watchdog: Fix code/comments mismatches
[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 #include <linux/mm.h>
13 #include <linux/cpu.h>
14 #include <linux/nmi.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/freezer.h>
18 #include <linux/kthread.h>
19 #include <linux/lockdep.h>
20 #include <linux/notifier.h>
21 #include <linux/module.h>
22 #include <linux/sysctl.h>
23
24 #include <asm/irq_regs.h>
25 #include <linux/perf_event.h>
26
27 int watchdog_enabled = 1;
28 int __read_mostly watchdog_thresh = 10;
29
30 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
31 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
32 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
33 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
34 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
35 #ifdef CONFIG_HARDLOCKUP_DETECTOR
36 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
37 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
38 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
39 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
40 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
41 #endif
42
43 /* boot commands */
44 /*
45  * Should we panic when a soft-lockup or hard-lockup occurs:
46  */
47 #ifdef CONFIG_HARDLOCKUP_DETECTOR
48 static int hardlockup_panic =
49                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
50
51 static int __init hardlockup_panic_setup(char *str)
52 {
53         if (!strncmp(str, "panic", 5))
54                 hardlockup_panic = 1;
55         else if (!strncmp(str, "nopanic", 7))
56                 hardlockup_panic = 0;
57         else if (!strncmp(str, "0", 1))
58                 watchdog_enabled = 0;
59         return 1;
60 }
61 __setup("nmi_watchdog=", hardlockup_panic_setup);
62 #endif
63
64 unsigned int __read_mostly softlockup_panic =
65                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
66
67 static int __init softlockup_panic_setup(char *str)
68 {
69         softlockup_panic = simple_strtoul(str, NULL, 0);
70
71         return 1;
72 }
73 __setup("softlockup_panic=", softlockup_panic_setup);
74
75 static int __init nowatchdog_setup(char *str)
76 {
77         watchdog_enabled = 0;
78         return 1;
79 }
80 __setup("nowatchdog", nowatchdog_setup);
81
82 /* deprecated */
83 static int __init nosoftlockup_setup(char *str)
84 {
85         watchdog_enabled = 0;
86         return 1;
87 }
88 __setup("nosoftlockup", nosoftlockup_setup);
89 /*  */
90
91 /*
92  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
93  * lockups can have false positives under extreme conditions. So we generally
94  * want a higher threshold for soft lockups than for hard lockups. So we couple
95  * the thresholds with a factor: we make the soft threshold twice the amount of
96  * time the hard threshold is.
97  */
98 static int get_softlockup_thresh(void)
99 {
100         return watchdog_thresh * 2;
101 }
102
103 /*
104  * Returns seconds, approximately.  We don't need nanosecond
105  * resolution, and we don't need to waste time with a big divide when
106  * 2^30ns == 1.074s.
107  */
108 static unsigned long get_timestamp(int this_cpu)
109 {
110         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
111 }
112
113 static unsigned long get_sample_period(void)
114 {
115         /*
116          * convert watchdog_thresh from seconds to ns
117          * the divide by 5 is to give hrtimer several chances (two
118          * or three with the current relation between the soft
119          * and hard thresholds) to increment before the
120          * hardlockup detector generates a warning
121          */
122         return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
123 }
124
125 /* Commands for resetting the watchdog */
126 static void __touch_watchdog(void)
127 {
128         int this_cpu = smp_processor_id();
129
130         __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
131 }
132
133 void touch_softlockup_watchdog(void)
134 {
135         __this_cpu_write(watchdog_touch_ts, 0);
136 }
137 EXPORT_SYMBOL(touch_softlockup_watchdog);
138
139 void touch_all_softlockup_watchdogs(void)
140 {
141         int cpu;
142
143         /*
144          * this is done lockless
145          * do we care if a 0 races with a timestamp?
