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TOMOYO Linux Cross Reference
Linux/kernel/watchdog.c

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  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 #include <linux/sched/rt.h>
 27 
 28 #include <asm/irq_regs.h>
 29 #include <linux/kvm_para.h>
 30 #include <linux/perf_event.h>
 31 
 32 int watchdog_user_enabled = 1;
 33 int __read_mostly watchdog_thresh = 10;
 34 static int __read_mostly watchdog_running;
 35 static u64 __read_mostly sample_period;
 36 
 37 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 38 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 39 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 40 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 41 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 42 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 43 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 44 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 45 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
 46 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
 47 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 48 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
 49 #endif
 50 
 51 /* boot commands */
 52 /*
 53  * Should we panic when a soft-lockup or hard-lockup occurs:
 54  */
 55 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 56 static int hardlockup_panic =
 57                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
 58 
 59 static int __init hardlockup_panic_setup(char *str)
 60 {
 61         if (!strncmp(str, "panic", 5))
 62                 hardlockup_panic = 1;
 63         else if (!strncmp(str, "nopanic", 7))
 64                 hardlockup_panic = 0;
 65         else if (!strncmp(str, "", 1))
 66                 watchdog_user_enabled = 0;
 67         return 1;
 68 }
 69 __setup("nmi_watchdog=", hardlockup_panic_setup);
 70 #endif
 71 
 72 unsigned int __read_mostly softlockup_panic =
 73                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 74 
 75 static int __init softlockup_panic_setup(char *str)
 76 {
 77         softlockup_panic = simple_strtoul(str, NULL, 0);
 78 
 79         return 1;
 80 }
 81 __setup("softlockup_panic=", softlockup_panic_setup);
 82 
 83 static int __init nowatchdog_setup(char *str)
 84 {
 85         watchdog_user_enabled = 0;
 86         return 1;
 87 }
 88 __setup("nowatchdog", nowatchdog_setup);
 89 
 90 /* deprecated */
 91 static int __init nosoftlockup_setup(char *str)
 92 {
 93         watchdog_user_enabled = 0;
 94         return 1;
 95 }
 96 __setup("nosoftlockup", nosoftlockup_setup);
 97 /*  */
 98 
 99 /*
100  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
101  * lockups can have false positives under extreme conditions. So we generally
102  * want a higher threshold for soft lockups than for hard lockups. So we couple
103  * the thresholds with a factor: we make the soft threshold twice the amount of
104  * time the hard threshold is.
105  */
106 static int get_softlockup_thresh(void)
107 {
108         return watchdog_thresh * 2;
109 }
110 
111 /*
112  * Returns seconds, approximately.  We don't need nanosecond
113  * resolution, and we don't need to waste time with a big divide when
114  * 2^30ns == 1.074s.
115  */
116 static unsigned long get_timestamp(void)
117 {
118         return local_clock() >> 30LL;  /* 2^30 ~= 10^9 */
119 }
120 
121 static void set_sample_period(void)
122 {
123         /*
124          * convert watchdog_thresh from seconds to ns
125          * the divide by 5 is to give hrtimer several chances (two
126          * or three with the current relation between the soft
127          * and hard thresholds) to increment before the
128          * hardlockup detector generates a warning
129          */
130         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
131 }
132 
133 /* Commands for resetting the watchdog */
134 static void __touch_watchdog(void)
135 {
136         __this_cpu_write(watchdog_touch_ts, get_timestamp());
137 }
138 
139 void touch_softlockup_watchdog(void)
140 {
141         __this_cpu_write(watchdog_touch_ts, 0);
142 }
143 EXPORT_SYMBOL(touch_softlockup_watchdog);
144 
145 void touch_all_softlockup_watchdogs(void)
146 {
147         int cpu;
148 
149         /*
150          * this is done lockless
151          * do we care if a 0 races with a timestamp?
