kthread: rename probe_kthread_data() to kthread_probe_data()
[linux-2.6-block.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/module.h>
19 #include <linux/sysctl.h>
20 #include <linux/smpboot.h>
21 #include <linux/sched/rt.h>
22 #include <linux/tick.h>
23 #include <linux/workqueue.h>
24
25 #include <asm/irq_regs.h>
26 #include <linux/kvm_para.h>
27 #include <linux/perf_event.h>
28 #include <linux/kthread.h>
29
30 /*
31  * The run state of the lockup detectors is controlled by the content of the
32  * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
33  * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
34  *
35  * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
36  * are variables that are only used as an 'interface' between the parameters
37  * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
38  * 'watchdog_thresh' variable is handled differently because its value is not
39  * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
40  * is equal zero.
41  */
42 #define NMI_WATCHDOG_ENABLED_BIT   0
43 #define SOFT_WATCHDOG_ENABLED_BIT  1
44 #define NMI_WATCHDOG_ENABLED      (1 << NMI_WATCHDOG_ENABLED_BIT)
45 #define SOFT_WATCHDOG_ENABLED     (1 << SOFT_WATCHDOG_ENABLED_BIT)
46
47 static DEFINE_MUTEX(watchdog_proc_mutex);
48
49 #ifdef CONFIG_HARDLOCKUP_DETECTOR
50 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
51 #else
52 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
53 #endif
54 int __read_mostly nmi_watchdog_enabled;
55 int __read_mostly soft_watchdog_enabled;
56 int __read_mostly watchdog_user_enabled;
57 int __read_mostly watchdog_thresh = 10;
58
59 #ifdef CONFIG_SMP
60 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
61 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
62 #else
63 #define sysctl_softlockup_all_cpu_backtrace 0
64 #define sysctl_hardlockup_all_cpu_backtrace 0
65 #endif
66 static struct cpumask watchdog_cpumask __read_mostly;
67 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
68
69 /* Helper for online, unparked cpus. */
70 #define for_each_watchdog_cpu(cpu) \
71         for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
72
73 /*
74  * The 'watchdog_running' variable is set to 1 when the watchdog threads
75  * are registered/started and is set to 0 when the watchdog threads are
76  * unregistered/stopped, so it is an indicator whether the threads exist.
77  */
78 static int __read_mostly watchdog_running;
79 /*
80  * If a subsystem has a need to deactivate the watchdog temporarily, it
81  * can use the suspend/resume interface to achieve this. The content of
82  * the 'watchdog_suspended' variable reflects this state. Existing threads
83  * are parked/unparked by the lockup_detector_{suspend|resume} functions
84  * (see comment blocks pertaining to those functions for further details).
85  *
86  * 'watchdog_suspended' also prevents threads from being registered/started
87  * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
88  * of 'watchdog_running' cannot change while the watchdog is deactivated
89  * temporarily (see related code in 'proc' handlers).
90  */
91 static int __read_mostly watchdog_suspended;
92
93 static u64 __read_mostly sample_period;
94
95 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
96 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
97 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
98 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
99 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
100 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
101 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
102 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
103 #ifdef CONFIG_HARDLOCKUP_DETECTOR
104 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
105 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
106 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
107 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
108 #endif
109 static unsigned long soft_lockup_nmi_warn;
110
111 /* boot commands */
112 /*
113  * Should we panic when a soft-lockup or hard-lockup occurs:
114  */
115 #ifdef CONFIG_HARDLOCKUP_DETECTOR
116 unsigned int __read_mostly hardlockup_panic =
117                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
118 static unsigned long hardlockup_allcpu_dumped;
119 /*
120  * We may not want to enable hard lockup detection by default in all cases,
121  * for example when running the kernel as a guest on a hypervisor. In these
122  * cases this function can be called to disable hard lockup detection. This
123  * function should only be executed once by the boot processor before the
124  * kernel command line parameters are parsed, because otherwise it is not
125  * possible to override this in hardlockup_panic_setup().
