
167 | ||
58687acb DZ |
168 | static int __init nosoftlockup_setup(char *str) |
169 | { | |
195daf66 | 170 | watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; |
58687acb DZ |
171 | return 1; |
172 | } | |
173 | __setup("nosoftlockup", nosoftlockup_setup); | |
195daf66 | 174 | |
ed235875 AT |
175 | #ifdef CONFIG_SMP |
176 | static int __init softlockup_all_cpu_backtrace_setup(char *str) | |
177 | { | |
178 | sysctl_softlockup_all_cpu_backtrace = | |
179 | !!simple_strtol(str, NULL, 0); | |
180 | return 1; | |
181 | } | |
182 | __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup); | |
05a4a952 | 183 | #ifdef CONFIG_HARDLOCKUP_DETECTOR |
55537871 JK |
184 | static int __init hardlockup_all_cpu_backtrace_setup(char *str) |
185 | { | |
186 | sysctl_hardlockup_all_cpu_backtrace = | |
187 | !!simple_strtol(str, NULL, 0); | |
188 | return 1; | |
189 | } | |
190 | __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup); | |
ed235875 | 191 | #endif |
05a4a952 | 192 | #endif |
58687acb | 193 | |
941154bd TG |
194 | static void __lockup_detector_cleanup(void); |
195 | ||
4eec42f3 MSB |
196 | /* |
197 | * Hard-lockup warnings should be triggered after just a few seconds. Soft- | |
198 | * lockups can have false positives under extreme conditions. So we generally | |
199 | * want a higher threshold for soft lockups than for hard lockups. So we couple | |
200 | * the thresholds with a factor: we make the soft threshold twice the amount of | |
201 | * time the hard threshold is. | |
202 | */ | |
6e9101ae | 203 | static int get_softlockup_thresh(void) |
4eec42f3 MSB |
204 | { |
205 | return watchdog_thresh * 2; | |
206 | } | |
58687acb DZ |
207 | |
208 | /* | |
209 | * Returns seconds, approximately. We don't need nanosecond | |
210 | * resolution, and we don't need to waste time with a big divide when | |
211 | * 2^30ns == 1.074s. | |
212 | */ | |
c06b4f19 | 213 | static unsigned long get_timestamp(void) |
58687acb | 214 | { |
545a2bf7 | 215 | return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ |
58687acb DZ |
216 | } |
217 | ||
0f34c400 | 218 | static void set_sample_period(void) |
58687acb DZ |
219 | { |
220 | /* | |
586692a5 | 221 | * convert watchdog_thresh from seconds to ns |
86f5e6a7 FLVC |
222 | * the divide by 5 is to give hrtimer several chances (two |
223 | * or three with the current relation between the soft | |
224 | * and hard thresholds) to increment before the | |
225 | * hardlockup detector generates a warning | |
58687acb | 226 | */ |
0f34c400 | 227 | sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); |
7edaeb68 | 228 | watchdog_update_hrtimer_threshold(sample_period); |
58687acb DZ |
229 | } |
230 | ||
231 | /* Commands for resetting the watchdog */ | |
232 | static void __touch_watchdog(void) | |
233 | { | |
c06b4f19 | 234 | __this_cpu_write(watchdog_touch_ts, get_timestamp()); |
58687acb DZ |
235 | } |
236 | ||
03e0d461 TH |
237 | /** |
238 | * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls | |
239 | * | |
240 | * Call when the scheduler may have stalled for legitimate reasons | |
241 | * preventing the watchdog task from executing - e.g. the scheduler | |
242 | * entering idle state. This should only be used for scheduler events. | |
243 | * Use touch_softlockup_watchdog() for everything else. | |
244 | */ | |
245 | void touch_softlockup_watchdog_sched(void) | |
