df30ee08bdd42161105a9564871cc80491d0b7aa
[linux-2.6.git] / kernel / watchdog.c
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/perf_event.h>
28
29 int watchdog_enabled = 1;
30 int __read_mostly watchdog_thresh = 10;
31
32 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
33 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
34 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
35 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
36 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
37 #ifdef CONFIG_HARDLOCKUP_DETECTOR
38 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
39 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
40 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
42 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
43 #endif
44
45 /* boot commands */
46 /*
47  * Should we panic when a soft-lockup or hard-lockup occurs:
48  */
49 #ifdef CONFIG_HARDLOCKUP_DETECTOR
50 static int hardlockup_panic =
51                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
52
53 static int __init hardlockup_panic_setup(char *str)
54 {
55         if (!strncmp(str, "panic", 5))
56                 hardlockup_panic = 1;
57         else if (!strncmp(str, "nopanic", 7))
58                 hardlockup_panic = 0;
59         else if (!strncmp(str, "0", 1))
60                 watchdog_enabled = 0;
61         return 1;
62 }
63 __setup("nmi_watchdog=", hardlockup_panic_setup);
64 #endif
65
66 unsigned int __read_mostly softlockup_panic =
67                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
68
69 static 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
77 static int __init nowatchdog_setup(char *str)
78 {
79         watchdog_enabled = 0;
80         return 1;
81 }
82 __setup("nowatchdog", nowatchdog_setup);
83
84 /* deprecated */
85 static int __init nosoftlockup_setup(char *str)
86 {
87         watchdog_enabled = 0;
88         return 1;
89 }
90 __setup("nosoftlockup", nosoftlockup_setup);
91 /*  */
92
93 /*
94  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
95  * lockups can have false positives under extreme conditions. So we generally
96  * want a higher threshold for soft lockups than for hard lockups. So we couple
97  * the thresholds with a factor: we make the soft threshold twice the amount of
98  * time the hard threshold is.
99  */
100 static int get_softlockup_thresh(void)
101 {
102         return watchdog_thresh * 2;
103 }
104
105 /*
106  * Returns seconds, approximately.  We don't need nanosecond
107  * resolution, and we don't need to waste time with a big divide when
108  * 2^30ns == 1.074s.
109  */
110 static unsigned long get_timestamp(int this_cpu)
111 {
112         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
113 }
114
115 static unsigned long get_sample_period(void)
116 {
117         /*
118          * convert watchdog_thresh from seconds to ns
119          * the divide by 5 is to give hrtimer several chances (two
120          * or three with the current relation between the soft
121          * and hard thresholds) to increment before the
122          * hardlockup detector generates a warning
123          */
124         return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
125 }
126
127 /* Commands for resetting the watchdog */
128 static 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
135 void touch_softlockup_watchdog(void)
136 {
137         __this_cpu_write(watchdog_touch_ts, 0);
138 }
139 EXPORT_SYMBOL(touch_softlockup_watchdog);
140
141 void 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
155 void 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 }
167 EXPORT_SYMBOL(touch_nmi_watchdog);
168
169 #endif
170
171 void 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 */
179 static 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
191 static 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
204 static 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 */
213 static 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 }
250 static void watchdog_interrupt_count(void)
251 {
252         __this_cpu_inc(hrtimer_interrupts);
253 }
254 #else
255 static inline void watchdog_interrupt_count(void) { return; }
256 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
257
258 /* watchdog kicker functions */
259 static 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_EMERG "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  */
322 static int watchdog(void *unused)
323 {
324         struct sched_param param = { .sched_priority = 0 };
325         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
326
327         /* initialize timestamp */
328         __touch_watchdog();
329
330         /* kick off the timer for the hardlockup detector */
331         /* done here because hrtimer_start can only pin to smp_processor_id() */
332         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
333                       HRTIMER_MODE_REL_PINNED);
334
335         set_current_state(TASK_INTERRUPTIBLE);
336         /*
337          * Run briefly (kicked by the hrtimer callback function) once every
338          * get_sample_period() seconds (4 seconds by default) to reset the
339          * softlockup timestamp. If this gets delayed for more than
340          * 2*watchdog_thresh seconds then the debug-printout triggers in
341          * 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         /*
353          * Drop the policy/priority elevation during thread exit to avoid a
354          * scheduling latency spike.