126  */
127 void hardlockup_detector_disable(void)
128 {
129         watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
130 }
131
132 static int __init hardlockup_panic_setup(char *str)
133 {
134         if (!strncmp(str, "panic", 5))
135                 hardlockup_panic = 1;
136         else if (!strncmp(str, "nopanic", 7))
137                 hardlockup_panic = 0;
138         else if (!strncmp(str, "0", 1))
139                 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
140         else if (!strncmp(str, "1", 1))
141                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
142         return 1;
143 }
144 __setup("nmi_watchdog=", hardlockup_panic_setup);
145 #endif
146
147 unsigned int __read_mostly softlockup_panic =
148                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
149
150 static int __init softlockup_panic_setup(char *str)
151 {
152         softlockup_panic = simple_strtoul(str, NULL, 0);
153
154         return 1;
155 }
156 __setup("softlockup_panic=", softlockup_panic_setup);
157
158 static int __init nowatchdog_setup(char *str)
159 {
160         watchdog_enabled = 0;
161         return 1;
162 }
163 __setup("nowatchdog", nowatchdog_setup);
164
165 static int __init nosoftlockup_setup(char *str)
166 {
167         watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
168         return 1;
169 }
170 __setup("nosoftlockup", nosoftlockup_setup);
171
172 #ifdef CONFIG_SMP
173 static int __init softlockup_all_cpu_backtrace_setup(char *str)
174 {
175         sysctl_softlockup_all_cpu_backtrace =
176                 !!simple_strtol(str, NULL, 0);
177         return 1;
178 }
179 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
180 static int __init hardlockup_all_cpu_backtrace_setup(char *str)
181 {
182         sysctl_hardlockup_all_cpu_backtrace =
183                 !!simple_strtol(str, NULL, 0);
184         return 1;
185 }
186 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
187 #endif
188
189 /*
190  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
191  * lockups can have false positives under extreme conditions. So we generally
192  * want a higher threshold for soft lockups than for hard lockups. So we couple
193  * the thresholds with a factor: we make the soft threshold twice the amount of
194  * time the hard threshold is.
195  */
196 static int get_softlockup_thresh(void)
197 {
198         return watchdog_thresh * 2;
199 }
200
201 /*
202  * Returns seconds, approximately.  We don't need nanosecond
203  * resolution, and we don't need to waste time with a big divide when
204  * 2^30ns == 1.074s.
205  */
206 static unsigned long get_timestamp(void)
207 {
208         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
209 }
210
211 static void set_sample_period(void)
212 {
213         /*
214          * convert watchdog_thresh from seconds to ns
215          * the divide by 5 is to give hrtimer several chances (two
216          * or three with the current relation between the soft
217          * and hard thresholds) to increment before the
218          * hardlockup detector generates a warning
219          */
220         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
221 }
222
223 /* Commands for resetting the watchdog */
224 static void __touch_watchdog(void)
225 {
226         __this_cpu_write(watchdog_touch_ts, get_timestamp());
227 }
228
229 /**
230  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
231  *
232  * Call when the scheduler may have stalled for legitimate reasons
233  * preventing the watchdog task from executing - e.g. the scheduler
234  * entering idle state.  This should only be used for scheduler events.
235  * Use touch_softlockup_watchdog() for everything else.
236  */
237 void touch_softlockup_watchdog_sched(void)
238 {
239         /*
240          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
241          * gets zeroed here, so use the raw_ operation.
242          */
243         raw_cpu_write(watchdog_touch_ts, 0);
244 }
245
246 void touch_softlockup_watchdog(void)
247 {
248         touch_softlockup_watchdog_sched();
249         wq_watchdog_touch(raw_smp_processor_id());
250 }
251 EXPORT_SYMBOL(touch_softlockup_watchdog);
252
253 void touch_all_softlockup_watchdogs(void)
254 {
255         int cpu;
256
257         /*
258          * this is done lockless
259          * do we care if a 0 races with a timestamp?