58687acb | 246 | { |
7861144b AM |
247 | /* |
248 | * Preemption can be enabled. It doesn't matter which CPU's timestamp | |
249 | * gets zeroed here, so use the raw_ operation. | |
250 | */ | |
251 | raw_cpu_write(watchdog_touch_ts, 0); | |
58687acb | 252 | } |
03e0d461 TH |
253 | |
254 | void touch_softlockup_watchdog(void) | |
255 | { | |
256 | touch_softlockup_watchdog_sched(); | |
82607adc | 257 | wq_watchdog_touch(raw_smp_processor_id()); |
03e0d461 | 258 | } |
0167c781 | 259 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
58687acb | 260 | |
332fbdbc | 261 | void touch_all_softlockup_watchdogs(void) |
58687acb DZ |
262 | { |
263 | int cpu; | |
264 | ||
265 | /* | |
266 | * this is done lockless | |
267 | * do we care if a 0 races with a timestamp? | |
268 | * all it means is the softlock check starts one cycle later | |
269 | */ | |
fe4ba3c3 | 270 | for_each_watchdog_cpu(cpu) |
58687acb | 271 | per_cpu(watchdog_touch_ts, cpu) = 0; |
82607adc | 272 | wq_watchdog_touch(-1); |
58687acb DZ |
273 | } |
274 | ||
58687acb DZ |
275 | void touch_softlockup_watchdog_sync(void) |
276 | { | |
f7f66b05 CL |
277 | __this_cpu_write(softlockup_touch_sync, true); |
278 | __this_cpu_write(watchdog_touch_ts, 0); | |
58687acb DZ |
279 | } |
280 | ||
26e09c6e | 281 | static int is_softlockup(unsigned long touch_ts) |
58687acb | 282 | { |
c06b4f19 | 283 | unsigned long now = get_timestamp(); |
58687acb | 284 | |
39d2da21 | 285 | if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ |
195daf66 UO |
286 | /* Warn about unreasonable delays. */ |
287 | if (time_after(now, touch_ts + get_softlockup_thresh())) | |
288 | return now - touch_ts; | |
289 | } | |
58687acb DZ |
290 | return 0; |
291 | } | |
292 | ||
05a4a952 NP |
293 | /* watchdog detector functions */ |
294 | bool is_hardlockup(void) | |
58687acb | 295 | { |
05a4a952 | 296 | unsigned long hrint = __this_cpu_read(hrtimer_interrupts); |
bcd951cf | 297 | |
05a4a952 NP |
298 | if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) |
299 | return true; | |
300 | ||
301 | __this_cpu_write(hrtimer_interrupts_saved, hrint); | |
302 | return false; | |
73ce0511 | 303 | } |
05a4a952 NP |
304 | |
305 | static void watchdog_interrupt_count(void) | |
73ce0511 | 306 | { |
05a4a952 | 307 | __this_cpu_inc(hrtimer_interrupts); |
73ce0511 | 308 | } |
58687acb | 309 | |
58cf690a UO |
310 | static int watchdog_enable_all_cpus(void); |
311 | static void watchdog_disable_all_cpus(void); | |
312 | ||
58687acb DZ |
313 | /* watchdog kicker functions */ |
314 | static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) | |
315 | { | |
909ea964 | 316 | unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts); |
58687acb DZ |
317 | struct pt_regs *regs = get_irq_regs(); |
318 | int duration; | |
ed235875 | 319 | int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; |
58687acb | 320 | |
01f0a027 | 321 | if (!watchdog_enabled) |
b94f5118 DZ |
322 | return HRTIMER_NORESTART; |
323 | ||
58687acb DZ |
324 | /* kick the hardlockup detector */ |
325 | watchdog_interrupt_count(); | |
326 | ||
327 | /* kick the softlockup detector */ | |
909ea964 | 328 | wake_up_process(__this_cpu_read(softlockup_watchdog)); |
58687acb DZ |
329 | |
330 | /* .. and repeat */ | |
0f34c400 | 331 | hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); |
58687acb DZ |
332 | |
333 | if (touch_ts == 0) { | |
