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CommitLineData
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1/*
2 * Detect hard and soft lockups on a system
3 *
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
5 *
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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
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9 * to those contributors as well.
10 */
11
4501980a
AM
12#define pr_fmt(fmt) "NMI watchdog: " fmt
13
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14#include <linux/mm.h>
15#include <linux/cpu.h>
16#include <linux/nmi.h>
17#include <linux/init.h>
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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>
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27
28#include <asm/irq_regs.h>
5d1c0f4a 29#include <linux/kvm_para.h>
81a4beef 30#include <linux/kthread.h>
58687acb 31
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32static DEFINE_MUTEX(watchdog_proc_mutex);
33
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34#if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR)
35unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
84d56e66 36#else
249e52e3 37unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
84d56e66
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38#endif
39int __read_mostly nmi_watchdog_enabled;
40int __read_mostly soft_watchdog_enabled;
41int __read_mostly watchdog_user_enabled;
4eec42f3 42int __read_mostly watchdog_thresh = 10;
84d56e66 43
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44#ifdef CONFIG_SMP
45int __read_mostly sysctl_softlockup_all_cpu_backtrace;
55537871 46int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
ed235875 47#endif
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48static struct cpumask watchdog_cpumask __read_mostly;
49unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
50
51/* Helper for online, unparked cpus. */
52#define for_each_watchdog_cpu(cpu) \
53 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
ed235875 54
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55atomic_t watchdog_park_in_progress = ATOMIC_INIT(0);
56
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57/*
58 * The 'watchdog_running' variable is set to 1 when the watchdog threads
59 * are registered/started and is set to 0 when the watchdog threads are
60 * unregistered/stopped, so it is an indicator whether the threads exist.
61 */
3c00ea82 62static int __read_mostly watchdog_running;
ec6a9066
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63/*
64 * If a subsystem has a need to deactivate the watchdog temporarily, it
65 * can use the suspend/resume interface to achieve this. The content of
66 * the 'watchdog_suspended' variable reflects this state. Existing threads
67 * are parked/unparked by the lockup_detector_{suspend|resume} functions
68 * (see comment blocks pertaining to those functions for further details).
69 *
70 * 'watchdog_suspended' also prevents threads from being registered/started
71 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
72 * of 'watchdog_running' cannot change while the watchdog is deactivated
73 * temporarily (see related code in 'proc' handlers).
74 */
75static int __read_mostly watchdog_suspended;
76
0f34c400 77static u64 __read_mostly sample_period;
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78
79static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
80static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
81static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
82static DEFINE_PER_CPU(bool, softlockup_touch_sync);
58687acb 83static DEFINE_PER_CPU(bool, soft_watchdog_warn);
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84static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
85static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
b1a8de1f 86static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
58687acb 87static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
ed235875 88static unsigned long soft_lockup_nmi_warn;
58687acb 89
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90unsigned int __read_mostly softlockup_panic =
91 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
92
93static int __init softlockup_panic_setup(char *str)
94{
95 softlockup_panic = simple_strtoul(str, NULL, 0);
96
97 return 1;
98}
99__setup("softlockup_panic=", softlockup_panic_setup);
100
101static int __init nowatchdog_setup(char *str)
102{
195daf66 103 watchdog_enabled = 0;
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104 return 1;
105}
106__setup("nowatchdog", nowatchdog_setup);
107
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108static int __init nosoftlockup_setup(char *str)
109{
195daf66 110 watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
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111 return 1;
112}
113__setup("nosoftlockup", nosoftlockup_setup);
195daf66 114
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115#ifdef CONFIG_SMP
116static int __init softlockup_all_cpu_backtrace_setup(char *str)
117{
118 sysctl_softlockup_all_cpu_backtrace =
119 !!simple_strtol(str, NULL, 0);
120 return 1;
121}
122__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
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123static int __init hardlockup_all_cpu_backtrace_setup(char *str)
124{
125 sysctl_hardlockup_all_cpu_backtrace =
126 !!simple_strtol(str, NULL, 0);
127 return 1;
128}
129__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
ed235875 130#endif
58687acb 131
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132/*
133 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
134 * lockups can have false positives under extreme conditions. So we generally
135 * want a higher threshold for soft lockups than for hard lockups. So we couple
136 * the thresholds with a factor: we make the soft threshold twice the amount of
137 * time the hard threshold is.
