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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 *
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
9 * to those contributors as well.
10 */
11
12#define pr_fmt(fmt) "NMI watchdog: " fmt
13
14#include <linux/mm.h>
15#include <linux/cpu.h>
16#include <linux/nmi.h>
17#include <linux/init.h>
18#include <linux/delay.h>
19#include <linux/freezer.h>
20#include <linux/kthread.h>
21#include <linux/lockdep.h>
22#include <linux/notifier.h>
23#include <linux/module.h>
24#include <linux/sysctl.h>
25
26#include <asm/irq_regs.h>
27#include <linux/kvm_para.h>
28#include <linux/perf_event.h>
29
30int watchdog_enabled = 1;
31int __read_mostly watchdog_thresh = 10;
32
33static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
34static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
35static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
36static DEFINE_PER_CPU(bool, softlockup_touch_sync);
37static DEFINE_PER_CPU(bool, soft_watchdog_warn);
38#ifdef CONFIG_HARDLOCKUP_DETECTOR
39static DEFINE_PER_CPU(bool, hard_watchdog_warn);
40static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
41static 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
46/* boot commands */
47/*
48 * Should we panic when a soft-lockup or hard-lockup occurs:
49 */
50#ifdef CONFIG_HARDLOCKUP_DETECTOR
51static int hardlockup_panic =
52 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
53
54static int __init hardlockup_panic_setup(char *str)
55{
56 if (!strncmp(str, "panic", 5))
57 hardlockup_panic = 1;
58 else if (!strncmp(str, "nopanic", 7))
59 hardlockup_panic = 0;
60 else if (!strncmp(str, "0", 1))
61 watchdog_enabled = 0;
62 return 1;
63}
64__setup("nmi_watchdog=", hardlockup_panic_setup);
65#endif
66
67unsigned int __read_mostly softlockup_panic =
68 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
69
70static int __init softlockup_panic_setup(char *str)
71{
72 softlockup_panic = simple_strtoul(str, NULL, 0);
73
74 return 1;
75}
76__setup("softlockup_panic=", softlockup_panic_setup);
77
78static int __init nowatchdog_setup(char *str)
79{
80 watchdog_enabled = 0;
81 return 1;
82}
83__setup("nowatchdog", nowatchdog_setup);
84
85/* deprecated */
86static int __init nosoftlockup_setup(char *str)
87{
88 watchdog_enabled = 0;
89 return 1;
90}
91__setup("nosoftlockup", nosoftlockup_setup);
92/* */
93
94/*
95 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
96 * lockups can have false positives under extreme conditions. So we generally
97 * want a higher threshold for soft lockups than for hard lockups. So we couple
98 * the thresholds with a factor: we make the soft threshold twice the amount of
99 * time the hard threshold is.
100 */
101static int get_softlockup_thresh(void)
102{
103 return watchdog_thresh * 2;
104}
105
106/*
107 * Returns seconds, approximately. We don't need nanosecond
108 * resolution, and we don't need to waste time with a big divide when
109 * 2^30ns == 1.074s.
110 */
111static unsigned long get_timestamp(int this_cpu)
112{
113 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
114}
115
116static unsigned long get_sample_period(void)
117{
118 /*
119 * convert watchdog_thresh from seconds to ns
120 * the divide by 5 is to give hrtimer several chances (two
121 * or three with the current relation between the soft
122 * and hard thresholds) to increment before the
123 * hardlockup detector generates a warning
124 */
125 return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
126}
127
128/* Commands for resetting the watchdog */
129static void __touch_watchdog(void)
130{
131 int this_cpu = smp_processor_id();
132
133 __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
134}
135
136void touch_softlockup_watchdog(void)
137{
138 __this_cpu_write(watchdog_touch_ts, 0);
139}
140EXPORT_SYMBOL(touch_softlockup_watchdog);
141
142void touch_all_softlockup_watchdogs(void)
143{
144 int cpu;
145
146 /*
147 * this is done lockless
148 * do we care if a 0 races with a timestamp?