909ea964 | 334 | if (unlikely(__this_cpu_read(softlockup_touch_sync))) { |
58687acb DZ |
335 | /* |
336 | * If the time stamp was touched atomically | |
337 | * make sure the scheduler tick is up to date. | |
338 | */ | |
909ea964 | 339 | __this_cpu_write(softlockup_touch_sync, false); |
58687acb DZ |
340 | sched_clock_tick(); |
341 | } | |
5d1c0f4a EM |
342 | |
343 | /* Clear the guest paused flag on watchdog reset */ | |
344 | kvm_check_and_clear_guest_paused(); | |
58687acb DZ |
345 | __touch_watchdog(); |
346 | return HRTIMER_RESTART; | |
347 | } | |
348 | ||
349 | /* check for a softlockup | |
350 | * This is done by making sure a high priority task is | |
351 | * being scheduled. The task touches the watchdog to | |
352 | * indicate it is getting cpu time. If it hasn't then | |
353 | * this is a good indication some task is hogging the cpu | |
354 | */ | |
26e09c6e | 355 | duration = is_softlockup(touch_ts); |
58687acb | 356 | if (unlikely(duration)) { |
5d1c0f4a EM |
357 | /* |
358 | * If a virtual machine is stopped by the host it can look to | |
359 | * the watchdog like a soft lockup, check to see if the host | |
360 | * stopped the vm before we issue the warning | |
361 | */ | |
362 | if (kvm_check_and_clear_guest_paused()) | |
363 | return HRTIMER_RESTART; | |
364 | ||
58687acb | 365 | /* only warn once */ |
b1a8de1f | 366 | if (__this_cpu_read(soft_watchdog_warn) == true) { |
367 | /* | |
368 | * When multiple processes are causing softlockups the | |
369 | * softlockup detector only warns on the first one | |
370 | * because the code relies on a full quiet cycle to | |
371 | * re-arm. The second process prevents the quiet cycle | |
372 | * and never gets reported. Use task pointers to detect | |
373 | * this. | |
374 | */ | |
375 | if (__this_cpu_read(softlockup_task_ptr_saved) != | |
376 | current) { | |
377 | __this_cpu_write(soft_watchdog_warn, false); | |
378 | __touch_watchdog(); | |
379 | } | |
58687acb | 380 | return HRTIMER_RESTART; |
b1a8de1f | 381 | } |
58687acb | 382 | |
ed235875 AT |
383 | if (softlockup_all_cpu_backtrace) { |
384 | /* Prevent multiple soft-lockup reports if one cpu is already | |
385 | * engaged in dumping cpu back traces | |
386 | */ | |
387 | if (test_and_set_bit(0, &soft_lockup_nmi_warn)) { | |
388 | /* Someone else will report us. Let's give up */ | |
389 | __this_cpu_write(soft_watchdog_warn, true); | |
390 | return HRTIMER_RESTART; | |
391 | } | |
392 | } | |
393 | ||
656c3b79 | 394 | pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", |
26e09c6e | 395 | smp_processor_id(), duration, |
58687acb | 396 | current->comm, task_pid_nr(current)); |
b1a8de1f | 397 | __this_cpu_write(softlockup_task_ptr_saved, current); |
58687acb DZ |
398 | print_modules(); |
399 | print_irqtrace_events(current); | |
400 | if (regs) | |
401 | show_regs(regs); | |
402 | else | |
403 | dump_stack(); | |
404 | ||
ed235875 AT |
405 | if (softlockup_all_cpu_backtrace) { |
406 | /* Avoid generating two back traces for current | |
407 | * given that one is already made above | |
408 | */ | |
409 | trigger_allbutself_cpu_backtrace(); | |
410 | ||
411 | clear_bit(0, &soft_lockup_nmi_warn); | |
412 | /* Barrier to sync with other cpus */ | |
413 | smp_mb__after_atomic(); | |
414 | } | |
415 | ||
69361eef | 416 | add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); |