138 */
6e9101ae 139static int get_softlockup_thresh(void)
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MSB
140{
141 return watchdog_thresh * 2;
142}
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143
144/*
145 * Returns seconds, approximately. We don't need nanosecond
146 * resolution, and we don't need to waste time with a big divide when
147 * 2^30ns == 1.074s.
148 */
c06b4f19 149static unsigned long get_timestamp(void)
58687acb 150{
545a2bf7 151 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
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152}
153
0f34c400 154static void set_sample_period(void)
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155{
156 /*
586692a5 157 * convert watchdog_thresh from seconds to ns
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158 * the divide by 5 is to give hrtimer several chances (two
159 * or three with the current relation between the soft
160 * and hard thresholds) to increment before the
161 * hardlockup detector generates a warning
58687acb 162 */
0f34c400 163 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
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164}
165
166/* Commands for resetting the watchdog */
167static void __touch_watchdog(void)
168{
c06b4f19 169 __this_cpu_write(watchdog_touch_ts, get_timestamp());
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170}
171
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TH
172/**
173 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
174 *
175 * Call when the scheduler may have stalled for legitimate reasons
176 * preventing the watchdog task from executing - e.g. the scheduler
177 * entering idle state. This should only be used for scheduler events.
178 * Use touch_softlockup_watchdog() for everything else.
179 */
180void touch_softlockup_watchdog_sched(void)
58687acb 181{
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AM
182 /*
183 * Preemption can be enabled. It doesn't matter which CPU's timestamp
184 * gets zeroed here, so use the raw_ operation.
185 */
186 raw_cpu_write(watchdog_touch_ts, 0);
58687acb 187}
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TH
188
189void touch_softlockup_watchdog(void)
190{
191 touch_softlockup_watchdog_sched();
82607adc 192 wq_watchdog_touch(raw_smp_processor_id());
03e0d461 193}
0167c781 194EXPORT_SYMBOL(touch_softlockup_watchdog);
58687acb 195
332fbdbc 196void touch_all_softlockup_watchdogs(void)
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197{
198 int cpu;
199
200 /*
201 * this is done lockless
202 * do we care if a 0 races with a timestamp?
203 * all it means is the softlock check starts one cycle later
204 */
fe4ba3c3 205 for_each_watchdog_cpu(cpu)
58687acb 206 per_cpu(watchdog_touch_ts, cpu) = 0;
82607adc 207 wq_watchdog_touch(-1);
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208}
209
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210void touch_softlockup_watchdog_sync(void)
211{
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CL
212 __this_cpu_write(softlockup_touch_sync, true);
213 __this_cpu_write(watchdog_touch_ts, 0);
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214}
215
58687acb 216/* watchdog detector functions */
249e52e3 217bool is_hardlockup(void)
58687acb 218{
909ea964 219 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
58687acb 220
909ea964 221 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
451637e4 222 return true;
58687acb 223
909ea964 224 __this_cpu_write(hrtimer_interrupts_saved, hrint);
451637e4 225 return false;
58687acb 226}
58687acb 227
26e09c6e 228static int is_softlockup(unsigned long touch_ts)
58687acb 229{
c06b4f19 230 unsigned long now = get_timestamp();
58687acb 231
39d2da21 232 if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
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UO
233 /* Warn about unreasonable delays. */
234 if (time_after(now, touch_ts + get_softlockup_thresh()))
235 return now - touch_ts;
236 }
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237 return 0;
238}
239
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240static void watchdog_interrupt_count(void)
241{
909ea964 242 __this_cpu_inc(hrtimer_interrupts);
58687acb 243}
bcd951cf 244
73ce0511
BM
245/*
246 * These two functions are mostly architecture specific
247 * defining them as weak here.