146          * all it means is the softlock check starts one cycle later
147          */
148         for_each_online_cpu(cpu)
149                 per_cpu(watchdog_touch_ts, cpu) = 0;
150 }
151
152 #ifdef CONFIG_HARDLOCKUP_DETECTOR
153 void touch_nmi_watchdog(void)
154 {
155         if (watchdog_enabled) {
156                 unsigned cpu;
157
158                 for_each_present_cpu(cpu) {
159                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
160                                 per_cpu(watchdog_nmi_touch, cpu) = true;
161                 }
162         }
163         touch_softlockup_watchdog();
164 }
165 EXPORT_SYMBOL(touch_nmi_watchdog);
166
167 #endif
168
169 void touch_softlockup_watchdog_sync(void)
170 {
171         __raw_get_cpu_var(softlockup_touch_sync) = true;
172         __raw_get_cpu_var(watchdog_touch_ts) = 0;
173 }
174
175 #ifdef CONFIG_HARDLOCKUP_DETECTOR
176 /* watchdog detector functions */
177 static int is_hardlockup(void)
178 {
179         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
180
181         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
182                 return 1;
183
184         __this_cpu_write(hrtimer_interrupts_saved, hrint);
185         return 0;
186 }
187 #endif
188
189 static int is_softlockup(unsigned long touch_ts)
190 {
191         unsigned long now = get_timestamp(smp_processor_id());
192
193         /* Warn about unreasonable delays: */
194         if (time_after(now, touch_ts + get_softlockup_thresh()))
195                 return now - touch_ts;
196
197         return 0;
198 }
199
200 #ifdef CONFIG_HARDLOCKUP_DETECTOR
201
202 static struct perf_event_attr wd_hw_attr = {
203         .type           = PERF_TYPE_HARDWARE,
204         .config         = PERF_COUNT_HW_CPU_CYCLES,
205         .size           = sizeof(struct perf_event_attr),
206         .pinned         = 1,
207         .disabled       = 1,
208 };
209
210 /* Callback function for perf event subsystem */
211 static void watchdog_overflow_callback(struct perf_event *event,
212                  struct perf_sample_data *data,
213                  struct pt_regs *regs)
214 {
215         /* Ensure the watchdog never gets throttled */
216         event->hw.interrupts = 0;
217
218         if (__this_cpu_read(watchdog_nmi_touch) == true) {
219                 __this_cpu_write(watchdog_nmi_touch, false);
220                 return;
221         }
222
223         /* check for a hardlockup
224          * This is done by making sure our timer interrupt
225          * is incrementing.  The timer interrupt should have
226          * fired multiple times before we overflow'd.  If it hasn't
227          * then this is a good indication the cpu is stuck
228          */
229         if (is_hardlockup()) {
230                 int this_cpu = smp_processor_id();
231
232                 /* only print hardlockups once */
233                 if (__this_cpu_read(hard_watchdog_warn) == true)
234                         return;
235
236                 if (hardlockup_panic)
237                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
238                 else
239                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
240
241                 __this_cpu_write(hard_watchdog_warn, true);
242                 return;
243         }
244
245         __this_cpu_write(hard_watchdog_warn, false);
246         return;
247 }
248 static void watchdog_interrupt_count(void)
249 {
250         __this_cpu_inc(hrtimer_interrupts);
251 }
252 #else
253 static inline void watchdog_interrupt_count(void) { return; }
254 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
255
256 /* watchdog kicker functions */
257 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
258 {
259         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
260         struct pt_regs *regs = get_irq_regs();
261         int duration;
262
263         /* kick the hardlockup detector */
264         watchdog_interrupt_count();
265
266         /* kick the softlockup detector */
267         wake_up_process(__this_cpu_read(softlockup_watchdog));
268
269         /* .. and repeat */
270         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
271
272         if (touch_ts == 0) {
273                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
274                         /*
275                          * If the time stamp was touched atomically
276                          * make sure the scheduler tick is up to date.