58687acb DZ |
417 | if (softlockup_panic) |
418 | panic("softlockup: hung tasks"); | |
909ea964 | 419 | __this_cpu_write(soft_watchdog_warn, true); |
58687acb | 420 | } else |
909ea964 | 421 | __this_cpu_write(soft_watchdog_warn, false); |
58687acb DZ |
422 | |
423 | return HRTIMER_RESTART; | |
424 | } | |
425 | ||
bcd951cf TG |
426 | static void watchdog_set_prio(unsigned int policy, unsigned int prio) |
427 | { | |
428 | struct sched_param param = { .sched_priority = prio }; | |
58687acb | 429 | |
bcd951cf TG |
430 | sched_setscheduler(current, policy, ¶m); |
431 | } | |
432 | ||
433 | static void watchdog_enable(unsigned int cpu) | |
58687acb | 434 | { |
01f0a027 | 435 | struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); |
58687acb | 436 | |
01f0a027 TG |
437 | /* |
438 | * Start the timer first to prevent the NMI watchdog triggering | |
439 | * before the timer has a chance to fire. | |
440 | */ | |
3935e895 BM |
441 | hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
442 | hrtimer->function = watchdog_timer_fn; | |
01f0a027 TG |
443 | hrtimer_start(hrtimer, ns_to_ktime(sample_period), |
444 | HRTIMER_MODE_REL_PINNED); | |
3935e895 | 445 | |
01f0a027 TG |
446 | /* Initialize timestamp */ |
447 | __touch_watchdog(); | |
bcd951cf TG |
448 | /* Enable the perf event */ |
449 | watchdog_nmi_enable(cpu); | |
58687acb | 450 | |
bcd951cf | 451 | watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); |
bcd951cf | 452 | } |
58687acb | 453 | |
bcd951cf TG |
454 | static void watchdog_disable(unsigned int cpu) |
455 | { | |
01f0a027 | 456 | struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); |
58687acb | 457 | |
bcd951cf | 458 | watchdog_set_prio(SCHED_NORMAL, 0); |
01f0a027 TG |
459 | /* |
460 | * Disable the perf event first. That prevents that a large delay | |
461 | * between disabling the timer and disabling the perf event causes | |
462 | * the perf NMI to detect a false positive. | |
463 | */ | |
bcd951cf | 464 | watchdog_nmi_disable(cpu); |
01f0a027 | 465 | hrtimer_cancel(hrtimer); |
58687acb DZ |
466 | } |
467 | ||
b8900bc0 FW |
468 | static void watchdog_cleanup(unsigned int cpu, bool online) |
469 | { | |
470 | watchdog_disable(cpu); | |
471 | } | |
472 | ||
bcd951cf TG |
473 | static int watchdog_should_run(unsigned int cpu) |
474 | { | |
475 | return __this_cpu_read(hrtimer_interrupts) != | |
476 | __this_cpu_read(soft_lockup_hrtimer_cnt); | |
477 | } | |
478 | ||
479 | /* | |
480 | * The watchdog thread function - touches the timestamp. | |
481 | * | |
0f34c400 | 482 | * It only runs once every sample_period seconds (4 seconds by |
bcd951cf TG |
483 | * default) to reset the softlockup timestamp. If this gets delayed |
484 | * for more than 2*watchdog_thresh seconds then the debug-printout | |
485 | * triggers in watchdog_timer_fn(). | |
486 | */ | |
487 | static void watchdog(unsigned int cpu) | |
488 | { | |
489 | __this_cpu_write(soft_lockup_hrtimer_cnt, | |
490 | __this_cpu_read(hrtimer_interrupts)); | |
491 | __touch_watchdog(); | |
492 | } | |
58687acb | 493 | |
b8900bc0 FW |
494 | static struct smp_hotplug_thread watchdog_threads = { |
495 | .store = &softlockup_watchdog, | |
496 | .thread_should_run = watchdog_should_run, | |
497 | .thread_fn = watchdog, | |
498 | .thread_comm = "watchdog/%u", | |
499 | .setup = watchdog_enable, | |
500 | .cleanup = watchdog_cleanup, | |