260          * all it means is the softlock check starts one cycle later
261          */
262         for_each_watchdog_cpu(cpu)
263                 per_cpu(watchdog_touch_ts, cpu) = 0;
264         wq_watchdog_touch(-1);
265 }
266
267 #ifdef CONFIG_HARDLOCKUP_DETECTOR
268 void touch_nmi_watchdog(void)
269 {
270         /*
271          * Using __raw here because some code paths have
272          * preemption enabled.  If preemption is enabled
273          * then interrupts should be enabled too, in which
274          * case we shouldn't have to worry about the watchdog
275          * going off.
276          */
277         raw_cpu_write(watchdog_nmi_touch, true);
278         touch_softlockup_watchdog();
279 }
280 EXPORT_SYMBOL(touch_nmi_watchdog);
281
282 #endif
283
284 void touch_softlockup_watchdog_sync(void)
285 {
286         __this_cpu_write(softlockup_touch_sync, true);
287         __this_cpu_write(watchdog_touch_ts, 0);
288 }
289
290 #ifdef CONFIG_HARDLOCKUP_DETECTOR
291 /* watchdog detector functions */
292 static bool is_hardlockup(void)
293 {
294         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
295
296         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
297                 return true;
298
299         __this_cpu_write(hrtimer_interrupts_saved, hrint);
300         return false;
301 }
302 #endif
303
304 static int is_softlockup(unsigned long touch_ts)
305 {
306         unsigned long now = get_timestamp();
307
308         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
309                 /* Warn about unreasonable delays. */
310                 if (time_after(now, touch_ts + get_softlockup_thresh()))
311                         return now - touch_ts;
312         }
313         return 0;
314 }
315
316 #ifdef CONFIG_HARDLOCKUP_DETECTOR
317
318 static struct perf_event_attr wd_hw_attr = {
319         .type           = PERF_TYPE_HARDWARE,
320         .config         = PERF_COUNT_HW_CPU_CYCLES,
321         .size           = sizeof(struct perf_event_attr),
322         .pinned         = 1,
323         .disabled       = 1,
324 };
325
326 /* Callback function for perf event subsystem */
327 static void watchdog_overflow_callback(struct perf_event *event,
328                  struct perf_sample_data *data,
329                  struct pt_regs *regs)
330 {
331         /* Ensure the watchdog never gets throttled */
332         event->hw.interrupts = 0;
333
334         if (__this_cpu_read(watchdog_nmi_touch) == true) {
335                 __this_cpu_write(watchdog_nmi_touch, false);
336                 return;
337         }
338
339         /* check for a hardlockup
340          * This is done by making sure our timer interrupt
341          * is incrementing.  The timer interrupt should have
342          * fired multiple times before we overflow'd.  If it hasn't
343          * then this is a good indication the cpu is stuck
344          */
345         if (is_hardlockup()) {
346                 int this_cpu = smp_processor_id();
347                 struct pt_regs *regs = get_irq_regs();
348
349                 /* only print hardlockups once */
350                 if (__this_cpu_read(hard_watchdog_warn) == true)
351                         return;
352
353                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
354                 print_modules();
355                 print_irqtrace_events(current);
356                 if (regs)
357                         show_regs(regs);
358                 else
359                         dump_stack();
360
361                 /*
362                  * Perform all-CPU dump only once to avoid multiple hardlockups
363                  * generating interleaving traces
364                  */
365                 if (sysctl_hardlockup_all_cpu_backtrace &&
366                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
367                         trigger_allbutself_cpu_backtrace();
368
369                 if (hardlockup_panic)
370                         nmi_panic(regs, "Hard LOCKUP");
371
372                 __this_cpu_write(hard_watchdog_warn, true);
373                 return;
374         }
375
376         __this_cpu_write(hard_watchdog_warn, false);
377         return;
378 }
379 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
380
381 static void watchdog_interrupt_count(void)
382 {
383         __this_cpu_inc(hrtimer_interrupts);
384 }
385
386 static int watchdog_nmi_enable(unsigned int cpu);
387 static void watchdog_nmi_disable(unsigned int cpu);
388
389 static int watchdog_enable_all_cpus(void);
390 static void watchdog_disable_all_cpus(void);
391
392 /* watchdog kicker functions */
393 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
394 {
395         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
396         struct pt_regs *regs = get_irq_regs();
397         int duration;
398         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
399
400         /* kick the hardlockup detector */
401         watchdog_interrupt_count();
402
403         /* kick the softlockup detector */
404         wake_up_process(__this_cpu_read(softlockup_watchdog));
405
406         /* .. and repeat */
407         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
408
409         if (touch_ts == 0) {
410                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
411                         /*
412                          * If the time stamp was touched atomically
413                          * make sure the scheduler tick is up to date.
