Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[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  * 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
30 int watchdog_enabled;
31 int __read_mostly softlockup_thresh = 60;
32
33 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
34 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
35 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
36 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
37 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
38 #ifdef CONFIG_HARDLOCKUP_DETECTOR
39 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
40 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
42 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
43 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
44 #endif
45
46 static int no_watchdog;
47
48
49 /* boot commands */
50 /*
51  * Should we panic when a soft-lockup or hard-lockup occurs:
52  */
53 #ifdef CONFIG_HARDLOCKUP_DETECTOR
54 static int hardlockup_panic;
55
56 static int __init hardlockup_panic_setup(char *str)
57 {
58         if (!strncmp(str, "panic", 5))
59                 hardlockup_panic = 1;
60         else if (!strncmp(str, "0", 1))
61                 no_watchdog = 1;
62         return 1;
63 }
64 __setup("nmi_watchdog=", hardlockup_panic_setup);
65 #endif
66
67 unsigned int __read_mostly softlockup_panic =
68                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
69
70 static 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
78 static int __init nowatchdog_setup(char *str)
79 {
80         no_watchdog = 1;
81         return 1;
82 }
83 __setup("nowatchdog", nowatchdog_setup);
84
85 /* deprecated */
86 static int __init nosoftlockup_setup(char *str)
87 {
88         no_watchdog = 1;
89         return 1;
90 }
91 __setup("nosoftlockup", nosoftlockup_setup);
92 /*  */
93
94
95 /*
96  * Returns seconds, approximately.  We don't need nanosecond
97  * resolution, and we don't need to waste time with a big divide when
98  * 2^30ns == 1.074s.
99  */
100 static unsigned long get_timestamp(int this_cpu)
101 {
102         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
103 }
104
105 static unsigned long get_sample_period(void)
106 {
107         /*
108          * convert softlockup_thresh from seconds to ns
109          * the divide by 5 is to give hrtimer 5 chances to
110          * increment before the hardlockup detector generates
111          * a warning
112          */
113         return softlockup_thresh / 5 * NSEC_PER_SEC;
114 }
115
116 /* Commands for resetting the watchdog */
117 static void __touch_watchdog(void)
118 {
119         int this_cpu = smp_processor_id();
120
121         __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
122 }
123
124 void touch_softlockup_watchdog(void)
125 {
126         __raw_get_cpu_var(watchdog_touch_ts) = 0;
127 }
128 EXPORT_SYMBOL(touch_softlockup_watchdog);
129
130 void touch_all_softlockup_watchdogs(void)
131 {
132         int cpu;
133
134         /*
135          * this is done lockless
136          * do we care if a 0 races with a timestamp?
137          * all it means is the softlock check starts one cycle later
138          */
139         for_each_online_cpu(cpu)
140                 per_cpu(watchdog_touch_ts, cpu) = 0;
141 }
142
143 #ifdef CONFIG_HARDLOCKUP_DETECTOR
144 void touch_nmi_watchdog(void)
145 {
146         if (watchdog_enabled) {
147                 unsigned cpu;
148
149                 for_each_present_cpu(cpu) {
150                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
151                                 per_cpu(watchdog_nmi_touch, cpu) = true;
152                 }
153         }
154         touch_softlockup_watchdog();
155 }
156 EXPORT_SYMBOL(touch_nmi_watchdog);
157
158 #endif
159
160 void touch_softlockup_watchdog_sync(void)
161 {
162         __raw_get_cpu_var(softlockup_touch_sync) = true;
163         __raw_get_cpu_var(watchdog_touch_ts) = 0;
164 }
165
166 #ifdef CONFIG_HARDLOCKUP_DETECTOR
167 /* watchdog detector functions */
168 static int is_hardlockup(void)
169 {
170         unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
171
172         if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
173                 return 1;
174
175         __get_cpu_var(hrtimer_interrupts_saved) = hrint;
176         return 0;
177 }
178 #endif
179
180 static int is_softlockup(unsigned long touch_ts)
181 {
182         unsigned long now = get_timestamp(smp_processor_id());
183
184         /* Warn about unreasonable delays: */
185         if (time_after(now, touch_ts + softlockup_thresh))
186                 return now - touch_ts;
187
188         return 0;
189 }
190
191 #ifdef CONFIG_HARDLOCKUP_DETECTOR
192 static struct perf_event_attr wd_hw_attr = {
193         .type           = PERF_TYPE_HARDWARE,
194         .config         = PERF_COUNT_HW_CPU_CYCLES,
195         .size           = sizeof(struct perf_event_attr),
196         .pinned         = 1,
197         .disabled       = 1,
198 };
199
200 /* Callback function for perf event subsystem */
201 static void watchdog_overflow_callback(struct perf_event *event, int nmi,
202                  struct perf_sample_data *data,
203                  struct pt_regs *regs)
204 {
205         /* Ensure the watchdog never gets throttled */
206         event->hw.interrupts = 0;
207
208         if (__get_cpu_var(watchdog_nmi_touch) == true) {
209                 __get_cpu_var(watchdog_nmi_touch) = false;
210                 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()) {
220                 int this_cpu = smp_processor_id();
221
222                 /* only print hardlockups once */
223                 if (__get_cpu_var(hard_watchdog_warn) == true)
224                         return;
225
226                 if (hardlockup_panic)
227                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
228                 else
229                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
230
231                 __get_cpu_var(hard_watchdog_warn) = true;
232                 return;
233         }
234
235         __get_cpu_var(hard_watchdog_warn) = false;
236         return;
237 }
238 static void watchdog_interrupt_count(void)
239 {
240         __get_cpu_var(hrtimer_interrupts)++;
241 }
242 #else
243 static inline void watchdog_interrupt_count(void) { return; }
244 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
245
246 /* watchdog kicker functions */
247 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
248 {
249         unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
250         struct pt_regs *regs = get_irq_regs();
251         int duration;
252
253         /* kick the hardlockup detector */
254         watchdog_interrupt_count();
255
256         /* kick the softlockup detector */
257         wake_up_process(__get_cpu_var(softlockup_watchdog));
258
259         /* .. and repeat */
260         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
261
262         if (touch_ts == 0) {
263                 if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
264                         /*
265                          * If the time stamp was touched atomically
266                          * make sure the scheduler tick is up to date.
