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Don Zickus58687ac2010-05-07 17:11:44 -04001/*
2 * Detect hard and soft lockups on a system
3 *
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
5 *
6 * this code detects hard lockups: incidents in where on a CPU
7 * the kernel does not respond to anything except NMI.
8 *
9 * Note: Most of this code is borrowed heavily from softlockup.c,
10 * so thanks to Ingo for the initial implementation.
11 * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
12 * to those contributors as well.
13 */
14
15#include <linux/mm.h>
16#include <linux/cpu.h>
17#include <linux/nmi.h>
18#include <linux/init.h>
19#include <linux/delay.h>
20#include <linux/freezer.h>
21#include <linux/kthread.h>
22#include <linux/lockdep.h>
23#include <linux/notifier.h>
24#include <linux/module.h>
25#include <linux/sysctl.h>
26
27#include <asm/irq_regs.h>
28#include <linux/perf_event.h>
29
30int watchdog_enabled;
31int __read_mostly softlockup_thresh = 60;
32
33static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
Don Zickusd7c54732010-05-07 17:11:51 -040034static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
Don Zickus58687ac2010-05-07 17:11:44 -040035static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
36static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
37static DEFINE_PER_CPU(bool, softlockup_touch_sync);
38static DEFINE_PER_CPU(bool, hard_watchdog_warn);
39static DEFINE_PER_CPU(bool, soft_watchdog_warn);
Frederic Weisbecker23637d42010-05-15 23:15:20 +020040#ifdef CONFIG_HARDLOCKUP_DETECTOR
Don Zickus58687ac2010-05-07 17:11:44 -040041static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
42static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
43static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
44#endif
45
46static int __read_mostly did_panic;
47static int __initdata no_watchdog;
48
49
50/* boot commands */
51/*
52 * Should we panic when a soft-lockup or hard-lockup occurs:
53 */
Frederic Weisbecker23637d42010-05-15 23:15:20 +020054#ifdef CONFIG_HARDLOCKUP_DETECTOR
Don Zickus58687ac2010-05-07 17:11:44 -040055static int hardlockup_panic;
56
57static int __init hardlockup_panic_setup(char *str)
58{
59 if (!strncmp(str, "panic", 5))
60 hardlockup_panic = 1;
61 return 1;
62}
63__setup("nmi_watchdog=", hardlockup_panic_setup);
64#endif
65
66unsigned int __read_mostly softlockup_panic =
67 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
68
69static int __init softlockup_panic_setup(char *str)
70{
71 softlockup_panic = simple_strtoul(str, NULL, 0);
72
73 return 1;
74}
75__setup("softlockup_panic=", softlockup_panic_setup);
76
77static int __init nowatchdog_setup(char *str)
78{
79 no_watchdog = 1;
80 return 1;
81}
82__setup("nowatchdog", nowatchdog_setup);
83
84/* deprecated */
85static int __init nosoftlockup_setup(char *str)
86{
87 no_watchdog = 1;
88 return 1;
89}
90__setup("nosoftlockup", nosoftlockup_setup);
91/* */
92
93
94/*
95 * Returns seconds, approximately. We don't need nanosecond
96 * resolution, and we don't need to waste time with a big divide when
97 * 2^30ns == 1.074s.
98 */
99static unsigned long get_timestamp(int this_cpu)
100{
101 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
102}
103
104static unsigned long get_sample_period(void)
105{
106 /*
107 * convert softlockup_thresh from seconds to ns
108 * the divide by 5 is to give hrtimer 5 chances to
109 * increment before the hardlockup detector generates
110 * a warning
111 */
112 return softlockup_thresh / 5 * NSEC_PER_SEC;
113}
114
115/* Commands for resetting the watchdog */
116static void __touch_watchdog(void)
117{
118 int this_cpu = raw_smp_processor_id();
119
120 __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
121}
122
Don Zickus332fbdb2010-05-07 17:11:45 -0400123void touch_softlockup_watchdog(void)
Don Zickus58687ac2010-05-07 17:11:44 -0400124{
125 __get_cpu_var(watchdog_touch_ts) = 0;
126}
Ingo Molnar0167c782010-05-13 08:53:33 +0200127EXPORT_SYMBOL(touch_softlockup_watchdog);
Don Zickus58687ac2010-05-07 17:11:44 -0400128
Don Zickus332fbdb2010-05-07 17:11:45 -0400129void touch_all_softlockup_watchdogs(void)
Don Zickus58687ac2010-05-07 17:11:44 -0400130{
131 int cpu;
132
133 /*
134 * this is done lockless
135 * do we care if a 0 races with a timestamp?
