Merge tag 'please-pull-naveen' of git://git.kernel.org/pub/scm/linux/kernel/git/ras...
[linux-3.10.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/kvm_para.h>
28 #include <linux/perf_event.h>
29
30 int watchdog_enabled = 1;
31 int __read_mostly watchdog_thresh = 10;
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 /* boot commands */
47 /*
48  * Should we panic when a soft-lockup or hard-lockup occurs:
49  */
50 #ifdef CONFIG_HARDLOCKUP_DETECTOR
51 static int hardlockup_panic =
52                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
53
54 static 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
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         watchdog_enabled = 0;
81         return 1;
82 }
83 __setup("nowatchdog", nowatchdog_setup);
84
85 /* deprecated */
86 static 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  */
101 static 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  */
111 static unsigned long get_timestamp(int this_cpu)
112 {
113         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
114 }
115
116 static 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 */
129 static 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
136 void touch_softlockup_watchdog(void)
137 {
138         __this_cpu_write(watchdog_touch_ts, 0);
139 }
140 EXPORT_SYMBOL(touch_softlockup_watchdog);
141
142 void 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
156 void 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 }
168 EXPORT_SYMBOL(touch_nmi_watchdog);
169
170 #endif
171
172 void 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 */
180 static 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
192 static 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
205 static 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 */
214 static 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 }
251 static void watchdog_interrupt_count(void)
252 {
253         __this_cpu_inc(hrtimer_interrupts);
254 }
255 #else
256 static inline void watchdog_interrupt_count(void) { return; }
257 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
258
259 /* watchdog kicker functions */
260 static 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  */
334 static 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, &param);
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  */
380 static unsigned long cpu0_err;
381
382 static 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 */
428 out_save:
429         per_cpu(watchdog_ev, cpu) = event;
430 out_enable:
431         perf_event_enable(per_cpu(watchdog_ev, cpu));
432 out:
433         return 0;
434 }
435
436 static 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
450 static int watchdog_nmi_enable(int cpu) { return 0; }
451 static void watchdog_nmi_disable(int cpu) { return; }
452 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
453
454 /* prepare/enable/disable routines */
455 static 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
464 static 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, &param);
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
495 out:
496         return err;
497 }
498
499 static 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
522 static 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
539 static 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
555 int 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
569 out:
570         return ret;
571 }
572 #endif /* CONFIG_SYSCTL */
573
574
575 /*
576  * Create/destroy watchdog threads as CPUs come and go:
577  */
578 static int __cpuinit
579 cpu_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
613 static struct notifier_block __cpuinitdata cpu_nfb = {
614         .notifier_call = cpu_callback
615 };
616
617 void __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 }