501 | .park = watchdog_disable, | |
502 | .unpark = watchdog_enable, | |
503 | }; | |
504 | ||
81a4beef UO |
505 | /* |
506 | * park all watchdog threads that are specified in 'watchdog_cpumask' | |
ee7fed54 UO |
507 | * |
508 | * This function returns an error if kthread_park() of a watchdog thread | |
509 | * fails. In this situation, the watchdog threads of some CPUs can already | |
510 | * be parked and the watchdog threads of other CPUs can still be runnable. | |
511 | * Callers are expected to handle this special condition as appropriate in | |
512 | * their context. | |
a2a45b85 UO |
513 | * |
514 | * This function may only be called in a context that is protected against | |
515 | * races with CPU hotplug - for example, via get_online_cpus(). | |
81a4beef UO |
516 | */ |
517 | static int watchdog_park_threads(void) | |
518 | { | |
519 | int cpu, ret = 0; | |
520 | ||
81a4beef UO |
521 | for_each_watchdog_cpu(cpu) { |
522 | ret = kthread_park(per_cpu(softlockup_watchdog, cpu)); | |
523 | if (ret) | |
524 | break; | |
525 | } | |
81a4beef UO |
526 | return ret; |
527 | } | |
528 | ||
529 | /* | |
530 | * unpark all watchdog threads that are specified in 'watchdog_cpumask' | |
a2a45b85 UO |
531 | * |
532 | * This function may only be called in a context that is protected against | |
533 | * races with CPU hotplug - for example, via get_online_cpus(). | |
81a4beef UO |
534 | */ |
535 | static void watchdog_unpark_threads(void) | |
536 | { | |
537 | int cpu; | |
538 | ||
81a4beef UO |
539 | for_each_watchdog_cpu(cpu) |
540 | kthread_unpark(per_cpu(softlockup_watchdog, cpu)); | |
81a4beef UO |
541 | } |
542 | ||
b43cb43c | 543 | static int update_watchdog_all_cpus(void) |
9809b18f | 544 | { |
b43cb43c UO |
545 | int ret; |
546 | ||
547 | ret = watchdog_park_threads(); | |
548 | if (ret) | |
549 | return ret; | |
550 | ||
d4bdd0b2 | 551 | watchdog_unpark_threads(); |
b43cb43c UO |
552 | |
553 | return 0; | |
9809b18f MH |
554 | } |
555 | ||
b2f57c3a | 556 | static int watchdog_enable_all_cpus(void) |
58687acb | 557 | { |
b8900bc0 | 558 | int err = 0; |
58687acb | 559 | |
3c00ea82 | 560 | if (!watchdog_running) { |
230ec939 FW |
561 | err = smpboot_register_percpu_thread_cpumask(&watchdog_threads, |
562 | &watchdog_cpumask); | |
b8900bc0 FW |
563 | if (err) |
564 | pr_err("Failed to create watchdog threads, disabled\n"); | |
230ec939 | 565 | else |
3c00ea82 | 566 | watchdog_running = 1; |
b2f57c3a UO |
567 | } else { |
568 | /* | |
569 | * Enable/disable the lockup detectors or | |
570 | * change the sample period 'on the fly'. | |
571 | */ | |
b43cb43c UO |
572 | err = update_watchdog_all_cpus(); |
573 | ||
574 | if (err) { | |
575 | watchdog_disable_all_cpus(); | |
576 | pr_err("Failed to update lockup detectors, disabled\n"); | |
577 | } | |
bcd951cf | 578 | } |
b8900bc0 | 579 | |
b43cb43c UO |
580 | if (err) |
581 | watchdog_enabled = 0; | |
582 | ||
b8900bc0 | 583 | return err; |
58687acb DZ |
584 | } |
585 | ||
586 | static void watchdog_disable_all_cpus(void) | |
587 | { | |
3c00ea82 FW |
588 | if (watchdog_running) { |
589 | watchdog_running = 0; | |
b8900bc0 | 590 | smpboot_unregister_percpu_thread(&watchdog_threads); |
bcd951cf | 591 | } |
58687acb DZ |
592 | } |
593 | ||
2b9d7f23 TG |
594 | #else /* CONFIG_SOFTLOCKUP_DETECTOR */ |
595 | static inline int watchdog_park_threads(void) { return 0; } | |