277                          */
278                         __this_cpu_write(softlockup_touch_sync, false);
279                         sched_clock_tick();
280                 }
281                 __touch_watchdog();
282                 return HRTIMER_RESTART;
283         }
284
285         /* check for a softlockup
286          * This is done by making sure a high priority task is
287          * being scheduled.  The task touches the watchdog to
288          * indicate it is getting cpu time.  If it hasn't then
289          * this is a good indication some task is hogging the cpu
290          */
291         duration = is_softlockup(touch_ts);
292         if (unlikely(duration)) {
293                 /* only warn once */
294                 if (__this_cpu_read(soft_watchdog_warn) == true)
295                         return HRTIMER_RESTART;
296
297                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
298                         smp_processor_id(), duration,
299                         current->comm, task_pid_nr(current));
300                 print_modules();
301                 print_irqtrace_events(current);
302                 if (regs)
303                         show_regs(regs);
304                 else
305                         dump_stack();
306
307                 if (softlockup_panic)
308                         panic("softlockup: hung tasks");
309                 __this_cpu_write(soft_watchdog_warn, true);
310         } else
311                 __this_cpu_write(soft_watchdog_warn, false);
312
313         return HRTIMER_RESTART;
314 }
315
316
317 /*
318  * The watchdog thread - touches the timestamp.
319  */
320 static int watchdog(void *unused)
321 {
322         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
323         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
324
325         sched_setscheduler(current, SCHED_FIFO, &param);
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         __set_current_state(TASK_RUNNING);
353         param.sched_priority = 0;
354         sched_setscheduler(current, SCHED_NORMAL, &param);
355         return 0;
356 }
357
358
359 #ifdef CONFIG_HARDLOCKUP_DETECTOR
360 static int watchdog_nmi_enable(int cpu)
361 {
362         struct perf_event_attr *wd_attr;
363         struct perf_event *event = per_cpu(watchdog_ev, cpu);
364
365         /* is it already setup and enabled? */
366         if (event && event->state > PERF_EVENT_STATE_OFF)
367                 goto out;
368
369         /* it is setup but not enabled */
370         if (event != NULL)
371                 goto out_enable;
372
373         wd_attr = &wd_hw_attr;
374         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
375
376         /* Try to register using hardware perf events */
377         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
378         if (!IS_ERR(event)) {
379                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
380                 goto out_save;
381         }
382
383
384         /* vary the KERN level based on the returned errno */
385         if (PTR_ERR(event) == -EOPNOTSUPP)
386                 printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
387         else if (PTR_ERR(event) == -ENOENT)
388                 printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
389         else
390                 printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
391         return PTR_ERR(event);
392
393         /* success path */
394 out_save:
395         per_cpu(watchdog_ev, cpu) = event;
396 out_enable:
397         perf_event_enable(per_cpu(watchdog_ev, cpu));
398 out:
399         return 0;
400 }
401
402 static void watchdog_nmi_disable(int cpu)
403 {
404         struct perf_event *event = per_cpu(watchdog_ev, cpu);
405
406         if (event) {
407                 perf_event_disable(event);
408                 per_cpu(watchdog_ev, cpu) = NULL;
409
410                 /* should be in cleanup, but blocks oprofile */
411                 perf_event_release_kernel(event);
412         }
413         return;
414 }
415 #else
416 static int watchdog_nmi_enable(int cpu) { return 0; }
417 static void watchdog_nmi_disable(int cpu) { return; }
418 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
419
420 /* prepare/enable/disable routines */
421 static void watchdog_prepare_cpu(int cpu)
422 {
423         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
424
425         WARN_ON(per_cpu(softlockup_watchdog, cpu));
426         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
427         hrtimer->function = watchdog_timer_fn;
428 }
429
430 static int watchdog_enable(int cpu)
431 {
432         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
433         int err = 0;
434
435         /* enable the perf event */
436         err = watchdog_nmi_enable(cpu);