248 */
249int __weak watchdog_nmi_enable(unsigned int cpu)
250{
251 return 0;
252}
253void __weak watchdog_nmi_disable(unsigned int cpu)
254{
255}
58687acb 256
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UO
257static int watchdog_enable_all_cpus(void);
258static void watchdog_disable_all_cpus(void);
259
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260/* watchdog kicker functions */
261static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
262{
909ea964 263 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
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264 struct pt_regs *regs = get_irq_regs();
265 int duration;
ed235875 266 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
58687acb 267
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268 if (atomic_read(&watchdog_park_in_progress) != 0)
269 return HRTIMER_NORESTART;
270
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271 /* kick the hardlockup detector */
272 watchdog_interrupt_count();
273
274 /* kick the softlockup detector */
909ea964 275 wake_up_process(__this_cpu_read(softlockup_watchdog));
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276
277 /* .. and repeat */
0f34c400 278 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
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279
280 if (touch_ts == 0) {
909ea964 281 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
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282 /*
283 * If the time stamp was touched atomically
284 * make sure the scheduler tick is up to date.
285 */
909ea964 286 __this_cpu_write(softlockup_touch_sync, false);
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287 sched_clock_tick();
288 }
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289
290 /* Clear the guest paused flag on watchdog reset */
291 kvm_check_and_clear_guest_paused();
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292 __touch_watchdog();
293 return HRTIMER_RESTART;
294 }
295
296 /* check for a softlockup
297 * This is done by making sure a high priority task is
298 * being scheduled. The task touches the watchdog to
299 * indicate it is getting cpu time. If it hasn't then
300 * this is a good indication some task is hogging the cpu
301 */
26e09c6e 302 duration = is_softlockup(touch_ts);
58687acb 303 if (unlikely(duration)) {
5d1c0f4a
EM
304 /*
305 * If a virtual machine is stopped by the host it can look to
306 * the watchdog like a soft lockup, check to see if the host
307 * stopped the vm before we issue the warning
308 */
309 if (kvm_check_and_clear_guest_paused())
310 return HRTIMER_RESTART;
311
58687acb 312 /* only warn once */
b1a8de1f 313 if (__this_cpu_read(soft_watchdog_warn) == true) {
314 /*
315 * When multiple processes are causing softlockups the
316 * softlockup detector only warns on the first one
317 * because the code relies on a full quiet cycle to
318 * re-arm. The second process prevents the quiet cycle
319 * and never gets reported. Use task pointers to detect
320 * this.
321 */
322 if (__this_cpu_read(softlockup_task_ptr_saved) !=
323 current) {
324 __this_cpu_write(soft_watchdog_warn, false);
325 __touch_watchdog();
326 }
58687acb 327 return HRTIMER_RESTART;
b1a8de1f 328 }
58687acb 329
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AT
330 if (softlockup_all_cpu_backtrace) {
331 /* Prevent multiple soft-lockup reports if one cpu is already
332 * engaged in dumping cpu back traces
333 */
334 if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
335 /* Someone else will report us. Let's give up */
336 __this_cpu_write(soft_watchdog_warn, true);
337 return HRTIMER_RESTART;
338 }
339 }
340
656c3b79 341 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
26e09c6e 342 smp_processor_id(), duration,
58687acb 343 current->comm, task_pid_nr(current));
b1a8de1f 344 __this_cpu_write(softlockup_task_ptr_saved, current);
58687acb
DZ
345 print_modules();
346 print_irqtrace_events(current);
347 if (regs)
348 show_regs(regs);
349 else
350 dump_stack();
351
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AT
352 if (softlockup_all_cpu_backtrace) {
353 /* Avoid generating two back traces for current
354 * given that one is already made above
355 */
356 trigger_allbutself_cpu_backtrace();
