c1e0b5f429b6b91c9b80c0173f8c8668541fbde8
[firefly-linux-kernel-4.4.55.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
24 #include <asm/irq_regs.h>
25 #include <linux/kvm_para.h>
26 #include <linux/perf_event.h>
27 #include <linux/kthread.h>
28
29 /*
30  * The run state of the lockup detectors is controlled by the content of the
31  * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
32  * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
33  *
34  * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
35  * are variables that are only used as an 'interface' between the parameters
36  * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
37  * 'watchdog_thresh' variable is handled differently because its value is not
38  * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
39  * is equal zero.
40  */
41 #define NMI_WATCHDOG_ENABLED_BIT   0
42 #define SOFT_WATCHDOG_ENABLED_BIT  1
43 #define NMI_WATCHDOG_ENABLED      (1 << NMI_WATCHDOG_ENABLED_BIT)
44 #define SOFT_WATCHDOG_ENABLED     (1 << SOFT_WATCHDOG_ENABLED_BIT)
45
46 static DEFINE_MUTEX(watchdog_proc_mutex);
47
48 #ifdef CONFIG_HARDLOCKUP_DETECTOR
49 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
50 #else
51 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
52 #endif
53 int __read_mostly nmi_watchdog_enabled;
54 int __read_mostly soft_watchdog_enabled;
55 int __read_mostly watchdog_user_enabled;
56 int __read_mostly watchdog_thresh = 10;
57
58 #ifdef CONFIG_SMP
59 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
60 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
61 #else
62 #define sysctl_softlockup_all_cpu_backtrace 0
63 #define sysctl_hardlockup_all_cpu_backtrace 0
64 #endif
65 static struct cpumask watchdog_cpumask __read_mostly;
66 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
67
68 /* Helper for online, unparked cpus. */
69 #define for_each_watchdog_cpu(cpu) \
70         for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
71
72 /*
73  * The 'watchdog_running' variable is set to 1 when the watchdog threads
74  * are registered/started and is set to 0 when the watchdog threads are
75  * unregistered/stopped, so it is an indicator whether the threads exist.
76  */
77 static int __read_mostly watchdog_running;
78 /*
79  * If a subsystem has a need to deactivate the watchdog temporarily, it
80  * can use the suspend/resume interface to achieve this. The content of
81  * the 'watchdog_suspended' variable reflects this state. Existing threads
82  * are parked/unparked by the lockup_detector_{suspend|resume} functions
83  * (see comment blocks pertaining to those functions for further details).
84  *
85  * 'watchdog_suspended' also prevents threads from being registered/started
86  * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
87  * of 'watchdog_running' cannot change while the watchdog is deactivated
88  * temporarily (see related code in 'proc' handlers).
89  */
90 static int __read_mostly watchdog_suspended;
91
92 static u64 __read_mostly sample_period;
93
94 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
95 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
96 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
97 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
98 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
99 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
100 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
101 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
102 #ifdef CONFIG_HARDLOCKUP_DETECTOR
103 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
104 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
105 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
106 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
107 #endif
108 static unsigned long soft_lockup_nmi_warn;
109
110 /* boot commands */
111 /*
112  * Should we panic when a soft-lockup or hard-lockup occurs:
113  */
114 #ifdef CONFIG_HARDLOCKUP_DETECTOR
115 unsigned int __read_mostly hardlockup_panic =
116                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
117 static unsigned long hardlockup_allcpu_dumped;
118 /*
119  * We may not want to enable hard lockup detection by default in all cases,
120  * for example when running the kernel as a guest on a hypervisor. In these
121  * cases this function can be called to disable hard lockup detection. This
122  * function should only be executed once by the boot processor before the
123  * kernel command line parameters are parsed, because otherwise it is not
124  * possible to override this in hardlockup_panic_setup().
