watchdog: store the watchdog sample period as a variable
[~shefty/rdma-dev.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 #include <linux/smpboot.h>
26
27 #include <asm/irq_regs.h>
28 #include <linux/kvm_para.h>
29 #include <linux/perf_event.h>
30
31 int watchdog_enabled = 1;
32 int __read_mostly watchdog_thresh = 10;
33 static int __read_mostly watchdog_disabled;
34 static u64 __read_mostly sample_period;
35
36 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
37 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
38 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
39 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
40 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
42 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
43 #ifdef CONFIG_HARDLOCKUP_DETECTOR
44 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
45 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
46 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
47 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
48 #endif
49
50 /* boot commands */
51 /*
52  * Should we panic when a soft-lockup or hard-lockup occurs:
53  */
54 #ifdef CONFIG_HARDLOCKUP_DETECTOR
55 static int hardlockup_panic =
56                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
57
58 static int __init hardlockup_panic_setup(char *str)
59 {
60         if (!strncmp(str, "panic", 5))
61                 hardlockup_panic = 1;
62         else if (!strncmp(str, "nopanic", 7))
63                 hardlockup_panic = 0;
64         else if (!strncmp(str, "0", 1))
65                 watchdog_enabled = 0;
66         return 1;
67 }
68 __setup("nmi_watchdog=", hardlockup_panic_setup);
69 #endif
70
71 unsigned int __read_mostly softlockup_panic =
72                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
73
74 static int __init softlockup_panic_setup(char *str)
75 {
76         softlockup_panic = simple_strtoul(str, NULL, 0);
77
78         return 1;
79 }
80 __setup("softlockup_panic=", softlockup_panic_setup);
81
82 static int __init nowatchdog_setup(char *str)
83 {
84         watchdog_enabled = 0;
85         return 1;
86 }
87 __setup("nowatchdog", nowatchdog_setup);
88
89 /* deprecated */
90 static int __init nosoftlockup_setup(char *str)
91 {
92         watchdog_enabled = 0;
93         return 1;
94 }
95 __setup("nosoftlockup", nosoftlockup_setup);
96 /*  */
97
98 /*
99  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
100  * lockups can have false positives under extreme conditions. So we generally
101  * want a higher threshold for soft lockups than for hard lockups. So we couple
102  * the thresholds with a factor: we make the soft threshold twice the amount of
103  * time the hard threshold is.
104  */
105 static int get_softlockup_thresh(void)
106 {
107         return watchdog_thresh * 2;
108 }
109
110 /*
111  * Returns seconds, approximately.  We don't need nanosecond
112  * resolution, and we don't need to waste time with a big divide when
113  * 2^30ns == 1.074s.
114  */
115 static unsigned long get_timestamp(int this_cpu)
116 {
117         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
118 }
119
120 static void set_sample_period(void)
121 {
122         /*
123          * convert watchdog_thresh from seconds to ns
124          * the divide by 5 is to give hrtimer several chances (two
125          * or three with the current relation between the soft
126          * and hard thresholds) to increment before the
127          * hardlockup detector generates a warning
128          */
129         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
130 }
131
132 /* Commands for resetting the watchdog */
133 static void __touch_watchdog(void)
134 {
135         int this_cpu = smp_processor_id();
136
137         __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
138 }
139
140 void touch_softlockup_watchdog(void)
141 {
142         __this_cpu_write(watchdog_touch_ts, 0);
143 }
144 EXPORT_SYMBOL(touch_softlockup_watchdog);
145
146 void touch_all_softlockup_watchdogs(void)
147 {
148         int cpu;
149
150         /*
151          * this is done lockless
152          * do we care if a 0 races with a timestamp?