437
438         /* Regardless of err above, fall through and start softlockup */
439
440         /* create the watchdog thread */
441         if (!p) {
442                 p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
443                 if (IS_ERR(p)) {
444                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
445                         if (!err) {
446                                 /* if hardlockup hasn't already set this */
447                                 err = PTR_ERR(p);
448                                 /* and disable the perf event */
449                                 watchdog_nmi_disable(cpu);
450                         }
451                         goto out;
452                 }
453                 kthread_bind(p, cpu);
454                 per_cpu(watchdog_touch_ts, cpu) = 0;
455                 per_cpu(softlockup_watchdog, cpu) = p;
456                 wake_up_process(p);
457         }
458
459 out:
460         return err;
461 }
462
463 static void watchdog_disable(int cpu)
464 {
465         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
466         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
467
468         /*
469          * cancel the timer first to stop incrementing the stats
470          * and waking up the kthread
471          */
472         hrtimer_cancel(hrtimer);
473
474         /* disable the perf event */
475         watchdog_nmi_disable(cpu);
476
477         /* stop the watchdog thread */
478         if (p) {
479                 per_cpu(softlockup_watchdog, cpu) = NULL;
480                 kthread_stop(p);
481         }
482 }
483
484 /* sysctl functions */
485 #ifdef CONFIG_SYSCTL
486 static void watchdog_enable_all_cpus(void)
487 {
488         int cpu;
489
490         watchdog_enabled = 0;
491
492         for_each_online_cpu(cpu)
493                 if (!watchdog_enable(cpu))
494                         /* if any cpu succeeds, watchdog is considered
495                            enabled for the system */
496                         watchdog_enabled = 1;
497
498         if (!watchdog_enabled)
499                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
500
501 }
502
503 static void watchdog_disable_all_cpus(void)
504 {
505         int cpu;
506
507         for_each_online_cpu(cpu)
508                 watchdog_disable(cpu);
509
510         /* if all watchdogs are disabled, then they are disabled for the system */
511         watchdog_enabled = 0;
512 }
513
514
515 /*
516  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
517  */
518
519 int proc_dowatchdog(struct ctl_table *table, int write,
520                     void __user *buffer, size_t *lenp, loff_t *ppos)
521 {
522         int ret;
523
524         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
525         if (ret || !write)
526                 goto out;
527
528         if (watchdog_enabled && watchdog_thresh)
529                 watchdog_enable_all_cpus();
530         else
531                 watchdog_disable_all_cpus();
532
533 out:
534         return ret;
535 }
536 #endif /* CONFIG_SYSCTL */
537
538
539 /*
540  * Create/destroy watchdog threads as CPUs come and go:
541  */
542 static int __cpuinit
543 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
544 {
545         int hotcpu = (unsigned long)hcpu;
546
547         switch (action) {
548         case CPU_UP_PREPARE:
549         case CPU_UP_PREPARE_FROZEN:
550                 watchdog_prepare_cpu(hotcpu);
551                 break;
552         case CPU_ONLINE:
553         case CPU_ONLINE_FROZEN:
554                 if (watchdog_enabled)
555                         watchdog_enable(hotcpu);
556                 break;
557 #ifdef CONFIG_HOTPLUG_CPU
558         case CPU_UP_CANCELED:
559         case CPU_UP_CANCELED_FROZEN:
560                 watchdog_disable(hotcpu);
561                 break;
562         case CPU_DEAD:
563         case CPU_DEAD_FROZEN:
564                 watchdog_disable(hotcpu);
565                 break;
566 #endif /* CONFIG_HOTPLUG_CPU */
567         }
568
569         /*
570          * hardlockup and softlockup are not important enough
571          * to block cpu bring up.  Just always succeed and
572          * rely on printk output to flag problems.
573          */
574         return NOTIFY_OK;
575 }
576
577 static struct notifier_block __cpuinitdata cpu_nfb = {
578         .notifier_call = cpu_callback
579 };
580
581 void __init lockup_detector_init(void)
582 {
583         void *cpu = (void *)(long)smp_processor_id();
584         int err;
585
586         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
587         WARN_ON(notifier_to_errno(err));
588
589         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
590         register_cpu_notifier(&cpu_nfb);
591
592         return;
593 }