125  */
126 void hardlockup_detector_disable(void)
127 {
128         watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
129 }
130
131 static int __init hardlockup_panic_setup(char *str)
132 {
133         if (!strncmp(str, "panic", 5))
134                 hardlockup_panic = 1;
135         else if (!strncmp(str, "nopanic", 7))
136                 hardlockup_panic = 0;
137         else if (!strncmp(str, "0", 1))
138                 watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
139         else if (!strncmp(str, "1", 1))
140                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
141         return 1;
142 }
143 __setup("nmi_watchdog=", hardlockup_panic_setup);
144 #endif
145
146 unsigned int __read_mostly softlockup_panic =
147                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
148
149 static int __init softlockup_panic_setup(char *str)
150 {
151         softlockup_panic = simple_strtoul(str, NULL, 0);
152
153         return 1;
154 }
155 __setup("softlockup_panic=", softlockup_panic_setup);
156
157 static int __init nowatchdog_setup(char *str)
158 {
159         watchdog_enabled = 0;
160         return 1;
161 }
162 __setup("nowatchdog", nowatchdog_setup);
163
164 static int __init nosoftlockup_setup(char *str)
165 {
166         watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
167         return 1;
168 }
169 __setup("nosoftlockup", nosoftlockup_setup);
170
171 #ifdef CONFIG_SMP
172 static int __init softlockup_all_cpu_backtrace_setup(char *str)
173 {
174         sysctl_softlockup_all_cpu_backtrace =
175                 !!simple_strtol(str, NULL, 0);
176         return 1;
177 }
178 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
179 static int __init hardlockup_all_cpu_backtrace_setup(char *str)
180 {
181         sysctl_hardlockup_all_cpu_backtrace =
182                 !!simple_strtol(str, NULL, 0);
183         return 1;
184 }
185 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
186 #endif
187
188 /*
189  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
190  * lockups can have false positives under extreme conditions. So we generally
191  * want a higher threshold for soft lockups than for hard lockups. So we couple
192  * the thresholds with a factor: we make the soft threshold twice the amount of
193  * time the hard threshold is.
194  */
195 static int get_softlockup_thresh(void)
196 {
197         return watchdog_thresh * 2;
198 }
199
200 /*
201  * Returns seconds, approximately.  We don't need nanosecond
202  * resolution, and we don't need to waste time with a big divide when
203  * 2^30ns == 1.074s.
204  */
205 static unsigned long get_timestamp(void)
206 {
207         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
208 }
209
210 static void set_sample_period(void)
211 {
212         /*
213          * convert watchdog_thresh from seconds to ns
214          * the divide by 5 is to give hrtimer several chances (two
215          * or three with the current relation between the soft
216          * and hard thresholds) to increment before the
217          * hardlockup detector generates a warning
218          */
219         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
220 }
221
222 /* Commands for resetting the watchdog */
223 static void __touch_watchdog(void)
224 {
225         __this_cpu_write(watchdog_touch_ts, get_timestamp());
226 }
227
228 void touch_softlockup_watchdog(void)
229 {
230         /*
231          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
232          * gets zeroed here, so use the raw_ operation.
233          */
234         raw_cpu_write(watchdog_touch_ts, 0);
235 }
236 EXPORT_SYMBOL(touch_softlockup_watchdog);
237
238 void touch_all_softlockup_watchdogs(void)
239 {
240         int cpu;
241
242         /*
243          * this is done lockless
244          * do we care if a 0 races with a timestamp?
245          * all it means is the softlock check starts one cycle later
246          */
247         for_each_watchdog_cpu(cpu)
248                 per_cpu(watchdog_touch_ts, cpu) = 0;
249 }
250
251 #ifdef CONFIG_HARDLOCKUP_DETECTOR
252 void touch_nmi_watchdog(void)
253 {
254         /*
255          * Using __raw here because some code paths have
256          * preemption enabled.  If preemption is enabled
257          * then interrupts should be enabled too, in which
258          * case we shouldn't have to worry about the watchdog
259          * going off.