152          * all it means is the softlock check starts one cycle later
153          */
154         for_each_online_cpu(cpu)
155                 per_cpu(watchdog_touch_ts, cpu) = 0;
156 }
157 
158 #ifdef CONFIG_HARDLOCKUP_DETECTOR
159 void touch_nmi_watchdog(void)
160 {
161         if (watchdog_user_enabled) {
162                 unsigned cpu;
163 
164                 for_each_present_cpu(cpu) {
165                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
166                                 per_cpu(watchdog_nmi_touch, cpu) = true;
167                 }
168         }
169         touch_softlockup_watchdog();
170 }
171 EXPORT_SYMBOL(touch_nmi_watchdog);
172 
173 #endif
174 
175 void touch_softlockup_watchdog_sync(void)
176 {
177         __raw_get_cpu_var(softlockup_touch_sync) = true;
178         __raw_get_cpu_var(watchdog_touch_ts) = 0;
179 }
180 
181 #ifdef CONFIG_HARDLOCKUP_DETECTOR
182 /* watchdog detector functions */
183 static int is_hardlockup(void)
184 {
185         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
186 
187         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
188                 return 1;
189 
190         __this_cpu_write(hrtimer_interrupts_saved, hrint);
191         return 0;
192 }
193 #endif
194 
195 static int is_softlockup(unsigned long touch_ts)
196 {
197         unsigned long now = get_timestamp();
198 
199         /* Warn about unreasonable delays: */
200         if (time_after(now, touch_ts + get_softlockup_thresh()))
201                 return now - touch_ts;
202 
203         return 0;
204 }
205 
206 #ifdef CONFIG_HARDLOCKUP_DETECTOR
207 
208 static struct perf_event_attr wd_hw_attr = {
209         .type           = PERF_TYPE_HARDWARE,
210         .config         = PERF_COUNT_HW_CPU_CYCLES,
211         .size           = sizeof(struct perf_event_attr),
212         .pinned         = 1,
213         .disabled       = 1,
214 };
215 
216 /* Callback function for perf event subsystem */
217 static void watchdog_overflow_callback(struct perf_event *event,
218                  struct perf_sample_data *data,
219                  struct pt_regs *regs)
220 {
221         /* Ensure the watchdog never gets throttled */
222         event->hw.interrupts = 0;
223 
224         if (__this_cpu_read(watchdog_nmi_touch) == true) {
225                 __this_cpu_write(watchdog_nmi_touch, false);
226                 return;
227         }
228 
229         /* check for a hardlockup
230          * This is done by making sure our timer interrupt
231          * is incrementing.  The timer interrupt should have
232          * fired multiple times before we overflow'd.  If it hasn't
233          * then this is a good indication the cpu is stuck
234          */
235         if (is_hardlockup()) {
236                 int this_cpu = smp_processor_id();
237 
238                 /* only print hardlockups once */
239                 if (__this_cpu_read(hard_watchdog_warn) == true)
240                         return;
241 
242                 if (hardlockup_panic)
243                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
244                 else
245                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
246 
247                 __this_cpu_write(hard_watchdog_warn, true);
248                 return;
249         }
250 
251         __this_cpu_write(hard_watchdog_warn, false);
252         return;
253 }
254 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
255 
256 static void watchdog_interrupt_count(void)
257 {
258         __this_cpu_inc(hrtimer_interrupts);
259 }
260 
261 static int watchdog_nmi_enable(unsigned int cpu);
262 static void watchdog_nmi_disable(unsigned int cpu);
263 
264 /* watchdog kicker functions */
265 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
266 {
267         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
268         struct pt_regs *regs = get_irq_regs();
269         int duration;
270 
271         /* kick the hardlockup detector */
272         watchdog_interrupt_count();
273 
274         /* kick the softlockup detector */
275         wake_up_process(__this_cpu_read(softlockup_watchdog));
276 
277         /* .. and repeat */
278         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
279 
280         if (touch_ts == 0) {
281                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
282                         /*
283                          * If the time stamp was touched atomically
284                          * make sure the scheduler tick is up to date.