149 * all it means is the softlock check starts one cycle later
150 */
151 for_each_online_cpu(cpu)
152 per_cpu(watchdog_touch_ts, cpu) = 0;
153}
154
155#ifdef CONFIG_HARDLOCKUP_DETECTOR
156void touch_nmi_watchdog(void)
157{
158 if (watchdog_enabled) {
159 unsigned cpu;
160
161 for_each_present_cpu(cpu) {
162 if (per_cpu(watchdog_nmi_touch, cpu) != true)
163 per_cpu(watchdog_nmi_touch, cpu) = true;
164 }
165 }
166 touch_softlockup_watchdog();
167}
168EXPORT_SYMBOL(touch_nmi_watchdog);
169
170#endif
171
172void touch_softlockup_watchdog_sync(void)
173{
174 __raw_get_cpu_var(softlockup_touch_sync) = true;
175 __raw_get_cpu_var(watchdog_touch_ts) = 0;
176}
177
178#ifdef CONFIG_HARDLOCKUP_DETECTOR
179/* watchdog detector functions */
180static int is_hardlockup(void)
181{
182 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
183
184 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
185 return 1;
186
187 __this_cpu_write(hrtimer_interrupts_saved, hrint);
188 return 0;
189}
190#endif
191
192static int is_softlockup(unsigned long touch_ts)
193{
194 unsigned long now = get_timestamp(smp_processor_id());
195
196 /* Warn about unreasonable delays: */
197 if (time_after(now, touch_ts + get_softlockup_thresh()))
198 return now - touch_ts;
199
200 return 0;
201}
202
203#ifdef CONFIG_HARDLOCKUP_DETECTOR
204
205static struct perf_event_attr wd_hw_attr = {
206 .type = PERF_TYPE_HARDWARE,
207 .config = PERF_COUNT_HW_CPU_CYCLES,
208 .size = sizeof(struct perf_event_attr),
209 .pinned = 1,
210 .disabled = 1,
211};
212
213/* Callback function for perf event subsystem */
214static void watchdog_overflow_callback(struct perf_event *event,
215 struct perf_sample_data *data,
216 struct pt_regs *regs)
217{
218 /* Ensure the watchdog never gets throttled */
219 event->hw.interrupts = 0;
220
221 if (__this_cpu_read(watchdog_nmi_touch) == true) {
222 __this_cpu_write(watchdog_nmi_touch, false);
223 return;
224 }
225
226 /* check for a hardlockup
227 * This is done by making sure our timer interrupt
228 * is incrementing. The timer interrupt should have
229 * fired multiple times before we overflow'd. If it hasn't
230 * then this is a good indication the cpu is stuck
231 */
232 if (is_hardlockup()) {
233 int this_cpu = smp_processor_id();
234
235 /* only print hardlockups once */
236 if (__this_cpu_read(hard_watchdog_warn) == true)
237 return;
238
239 if (hardlockup_panic)
240 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
241 else
242 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
243
244 __this_cpu_write(hard_watchdog_warn, true);
245 return;
246 }
247
248 __this_cpu_write(hard_watchdog_warn, false);
249 return;
250}
251static void watchdog_interrupt_count(void)
252{
253 __this_cpu_inc(hrtimer_interrupts);
254}
255#else
256static inline void watchdog_interrupt_count(void) { return; }
257#endif /* CONFIG_HARDLOCKUP_DETECTOR */
258
259/* watchdog kicker functions */
260static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
261{
262 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
263 struct pt_regs *regs = get_irq_regs();
264 int duration;
265
266 /* kick the hardlockup detector */
267 watchdog_interrupt_count();
268
269 /* kick the softlockup detector */
270 wake_up_process(__this_cpu_read(softlockup_watchdog));
271
272 /* .. and repeat */
273 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
274
275 if (touch_ts == 0) {
276 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
277 /*
278 * If the time stamp was touched atomically
279 * make sure the scheduler tick is up to date.