153          * all it means is the softlock check starts one cycle later
154          */
155         for_each_online_cpu(cpu)
156                 per_cpu(watchdog_touch_ts, cpu) = 0;
157 }
158
159 #ifdef CONFIG_HARDLOCKUP_DETECTOR
160 void touch_nmi_watchdog(void)
161 {
162         if (watchdog_enabled) {
163                 unsigned cpu;
164
165                 for_each_present_cpu(cpu) {
166                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
167                                 per_cpu(watchdog_nmi_touch, cpu) = true;
168                 }
169         }
170         touch_softlockup_watchdog();
171 }
172 EXPORT_SYMBOL(touch_nmi_watchdog);
173
174 #endif
175
176 void touch_softlockup_watchdog_sync(void)
177 {
178         __raw_get_cpu_var(softlockup_touch_sync) = true;
179         __raw_get_cpu_var(watchdog_touch_ts) = 0;
180 }
181
182 #ifdef CONFIG_HARDLOCKUP_DETECTOR
183 /* watchdog detector functions */
184 static int is_hardlockup(void)
185 {
186         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
187
188         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
189                 return 1;
190
191         __this_cpu_write(hrtimer_interrupts_saved, hrint);
192         return 0;
193 }
194 #endif
195
196 static int is_softlockup(unsigned long touch_ts)
197 {
198         unsigned long now = get_timestamp(smp_processor_id());
199
200         /* Warn about unreasonable delays: */
201         if (time_after(now, touch_ts + get_softlockup_thresh()))
202                 return now - touch_ts;
203
204         return 0;
205 }
206
207 #ifdef CONFIG_HARDLOCKUP_DETECTOR
208
209 static struct perf_event_attr wd_hw_attr = {
210         .type           = PERF_TYPE_HARDWARE,
211         .config         = PERF_COUNT_HW_CPU_CYCLES,
212         .size           = sizeof(struct perf_event_attr),
213         .pinned         = 1,
214         .disabled       = 1,
215 };
216
217 /* Callback function for perf event subsystem */
218 static void watchdog_overflow_callback(struct perf_event *event,
219                  struct perf_sample_data *data,
220                  struct pt_regs *regs)
221 {
222         /* Ensure the watchdog never gets throttled */
223         event->hw.interrupts = 0;
224
225         if (__this_cpu_read(watchdog_nmi_touch) == true) {
226                 __this_cpu_write(watchdog_nmi_touch, false);
227                 return;
228         }
229
230         /* check for a hardlockup
231          * This is done by making sure our timer interrupt
232          * is incrementing.  The timer interrupt should have
233          * fired multiple times before we overflow'd.  If it hasn't
234          * then this is a good indication the cpu is stuck
235          */
236         if (is_hardlockup()) {
237                 int this_cpu = smp_processor_id();
238
239                 /* only print hardlockups once */
240                 if (__this_cpu_read(hard_watchdog_warn) == true)
241                         return;
242
243                 if (hardlockup_panic)
244                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
245                 else
246                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
247
248                 __this_cpu_write(hard_watchdog_warn, true);
249                 return;
250         }
251
252         __this_cpu_write(hard_watchdog_warn, false);
253         return;
254 }
255 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
256
257 static void watchdog_interrupt_count(void)
258 {
259         __this_cpu_inc(hrtimer_interrupts);
260 }
261
262 static int watchdog_nmi_enable(unsigned int cpu);
263 static void watchdog_nmi_disable(unsigned int cpu);
264
265 /* watchdog kicker functions */
266 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
267 {
268         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
269         struct pt_regs *regs = get_irq_regs();
270         int duration;
271
272         /* kick the hardlockup detector */
273         watchdog_interrupt_count();
274
275         /* kick the softlockup detector */
276         wake_up_process(__this_cpu_read(softlockup_watchdog));
277
278         /* .. and repeat */
279         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
280
281         if (touch_ts == 0) {
282                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
283                         /*
284                          * If the time stamp was touched atomically
285                          * make sure the scheduler tick is up to date.