357
358 clear_bit(0, &soft_lockup_nmi_warn);
359 /* Barrier to sync with other cpus */
360 smp_mb__after_atomic();
361 }
362
69361eef 363 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
58687acb
DZ
364 if (softlockup_panic)
365 panic("softlockup: hung tasks");
909ea964 366 __this_cpu_write(soft_watchdog_warn, true);
58687acb 367 } else
909ea964 368 __this_cpu_write(soft_watchdog_warn, false);
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DZ
369
370 return HRTIMER_RESTART;
371}
372
bcd951cf
TG
373static void watchdog_set_prio(unsigned int policy, unsigned int prio)
374{
375 struct sched_param param = { .sched_priority = prio };
58687acb 376
bcd951cf
TG
377 sched_setscheduler(current, policy, &param);
378}
379
380static void watchdog_enable(unsigned int cpu)
58687acb 381{
f7f66b05 382 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
58687acb 383
3935e895
BM
384 /* kick off the timer for the hardlockup detector */
385 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
386 hrtimer->function = watchdog_timer_fn;
387
bcd951cf
TG
388 /* Enable the perf event */
389 watchdog_nmi_enable(cpu);
58687acb 390
58687acb 391 /* done here because hrtimer_start can only pin to smp_processor_id() */
0f34c400 392 hrtimer_start(hrtimer, ns_to_ktime(sample_period),
58687acb
DZ
393 HRTIMER_MODE_REL_PINNED);
394
bcd951cf
TG
395 /* initialize timestamp */
396 watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
397 __touch_watchdog();
398}
58687acb 399
bcd951cf
TG
400static void watchdog_disable(unsigned int cpu)
401{
f7f66b05 402 struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
58687acb 403
bcd951cf
TG
404 watchdog_set_prio(SCHED_NORMAL, 0);
405 hrtimer_cancel(hrtimer);
406 /* disable the perf event */
407 watchdog_nmi_disable(cpu);
58687acb
DZ
408}
409
b8900bc0
FW
410static void watchdog_cleanup(unsigned int cpu, bool online)
411{
412 watchdog_disable(cpu);
413}
414
bcd951cf
TG
415static int watchdog_should_run(unsigned int cpu)
416{
417 return __this_cpu_read(hrtimer_interrupts) !=
418 __this_cpu_read(soft_lockup_hrtimer_cnt);
419}
420
421/*
422 * The watchdog thread function - touches the timestamp.
423 *
0f34c400 424 * It only runs once every sample_period seconds (4 seconds by
bcd951cf
TG
425 * default) to reset the softlockup timestamp. If this gets delayed
426 * for more than 2*watchdog_thresh seconds then the debug-printout
427 * triggers in watchdog_timer_fn().
428 */
429static void watchdog(unsigned int cpu)
430{
431 __this_cpu_write(soft_lockup_hrtimer_cnt,
432 __this_cpu_read(hrtimer_interrupts));
433 __touch_watchdog();
bcfba4f4
UO
434
435 /*
436 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
437 * failure path. Check for failures that can occur asynchronously -
438 * for example, when CPUs are on-lined - and shut down the hardware
439 * perf event on each CPU accordingly.
440 *
441 * The only non-obvious place this bit can be cleared is through
442 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
443 * pr_info here would be too noisy as it would result in a message
444 * every few seconds if the hardlockup was disabled but the softlockup
445 * enabled.
446 */
447 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
448 watchdog_nmi_disable(cpu);
bcd951cf 449}
58687acb 450
b8900bc0
FW
451static struct smp_hotplug_thread watchdog_threads = {
452 .store = &softlockup_watchdog,
453 .thread_should_run = watchdog_should_run,
454 .thread_fn = watchdog,
455 .thread_comm = "watchdog/%u",
456 .setup = watchdog_enable,
457 .cleanup = watchdog_cleanup,
458 .park = watchdog_disable,
459 .unpark = watchdog_enable,
460};
461
81a4beef
UO
462/*
463 * park all watchdog threads that are specified in 'watchdog_cpumask'
ee7fed54
UO
464 *
465 * This function returns an error if kthread_park() of a watchdog thread
466 * fails. In this situation, the watchdog threads of some CPUs can already
467 * be parked and the watchdog threads of other CPUs can still be runnable.
468 * Callers are expected to handle this special condition as appropriate in
469 * their context.
a2a45b85
UO
470 *
471 * This function may only be called in a context that is protected against
472 * races with CPU hotplug - for example, via get_online_cpus().