280 */
281 __this_cpu_write(softlockup_touch_sync, false);
282 sched_clock_tick();
283 }
284
285 /* Clear the guest paused flag on watchdog reset */
286 kvm_check_and_clear_guest_paused();
287 __touch_watchdog();
288 return HRTIMER_RESTART;
289 }
290
291 /* check for a softlockup
292 * This is done by making sure a high priority task is
293 * being scheduled. The task touches the watchdog to
294 * indicate it is getting cpu time. If it hasn't then
295 * this is a good indication some task is hogging the cpu
296 */
297 duration = is_softlockup(touch_ts);
298 if (unlikely(duration)) {
299 /*
300 * If a virtual machine is stopped by the host it can look to
301 * the watchdog like a soft lockup, check to see if the host
302 * stopped the vm before we issue the warning
303 */
304 if (kvm_check_and_clear_guest_paused())
305 return HRTIMER_RESTART;
306
307 /* only warn once */
308 if (__this_cpu_read(soft_watchdog_warn) == true)
309 return HRTIMER_RESTART;
310
311 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
312 smp_processor_id(), duration,
313 current->comm, task_pid_nr(current));
314 print_modules();
315 print_irqtrace_events(current);
316 if (regs)
317 show_regs(regs);
318 else
319 dump_stack();
320
321 if (softlockup_panic)
322 panic("softlockup: hung tasks");
323 __this_cpu_write(soft_watchdog_warn, true);
324 } else
325 __this_cpu_write(soft_watchdog_warn, false);
326
327 return HRTIMER_RESTART;
328}
329
330
331/*
332 * The watchdog thread - touches the timestamp.
333 */
334static int watchdog(void *unused)
335{
336 struct sched_param param = { .sched_priority = 0 };
337 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
338
339 /* initialize timestamp */
340 __touch_watchdog();
341
342 /* kick off the timer for the hardlockup detector */
343 /* done here because hrtimer_start can only pin to smp_processor_id() */
344 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
345 HRTIMER_MODE_REL_PINNED);
346
347 set_current_state(TASK_INTERRUPTIBLE);
348 /*
349 * Run briefly (kicked by the hrtimer callback function) once every
350 * get_sample_period() seconds (4 seconds by default) to reset the
351 * softlockup timestamp. If this gets delayed for more than
352 * 2*watchdog_thresh seconds then the debug-printout triggers in
353 * watchdog_timer_fn().
354 */
355 while (!kthread_should_stop()) {
356 __touch_watchdog();
357 schedule();
358
359 if (kthread_should_stop())
360 break;
361
362 set_current_state(TASK_INTERRUPTIBLE);
363 }
364 /*
365 * Drop the policy/priority elevation during thread exit to avoid a
366 * scheduling latency spike.
367 */
368 __set_current_state(TASK_RUNNING);
369 sched_setscheduler(current, SCHED_NORMAL, ¶m);
370 return 0;
371}
372
373
374#ifdef CONFIG_HARDLOCKUP_DETECTOR
375/*
376 * People like the simple clean cpu node info on boot.
377 * Reduce the watchdog noise by only printing messages
378 * that are different from what cpu0 displayed.
379 */
380static unsigned long cpu0_err;
381
382static int watchdog_nmi_enable(int cpu)
383{
384 struct perf_event_attr *wd_attr;
385 struct perf_event *event = per_cpu(watchdog_ev, cpu);
386
387 /* is it already setup and enabled? */
388 if (event && event->state > PERF_EVENT_STATE_OFF)
389 goto out;
390
391 /* it is setup but not enabled */
392 if (event != NULL)
393 goto out_enable;
394
395 wd_attr = &wd_hw_attr;
396 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
397
398 /* Try to register using hardware perf events */
399 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
400
401 /* save cpu0 error for future comparision */
402 if (cpu == 0 && IS_ERR(event))
403 cpu0_err = PTR_ERR(event);
404
405 if (!IS_ERR(event)) {
406 /* only print for cpu0 or different than cpu0 */
407 if (cpu == 0 || cpu0_err)
408 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
409 goto out_save;
410 }
411
412 /* skip displaying the same error again */
413 if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
414 return PTR_ERR(event);
415
416 /* vary the KERN level based on the returned errno */
417 if (PTR_ERR(event) == -EOPNOTSUPP)
418 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
419 else if (PTR_ERR(event) == -ENOENT)
420 pr_warning("disabled (cpu%i): hardware events not enabled\n",
421 cpu);
422 else
423 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
424 cpu, PTR_ERR(event));
425 return PTR_ERR(event);
426
427 /* success path */