267                          */
268                         __get_cpu_var(softlockup_touch_sync) = false;
269                         sched_clock_tick();
270                 }
271                 __touch_watchdog();
272                 return HRTIMER_RESTART;
273         }
274
275         /* check for a softlockup
276          * This is done by making sure a high priority task is
277          * being scheduled.  The task touches the watchdog to
278          * indicate it is getting cpu time.  If it hasn't then
279          * this is a good indication some task is hogging the cpu
280          */
281         duration = is_softlockup(touch_ts);
282         if (unlikely(duration)) {
283                 /* only warn once */
284                 if (__get_cpu_var(soft_watchdog_warn) == true)
285                         return HRTIMER_RESTART;
286
287                 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
288                         smp_processor_id(), duration,
289                         current->comm, task_pid_nr(current));
290                 print_modules();
291                 print_irqtrace_events(current);
292                 if (regs)
293                         show_regs(regs);
294                 else
295                         dump_stack();
296
297                 if (softlockup_panic)
298                         panic("softlockup: hung tasks");
299                 __get_cpu_var(soft_watchdog_warn) = true;
300         } else
301                 __get_cpu_var(soft_watchdog_warn) = false;
302
303         return HRTIMER_RESTART;
304 }
305
306
307 /*
308  * The watchdog thread - touches the timestamp.
309  */
310 static int watchdog(void *unused)
311 {
312         static struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
313         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
314
315         sched_setscheduler(current, SCHED_FIFO, &param);
316
317         /* initialize timestamp */
318         __touch_watchdog();
319
320         /* kick off the timer for the hardlockup detector */
321         /* done here because hrtimer_start can only pin to smp_processor_id() */
322         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
323                       HRTIMER_MODE_REL_PINNED);
324
325         set_current_state(TASK_INTERRUPTIBLE);
326         /*
327          * Run briefly once per second to reset the softlockup timestamp.
328          * If this gets delayed for more than 60 seconds then the
329          * debug-printout triggers in watchdog_timer_fn().
330          */
331         while (!kthread_should_stop()) {
332                 __touch_watchdog();
333                 schedule();
334
335                 if (kthread_should_stop())
336                         break;
337
338                 set_current_state(TASK_INTERRUPTIBLE);
339         }
340         __set_current_state(TASK_RUNNING);
341
342         return 0;
343 }
344
345
346 #ifdef CONFIG_HARDLOCKUP_DETECTOR
347 static int watchdog_nmi_enable(int cpu)
348 {
349         struct perf_event_attr *wd_attr;
350         struct perf_event *event = per_cpu(watchdog_ev, cpu);
351
352         /* is it already setup and enabled? */
353         if (event && event->state > PERF_EVENT_STATE_OFF)
354                 goto out;
355
356         /* it is setup but not enabled */
357         if (event != NULL)
358                 goto out_enable;
359
360         /* Try to register using hardware perf events */
361         wd_attr = &wd_hw_attr;
362         wd_attr->sample_period = hw_nmi_get_sample_period();
363         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback);
364         if (!IS_ERR(event)) {
365                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
366                 goto out_save;
367         }
368
369         printk(KERN_ERR "NMI watchdog disabled for cpu%i: unable to create perf event: %ld\n",
370                cpu, PTR_ERR(event));
371         return PTR_ERR(event);
372
373         /* success path */
374 out_save:
375         per_cpu(watchdog_ev, cpu) = event;
376 out_enable:
377         perf_event_enable(per_cpu(watchdog_ev, cpu));
378 out:
379         return 0;
380 }
381
382 static void watchdog_nmi_disable(int cpu)
383 {
384         struct perf_event *event = per_cpu(watchdog_ev, cpu);
385
386         if (event) {
387                 perf_event_disable(event);
388                 per_cpu(watchdog_ev, cpu) = NULL;
389
390                 /* should be in cleanup, but blocks oprofile */
391                 perf_event_release_kernel(event);
392         }
393         return;
394 }
395 #else
396 static int watchdog_nmi_enable(int cpu) { return 0; }
397 static void watchdog_nmi_disable(int cpu) { return; }
398 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
399
400 /* prepare/enable/disable routines */
401 static int watchdog_prepare_cpu(int cpu)
402 {