414                          */
415                         __this_cpu_write(softlockup_touch_sync, false);
416                         sched_clock_tick();
417                 }
418
419                 /* Clear the guest paused flag on watchdog reset */
420                 kvm_check_and_clear_guest_paused();
421                 __touch_watchdog();
422                 return HRTIMER_RESTART;
423         }
424
425         /* check for a softlockup
426          * This is done by making sure a high priority task is
427          * being scheduled.  The task touches the watchdog to
428          * indicate it is getting cpu time.  If it hasn't then
429          * this is a good indication some task is hogging the cpu
430          */
431         duration = is_softlockup(touch_ts);
432         if (unlikely(duration)) {
433                 /*
434                  * If a virtual machine is stopped by the host it can look to
435                  * the watchdog like a soft lockup, check to see if the host
436                  * stopped the vm before we issue the warning
437                  */
438                 if (kvm_check_and_clear_guest_paused())
439                         return HRTIMER_RESTART;
440
441                 /* only warn once */
442                 if (__this_cpu_read(soft_watchdog_warn) == true) {
443                         /*
444                          * When multiple processes are causing softlockups the
445                          * softlockup detector only warns on the first one
446                          * because the code relies on a full quiet cycle to
447                          * re-arm.  The second process prevents the quiet cycle
448                          * and never gets reported.  Use task pointers to detect
449                          * this.
450                          */
451                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
452                             current) {
453                                 __this_cpu_write(soft_watchdog_warn, false);
454                                 __touch_watchdog();
455                         }
456                         return HRTIMER_RESTART;
457                 }
458
459                 if (softlockup_all_cpu_backtrace) {
460                         /* Prevent multiple soft-lockup reports if one cpu is already
461                          * engaged in dumping cpu back traces
462                          */
463                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
464                                 /* Someone else will report us. Let's give up */
465                                 __this_cpu_write(soft_watchdog_warn, true);
466                                 return HRTIMER_RESTART;
467                         }
468                 }
469
470                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
471                         smp_processor_id(), duration,
472                         current->comm, task_pid_nr(current));
473                 __this_cpu_write(softlockup_task_ptr_saved, current);
474                 print_modules();
475                 print_irqtrace_events(current);
476                 if (regs)
477                         show_regs(regs);
478                 else
479                         dump_stack();
480
481                 if (softlockup_all_cpu_backtrace) {
482                         /* Avoid generating two back traces for current
483                          * given that one is already made above
484                          */
485                         trigger_allbutself_cpu_backtrace();
486
487                         clear_bit(0, &soft_lockup_nmi_warn);
488                         /* Barrier to sync with other cpus */
489                         smp_mb__after_atomic();
490                 }
491
492                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
493                 if (softlockup_panic)
494                         panic("softlockup: hung tasks");
495                 __this_cpu_write(soft_watchdog_warn, true);
496         } else
497                 __this_cpu_write(soft_watchdog_warn, false);
498
499         return HRTIMER_RESTART;
500 }
501
502 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
503 {
504         struct sched_param param = { .sched_priority = prio };
505
506         sched_setscheduler(current, policy, &param);
507 }
508
509 static void watchdog_enable(unsigned int cpu)
510 {
511         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
512
513         /* kick off the timer for the hardlockup detector */
514         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
515         hrtimer->function = watchdog_timer_fn;
516
517         /* Enable the perf event */
518         watchdog_nmi_enable(cpu);
519
520         /* done here because hrtimer_start can only pin to smp_processor_id() */
521         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
522                       HRTIMER_MODE_REL_PINNED);
523
524         /* initialize timestamp */
525         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
526         __touch_watchdog();
527 }
528
529 static void watchdog_disable(unsigned int cpu)
530 {
531         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
532
533         watchdog_set_prio(SCHED_NORMAL, 0);
534         hrtimer_cancel(hrtimer);
535         /* disable the perf event */
536         watchdog_nmi_disable(cpu);
537 }
538
539 static void watchdog_cleanup(unsigned int cpu, bool online)
540 {
541         watchdog_disable(cpu);
542 }
543
544 static int watchdog_should_run(unsigned int cpu)
545 {
546         return __this_cpu_read(hrtimer_interrupts) !=
547                 __this_cpu_read(soft_lockup_hrtimer_cnt);
548 }
549
550 /*
551  * The watchdog thread function - touches the timestamp.