260          */
261         raw_cpu_write(watchdog_nmi_touch, true);
262         touch_softlockup_watchdog();
263 }
264 EXPORT_SYMBOL(touch_nmi_watchdog);
265
266 #endif
267
268 void touch_softlockup_watchdog_sync(void)
269 {
270         __this_cpu_write(softlockup_touch_sync, true);
271         __this_cpu_write(watchdog_touch_ts, 0);
272 }
273
274 #ifdef CONFIG_HARDLOCKUP_DETECTOR
275 /* watchdog detector functions */
276 static bool is_hardlockup(void)
277 {
278         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
279
280         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
281                 return true;
282
283         __this_cpu_write(hrtimer_interrupts_saved, hrint);
284         return false;
285 }
286 #endif
287
288 static int is_softlockup(unsigned long touch_ts)
289 {
290         unsigned long now = get_timestamp();
291
292         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
293                 /* Warn about unreasonable delays. */
294                 if (time_after(now, touch_ts + get_softlockup_thresh()))
295                         return now - touch_ts;
296         }
297         return 0;
298 }
299
300 #ifdef CONFIG_HARDLOCKUP_DETECTOR
301
302 static struct perf_event_attr wd_hw_attr = {
303         .type           = PERF_TYPE_HARDWARE,
304         .config         = PERF_COUNT_HW_CPU_CYCLES,
305         .size           = sizeof(struct perf_event_attr),
306         .pinned         = 1,
307         .disabled       = 1,
308 };
309
310 /* Callback function for perf event subsystem */
311 static void watchdog_overflow_callback(struct perf_event *event,
312                  struct perf_sample_data *data,
313                  struct pt_regs *regs)
314 {
315         /* Ensure the watchdog never gets throttled */
316         event->hw.interrupts = 0;
317
318         if (__this_cpu_read(watchdog_nmi_touch) == true) {
319                 __this_cpu_write(watchdog_nmi_touch, false);
320                 return;
321         }
322
323         /* check for a hardlockup
324          * This is done by making sure our timer interrupt
325          * is incrementing.  The timer interrupt should have
326          * fired multiple times before we overflow'd.  If it hasn't
327          * then this is a good indication the cpu is stuck
328          */
329         if (is_hardlockup()) {
330                 int this_cpu = smp_processor_id();
331
332                 /* only print hardlockups once */
333                 if (__this_cpu_read(hard_watchdog_warn) == true)
334                         return;
335
336                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
337                 print_modules();
338                 print_irqtrace_events(current);
339                 if (regs)
340                         show_regs(regs);
341                 else
342                         dump_stack();
343
344                 /*
345                  * Perform all-CPU dump only once to avoid multiple hardlockups
346                  * generating interleaving traces
347                  */
348                 if (sysctl_hardlockup_all_cpu_backtrace &&
349                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
350                         trigger_allbutself_cpu_backtrace();
351
352                 if (hardlockup_panic)
353                         panic("Hard LOCKUP");
354
355                 __this_cpu_write(hard_watchdog_warn, true);
356                 return;
357         }
358
359         __this_cpu_write(hard_watchdog_warn, false);
360         return;
361 }
362 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
363
364 static void watchdog_interrupt_count(void)
365 {
366         __this_cpu_inc(hrtimer_interrupts);
367 }
368
369 static int watchdog_nmi_enable(unsigned int cpu);
370 static void watchdog_nmi_disable(unsigned int cpu);
371
372 static int watchdog_enable_all_cpus(void);
373 static void watchdog_disable_all_cpus(void);
374
375 /* watchdog kicker functions */
376 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
377 {
378         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
379         struct pt_regs *regs = get_irq_regs();
380         int duration;
381         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
382
383         /* kick the hardlockup detector */
384         watchdog_interrupt_count();
385
386         /* kick the softlockup detector */
387         wake_up_process(__this_cpu_read(softlockup_watchdog));
388
389         /* .. and repeat */
390         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
391
392         if (touch_ts == 0) {
393                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
394                         /*
395                          * If the time stamp was touched atomically
396                          * make sure the scheduler tick is up to date.
397                          */
398                         __this_cpu_write(softlockup_touch_sync, false);
399                         sched_clock_tick();
400                 }
401
402                 /* Clear the guest paused flag on watchdog reset */
403                 kvm_check_and_clear_guest_paused();
404                 __touch_watchdog();
405                 return HRTIMER_RESTART;
406         }
407
408         /* check for a softlockup
409          * This is done by making sure a high priority task is
410          * being scheduled.  The task touches the watchdog to
411          * indicate it is getting cpu time.  If it hasn't then
412          * this is a good indication some task is hogging the cpu
413          */
414         duration = is_softlockup(touch_ts);
415         if (unlikely(duration)) {
416                 /*
417                  * If a virtual machine is stopped by the host it can look to
418                  * the watchdog like a soft lockup, check to see if the host
419                  * stopped the vm before we issue the warning
420                  */
421                 if (kvm_check_and_clear_guest_paused())
422                         return HRTIMER_RESTART;
423
424                 /* only warn once */
425                 if (__this_cpu_read(soft_watchdog_warn) == true) {
426                         /*
427                          * When multiple processes are causing softlockups the
428                          * softlockup detector only warns on the first one
429                          * because the code relies on a full quiet cycle to
430                          * re-arm.  The second process prevents the quiet cycle
431                          * and never gets reported.  Use task pointers to detect
432                          * this.