81a4beef
UO
473 */
474static int watchdog_park_threads(void)
475{
476 int cpu, ret = 0;
477
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DZ
478 atomic_set(&watchdog_park_in_progress, 1);
479
81a4beef
UO
480 for_each_watchdog_cpu(cpu) {
481 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
482 if (ret)
483 break;
484 }
81a4beef 485
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DZ
486 atomic_set(&watchdog_park_in_progress, 0);
487
81a4beef
UO
488 return ret;
489}
490
491/*
492 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
a2a45b85
UO
493 *
494 * This function may only be called in a context that is protected against
495 * races with CPU hotplug - for example, via get_online_cpus().
81a4beef
UO
496 */
497static void watchdog_unpark_threads(void)
498{
499 int cpu;
500
81a4beef
UO
501 for_each_watchdog_cpu(cpu)
502 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
81a4beef
UO
503}
504
8c073d27
UO
505/*
506 * Suspend the hard and soft lockup detector by parking the watchdog threads.
507 */
ec6a9066 508int lockup_detector_suspend(void)
8c073d27
UO
509{
510 int ret = 0;
511
ee89e71e 512 get_online_cpus();
8c073d27
UO
513 mutex_lock(&watchdog_proc_mutex);
514 /*
515 * Multiple suspend requests can be active in parallel (counted by
516 * the 'watchdog_suspended' variable). If the watchdog threads are
517 * running, the first caller takes care that they will be parked.
518 * The state of 'watchdog_running' cannot change while a suspend
ec6a9066 519 * request is active (see related code in 'proc' handlers).
8c073d27
UO
520 */
521 if (watchdog_running && !watchdog_suspended)
522 ret = watchdog_park_threads();
523
524 if (ret == 0)
525 watchdog_suspended++;
c993590c
UO
526 else {
527 watchdog_disable_all_cpus();
528 pr_err("Failed to suspend lockup detectors, disabled\n");
529 watchdog_enabled = 0;
530 }
8c073d27
UO
531
532 mutex_unlock(&watchdog_proc_mutex);
533
534 return ret;
535}
536
537/*
538 * Resume the hard and soft lockup detector by unparking the watchdog threads.
539 */
ec6a9066 540void lockup_detector_resume(void)
8c073d27
UO
541{
542 mutex_lock(&watchdog_proc_mutex);
543
544 watchdog_suspended--;
545 /*
546 * The watchdog threads are unparked if they were previously running
547 * and if there is no more active suspend request.
548 */
549 if (watchdog_running && !watchdog_suspended)
550 watchdog_unpark_threads();
551
552 mutex_unlock(&watchdog_proc_mutex);
ee89e71e 553 put_online_cpus();
8c073d27
UO
554}
555
b43cb43c 556static int update_watchdog_all_cpus(void)
9809b18f 557{
b43cb43c
UO
558 int ret;
559
560 ret = watchdog_park_threads();
561 if (ret)
562 return ret;
563
d4bdd0b2 564 watchdog_unpark_threads();
b43cb43c
UO
565
566 return 0;
9809b18f
MH
567}
568
b2f57c3a 569static int watchdog_enable_all_cpus(void)
58687acb 570{
b8900bc0 571 int err = 0;
58687acb 572
3c00ea82 573 if (!watchdog_running) {
230ec939
FW
574 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
575 &watchdog_cpumask);
b8900bc0
FW
576 if (err)
577 pr_err("Failed to create watchdog threads, disabled\n");
230ec939 578 else
3c00ea82 579 watchdog_running = 1;
b2f57c3a
UO
580 } else {
581 /*
582 * Enable/disable the lockup detectors or
583 * change the sample period 'on the fly'.
584 */
b43cb43c
UO
585 err = update_watchdog_all_cpus();
586
587 if (err) {
588 watchdog_disable_all_cpus();
589 pr_err("Failed to update lockup detectors, disabled\n");
590 }
bcd951cf 591 }
b8900bc0 592
b43cb43c
UO
593 if (err)
594 watchdog_enabled = 0;
595
b8900bc0 596 return err;
58687acb
DZ
597}
598
599static void watchdog_disable_all_cpus(void)
600{
3c00ea82
FW
601 if (watchdog_running) {
602 watchdog_running = 0;
b8900bc0 603 smpboot_unregister_percpu_thread(&watchdog_threads);
bcd951cf 604 }
58687acb
DZ
605}
606
58cf690a
UO
607#ifdef CONFIG_SYSCTL
608
58687acb 609/*
a0c9cbb9
UO
610 * Update the run state of the lockup detectors.