552  *
553  * It only runs once every sample_period seconds (4 seconds by
554  * default) to reset the softlockup timestamp. If this gets delayed
555  * for more than 2*watchdog_thresh seconds then the debug-printout
556  * triggers in watchdog_timer_fn().
557  */
558 static void watchdog(unsigned int cpu)
559 {
560         __this_cpu_write(soft_lockup_hrtimer_cnt,
561                          __this_cpu_read(hrtimer_interrupts));
562         __touch_watchdog();
563
564         /*
565          * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
566          * failure path. Check for failures that can occur asynchronously -
567          * for example, when CPUs are on-lined - and shut down the hardware
568          * perf event on each CPU accordingly.
569          *
570          * The only non-obvious place this bit can be cleared is through
571          * watchdog_nmi_enable(), so a pr_info() is placed there.  Placing a
572          * pr_info here would be too noisy as it would result in a message
573          * every few seconds if the hardlockup was disabled but the softlockup
574          * enabled.
575          */
576         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
577                 watchdog_nmi_disable(cpu);
578 }
579
580 #ifdef CONFIG_HARDLOCKUP_DETECTOR
581 /*
582  * People like the simple clean cpu node info on boot.
583  * Reduce the watchdog noise by only printing messages
584  * that are different from what cpu0 displayed.
585  */
586 static unsigned long cpu0_err;
587
588 static int watchdog_nmi_enable(unsigned int cpu)
589 {
590         struct perf_event_attr *wd_attr;
591         struct perf_event *event = per_cpu(watchdog_ev, cpu);
592
593         /* nothing to do if the hard lockup detector is disabled */
594         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
595                 goto out;
596
597         /* is it already setup and enabled? */
598         if (event && event->state > PERF_EVENT_STATE_OFF)
599                 goto out;
600
601         /* it is setup but not enabled */
602         if (event != NULL)
603                 goto out_enable;
604
605         wd_attr = &wd_hw_attr;
606         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
607
608         /* Try to register using hardware perf events */
609         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
610
611         /* save cpu0 error for future comparision */
612         if (cpu == 0 && IS_ERR(event))
613                 cpu0_err = PTR_ERR(event);
614
615         if (!IS_ERR(event)) {
616                 /* only print for cpu0 or different than cpu0 */
617                 if (cpu == 0 || cpu0_err)
618                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
619                 goto out_save;
620         }
621
622         /*
623          * Disable the hard lockup detector if _any_ CPU fails to set up
624          * set up the hardware perf event. The watchdog() function checks
625          * the NMI_WATCHDOG_ENABLED bit periodically.
626          *
627          * The barriers are for syncing up watchdog_enabled across all the
628          * cpus, as clear_bit() does not use barriers.