136 * all it means is the softlock check starts one cycle later
137 */
138 for_each_online_cpu(cpu)
139 per_cpu(watchdog_touch_ts, cpu) = 0;
140}
141
142void touch_nmi_watchdog(void)
143{
Don Zickusd7c54732010-05-07 17:11:51 -0400144 __get_cpu_var(watchdog_nmi_touch) = true;
Don Zickus332fbdb2010-05-07 17:11:45 -0400145 touch_softlockup_watchdog();
Don Zickus58687ac2010-05-07 17:11:44 -0400146}
147EXPORT_SYMBOL(touch_nmi_watchdog);
148
Don Zickus58687ac2010-05-07 17:11:44 -0400149void touch_softlockup_watchdog_sync(void)
150{
151 __raw_get_cpu_var(softlockup_touch_sync) = true;
152 __raw_get_cpu_var(watchdog_touch_ts) = 0;
153}
154
Frederic Weisbecker23637d42010-05-15 23:15:20 +0200155#ifdef CONFIG_HARDLOCKUP_DETECTOR
Don Zickus58687ac2010-05-07 17:11:44 -0400156/* watchdog detector functions */
157static int is_hardlockup(int cpu)
158{
159 unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
160
161 if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
162 return 1;
163
164 per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
165 return 0;
166}
167#endif
168
169static int is_softlockup(unsigned long touch_ts, int cpu)
170{
171 unsigned long now = get_timestamp(cpu);
172
173 /* Warn about unreasonable delays: */
174 if (time_after(now, touch_ts + softlockup_thresh))
175 return now - touch_ts;
176
177 return 0;
178}
179
180static int
181watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
182{
183 did_panic = 1;
184
185 return NOTIFY_DONE;
186}
187
188static struct notifier_block panic_block = {
189 .notifier_call = watchdog_panic,
190};
191
Frederic Weisbecker23637d42010-05-15 23:15:20 +0200192#ifdef CONFIG_HARDLOCKUP_DETECTOR
Don Zickus58687ac2010-05-07 17:11:44 -0400193static struct perf_event_attr wd_hw_attr = {
194 .type = PERF_TYPE_HARDWARE,
195 .config = PERF_COUNT_HW_CPU_CYCLES,
196 .size = sizeof(struct perf_event_attr),
197 .pinned = 1,
198 .disabled = 1,
199};
200
201/* Callback function for perf event subsystem */
202void watchdog_overflow_callback(struct perf_event *event, int nmi,
203 struct perf_sample_data *data,
204 struct pt_regs *regs)
205{
206 int this_cpu = smp_processor_id();
Don Zickus58687ac2010-05-07 17:11:44 -0400207
Don Zickusd7c54732010-05-07 17:11:51 -0400208 if (__get_cpu_var(watchdog_nmi_touch) == true) {
209 __get_cpu_var(watchdog_nmi_touch) = false;
Don Zickus58687ac2010-05-07 17:11:44 -0400210 return;
211 }
212
213 /* check for a hardlockup
214 * This is done by making sure our timer interrupt
215 * is incrementing. The timer interrupt should have
216 * fired multiple times before we overflow'd. If it hasn't
217 * then this is a good indication the cpu is stuck
218 */
219 if (is_hardlockup(this_cpu)) {
220 /* only print hardlockups once */
221 if (__get_cpu_var(hard_watchdog_warn) == true)
222 return;
223
224 if (hardlockup_panic)
225 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
226 else
227 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
228
229 __get_cpu_var(hard_watchdog_warn) = true;
230 return;
231 }
232
233 __get_cpu_var(hard_watchdog_warn) = false;
234 return;
235}
236static void watchdog_interrupt_count(void)
237{
238 __get_cpu_var(hrtimer_interrupts)++;
239}
240#else
241static inline void watchdog_interrupt_count(void) { return; }
Frederic Weisbecker23637d42010-05-15 23:15:20 +0200242#endif /* CONFIG_HARDLOCKUP_DETECTOR */
Don Zickus58687ac2010-05-07 17:11:44 -0400243
244/* watchdog kicker functions */
245static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
246{
247 int this_cpu = smp_processor_id();
248 unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
249 struct pt_regs *regs = get_irq_regs();
250 int duration;
251
252 /* kick the hardlockup detector */
253 watchdog_interrupt_count();
254
255 /* kick the softlockup detector */
256 wake_up_process(__get_cpu_var(softlockup_watchdog));
257
258 /* .. and repeat */
259 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
260
261 if (touch_ts == 0) {
262 if (unlikely(per_cpu(softlockup_touch_sync, this_cpu))) {
263 /*
264 * If the time stamp was touched atomically
265 * make sure the scheduler tick is up to date.