596 | static inline void watchdog_unpark_threads(void) { } | |
597 | static inline int watchdog_enable_all_cpus(void) { return 0; } | |
598 | static inline void watchdog_disable_all_cpus(void) { } | |
599 | static inline void set_sample_period(void) { } | |
600 | #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ | |
05a4a952 | 601 | |
941154bd TG |
602 | static void __lockup_detector_cleanup(void) |
603 | { | |
604 | lockdep_assert_held(&watchdog_mutex); | |
605 | hardlockup_detector_perf_cleanup(); | |
606 | } | |
607 | ||
608 | /** | |
609 | * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes | |
610 | * | |
611 | * Caller must not hold the cpu hotplug rwsem. | |
612 | */ | |
613 | void lockup_detector_cleanup(void) | |
614 | { | |
615 | mutex_lock(&watchdog_mutex); | |
616 | __lockup_detector_cleanup(); | |
617 | mutex_unlock(&watchdog_mutex); | |
618 | } | |
619 | ||
6554fd8c TG |
620 | /** |
621 | * lockup_detector_soft_poweroff - Interface to stop lockup detector(s) | |
622 | * | |
623 | * Special interface for parisc. It prevents lockup detector warnings from | |
624 | * the default pm_poweroff() function which busy loops forever. | |
625 | */ | |
626 | void lockup_detector_soft_poweroff(void) | |
627 | { | |
628 | watchdog_enabled = 0; | |
629 | } | |
630 | ||
58cf690a UO |
631 | #ifdef CONFIG_SYSCTL |
632 | ||
58687acb | 633 | /* |
a0c9cbb9 UO |
634 | * Update the run state of the lockup detectors. |
635 | */ | |
636 | static int proc_watchdog_update(void) | |
637 | { | |
638 | int err = 0; | |
639 | ||
640 | /* | |
641 | * Watchdog threads won't be started if they are already active. | |
642 | * The 'watchdog_running' variable in watchdog_*_all_cpus() takes | |
643 | * care of this. If those threads are already active, the sample | |
644 | * period will be updated and the lockup detectors will be enabled | |
645 | * or disabled 'on the fly'. | |
646 | */ | |
647 | if (watchdog_enabled && watchdog_thresh) | |
b2f57c3a | 648 | err = watchdog_enable_all_cpus(); |
a0c9cbb9 UO |
649 | else |
650 | watchdog_disable_all_cpus(); | |
651 | ||
a10a842f NP |
652 | watchdog_nmi_reconfigure(); |
653 | ||
941154bd TG |
654 | __lockup_detector_cleanup(); |
655 | ||
a0c9cbb9 UO |
656 | return err; |
657 | ||
658 | } | |
659 | ||
ef246a21 UO |
660 | /* |
661 | * common function for watchdog, nmi_watchdog and soft_watchdog parameter | |
662 | * | |
663 | * caller | table->data points to | 'which' contains the flag(s) | |
664 | * -------------------|-----------------------|----------------------------- | |
665 | * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed | |
666 | * | | with SOFT_WATCHDOG_ENABLED | |
667 | * -------------------|-----------------------|----------------------------- | |
668 | * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED | |
669 | * -------------------|-----------------------|----------------------------- | |
670 | * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED | |
671 | */ | |
672 | static int proc_watchdog_common(int which, struct ctl_table *table, int write, | |
673 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
674 | { | |
675 | int err, old, new; | |
676 | int *watchdog_param = (int *)table->data; | |
677 | ||
b7a34981 | 678 | cpu_hotplug_disable(); |
946d1977 | 679 | mutex_lock(&watchdog_mutex); |
ef246a21 UO |
680 | |