611 */
612static int proc_watchdog_update(void)
613{
614 int err = 0;
615
616 /*
617 * Watchdog threads won't be started if they are already active.
618 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
619 * care of this. If those threads are already active, the sample
620 * period will be updated and the lockup detectors will be enabled
621 * or disabled 'on the fly'.
622 */
623 if (watchdog_enabled && watchdog_thresh)
b2f57c3a 624 err = watchdog_enable_all_cpus();
a0c9cbb9
UO
625 else
626 watchdog_disable_all_cpus();
627
628 return err;
629
630}
631
ef246a21
UO
632/*
633 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
634 *
635 * caller | table->data points to | 'which' contains the flag(s)
636 * -------------------|-----------------------|-----------------------------
637 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
638 * | | with SOFT_WATCHDOG_ENABLED
639 * -------------------|-----------------------|-----------------------------
640 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
641 * -------------------|-----------------------|-----------------------------
642 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
643 */
644static int proc_watchdog_common(int which, struct ctl_table *table, int write,
645 void __user *buffer, size_t *lenp, loff_t *ppos)
646{
647 int err, old, new;
648 int *watchdog_param = (int *)table->data;
649
8614ddef 650 get_online_cpus();
ef246a21
UO
651 mutex_lock(&watchdog_proc_mutex);
652
8c073d27
UO
653 if (watchdog_suspended) {
654 /* no parameter changes allowed while watchdog is suspended */
655 err = -EAGAIN;
656 goto out;
657 }
658
ef246a21
UO
659 /*
660 * If the parameter is being read return the state of the corresponding
661 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
662 * run state of the lockup detectors.
663 */
664 if (!write) {
665 *watchdog_param = (watchdog_enabled & which) != 0;
666 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
667 } else {
668 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
669 if (err)
670 goto out;
671
672 /*
673 * There is a race window between fetching the current value
674 * from 'watchdog_enabled' and storing the new value. During
675 * this race window, watchdog_nmi_enable() can sneak in and
676 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
677 * The 'cmpxchg' detects this race and the loop retries.
678 */
679 do {
680 old = watchdog_enabled;
681 /*
682 * If the parameter value is not zero set the
683 * corresponding bit(s), else clear it(them).
684 */
685 if (*watchdog_param)
686 new = old | which;
687 else
688 new = old & ~which;
689 } while (cmpxchg(&watchdog_enabled, old, new) != old);
690
691 /*
b43cb43c
UO
692 * Update the run state of the lockup detectors. There is _no_
693 * need to check the value returned by proc_watchdog_update()
694 * and to restore the previous value of 'watchdog_enabled' as
695 * both lockup detectors are disabled if proc_watchdog_update()
696 * returns an error.