428out_save:
429 per_cpu(watchdog_ev, cpu) = event;
430out_enable:
431 perf_event_enable(per_cpu(watchdog_ev, cpu));
432out:
433 return 0;
434}
435
436static void watchdog_nmi_disable(int cpu)
437{
438 struct perf_event *event = per_cpu(watchdog_ev, cpu);
439
440 if (event) {
441 perf_event_disable(event);
442 per_cpu(watchdog_ev, cpu) = NULL;
443
444 /* should be in cleanup, but blocks oprofile */
445 perf_event_release_kernel(event);
446 }
447 return;
448}
449#else
450static int watchdog_nmi_enable(int cpu) { return 0; }
451static void watchdog_nmi_disable(int cpu) { return; }
452#endif /* CONFIG_HARDLOCKUP_DETECTOR */
453
454/* prepare/enable/disable routines */
455static void watchdog_prepare_cpu(int cpu)
456{
457 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
458
459 WARN_ON(per_cpu(softlockup_watchdog, cpu));
460 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
461 hrtimer->function = watchdog_timer_fn;
462}
463
464static int watchdog_enable(int cpu)
465{
466 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
467 int err = 0;
468
469 /* enable the perf event */
470 err = watchdog_nmi_enable(cpu);
471
472 /* Regardless of err above, fall through and start softlockup */
473
474 /* create the watchdog thread */
475 if (!p) {
476 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
477 p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
478 if (IS_ERR(p)) {
479 pr_err("softlockup watchdog for %i failed\n", cpu);
480 if (!err) {
481 /* if hardlockup hasn't already set this */
482 err = PTR_ERR(p);
483 /* and disable the perf event */
484 watchdog_nmi_disable(cpu);
485 }
486 goto out;
487 }
488 sched_setscheduler(p, SCHED_FIFO, ¶m);
489 kthread_bind(p, cpu);
490 per_cpu(watchdog_touch_ts, cpu) = 0;
491 per_cpu(softlockup_watchdog, cpu) = p;
492 wake_up_process(p);
493 }
494
495out:
496 return err;
497}
498
499static void watchdog_disable(int cpu)
500{
501 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
502 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
503
504 /*
505 * cancel the timer first to stop incrementing the stats
506 * and waking up the kthread
507 */
508 hrtimer_cancel(hrtimer);
509
510 /* disable the perf event */
511 watchdog_nmi_disable(cpu);
512
513 /* stop the watchdog thread */
514 if (p) {
515 per_cpu(softlockup_watchdog, cpu) = NULL;
516 kthread_stop(p);
517 }
518}
519
520/* sysctl functions */
521#ifdef CONFIG_SYSCTL
522static void watchdog_enable_all_cpus(void)
523{
524 int cpu;
525
526 watchdog_enabled = 0;
527
528 for_each_online_cpu(cpu)
529 if (!watchdog_enable(cpu))
530 /* if any cpu succeeds, watchdog is considered
531 enabled for the system */
532 watchdog_enabled = 1;
533
534 if (!watchdog_enabled)
535 pr_err("failed to be enabled on some cpus\n");
536
537}
538
539static void watchdog_disable_all_cpus(void)
540{
541 int cpu;
542
543 for_each_online_cpu(cpu)
544 watchdog_disable(cpu);
545
546 /* if all watchdogs are disabled, then they are disabled for the system */
547 watchdog_enabled = 0;
548}
549
550
551/*
552 * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
553 */
554
555int proc_dowatchdog(struct ctl_table *table, int write,
556 void __user *buffer, size_t *lenp, loff_t *ppos)
557{
558 int ret;
559
560 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
561 if (ret || !write)
562 goto out;
563
564 if (watchdog_enabled && watchdog_thresh)
565 watchdog_enable_all_cpus();
566 else
567 watchdog_disable_all_cpus();
568
569out:
570 return ret;
571}
572#endif /* CONFIG_SYSCTL */
573
574
575/*
576 * Create/destroy watchdog threads as CPUs come and go:
577 */
578static int __cpuinit
579cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
580{
581 int hotcpu = (unsigned long)hcpu;
582
583 switch (action) {
584 case CPU_UP_PREPARE:
585 case CPU_UP_PREPARE_FROZEN:
586 watchdog_prepare_cpu(hotcpu);
587 break;
588 case CPU_ONLINE:
589 case CPU_ONLINE_FROZEN:
590 if (watchdog_enabled)
591 watchdog_enable(hotcpu);
592 break;
593#ifdef CONFIG_HOTPLUG_CPU
594 case CPU_UP_CANCELED:
595 case CPU_UP_CANCELED_FROZEN:
596 watchdog_disable(hotcpu);
597 break;
598 case CPU_DEAD:
599 case CPU_DEAD_FROZEN:
600 watchdog_disable(hotcpu);
601 break;
602#endif /* CONFIG_HOTPLUG_CPU */
603 }
604
605 /*
606 * hardlockup and softlockup are not important enough
607 * to block cpu bring up. Just always succeed and
608 * rely on printk output to flag problems.