629          */
630         smp_mb__before_atomic();
631         clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
632         smp_mb__after_atomic();
633
634         /* skip displaying the same error again */
635         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
636                 return PTR_ERR(event);
637
638         /* vary the KERN level based on the returned errno */
639         if (PTR_ERR(event) == -EOPNOTSUPP)
640                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
641         else if (PTR_ERR(event) == -ENOENT)
642                 pr_warn("disabled (cpu%i): hardware events not enabled\n",
643                          cpu);
644         else
645                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
646                         cpu, PTR_ERR(event));
647
648         pr_info("Shutting down hard lockup detector on all cpus\n");
649
650         return PTR_ERR(event);
651
652         /* success path */
653 out_save:
654         per_cpu(watchdog_ev, cpu) = event;
655 out_enable:
656         perf_event_enable(per_cpu(watchdog_ev, cpu));
657 out:
658         return 0;
659 }
660
661 static void watchdog_nmi_disable(unsigned int cpu)
662 {
663         struct perf_event *event = per_cpu(watchdog_ev, cpu);
664
665         if (event) {
666                 perf_event_disable(event);
667                 per_cpu(watchdog_ev, cpu) = NULL;
668
669                 /* should be in cleanup, but blocks oprofile */
670                 perf_event_release_kernel(event);
671         }
672         if (cpu == 0) {
673                 /* watchdog_nmi_enable() expects this to be zero initially. */
674                 cpu0_err = 0;
675         }
676 }
677
678 #else
679 static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
680 static void watchdog_nmi_disable(unsigned int cpu) { return; }
681 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
682
683 static struct smp_hotplug_thread watchdog_threads = {
684         .store                  = &softlockup_watchdog,
685         .thread_should_run      = watchdog_should_run,
686         .thread_fn              = watchdog,
687         .thread_comm            = "watchdog/%u",
688         .setup                  = watchdog_enable,
689         .cleanup                = watchdog_cleanup,
690         .park                   = watchdog_disable,
691         .unpark                 = watchdog_enable,
692 };
693
694 /*
695  * park all watchdog threads that are specified in 'watchdog_cpumask'
696  *
697  * This function returns an error if kthread_park() of a watchdog thread
698  * fails. In this situation, the watchdog threads of some CPUs can already
699  * be parked and the watchdog threads of other CPUs can still be runnable.
700  * Callers are expected to handle this special condition as appropriate in
701  * their context.
702  *
703  * This function may only be called in a context that is protected against
704  * races with CPU hotplug - for example, via get_online_cpus().
705  */
706 static int watchdog_park_threads(void)
707 {
708         int cpu, ret = 0;
709
710         for_each_watchdog_cpu(cpu) {
711                 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
712                 if (ret)
713                         break;
714         }
715
716         return ret;
717 }
718
719 /*
720  * unpark all watchdog threads that are specified in 'watchdog_cpumask'
721  *
722  * This function may only be called in a context that is protected against
723  * races with CPU hotplug - for example, via get_online_cpus().
724  */
725 static void watchdog_unpark_threads(void)
726 {
727         int cpu;
728
729         for_each_watchdog_cpu(cpu)
730                 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
731 }
732
733 /*
734  * Suspend the hard and soft lockup detector by parking the watchdog threads.
735  */
736 int lockup_detector_suspend(void)
737 {
738         int ret = 0;
739
740         get_online_cpus();
741         mutex_lock(&watchdog_proc_mutex);
742         /*
743          * Multiple suspend requests can be active in parallel (counted by
744          * the 'watchdog_suspended' variable). If the watchdog threads are
745          * running, the first caller takes care that they will be parked.
746          * The state of 'watchdog_running' cannot change while a suspend
747          * request is active (see related code in 'proc' handlers).
748          */
749         if (watchdog_running && !watchdog_suspended)
750                 ret = watchdog_park_threads();
751
752         if (ret == 0)
753                 watchdog_suspended++;
754         else {
755                 watchdog_disable_all_cpus();
756                 pr_err("Failed to suspend lockup detectors, disabled\n");
757                 watchdog_enabled = 0;
758         }
759
760         mutex_unlock(&watchdog_proc_mutex);
761
762         return ret;
763 }
764
765 /*
766  * Resume the hard and soft lockup detector by unparking the watchdog threads.
767  */
768 void lockup_detector_resume(void)
769 {
770         mutex_lock(&watchdog_proc_mutex);
771
772         watchdog_suspended--;
773         /*
774          * The watchdog threads are unparked if they were previously running
775          * and if there is no more active suspend request.