403         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
404
405         WARN_ON(per_cpu(softlockup_watchdog, cpu));
406         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
407         hrtimer->function = watchdog_timer_fn;
408
409         return 0;
410 }
411
412 static int watchdog_enable(int cpu)
413 {
414         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
415         int err;
416
417         /* enable the perf event */
418         err = watchdog_nmi_enable(cpu);
419         if (err)
420                 return err;
421
422         /* create the watchdog thread */
423         if (!p) {
424                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
425                 if (IS_ERR(p)) {
426                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
427                         return PTR_ERR(p);
428                 }
429                 kthread_bind(p, cpu);
430                 per_cpu(watchdog_touch_ts, cpu) = 0;
431                 per_cpu(softlockup_watchdog, cpu) = p;
432                 wake_up_process(p);
433         }
434
435         /* if any cpu succeeds, watchdog is considered enabled for the system */
436         watchdog_enabled = 1;
437
438         return 0;
439 }
440
441 static void watchdog_disable(int cpu)
442 {
443         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
444         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
445
446         /*
447          * cancel the timer first to stop incrementing the stats
448          * and waking up the kthread
449          */
450         hrtimer_cancel(hrtimer);
451
452         /* disable the perf event */
453         watchdog_nmi_disable(cpu);
454
455         /* stop the watchdog thread */
456         if (p) {
457                 per_cpu(softlockup_watchdog, cpu) = NULL;
458                 kthread_stop(p);
459         }
460 }
461
462 static void watchdog_enable_all_cpus(void)
463 {
464         int cpu;
465         int result = 0;
466
467         for_each_online_cpu(cpu)
468                 result += watchdog_enable(cpu);
469
470         if (result)
471                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
472
473 }
474
475 static void watchdog_disable_all_cpus(void)
476 {
477         int cpu;
478
479         if (no_watchdog)
480                 return;
481
482         for_each_online_cpu(cpu)
483                 watchdog_disable(cpu);
484
485         /* if all watchdogs are disabled, then they are disabled for the system */
486         watchdog_enabled = 0;
487 }
488
489
490 /* sysctl functions */
491 #ifdef CONFIG_SYSCTL
492 /*
493  * proc handler for /proc/sys/kernel/nmi_watchdog
494  */
495
496 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
497                      void __user *buffer, size_t *length, loff_t *ppos)
498 {
499         proc_dointvec(table, write, buffer, length, ppos);
500
501         if (watchdog_enabled)
502                 watchdog_enable_all_cpus();
503         else
504                 watchdog_disable_all_cpus();
505         return 0;
506 }
507
508 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
509                              void __user *buffer,
510                              size_t *lenp, loff_t *ppos)
511 {
512         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
513 }
514 #endif /* CONFIG_SYSCTL */
515
516
517 /*
518  * Create/destroy watchdog threads as CPUs come and go:
519  */
520 static int __cpuinit
521 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
522 {
523         int hotcpu = (unsigned long)hcpu;
524         int err = 0;
525
526         switch (action) {
527         case CPU_UP_PREPARE:
528         case CPU_UP_PREPARE_FROZEN:
529                 err = watchdog_prepare_cpu(hotcpu);
530                 break;
531         case CPU_ONLINE:
532         case CPU_ONLINE_FROZEN:
533                 err = watchdog_enable(hotcpu);
534                 break;
535 #ifdef CONFIG_HOTPLUG_CPU
536         case CPU_UP_CANCELED:
537         case CPU_UP_CANCELED_FROZEN:
538                 watchdog_disable(hotcpu);
539                 break;
540         case CPU_DEAD:
541         case CPU_DEAD_FROZEN:
542                 watchdog_disable(hotcpu);
543                 break;
544 #endif /* CONFIG_HOTPLUG_CPU */
545         }
546         return notifier_from_errno(err);
547 }
548
549 static struct notifier_block __cpuinitdata cpu_nfb = {
550         .notifier_call = cpu_callback
551 };
552
553 void __init lockup_detector_init(void)
554 {
555         void *cpu = (void *)(long)smp_processor_id();
556         int err;
557
558         if (no_watchdog)
559                 return;
560
561         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
562         WARN_ON(notifier_to_errno(err));
563
564         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
565         register_cpu_notifier(&cpu_nfb);
566
567         return;
568 }