266 */
267 per_cpu(softlockup_touch_sync, this_cpu) = false;
268 sched_clock_tick();
269 }
270 __touch_watchdog();
271 return HRTIMER_RESTART;
272 }
273
274 /* check for a softlockup
275 * This is done by making sure a high priority task is
276 * being scheduled. The task touches the watchdog to
277 * indicate it is getting cpu time. If it hasn't then
278 * this is a good indication some task is hogging the cpu
279 */
280 duration = is_softlockup(touch_ts, this_cpu);
281 if (unlikely(duration)) {
282 /* only warn once */
283 if (__get_cpu_var(soft_watchdog_warn) == true)
284 return HRTIMER_RESTART;
285
286 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
287 this_cpu, duration,
288 current->comm, task_pid_nr(current));
289 print_modules();
290 print_irqtrace_events(current);
291 if (regs)
292 show_regs(regs);
293 else
294 dump_stack();
295
296 if (softlockup_panic)
297 panic("softlockup: hung tasks");
298 __get_cpu_var(soft_watchdog_warn) = true;
299 } else
300 __get_cpu_var(soft_watchdog_warn) = false;
301
302 return HRTIMER_RESTART;
303}
304
305
306/*
307 * The watchdog thread - touches the timestamp.
308 */
309static int watchdog(void *__bind_cpu)
310{
311 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
312 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
313
314 sched_setscheduler(current, SCHED_FIFO, &param);
315
316 /* initialize timestamp */
317 __touch_watchdog();
318
319 /* kick off the timer for the hardlockup detector */
320 /* done here because hrtimer_start can only pin to smp_processor_id() */
321 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
322 HRTIMER_MODE_REL_PINNED);
323
324 set_current_state(TASK_INTERRUPTIBLE);
325 /*
326 * Run briefly once per second to reset the softlockup timestamp.
327 * If this gets delayed for more than 60 seconds then the
328 * debug-printout triggers in softlockup_tick().
329 */
330 while (!kthread_should_stop()) {
331 __touch_watchdog();
332 schedule();
333
334 if (kthread_should_stop())
335 break;
336
337 set_current_state(TASK_INTERRUPTIBLE);
338 }
339 __set_current_state(TASK_RUNNING);
340
341 return 0;
342}
343
344
Frederic Weisbecker23637d42010-05-15 23:15:20 +0200345#ifdef CONFIG_HARDLOCKUP_DETECTOR
Don Zickus58687ac2010-05-07 17:11:44 -0400346static int watchdog_nmi_enable(int cpu)
347{
348 struct perf_event_attr *wd_attr;
349 struct perf_event *event = per_cpu(watchdog_ev, cpu);
350
351 /* is it already setup and enabled? */
352 if (event && event->state > PERF_EVENT_STATE_OFF)
353 goto out;
354
355 /* it is setup but not enabled */
356 if (event != NULL)
357 goto out_enable;
358
359 /* Try to register using hardware perf events */
360 wd_attr = &wd_hw_attr;
361 wd_attr->sample_period = hw_nmi_get_sample_period();
362 event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
363 if (!IS_ERR(event)) {
364 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
365 goto out_save;
366 }
367
368 printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
369 return -1;
370
371 /* success path */
372out_save:
373 per_cpu(watchdog_ev, cpu) = event;
374out_enable:
375 perf_event_enable(per_cpu(watchdog_ev, cpu));
376out:
377 return 0;
378}
379
380static void watchdog_nmi_disable(int cpu)
381{
382 struct perf_event *event = per_cpu(watchdog_ev, cpu);
383
384 if (event) {
385 perf_event_disable(event);
386 per_cpu(watchdog_ev, cpu) = NULL;
387
388 /* should be in cleanup, but blocks oprofile */
389 perf_event_release_kernel(event);
390 }
391 return;
392}
393#else
394static int watchdog_nmi_enable(int cpu) { return 0; }
395static void watchdog_nmi_disable(int cpu) { return; }
Frederic Weisbecker23637d42010-05-15 23:15:20 +0200396#endif /* CONFIG_HARDLOCKUP_DETECTOR */
Don Zickus58687ac2010-05-07 17:11:44 -0400397
398/* prepare/enable/disable routines */
399static int watchdog_prepare_cpu(int cpu)
400{
401 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