776          */
777         if (watchdog_running && !watchdog_suspended)
778                 watchdog_unpark_threads();
779
780         mutex_unlock(&watchdog_proc_mutex);
781         put_online_cpus();
782 }
783
784 static int update_watchdog_all_cpus(void)
785 {
786         int ret;
787
788         ret = watchdog_park_threads();
789         if (ret)
790                 return ret;
791
792         watchdog_unpark_threads();
793
794         return 0;
795 }
796
797 static int watchdog_enable_all_cpus(void)
798 {
799         int err = 0;
800
801         if (!watchdog_running) {
802                 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
803                                                              &watchdog_cpumask);
804                 if (err)
805                         pr_err("Failed to create watchdog threads, disabled\n");
806                 else
807                         watchdog_running = 1;
808         } else {
809                 /*
810                  * Enable/disable the lockup detectors or
811                  * change the sample period 'on the fly'.
812                  */
813                 err = update_watchdog_all_cpus();
814
815                 if (err) {
816                         watchdog_disable_all_cpus();
817                         pr_err("Failed to update lockup detectors, disabled\n");
818                 }
819         }
820
821         if (err)
822                 watchdog_enabled = 0;
823
824         return err;
825 }
826
827 static void watchdog_disable_all_cpus(void)
828 {
829         if (watchdog_running) {
830                 watchdog_running = 0;
831                 smpboot_unregister_percpu_thread(&watchdog_threads);
832         }
833 }
834
835 #ifdef CONFIG_SYSCTL
836
837 /*
838  * Update the run state of the lockup detectors.
839  */
840 static int proc_watchdog_update(void)
841 {
842         int err = 0;
843
844         /*
845          * Watchdog threads won't be started if they are already active.
846          * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
847          * care of this. If those threads are already active, the sample
848          * period will be updated and the lockup detectors will be enabled
849          * or disabled 'on the fly'.
850          */
851         if (watchdog_enabled && watchdog_thresh)
852                 err = watchdog_enable_all_cpus();
853         else
854                 watchdog_disable_all_cpus();
855
856         return err;
857
858 }
859
860 /*
861  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
862  *
863  * caller             | table->data points to | 'which' contains the flag(s)
864  * -------------------|-----------------------|-----------------------------
865  * proc_watchdog      | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
866  *                    |                       | with SOFT_WATCHDOG_ENABLED
867  * -------------------|-----------------------|-----------------------------
868  * proc_nmi_watchdog  | nmi_watchdog_enabled  | NMI_WATCHDOG_ENABLED
869  * -------------------|-----------------------|-----------------------------
870  * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
871  */
872 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
873                                 void __user *buffer, size_t *lenp, loff_t *ppos)
874 {
875         int err, old, new;
876         int *watchdog_param = (int *)table->data;
877
878         get_online_cpus();
879         mutex_lock(&watchdog_proc_mutex);
880
881         if (watchdog_suspended) {
882                 /* no parameter changes allowed while watchdog is suspended */
883                 err = -EAGAIN;
884                 goto out;
885         }
886
887         /*
888          * If the parameter is being read return the state of the corresponding
889          * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
890          * run state of the lockup detectors.
891          */
892         if (!write) {
893                 *watchdog_param = (watchdog_enabled & which) != 0;
894                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
895         } else {
896                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
897                 if (err)
898                         goto out;
899
900                 /*
901                  * There is a race window between fetching the current value
902                  * from 'watchdog_enabled' and storing the new value. During
903                  * this race window, watchdog_nmi_enable() can sneak in and
904                  * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
905                  * The 'cmpxchg' detects this race and the loop retries.
906                  */
907                 do {
908                         old = watchdog_enabled;
909                         /*
910                          * If the parameter value is not zero set the
911                          * corresponding bit(s), else clear it(them).
912                          */
913                         if (*watchdog_param)
914                                 new = old | which;
915                         else
916                                 new = old & ~which;
917                 } while (cmpxchg(&watchdog_enabled, old, new) != old);
918
919                 /*
920                  * Update the run state of the lockup detectors. There is _no_
921                  * need to check the value returned by proc_watchdog_update()
922                  * and to restore the previous value of 'watchdog_enabled' as
923                  * both lockup detectors are disabled if proc_watchdog_update()
924                  * returns an error.