681 | /* | |
682 | * If the parameter is being read return the state of the corresponding | |
683 | * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the | |
684 | * run state of the lockup detectors. | |
685 | */ | |
686 | if (!write) { | |
687 | *watchdog_param = (watchdog_enabled & which) != 0; | |
688 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
689 | } else { | |
690 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
691 | if (err) | |
692 | goto out; | |
693 | ||
694 | /* | |
695 | * There is a race window between fetching the current value | |
696 | * from 'watchdog_enabled' and storing the new value. During | |
697 | * this race window, watchdog_nmi_enable() can sneak in and | |
698 | * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'. | |
699 | * The 'cmpxchg' detects this race and the loop retries. | |
700 | */ | |
701 | do { | |
702 | old = watchdog_enabled; | |
703 | /* | |
704 | * If the parameter value is not zero set the | |
705 | * corresponding bit(s), else clear it(them). | |
706 | */ | |
707 | if (*watchdog_param) | |
708 | new = old | which; | |
709 | else | |
710 | new = old & ~which; | |
711 | } while (cmpxchg(&watchdog_enabled, old, new) != old); | |
712 | ||
713 | /* | |
b43cb43c UO |
714 | * Update the run state of the lockup detectors. There is _no_ |
715 | * need to check the value returned by proc_watchdog_update() | |
716 | * and to restore the previous value of 'watchdog_enabled' as | |
717 | * both lockup detectors are disabled if proc_watchdog_update() | |
718 | * returns an error. | |
ef246a21 | 719 | */ |
a1ee1932 JH |
720 | if (old == new) |
721 | goto out; | |
722 | ||
ef246a21 | 723 | err = proc_watchdog_update(); |
ef246a21 UO |
724 | } |
725 | out: | |
946d1977 | 726 | mutex_unlock(&watchdog_mutex); |
b7a34981 | 727 | cpu_hotplug_enable(); |
ef246a21 UO |
728 | return err; |
729 | } | |
730 | ||
83a80a39 UO |
731 | /* |
732 | * /proc/sys/kernel/watchdog | |
733 | */ | |
734 | int proc_watchdog(struct ctl_table *table, int write, | |
735 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
736 | { | |
737 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED, | |
738 | table, write, buffer, lenp, ppos); | |
739 | } | |
740 | ||
741 | /* | |
742 | * /proc/sys/kernel/nmi_watchdog | |
58687acb | 743 | */ |
83a80a39 UO |
744 | int proc_nmi_watchdog(struct ctl_table *table, int write, |
745 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
746 | { | |
747 | return proc_watchdog_common(NMI_WATCHDOG_ENABLED, | |
748 | table, write, buffer, lenp, ppos); | |
749 | } | |
750 | ||
751 | /* | |
752 | * /proc/sys/kernel/soft_watchdog | |
753 | */ | |
754 | int proc_soft_watchdog(struct ctl_table *table, int write, | |
755 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
756 | { | |
757 | return proc_watchdog_common(SOFT_WATCHDOG_ENABLED, | |
758 | table, write, buffer, lenp, ppos); | |
759 | } | |
58687acb | 760 | |
83a80a39 UO |
761 | /* |
762 | * /proc/sys/kernel/watchdog_thresh | |
763 | */ | |
764 | int proc_watchdog_thresh(struct ctl_table *table, int write, | |
765 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
58687acb | 766 | { |
a1ee1932 | 767 | int err, old, new; |
58687acb | 768 | |
b7a34981 | 769 | cpu_hotplug_disable(); |
946d1977 | 770 | mutex_lock(&watchdog_mutex); |
bcd951cf | 771 | |
83a80a39 | 772 | old = ACCESS_ONCE(watchdog_thresh); |