ef246a21 697 */
a1ee1932
JH
698 if (old == new)
699 goto out;
700
ef246a21 701 err = proc_watchdog_update();
ef246a21
UO
702 }
703out:
704 mutex_unlock(&watchdog_proc_mutex);
8614ddef 705 put_online_cpus();
ef246a21
UO
706 return err;
707}
708
83a80a39
UO
709/*
710 * /proc/sys/kernel/watchdog
711 */
712int proc_watchdog(struct ctl_table *table, int write,
713 void __user *buffer, size_t *lenp, loff_t *ppos)
714{
715 return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
716 table, write, buffer, lenp, ppos);
717}
718
719/*
720 * /proc/sys/kernel/nmi_watchdog
58687acb 721 */
83a80a39
UO
722int proc_nmi_watchdog(struct ctl_table *table, int write,
723 void __user *buffer, size_t *lenp, loff_t *ppos)
724{
725 return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
726 table, write, buffer, lenp, ppos);
727}
728
729/*
730 * /proc/sys/kernel/soft_watchdog
731 */
732int proc_soft_watchdog(struct ctl_table *table, int write,
733 void __user *buffer, size_t *lenp, loff_t *ppos)
734{
735 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
736 table, write, buffer, lenp, ppos);
737}
58687acb 738
83a80a39
UO
739/*
740 * /proc/sys/kernel/watchdog_thresh
741 */
742int proc_watchdog_thresh(struct ctl_table *table, int write,
743 void __user *buffer, size_t *lenp, loff_t *ppos)
58687acb 744{
a1ee1932 745 int err, old, new;
58687acb 746
8614ddef 747 get_online_cpus();
359e6fab 748 mutex_lock(&watchdog_proc_mutex);
bcd951cf 749
8c073d27
UO
750 if (watchdog_suspended) {
751 /* no parameter changes allowed while watchdog is suspended */
752 err = -EAGAIN;
753 goto out;
754 }
755
83a80a39 756 old = ACCESS_ONCE(watchdog_thresh);
b8900bc0 757 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
83a80a39 758
b8900bc0 759 if (err || !write)
359e6fab 760 goto out;
e04ab2bc 761
b66a2356 762 /*
d283c640 763 * Update the sample period. Restore on failure.
b66a2356 764 */
a1ee1932
JH
765 new = ACCESS_ONCE(watchdog_thresh);
766 if (old == new)
767 goto out;
768
83a80a39
UO
769 set_sample_period();
770 err = proc_watchdog_update();
d283c640 771 if (err) {
83a80a39 772 watchdog_thresh = old;
d283c640
UO
773 set_sample_period();
774 }
359e6fab
MH
775out:
776 mutex_unlock(&watchdog_proc_mutex);
8614ddef 777 put_online_cpus();
b8900bc0 778 return err;
58687acb 779}
fe4ba3c3
CM
780
781/*
782 * The cpumask is the mask of possible cpus that the watchdog can run
783 * on, not the mask of cpus it is actually running on. This allows the
784 * user to specify a mask that will include cpus that have not yet
785 * been brought online, if desired.
786 */
787int proc_watchdog_cpumask(struct ctl_table *table, int write,
788 void __user *buffer, size_t *lenp, loff_t *ppos)
789{
790 int err;
791
8614ddef 792 get_online_cpus();
fe4ba3c3 793 mutex_lock(&watchdog_proc_mutex);
8c073d27
UO
794
795 if (watchdog_suspended) {
796 /* no parameter changes allowed while watchdog is suspended */
797 err = -EAGAIN;
798 goto out;
799 }
800
fe4ba3c3
CM
801 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
802 if (!err && write) {
803 /* Remove impossible cpus to keep sysctl output cleaner. */
804 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
805 cpu_possible_mask);
806
807 if (watchdog_running) {
808 /*
809 * Failure would be due to being unable to allocate
810 * a temporary cpumask, so we are likely not in a
811 * position to do much else to make things better.
812 */
813 if (smpboot_update_cpumask_percpu_thread(
814 &watchdog_threads, &watchdog_cpumask) != 0)
815 pr_err("cpumask update failed\n");
816 }
817 }
8c073d27 818out:
fe4ba3c3 819 mutex_unlock(&watchdog_proc_mutex);
8614ddef 820 put_online_cpus();
fe4ba3c3
CM
821 return err;
822}
823
58687acb
DZ
824#endif /* CONFIG_SYSCTL */
825
004417a6 826void __init lockup_detector_init(void)
58687acb 827{
0f34c400 828 set_sample_period();
b8900bc0 829
fe4ba3c3
CM
830#ifdef CONFIG_NO_HZ_FULL
831 if (tick_nohz_full_enabled()) {
314b08ff
FW
832 pr_info("Disabling watchdog on nohz_full cores by default\n");
833 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
fe4ba3c3
CM
834 } else
835 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
836#else
837 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
838#endif
839
195daf66 840 if (watchdog_enabled)
b2f57c3a 841 watchdog_enable_all_cpus();
58687acb 842}