609 */
610 return NOTIFY_OK;
611}
612
613static struct notifier_block __cpuinitdata cpu_nfb = {
614 .notifier_call = cpu_callback
615};
616
617void __init lockup_detector_init(void)
618{
619 void *cpu = (void *)(long)smp_processor_id();
620 int err;
621
622 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
623 WARN_ON(notifier_to_errno(err));
624
625 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
626 register_cpu_notifier(&cpu_nfb);
627
628 return;
629}
1/*
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 = 1;
31int __read_mostly watchdog_thresh = 10;
32
33static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
34static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
35static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
36static DEFINE_PER_CPU(bool, softlockup_touch_sync);
37static DEFINE_PER_CPU(bool, soft_watchdog_warn);
38#ifdef CONFIG_HARDLOCKUP_DETECTOR
39static DEFINE_PER_CPU(bool, hard_watchdog_warn);
40static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
41static 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
46/* boot commands */
47/*
48 * Should we panic when a soft-lockup or hard-lockup occurs:
49 */
50#ifdef CONFIG_HARDLOCKUP_DETECTOR
51static int hardlockup_panic =
52 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
53
54static int __init hardlockup_panic_setup(char *str)
55{
56 if (!strncmp(str, "panic", 5))
57 hardlockup_panic = 1;
58 else if (!strncmp(str, "nopanic", 7))
59 hardlockup_panic = 0;
60 else if (!strncmp(str, "0", 1))
61 watchdog_enabled = 0;
62 return 1;
63}
64__setup("nmi_watchdog=", hardlockup_panic_setup);
65#endif
66
67unsigned int __read_mostly softlockup_panic =
68 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
69
70static int __init softlockup_panic_setup(char *str)
71{
72 softlockup_panic = simple_strtoul(str, NULL, 0);
73
74 return 1;
75}
76__setup("softlockup_panic=", softlockup_panic_setup);
77
78static int __init nowatchdog_setup(char *str)
79{
80 watchdog_enabled = 0;
81 return 1;
82}
83__setup("nowatchdog", nowatchdog_setup);
84
85/* deprecated */
86static int __init nosoftlockup_setup(char *str)
87{
88 watchdog_enabled = 0;
89 return 1;
90}
91__setup("nosoftlockup", nosoftlockup_setup);
92/* */
93
94/*
95 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
96 * lockups can have false positives under extreme conditions. So we generally
97 * want a higher threshold for soft lockups than for hard lockups. So we couple
98 * the thresholds with a factor: we make the soft threshold twice the amount of
99 * time the hard threshold is.
100 */
101static int get_softlockup_thresh(void)
102{
103 return watchdog_thresh * 2;
104}
105
106/*
107 * Returns seconds, approximately. We don't need nanosecond
108 * resolution, and we don't need to waste time with a big divide when
109 * 2^30ns == 1.074s.
110 */
111static unsigned long get_timestamp(int this_cpu)
112{
113 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
114}
115
116static unsigned long get_sample_period(void)
117{
118 /*
119 * convert watchdog_thresh from seconds to ns
120 * the divide by 5 is to give hrtimer 5 chances to
121 * increment before the hardlockup detector generates
122 * a warning
123 */
124 return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
125}
126
127/* Commands for resetting the watchdog */
128static void __touch_watchdog(void)
129{
130 int this_cpu = smp_processor_id();
131
132 __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
133}
134
135void touch_softlockup_watchdog(void)
136{
137 __this_cpu_write(watchdog_touch_ts, 0);
138}
139EXPORT_SYMBOL(touch_softlockup_watchdog);
140
141void touch_all_softlockup_watchdogs(void)
142{
143 int cpu;
144
145 /*
146 * this is done lockless
147 * do we care if a 0 races with a timestamp?