285                          */
286                         __this_cpu_write(softlockup_touch_sync, false);
287                         sched_clock_tick();
288                 }
289 
290                 /* Clear the guest paused flag on watchdog reset */
291                 kvm_check_and_clear_guest_paused();
292                 __touch_watchdog();
293                 return HRTIMER_RESTART;
294         }
295 
296         /* check for a softlockup
297          * This is done by making sure a high priority task is
298          * being scheduled.  The task touches the watchdog to
299          * indicate it is getting cpu time.  If it hasn't then
300          * this is a good indication some task is hogging the cpu
301          */
302         duration = is_softlockup(touch_ts);
303         if (unlikely(duration)) {
304                 /*
305                  * If a virtual machine is stopped by the host it can look to
306                  * the watchdog like a soft lockup, check to see if the host
307                  * stopped the vm before we issue the warning
308                  */
309                 if (kvm_check_and_clear_guest_paused())
310                         return HRTIMER_RESTART;
311 
312                 /* only warn once */
313                 if (__this_cpu_read(soft_watchdog_warn) == true)
314                         return HRTIMER_RESTART;
315 
316                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
317                         smp_processor_id(), duration,
318                         current->comm, task_pid_nr(current));
319                 print_modules();
320                 print_irqtrace_events(current);
321                 if (regs)
322                         show_regs(regs);
323                 else
324                         dump_stack();
325 
326                 if (softlockup_panic)
327                         panic("softlockup: hung tasks");
328                 __this_cpu_write(soft_watchdog_warn, true);
329         } else
330                 __this_cpu_write(soft_watchdog_warn, false);
331 
332         return HRTIMER_RESTART;
333 }
334 
335 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
336 {
337         struct sched_param param = { .sched_priority = prio };
338 
339         sched_setscheduler(current, policy, &param);
340 }
341 
342 static void watchdog_enable(unsigned int cpu)
343 {
344         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
345 
346         /* kick off the timer for the hardlockup detector */
347         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
348         hrtimer->function = watchdog_timer_fn;
349 
350         /* Enable the perf event */
351         watchdog_nmi_enable(cpu);
352 
353         /* done here because hrtimer_start can only pin to smp_processor_id() */
354         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
355                       HRTIMER_MODE_REL_PINNED);
356 
357         /* initialize timestamp */
358         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
359         __touch_watchdog();
360 }
361 
362 static void watchdog_disable(unsigned int cpu)
363 {
364         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
365 
366         watchdog_set_prio(SCHED_NORMAL, 0);
367         hrtimer_cancel(hrtimer);
368         /* disable the perf event */
369         watchdog_nmi_disable(cpu);
370 }
371 
372 static void watchdog_cleanup(unsigned int cpu, bool online)
373 {
374         watchdog_disable(cpu);
375 }
376 
377 static int watchdog_should_run(unsigned int cpu)
378 {
379         return __this_cpu_read(hrtimer_interrupts) !=
380                 __this_cpu_read(soft_lockup_hrtimer_cnt);
381 }
382 
383 /*
384  * The watchdog thread function - touches the timestamp.
385  *
386  * It only runs once every sample_period seconds (4 seconds by
387  * default) to reset the softlockup timestamp. If this gets delayed
388  * for more than 2*watchdog_thresh seconds then the debug-printout
389  * triggers in watchdog_timer_fn().
390  */
391 static void watchdog(unsigned int cpu)
392 {
393         __this_cpu_write(soft_lockup_hrtimer_cnt,
394                          __this_cpu_read(hrtimer_interrupts));
395         __touch_watchdog();
396 }
397 
398 #ifdef CONFIG_HARDLOCKUP_DETECTOR
399 /*
400  * People like the simple clean cpu node info on boot.
401  * Reduce the watchdog noise by only printing messages
402  * that are different from what cpu0 displayed.