925                  */
926                 if (old == new)
927                         goto out;
928
929                 err = proc_watchdog_update();
930         }
931 out:
932         mutex_unlock(&watchdog_proc_mutex);
933         put_online_cpus();
934         return err;
935 }
936
937 /*
938  * /proc/sys/kernel/watchdog
939  */
940 int proc_watchdog(struct ctl_table *table, int write,
941                   void __user *buffer, size_t *lenp, loff_t *ppos)
942 {
943         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
944                                     table, write, buffer, lenp, ppos);
945 }
946
947 /*
948  * /proc/sys/kernel/nmi_watchdog
949  */
950 int proc_nmi_watchdog(struct ctl_table *table, int write,
951                       void __user *buffer, size_t *lenp, loff_t *ppos)
952 {
953         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
954                                     table, write, buffer, lenp, ppos);
955 }
956
957 /*
958  * /proc/sys/kernel/soft_watchdog
959  */
960 int proc_soft_watchdog(struct ctl_table *table, int write,
961                         void __user *buffer, size_t *lenp, loff_t *ppos)
962 {
963         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
964                                     table, write, buffer, lenp, ppos);
965 }
966
967 /*
968  * /proc/sys/kernel/watchdog_thresh
969  */
970 int proc_watchdog_thresh(struct ctl_table *table, int write,
971                          void __user *buffer, size_t *lenp, loff_t *ppos)
972 {
973         int err, old, new;
974
975         get_online_cpus();
976         mutex_lock(&watchdog_proc_mutex);
977
978         if (watchdog_suspended) {
979                 /* no parameter changes allowed while watchdog is suspended */
980                 err = -EAGAIN;
981                 goto out;
982         }
983
984         old = ACCESS_ONCE(watchdog_thresh);
985         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
986
987         if (err || !write)
988                 goto out;
989
990         /*
991          * Update the sample period. Restore on failure.
992          */
993         new = ACCESS_ONCE(watchdog_thresh);
994         if (old == new)
995                 goto out;
996
997         set_sample_period();
998         err = proc_watchdog_update();
999         if (err) {
1000                 watchdog_thresh = old;
1001                 set_sample_period();
1002         }
1003 out:
1004         mutex_unlock(&watchdog_proc_mutex);
1005         put_online_cpus();
1006         return err;
1007 }
1008
1009 /*
1010  * The cpumask is the mask of possible cpus that the watchdog can run
1011  * on, not the mask of cpus it is actually running on.  This allows the
1012  * user to specify a mask that will include cpus that have not yet
1013  * been brought online, if desired.
1014  */
1015 int proc_watchdog_cpumask(struct ctl_table *table, int write,
1016                           void __user *buffer, size_t *lenp, loff_t *ppos)
1017 {
1018         int err;
1019
1020         get_online_cpus();
1021         mutex_lock(&watchdog_proc_mutex);
1022
1023         if (watchdog_suspended) {
1024                 /* no parameter changes allowed while watchdog is suspended */
1025                 err = -EAGAIN;
1026                 goto out;
1027         }
1028
1029         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1030         if (!err && write) {
1031                 /* Remove impossible cpus to keep sysctl output cleaner. */
1032                 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
1033                             cpu_possible_mask);
1034
1035                 if (watchdog_running) {
1036                         /*
1037                          * Failure would be due to being unable to allocate
1038                          * a temporary cpumask, so we are likely not in a
1039                          * position to do much else to make things better.
1040                          */
1041                         if (smpboot_update_cpumask_percpu_thread(
1042                                     &watchdog_threads, &watchdog_cpumask) != 0)
1043                                 pr_err("cpumask update failed\n");
1044                 }
1045         }
1046 out:
1047         mutex_unlock(&watchdog_proc_mutex);
1048         put_online_cpus();
1049         return err;
1050 }
1051
1052 #endif /* CONFIG_SYSCTL */
1053
1054 void __init lockup_detector_init(void)
1055 {
1056         set_sample_period();
1057
1058 #ifdef CONFIG_NO_HZ_FULL
1059         if (tick_nohz_full_enabled()) {
1060                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1061                 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
1062         } else
1063                 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1064 #else
1065         cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1066 #endif
1067
1068         if (watchdog_enabled)
1069                 watchdog_enable_all_cpus();
1070 }