148 * all it means is the softlock check starts one cycle later
149 */
150 for_each_online_cpu(cpu)
151 per_cpu(watchdog_touch_ts, cpu) = 0;
152}
153
154#ifdef CONFIG_HARDLOCKUP_DETECTOR
155void touch_nmi_watchdog(void)
156{
157 if (watchdog_enabled) {
158 unsigned cpu;
159
160 for_each_present_cpu(cpu) {
161 if (per_cpu(watchdog_nmi_touch, cpu) != true)
162 per_cpu(watchdog_nmi_touch, cpu) = true;
163 }
164 }
165 touch_softlockup_watchdog();
166}
167EXPORT_SYMBOL(touch_nmi_watchdog);
168
169#endif
170
171void touch_softlockup_watchdog_sync(void)
172{
173 __raw_get_cpu_var(softlockup_touch_sync) = true;
174 __raw_get_cpu_var(watchdog_touch_ts) = 0;
175}
176
177#ifdef CONFIG_HARDLOCKUP_DETECTOR
178/* watchdog detector functions */
179static int is_hardlockup(void)
180{
181 unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
182
183 if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
184 return 1;
185
186 __this_cpu_write(hrtimer_interrupts_saved, hrint);
187 return 0;
188}
189#endif
190
191static int is_softlockup(unsigned long touch_ts)
192{
193 unsigned long now = get_timestamp(smp_processor_id());
194
195 /* Warn about unreasonable delays: */
196 if (time_after(now, touch_ts + get_softlockup_thresh()))
197 return now - touch_ts;
198
199 return 0;
200}
201
202#ifdef CONFIG_HARDLOCKUP_DETECTOR
203
204static struct perf_event_attr wd_hw_attr = {
205 .type = PERF_TYPE_HARDWARE,
206 .config = PERF_COUNT_HW_CPU_CYCLES,
207 .size = sizeof(struct perf_event_attr),
208 .pinned = 1,
209 .disabled = 1,
210};
211
212/* Callback function for perf event subsystem */
213static void watchdog_overflow_callback(struct perf_event *event,
214 struct perf_sample_data *data,
215 struct pt_regs *regs)
216{
217 /* Ensure the watchdog never gets throttled */
218 event->hw.interrupts = 0;
219
220 if (__this_cpu_read(watchdog_nmi_touch) == true) {
221 __this_cpu_write(watchdog_nmi_touch, false);
222 return;
223 }
224
225 /* check for a hardlockup
226 * This is done by making sure our timer interrupt
227 * is incrementing. The timer interrupt should have
228 * fired multiple times before we overflow'd. If it hasn't
229 * then this is a good indication the cpu is stuck
230 */
231 if (is_hardlockup()) {
232 int this_cpu = smp_processor_id();
233
234 /* only print hardlockups once */
235 if (__this_cpu_read(hard_watchdog_warn) == true)
236 return;
237
238 if (hardlockup_panic)
239 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
240 else
241 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
242
243 __this_cpu_write(hard_watchdog_warn, true);
244 return;
245 }
246
247 __this_cpu_write(hard_watchdog_warn, false);
248 return;
249}
250static void watchdog_interrupt_count(void)
251{
252 __this_cpu_inc(hrtimer_interrupts);
253}
254#else
255static inline void watchdog_interrupt_count(void) { return; }
256#endif /* CONFIG_HARDLOCKUP_DETECTOR */
257
258/* watchdog kicker functions */
259static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
260{
261 unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
262 struct pt_regs *regs = get_irq_regs();
263 int duration;
264
265 /* kick the hardlockup detector */
266 watchdog_interrupt_count();
267
268 /* kick the softlockup detector */
269 wake_up_process(__this_cpu_read(softlockup_watchdog));
270
271 /* .. and repeat */
272 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
273
274 if (touch_ts == 0) {
275 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
276 /*
277 * If the time stamp was touched atomically
278 * make sure the scheduler tick is up to date.