403  */
404 static unsigned long cpu0_err;
405 
406 static int watchdog_nmi_enable(unsigned int cpu)
407 {
408         struct perf_event_attr *wd_attr;
409         struct perf_event *event = per_cpu(watchdog_ev, cpu);
410 
411         /* is it already setup and enabled? */
412         if (event && event->state > PERF_EVENT_STATE_OFF)
413                 goto out;
414 
415         /* it is setup but not enabled */
416         if (event != NULL)
417                 goto out_enable;
418 
419         wd_attr = &wd_hw_attr;
420         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
421 
422         /* Try to register using hardware perf events */
423         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
424 
425         /* save cpu0 error for future comparision */
426         if (cpu == 0 && IS_ERR(event))
427                 cpu0_err = PTR_ERR(event);
428 
429         if (!IS_ERR(event)) {
430                 /* only print for cpu0 or different than cpu0 */
431                 if (cpu == 0 || cpu0_err)
432                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
433                 goto out_save;
434         }
435 
436         /* skip displaying the same error again */
437         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
438                 return PTR_ERR(event);
439 
440         /* vary the KERN level based on the returned errno */
441         if (PTR_ERR(event) == -EOPNOTSUPP)
442                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
443         else if (PTR_ERR(event) == -ENOENT)
444                 pr_warning("disabled (cpu%i): hardware events not enabled\n",
445                          cpu);
446         else
447                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
448                         cpu, PTR_ERR(event));
449         return PTR_ERR(event);
450 
451         /* success path */
452 out_save:
453         per_cpu(watchdog_ev, cpu) = event;
454 out_enable:
455         perf_event_enable(per_cpu(watchdog_ev, cpu));
456 out:
457         return 0;
458 }
459 
460 static void watchdog_nmi_disable(unsigned int cpu)
461 {
462         struct perf_event *event = per_cpu(watchdog_ev, cpu);
463 
464         if (event) {
465                 perf_event_disable(event);
466                 per_cpu(watchdog_ev, cpu) = NULL;
467 
468                 /* should be in cleanup, but blocks oprofile */
469                 perf_event_release_kernel(event);
470         }
471         return;
472 }
473 #else
474 static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
475 static void watchdog_nmi_disable(unsigned int cpu) { return; }
476 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
477 
478 static struct smp_hotplug_thread watchdog_threads = {
479         .store                  = &softlockup_watchdog,
480         .thread_should_run      = watchdog_should_run,
481         .thread_fn              = watchdog,
482         .thread_comm            = "watchdog/%u",
483         .setup                  = watchdog_enable,
484         .cleanup                = watchdog_cleanup,
485         .park                   = watchdog_disable,
486         .unpark                 = watchdog_enable,
487 };
488 
489 static int watchdog_enable_all_cpus(void)
490 {
491         int err = 0;
492 
493         if (!watchdog_running) {
494                 err = smpboot_register_percpu_thread(&watchdog_threads);
495                 if (err)
496                         pr_err("Failed to create watchdog threads, disabled\n");
497                 else
498                         watchdog_running = 1;
499         }
500 
501         return err;
502 }
503 
504 /* prepare/enable/disable routines */
505 /* sysctl functions */
506 #ifdef CONFIG_SYSCTL
507 static void watchdog_disable_all_cpus(void)
508 {
509         if (watchdog_running) {
510                 watchdog_running = 0;
511                 smpboot_unregister_percpu_thread(&watchdog_threads);
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 err, old_thresh, old_enabled;
523 
524         old_thresh = ACCESS_ONCE(watchdog_thresh);
525         old_enabled = ACCESS_ONCE(watchdog_user_enabled);
526 
527         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
528         if (err || !write)
529                 return err;
530 
531         set_sample_period();
532         /*
533          * Watchdog threads shouldn't be enabled if they are
534          * disabled. The 'watchdog_running' variable check in
535          * watchdog_*_all_cpus() function takes care of this.
536          */
537         if (watchdog_user_enabled && watchdog_thresh)
538                 err = watchdog_enable_all_cpus();
539         else
540                 watchdog_disable_all_cpus();
541 
542         /* Restore old values on failure */
543         if (err) {
544                 watchdog_thresh = old_thresh;
545                 watchdog_user_enabled = old_enabled;
546         }
547 
548         return err;
549 }
550 #endif /* CONFIG_SYSCTL */
551 
552 void __init lockup_detector_init(void)
553 {
554         set_sample_period();
555 
556 #ifdef CONFIG_NO_HZ_FULL
557         if (watchdog_user_enabled) {
558                 watchdog_user_enabled = 0;
559                 pr_warning("Disabled lockup detectors by default for full dynticks\n");
560                 pr_warning("You can reactivate it with 'sysctl -w kernel.watchdog=1'\n");
561         }
562 #endif
563 
564         if (watchdog_user_enabled)
565                 watchdog_enable_all_cpus();
566 }
567 

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