b8900bc0 | 773 | err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
83a80a39 | 774 | |
b8900bc0 | 775 | if (err || !write) |
359e6fab | 776 | goto out; |
e04ab2bc | 777 | |
b66a2356 | 778 | /* |
d283c640 | 779 | * Update the sample period. Restore on failure. |
b66a2356 | 780 | */ |
a1ee1932 JH |
781 | new = ACCESS_ONCE(watchdog_thresh); |
782 | if (old == new) | |
783 | goto out; | |
784 | ||
83a80a39 UO |
785 | set_sample_period(); |
786 | err = proc_watchdog_update(); | |
d283c640 | 787 | if (err) { |
83a80a39 | 788 | watchdog_thresh = old; |
d283c640 UO |
789 | set_sample_period(); |
790 | } | |
359e6fab | 791 | out: |
946d1977 | 792 | mutex_unlock(&watchdog_mutex); |
b7a34981 | 793 | cpu_hotplug_enable(); |
b8900bc0 | 794 | return err; |
58687acb | 795 | } |
fe4ba3c3 | 796 | |
2b9d7f23 TG |
797 | static int watchdog_update_cpus(void) |
798 | { | |
799 | if (IS_ENABLED(CONFIG_SOFTLOCKUP_DETECTOR)) { | |
800 | return smpboot_update_cpumask_percpu_thread(&watchdog_threads, | |
801 | &watchdog_cpumask); | |
802 | } | |
803 | return 0; | |
804 | } | |
805 | ||
fe4ba3c3 CM |
806 | /* |
807 | * The cpumask is the mask of possible cpus that the watchdog can run | |
808 | * on, not the mask of cpus it is actually running on. This allows the | |
809 | * user to specify a mask that will include cpus that have not yet | |
810 | * been brought online, if desired. | |
811 | */ | |
812 | int proc_watchdog_cpumask(struct ctl_table *table, int write, | |
813 | void __user *buffer, size_t *lenp, loff_t *ppos) | |
814 | { | |
815 | int err; | |
816 | ||
b7a34981 | 817 | cpu_hotplug_disable(); |
946d1977 | 818 | mutex_lock(&watchdog_mutex); |
8c073d27 | 819 | |
fe4ba3c3 CM |
820 | err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); |
821 | if (!err && write) { | |
822 | /* Remove impossible cpus to keep sysctl output cleaner. */ | |
823 | cpumask_and(&watchdog_cpumask, &watchdog_cpumask, | |
824 | cpu_possible_mask); | |
825 | ||
826 | if (watchdog_running) { | |
827 | /* | |
828 | * Failure would be due to being unable to allocate | |
829 | * a temporary cpumask, so we are likely not in a | |
830 | * position to do much else to make things better. | |
831 | */ | |
a10a842f | 832 | if (watchdog_update_cpus() != 0) |
fe4ba3c3 CM |
833 | pr_err("cpumask update failed\n"); |
834 | } | |
a10a842f NP |
835 | |
836 | watchdog_nmi_reconfigure(); | |
941154bd | 837 | __lockup_detector_cleanup(); |
fe4ba3c3 | 838 | } |
5490125d | 839 | |
946d1977 | 840 | mutex_unlock(&watchdog_mutex); |
b7a34981 | 841 | cpu_hotplug_enable(); |
fe4ba3c3 CM |
842 | return err; |
843 | } | |
844 | ||
58687acb DZ |
845 | #endif /* CONFIG_SYSCTL */ |
846 | ||
004417a6 | 847 | void __init lockup_detector_init(void) |
58687acb | 848 | { |
0f34c400 | 849 | set_sample_period(); |
b8900bc0 | 850 | |
fe4ba3c3 CM |
851 | #ifdef CONFIG_NO_HZ_FULL |
852 | if (tick_nohz_full_enabled()) { | |
314b08ff FW |
853 | pr_info("Disabling watchdog on nohz_full cores by default\n"); |
854 | cpumask_copy(&watchdog_cpumask, housekeeping_mask); | |
fe4ba3c3 CM |
855 | } else |
856 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
857 | #else | |
858 | cpumask_copy(&watchdog_cpumask, cpu_possible_mask); | |
859 | #endif | |
860 | ||
195daf66 | 861 | if (watchdog_enabled) |
b2f57c3a | 862 | watchdog_enable_all_cpus(); |
58687acb | 863 | } |