279 */
280 __this_cpu_write(softlockup_touch_sync, false);
281 sched_clock_tick();
282 }
283 __touch_watchdog();
284 return HRTIMER_RESTART;
285 }
286
287 /* check for a softlockup
288 * This is done by making sure a high priority task is
289 * being scheduled. The task touches the watchdog to
290 * indicate it is getting cpu time. If it hasn't then
291 * this is a good indication some task is hogging the cpu
292 */
293 duration = is_softlockup(touch_ts);
294 if (unlikely(duration)) {
295 /* only warn once */
296 if (__this_cpu_read(soft_watchdog_warn) == true)
297 return HRTIMER_RESTART;
298
299 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
300 smp_processor_id(), duration,
301 current->comm, task_pid_nr(current));
302 print_modules();
303 print_irqtrace_events(current);
304 if (regs)
305 show_regs(regs);
306 else
307 dump_stack();
308
309 if (softlockup_panic)
310 panic("softlockup: hung tasks");
311 __this_cpu_write(soft_watchdog_warn, true);
312 } else
313 __this_cpu_write(soft_watchdog_warn, false);
314
315 return HRTIMER_RESTART;
316}
317
318
319/*
320 * The watchdog thread - touches the timestamp.
321 */
322static int watchdog(void *unused)
323{
324 static struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
325 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
326
327 sched_setscheduler(current, SCHED_FIFO, ¶m);
328
329 /* initialize timestamp */
330 __touch_watchdog();
331
332 /* kick off the timer for the hardlockup detector */
333 /* done here because hrtimer_start can only pin to smp_processor_id() */
334 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
335 HRTIMER_MODE_REL_PINNED);
336
337 set_current_state(TASK_INTERRUPTIBLE);
338 /*
339 * Run briefly once per second to reset the softlockup timestamp.
340 * If this gets delayed for more than 60 seconds then the
341 * debug-printout triggers in watchdog_timer_fn().
342 */
343 while (!kthread_should_stop()) {
344 __touch_watchdog();
345 schedule();
346
347 if (kthread_should_stop())
348 break;
349
350 set_current_state(TASK_INTERRUPTIBLE);
351 }
352 __set_current_state(TASK_RUNNING);
353
354 return 0;
355}
356
357
358#ifdef CONFIG_HARDLOCKUP_DETECTOR
359static int watchdog_nmi_enable(int cpu)
360{
361 struct perf_event_attr *wd_attr;
362 struct perf_event *event = per_cpu(watchdog_ev, cpu);
363
364 /* is it already setup and enabled? */
365 if (event && event->state > PERF_EVENT_STATE_OFF)
366 goto out;
367
368 /* it is setup but not enabled */
369 if (event != NULL)
370 goto out_enable;
371
372 wd_attr = &wd_hw_attr;
373 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
374
375 /* Try to register using hardware perf events */
376 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
377 if (!IS_ERR(event)) {
378 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
379 goto out_save;
380 }
381
382
383 /* vary the KERN level based on the returned errno */
384 if (PTR_ERR(event) == -EOPNOTSUPP)
385 printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
386 else if (PTR_ERR(event) == -ENOENT)
387 printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
388 else
389 printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
390 return PTR_ERR(event);
391
392 /* success path */
393out_save:
394 per_cpu(watchdog_ev, cpu) = event;
395out_enable:
396 perf_event_enable(per_cpu(watchdog_ev, cpu));
397out:
398 return 0;
399}
400
401static void watchdog_nmi_disable(int cpu)
402{
403 struct perf_event *event = per_cpu(watchdog_ev, cpu);
404
405 if (event) {
406 perf_event_disable(event);
407 per_cpu(watchdog_ev, cpu) = NULL;
408
409 /* should be in cleanup, but blocks oprofile */
410 perf_event_release_kernel(event);
411 }
412 return;
413}
414#else
415static int watchdog_nmi_enable(int cpu) { return 0; }
416static void watchdog_nmi_disable(int cpu) { return; }
417#endif /* CONFIG_HARDLOCKUP_DETECTOR */
418
419/* prepare/enable/disable routines */
420static void watchdog_prepare_cpu(int cpu)
421{
422 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