286                          */
287                         __this_cpu_write(softlockup_touch_sync, false);
288                         sched_clock_tick();
289                 }
290
291                 /* Clear the guest paused flag on watchdog reset */
292                 kvm_check_and_clear_guest_paused();
293                 __touch_watchdog();
294                 return HRTIMER_RESTART;
295         }
296
297         /* check for a softlockup
298          * This is done by making sure a high priority task is
299          * being scheduled.  The task touches the watchdog to
300          * indicate it is getting cpu time.  If it hasn't then
301          * this is a good indication some task is hogging the cpu
302          */
303         duration = is_softlockup(touch_ts);
304         if (unlikely(duration)) {
305                 /*
306                  * If a virtual machine is stopped by the host it can look to
307                  * the watchdog like a soft lockup, check to see if the host
308                  * stopped the vm before we issue the warning
309                  */
310                 if (kvm_check_and_clear_guest_paused())
311                         return HRTIMER_RESTART;
312
313                 /* only warn once */
314                 if (__this_cpu_read(soft_watchdog_warn) == true)
315                         return HRTIMER_RESTART;
316
317                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
318                         smp_processor_id(), duration,
319                         current->comm, task_pid_nr(current));
320                 print_modules();
321                 print_irqtrace_events(current);
322                 if (regs)
323                         show_regs(regs);
324                 else
325                         dump_stack();
326
327                 if (softlockup_panic)
328                         panic("softlockup: hung tasks");
329                 __this_cpu_write(soft_watchdog_warn, true);
330         } else
331                 __this_cpu_write(soft_watchdog_warn, false);
332
333         return HRTIMER_RESTART;
334 }
335
336 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
337 {
338         struct sched_param param = { .sched_priority = prio };
339
340         sched_setscheduler(current, policy, &param);
341 }
342
343 static void watchdog_enable(unsigned int cpu)
344 {
345         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
346
347         if (!watchdog_enabled) {
348                 kthread_park(current);
349                 return;
350         }
351
352         /* Enable the perf event */
353         watchdog_nmi_enable(cpu);
354
355         /* kick off the timer for the hardlockup detector */
356         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
357         hrtimer->function = watchdog_timer_fn;
358
359         /* done here because hrtimer_start can only pin to smp_processor_id() */
360         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
361                       HRTIMER_MODE_REL_PINNED);
362
363         /* initialize timestamp */
364         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
365         __touch_watchdog();
366 }
367
368 static void watchdog_disable(unsigned int cpu)
369 {
370         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
371
372         if (!watchdog_enabled)
373                 return;
374
375         watchdog_set_prio(SCHED_NORMAL, 0);
376         hrtimer_cancel(hrtimer);
377         /* disable the perf event */
378         watchdog_nmi_disable(cpu);
379 }
380
381 static int watchdog_should_run(unsigned int cpu)
382 {
383         return __this_cpu_read(hrtimer_interrupts) !=
384                 __this_cpu_read(soft_lockup_hrtimer_cnt);
385 }
386
387 /*
388  * The watchdog thread function - touches the timestamp.
389  *
390  * It only runs once every sample_period seconds (4 seconds by
391  * default) to reset the softlockup timestamp. If this gets delayed
392  * for more than 2*watchdog_thresh seconds then the debug-printout
393  * triggers in watchdog_timer_fn().
394  */
395 static void watchdog(unsigned int cpu)
396 {
397         __this_cpu_write(soft_lockup_hrtimer_cnt,
398                          __this_cpu_read(hrtimer_interrupts));
399         __touch_watchdog();
400 }
401
402 #ifdef CONFIG_HARDLOCKUP_DETECTOR
403 /*
404  * People like the simple clean cpu node info on boot.
405  * Reduce the watchdog noise by only printing messages
406  * that are different from what cpu0 displayed.