433                          */
434                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
435                             current) {
436                                 __this_cpu_write(soft_watchdog_warn, false);
437                                 __touch_watchdog();
438                         }
439                         return HRTIMER_RESTART;
440                 }
441
442                 if (softlockup_all_cpu_backtrace) {
443                         /* Prevent multiple soft-lockup reports if one cpu is already
444                          * engaged in dumping cpu back traces
445                          */
446                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
447                                 /* Someone else will report us. Let's give up */
448                                 __this_cpu_write(soft_watchdog_warn, true);
449                                 return HRTIMER_RESTART;
450                         }
451                 }
452
453                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
454                         smp_processor_id(), duration,
455                         current->comm, task_pid_nr(current));
456                 __this_cpu_write(softlockup_task_ptr_saved, current);
457                 print_modules();
458                 print_irqtrace_events(current);
459                 if (regs)
460                         show_regs(regs);
461                 else
462                         dump_stack();
463
464                 if (softlockup_all_cpu_backtrace) {
465                         /* Avoid generating two back traces for current
466                          * given that one is already made above
467                          */
468                         trigger_allbutself_cpu_backtrace();
469
470                         clear_bit(0, &soft_lockup_nmi_warn);
471                         /* Barrier to sync with other cpus */
472                         smp_mb__after_atomic();
473                 }
474
475                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
476                 if (softlockup_panic)
477                         panic("softlockup: hung tasks");
478                 __this_cpu_write(soft_watchdog_warn, true);
479         } else
480                 __this_cpu_write(soft_watchdog_warn, false);
481
482         return HRTIMER_RESTART;
483 }
484
485 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
486 {
487         struct sched_param param = { .sched_priority = prio };
488
489         sched_setscheduler(current, policy, &param);
490 }
491
492 static void watchdog_enable(unsigned int cpu)
493 {
494         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
495
496         /* kick off the timer for the hardlockup detector */
497         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
498         hrtimer->function = watchdog_timer_fn;
499
500         /* Enable the perf event */
501         watchdog_nmi_enable(cpu);
502
503         /* done here because hrtimer_start can only pin to smp_processor_id() */
504         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
505                       HRTIMER_MODE_REL_PINNED);
506
507         /* initialize timestamp */
508         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
509         __touch_watchdog();
510 }
511
512 static void watchdog_disable(unsigned int cpu)
513 {
514         struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
515
516         watchdog_set_prio(SCHED_NORMAL, 0);
517         hrtimer_cancel(hrtimer);
518         /* disable the perf event */
519         watchdog_nmi_disable(cpu);
520 }
521
522 static void watchdog_cleanup(unsigned int cpu, bool online)
523 {
524         watchdog_disable(cpu);
525 }
526
527 static int watchdog_should_run(unsigned int cpu)
528 {
529         return __this_cpu_read(hrtimer_interrupts) !=
530                 __this_cpu_read(soft_lockup_hrtimer_cnt);
531 }
532
533 /*
534  * The watchdog thread function - touches the timestamp.
535  *
536  * It only runs once every sample_period seconds (4 seconds by
537  * default) to reset the softlockup timestamp. If this gets delayed
538  * for more than 2*watchdog_thresh seconds then the debug-printout
539  * triggers in watchdog_timer_fn().
540  */
541 static void watchdog(unsigned int cpu)
542 {
543         __this_cpu_write(soft_lockup_hrtimer_cnt,
544                          __this_cpu_read(hrtimer_interrupts));
545         __touch_watchdog();
546
547         /*
548          * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
549          * failure path. Check for failures that can occur asynchronously -
550          * for example, when CPUs are on-lined - and shut down the hardware
551          * perf event on each CPU accordingly.