423
424 WARN_ON(per_cpu(softlockup_watchdog, cpu));
425 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
426 hrtimer->function = watchdog_timer_fn;
427}
428
429static int watchdog_enable(int cpu)
430{
431 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
432 int err = 0;
433
434 /* enable the perf event */
435 err = watchdog_nmi_enable(cpu);
436
437 /* Regardless of err above, fall through and start softlockup */
438
439 /* create the watchdog thread */
440 if (!p) {
441 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
442 if (IS_ERR(p)) {
443 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
444 if (!err) {
445 /* if hardlockup hasn't already set this */
446 err = PTR_ERR(p);
447 /* and disable the perf event */
448 watchdog_nmi_disable(cpu);
449 }
450 goto out;
451 }
452 kthread_bind(p, cpu);
453 per_cpu(watchdog_touch_ts, cpu) = 0;
454 per_cpu(softlockup_watchdog, cpu) = p;
455 wake_up_process(p);
456 }
457
458out:
459 return err;
460}
461
462static void watchdog_disable(int cpu)
463{
464 struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
465 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
466
467 /*
468 * cancel the timer first to stop incrementing the stats
469 * and waking up the kthread
470 */
471 hrtimer_cancel(hrtimer);
472
473 /* disable the perf event */
474 watchdog_nmi_disable(cpu);
475
476 /* stop the watchdog thread */
477 if (p) {
478 per_cpu(softlockup_watchdog, cpu) = NULL;
479 kthread_stop(p);
480 }
481}
482
483static void watchdog_enable_all_cpus(void)
484{
485 int cpu;
486
487 watchdog_enabled = 0;
488
489 for_each_online_cpu(cpu)
490 if (!watchdog_enable(cpu))
491 /* if any cpu succeeds, watchdog is considered
492 enabled for the system */
493 watchdog_enabled = 1;
494
495 if (!watchdog_enabled)
496 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
497
498}
499
500static void watchdog_disable_all_cpus(void)
501{
502 int cpu;
503
504 for_each_online_cpu(cpu)
505 watchdog_disable(cpu);
506
507 /* if all watchdogs are disabled, then they are disabled for the system */
508 watchdog_enabled = 0;
509}
510
511
512/* sysctl functions */
513#ifdef CONFIG_SYSCTL
514/*
515 * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
516 */
517
518int proc_dowatchdog(struct ctl_table *table, int write,
519 void __user *buffer, size_t *lenp, loff_t *ppos)
520{
521 int ret;
522
523 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
524 if (ret || !write)
525 goto out;
526
527 if (watchdog_enabled && watchdog_thresh)
528 watchdog_enable_all_cpus();
529 else
530 watchdog_disable_all_cpus();
531
532out:
533 return ret;
534}
535#endif /* CONFIG_SYSCTL */
536
537
538/*
539 * Create/destroy watchdog threads as CPUs come and go:
540 */
541static int __cpuinit
542cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
543{
544 int hotcpu = (unsigned long)hcpu;
545
546 switch (action) {
547 case CPU_UP_PREPARE:
548 case CPU_UP_PREPARE_FROZEN:
549 watchdog_prepare_cpu(hotcpu);
550 break;
551 case CPU_ONLINE:
552 case CPU_ONLINE_FROZEN:
553 if (watchdog_enabled)
554 watchdog_enable(hotcpu);
555 break;
556#ifdef CONFIG_HOTPLUG_CPU
557 case CPU_UP_CANCELED:
558 case CPU_UP_CANCELED_FROZEN:
559 watchdog_disable(hotcpu);
560 break;
561 case CPU_DEAD:
562 case CPU_DEAD_FROZEN:
563 watchdog_disable(hotcpu);
564 break;
565#endif /* CONFIG_HOTPLUG_CPU */
566 }
567
568 /*
569 * hardlockup and softlockup are not important enough
570 * to block cpu bring up. Just always succeed and
571 * rely on printk output to flag problems.
572 */
573 return NOTIFY_OK;
574}
575
576static struct notifier_block __cpuinitdata cpu_nfb = {
577 .notifier_call = cpu_callback
578};
579
580void __init lockup_detector_init(void)
581{
582 void *cpu = (void *)(long)smp_processor_id();
583 int err;
584
585 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
586 WARN_ON(notifier_to_errno(err));
587
588 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
589 register_cpu_notifier(&cpu_nfb);
590
591 return;
592}