355          */
356         __set_current_state(TASK_RUNNING);
357         sched_setscheduler(current, SCHED_NORMAL, &param);
358         return 0;
359 }
360
361
362 #ifdef CONFIG_HARDLOCKUP_DETECTOR
363 static int watchdog_nmi_enable(int cpu)
364 {
365         struct perf_event_attr *wd_attr;
366         struct perf_event *event = per_cpu(watchdog_ev, cpu);
367
368         /* is it already setup and enabled? */
369         if (event && event->state > PERF_EVENT_STATE_OFF)
370                 goto out;
371
372         /* it is setup but not enabled */
373         if (event != NULL)
374                 goto out_enable;
375
376         wd_attr = &wd_hw_attr;
377         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
378
379         /* Try to register using hardware perf events */
380         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
381         if (!IS_ERR(event)) {
382                 pr_info("enabled, takes one hw-pmu counter.\n");
383                 goto out_save;
384         }
385
386
387         /* vary the KERN level based on the returned errno */
388         if (PTR_ERR(event) == -EOPNOTSUPP)
389                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
390         else if (PTR_ERR(event) == -ENOENT)
391                 pr_warning("disabled (cpu%i): hardware events not enabled\n",
392                          cpu);
393         else
394                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
395                         cpu, PTR_ERR(event));
396         return PTR_ERR(event);
397
398         /* success path */
399 out_save:
400         per_cpu(watchdog_ev, cpu) = event;
401 out_enable:
402         perf_event_enable(per_cpu(watchdog_ev, cpu));
403 out:
404         return 0;
405 }
406
407 static void watchdog_nmi_disable(int cpu)
408 {
409         struct perf_event *event = per_cpu(watchdog_ev, cpu);
410
411         if (event) {
412                 perf_event_disable(event);
413                 per_cpu(watchdog_ev, cpu) = NULL;
414
415                 /* should be in cleanup, but blocks oprofile */
416                 perf_event_release_kernel(event);
417         }
418         return;
419 }
420 #else
421 static int watchdog_nmi_enable(int cpu) { return 0; }
422 static void watchdog_nmi_disable(int cpu) { return; }
423 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
424
425 /* prepare/enable/disable routines */
426 static void watchdog_prepare_cpu(int cpu)
427 {
428         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
429
430         WARN_ON(per_cpu(softlockup_watchdog, cpu));
431         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
432         hrtimer->function = watchdog_timer_fn;
433 }
434
435 static int watchdog_enable(int cpu)
436 {
437         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
438         int err = 0;
439
440         /* enable the perf event */
441         err = watchdog_nmi_enable(cpu);
442
443         /* Regardless of err above, fall through and start softlockup */
444
445         /* create the watchdog thread */
446         if (!p) {
447                 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
448                 p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
449                 if (IS_ERR(p)) {
450                         pr_err("softlockup watchdog for %i failed\n", cpu);
451                         if (!err) {
452                                 /* if hardlockup hasn't already set this */
453                                 err = PTR_ERR(p);
454                                 /* and disable the perf event */
455                                 watchdog_nmi_disable(cpu);
456                         }
457                         goto out;
458                 }
459                 sched_setscheduler(p, SCHED_FIFO, &param);
460                 kthread_bind(p, cpu);
461                 per_cpu(watchdog_touch_ts, cpu) = 0;
462                 per_cpu(softlockup_watchdog, cpu) = p;
463                 wake_up_process(p);
464         }
465
466 out:
467         return err;
468 }
469
470 static void watchdog_disable(int cpu)
471 {
472         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
473         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
474
475         /*
476          * cancel the timer first to stop incrementing the stats
477          * and waking up the kthread
478          */
479         hrtimer_cancel(hrtimer);
480
481         /* disable the perf event */
482         watchdog_nmi_disable(cpu);
483
484         /* stop the watchdog thread */
485         if (p) {
486                 per_cpu(softlockup_watchdog, cpu) = NULL;
487                 kthread_stop(p);
488         }
489 }
490
491 /* sysctl functions */
492 #ifdef CONFIG_SYSCTL
493 static void watchdog_enable_all_cpus(void)
494 {
495         int cpu;
496
497         watchdog_enabled = 0;
498
499         for_each_online_cpu(cpu)
500                 if (!watchdog_enable(cpu))
501                         /* if any cpu succeeds, watchdog is considered
502                            enabled for the system */
503                         watchdog_enabled = 1;
504
505         if (!watchdog_enabled)
506                 pr_err("failed to be enabled on some cpus\n");
507
508 }
509
510 static void watchdog_disable_all_cpus(void)
511 {
512         int cpu;
513
514         for_each_online_cpu(cpu)
515                 watchdog_disable(cpu);
516
517         /* if all watchdogs are disabled, then they are disabled for the system */
518         watchdog_enabled = 0;
519 }
520
521
522 /*
523  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
524  */
525
526 int proc_dowatchdog(struct ctl_table *table, int write,
527                     void __user *buffer, size_t *lenp, loff_t *ppos)
528 {
529         int ret;
530
531         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
532         if (ret || !write)
533                 goto out;
534
535         if (watchdog_enabled && watchdog_thresh)
536                 watchdog_enable_all_cpus();
537         else
538                 watchdog_disable_all_cpus();
539
540 out:
541         return ret;
542 }
543 #endif /* CONFIG_SYSCTL */
544
545
546 /*
547  * Create/destroy watchdog threads as CPUs come and go:
548  */
549 static int __cpuinit
550 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
551 {
552         int hotcpu = (unsigned long)hcpu;
553
554         switch (action) {
555         case CPU_UP_PREPARE:
556         case CPU_UP_PREPARE_FROZEN:
557                 watchdog_prepare_cpu(hotcpu);
558                 break;
559         case CPU_ONLINE:
560         case CPU_ONLINE_FROZEN:
561                 if (watchdog_enabled)
562                         watchdog_enable(hotcpu);
563                 break;
564 #ifdef CONFIG_HOTPLUG_CPU
565         case CPU_UP_CANCELED:
566         case CPU_UP_CANCELED_FROZEN:
567                 watchdog_disable(hotcpu);
568                 break;
569         case CPU_DEAD:
570         case CPU_DEAD_FROZEN:
571                 watchdog_disable(hotcpu);
572                 break;
573 #endif /* CONFIG_HOTPLUG_CPU */
574         }
575
576         /*
577          * hardlockup and softlockup are not important enough
578          * to block cpu bring up.  Just always succeed and
579          * rely on printk output to flag problems.
580          */
581         return NOTIFY_OK;
582 }
583
584 static struct notifier_block __cpuinitdata cpu_nfb = {
585         .notifier_call = cpu_callback
586 };
587
588 void __init lockup_detector_init(void)
589 {
590         void *cpu = (void *)(long)smp_processor_id();
591         int err;
592
593         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
594         WARN_ON(notifier_to_errno(err));
595
596         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
597         register_cpu_notifier(&cpu_nfb);
598
599         return;
600 }