402
403 WARN_ON(per_cpu(softlockup_watchdog, cpu));
404 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
405 hrtimer->function = watchdog_timer_fn;
406
407 return 0;
408}
409
410static int watchdog_enable(int cpu)
411{
412 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
413
414 /* enable the perf event */
415 if (watchdog_nmi_enable(cpu) != 0)
416 return -1;
417
418 /* create the watchdog thread */
419 if (!p) {
420 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
421 if (IS_ERR(p)) {
422 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
423 return -1;
424 }
425 kthread_bind(p, cpu);
426 per_cpu(watchdog_touch_ts, cpu) = 0;
427 per_cpu(softlockup_watchdog, cpu) = p;
428 wake_up_process(p);
429 }
430
431 return 0;
432}
433
434static void watchdog_disable(int cpu)
435{
436 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
437 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
438
439 /*
440 * cancel the timer first to stop incrementing the stats
441 * and waking up the kthread
442 */
443 hrtimer_cancel(hrtimer);
444
445 /* disable the perf event */
446 watchdog_nmi_disable(cpu);
447
448 /* stop the watchdog thread */
449 if (p) {
450 per_cpu(softlockup_watchdog, cpu) = NULL;
451 kthread_stop(p);
452 }
453
454 /* if any cpu succeeds, watchdog is considered enabled for the system */
455 watchdog_enabled = 1;
456}
457
458static void watchdog_enable_all_cpus(void)
459{
460 int cpu;
461 int result;
462
463 for_each_online_cpu(cpu)
464 result += watchdog_enable(cpu);
465
466 if (result)
467 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
468
469}
470
471static void watchdog_disable_all_cpus(void)
472{
473 int cpu;
474
475 for_each_online_cpu(cpu)
476 watchdog_disable(cpu);
477
478 /* if all watchdogs are disabled, then they are disabled for the system */
479 watchdog_enabled = 0;
480}
481
482
483/* sysctl functions */
484#ifdef CONFIG_SYSCTL
485/*
486 * proc handler for /proc/sys/kernel/nmi_watchdog
487 */
488
489int proc_dowatchdog_enabled(struct ctl_table *table, int write,
490 void __user *buffer, size_t *length, loff_t *ppos)
491{
492 proc_dointvec(table, write, buffer, length, ppos);
493
494 if (watchdog_enabled)
495 watchdog_enable_all_cpus();
496 else
497 watchdog_disable_all_cpus();
498 return 0;
499}
500
501int proc_dowatchdog_thresh(struct ctl_table *table, int write,
502 void __user *buffer,
503 size_t *lenp, loff_t *ppos)
504{
505 return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
506}
Don Zickus58687ac2010-05-07 17:11:44 -0400507#endif /* CONFIG_SYSCTL */
508
509
510/*
511 * Create/destroy watchdog threads as CPUs come and go:
512 */
513static int __cpuinit
514cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
515{
516 int hotcpu = (unsigned long)hcpu;
517
518 switch (action) {
519 case CPU_UP_PREPARE:
520 case CPU_UP_PREPARE_FROZEN:
521 if (watchdog_prepare_cpu(hotcpu))
522 return NOTIFY_BAD;
523 break;
524 case CPU_ONLINE:
525 case CPU_ONLINE_FROZEN:
526 if (watchdog_enable(hotcpu))
527 return NOTIFY_BAD;
528 break;
529#ifdef CONFIG_HOTPLUG_CPU
530 case CPU_UP_CANCELED:
531 case CPU_UP_CANCELED_FROZEN:
532 watchdog_disable(hotcpu);
533 break;
534 case CPU_DEAD:
535 case CPU_DEAD_FROZEN:
536 watchdog_disable(hotcpu);
537 break;
538#endif /* CONFIG_HOTPLUG_CPU */
539 }
540 return NOTIFY_OK;
541}
542
543static struct notifier_block __cpuinitdata cpu_nfb = {
544 .notifier_call = cpu_callback
545};
546
547static int __init spawn_watchdog_task(void)
548{
549 void *cpu = (void *)(long)smp_processor_id();
550 int err;
551
552 if (no_watchdog)
553 return 0;
554
555 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
556 WARN_ON(err == NOTIFY_BAD);
557
558 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
559 register_cpu_notifier(&cpu_nfb);
560
561 atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
562
563 return 0;
564}
565early_initcall(spawn_watchdog_task);