407  */
408 static unsigned long cpu0_err;
409
410 static int watchdog_nmi_enable(unsigned int cpu)
411 {
412         struct perf_event_attr *wd_attr;
413         struct perf_event *event = per_cpu(watchdog_ev, cpu);
414
415         /* is it already setup and enabled? */
416         if (event && event->state > PERF_EVENT_STATE_OFF)
417                 goto out;
418
419         /* it is setup but not enabled */
420         if (event != NULL)
421                 goto out_enable;
422
423         wd_attr = &wd_hw_attr;
424         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
425
426         /* Try to register using hardware perf events */
427         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
428
429         /* save cpu0 error for future comparision */
430         if (cpu == 0 && IS_ERR(event))
431                 cpu0_err = PTR_ERR(event);
432
433         if (!IS_ERR(event)) {
434                 /* only print for cpu0 or different than cpu0 */
435                 if (cpu == 0 || cpu0_err)
436                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
437                 goto out_save;
438         }
439
440         /* skip displaying the same error again */
441         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
442                 return PTR_ERR(event);
443
444         /* vary the KERN level based on the returned errno */
445         if (PTR_ERR(event) == -EOPNOTSUPP)
446                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
447         else if (PTR_ERR(event) == -ENOENT)
448                 pr_warning("disabled (cpu%i): hardware events not enabled\n",
449                          cpu);
450         else
451                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
452                         cpu, PTR_ERR(event));
453         return PTR_ERR(event);
454
455         /* success path */
456 out_save:
457         per_cpu(watchdog_ev, cpu) = event;
458 out_enable:
459         perf_event_enable(per_cpu(watchdog_ev, cpu));
460 out:
461         return 0;
462 }
463
464 static void watchdog_nmi_disable(unsigned int cpu)
465 {
466         struct perf_event *event = per_cpu(watchdog_ev, cpu);
467
468         if (event) {
469                 perf_event_disable(event);
470                 per_cpu(watchdog_ev, cpu) = NULL;
471
472                 /* should be in cleanup, but blocks oprofile */
473                 perf_event_release_kernel(event);
474         }
475         return;
476 }
477 #else
478 static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
479 static void watchdog_nmi_disable(unsigned int cpu) { return; }
480 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
481
482 /* prepare/enable/disable routines */
483 /* sysctl functions */
484 #ifdef CONFIG_SYSCTL
485 static void watchdog_enable_all_cpus(void)
486 {
487         unsigned int cpu;
488
489         if (watchdog_disabled) {
490                 watchdog_disabled = 0;
491                 for_each_online_cpu(cpu)
492                         kthread_unpark(per_cpu(softlockup_watchdog, cpu));
493         }
494 }
495
496 static void watchdog_disable_all_cpus(void)
497 {
498         unsigned int cpu;
499
500         if (!watchdog_disabled) {
501                 watchdog_disabled = 1;
502                 for_each_online_cpu(cpu)
503                         kthread_park(per_cpu(softlockup_watchdog, cpu));
504         }
505 }
506
507 /*
508  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
509  */
510
511 int proc_dowatchdog(struct ctl_table *table, int write,
512                     void __user *buffer, size_t *lenp, loff_t *ppos)
513 {
514         int ret;
515
516         if (watchdog_disabled < 0)
517                 return -ENODEV;
518
519         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
520         if (ret || !write)
521                 return ret;
522
523         set_sample_period();
524         if (watchdog_enabled && watchdog_thresh)
525                 watchdog_enable_all_cpus();
526         else
527                 watchdog_disable_all_cpus();
528
529         return ret;
530 }
531 #endif /* CONFIG_SYSCTL */
532
533 static struct smp_hotplug_thread watchdog_threads = {
534         .store                  = &softlockup_watchdog,
535         .thread_should_run      = watchdog_should_run,
536         .thread_fn              = watchdog,
537         .thread_comm            = "watchdog/%u",
538         .setup                  = watchdog_enable,
539         .park                   = watchdog_disable,
540         .unpark                 = watchdog_enable,
541 };
542
543 void __init lockup_detector_init(void)
544 {
545         set_sample_period();
546         if (smpboot_register_percpu_thread(&watchdog_threads)) {
547                 pr_err("Failed to create watchdog threads, disabled\n");
548                 watchdog_disabled = -ENODEV;
549         }
550 }