552          *
553          * The only non-obvious place this bit can be cleared is through
554          * watchdog_nmi_enable(), so a pr_info() is placed there.  Placing a
555          * pr_info here would be too noisy as it would result in a message
556          * every few seconds if the hardlockup was disabled but the softlockup
557          * enabled.
558          */
559         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
560                 watchdog_nmi_disable(cpu);
561 }
562
563 #ifdef CONFIG_HARDLOCKUP_DETECTOR
564 /*
565  * People like the simple clean cpu node info on boot.
566  * Reduce the watchdog noise by only printing messages
567  * that are different from what cpu0 displayed.
568  */
569 static unsigned long cpu0_err;
570
571 static int watchdog_nmi_enable(unsigned int cpu)
572 {
573         struct perf_event_attr *wd_attr;
574         struct perf_event *event = per_cpu(watchdog_ev, cpu);
575
576         /* nothing to do if the hard lockup detector is disabled */
577         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
578                 goto out;
579
580         /* is it already setup and enabled? */
581         if (event && event->state > PERF_EVENT_STATE_OFF)
582                 goto out;
583
584         /* it is setup but not enabled */
585         if (event != NULL)
586                 goto out_enable;
587
588         wd_attr = &wd_hw_attr;
589         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
590
591         /* Try to register using hardware perf events */
592         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
593
594         /* save cpu0 error for future comparision */
595         if (cpu == 0 && IS_ERR(event))
596                 cpu0_err = PTR_ERR(event);
597
598         if (!IS_ERR(event)) {
599                 /* only print for cpu0 or different than cpu0 */
600                 if (cpu == 0 || cpu0_err)
601                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
602                 goto out_save;
603         }
604
605         /*
606          * Disable the hard lockup detector if _any_ CPU fails to set up
607          * set up the hardware perf event. The watchdog() function checks
608          * the NMI_WATCHDOG_ENABLED bit periodically.
609          *
610          * The barriers are for syncing up watchdog_enabled across all the
611          * cpus, as clear_bit() does not use barriers.
612          */
613         smp_mb__before_atomic();
614         clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
615         smp_mb__after_atomic();
616
617         /* skip displaying the same error again */
618         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
619                 return PTR_ERR(event);
620
621         /* vary the KERN level based on the returned errno */
622         if (PTR_ERR(event) == -EOPNOTSUPP)
623                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
624         else if (PTR_ERR(event) == -ENOENT)
625                 pr_warn("disabled (cpu%i): hardware events not enabled\n",
626                          cpu);
627         else
628                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
629                         cpu, PTR_ERR(event));
630
631         pr_info("Shutting down hard lockup detector on all cpus\n");
632
633         return PTR_ERR(event);
634
635         /* success path */
636 out_save:
637         per_cpu(watchdog_ev, cpu) = event;
638 out_enable:
639         perf_event_enable(per_cpu(watchdog_ev, cpu));
640 out:
641         return 0;
642 }
643
644 static void watchdog_nmi_disable(unsigned int cpu)
645 {
646         struct perf_event *event = per_cpu(watchdog_ev, cpu);
647
648         if (event) {
649                 perf_event_disable(event);
650                 per_cpu(watchdog_ev, cpu) = NULL;
651
652                 /* should be in cleanup, but blocks oprofile */
653                 perf_event_release_kernel(event);
654         }
655         if (cpu == 0) {
656                 /* watchdog_nmi_enable() expects this to be zero initially. */
657                 cpu0_err = 0;
658         }
659 }
660
661 #else
662 static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
663 static void watchdog_nmi_disable(unsigned int cpu) { return; }
664 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
665
666 static struct smp_hotplug_thread watchdog_threads = {
667         .store                  = &softlockup_watchdog,
668         .thread_should_run      = watchdog_should_run,
669         .thread_fn              = watchdog,
670         .thread_comm            = "watchdog/%u",
671         .setup                  = watchdog_enable,
672         .cleanup                = watchdog_cleanup,
673         .park                   = watchdog_disable,
674         .unpark                 = watchdog_enable,
675 };
676
677 /*
678  * park all watchdog threads that are specified in 'watchdog_cpumask'
679  *
680  * This function returns an error if kthread_park() of a watchdog thread
681  * fails. In this situation, the watchdog threads of some CPUs can already
682  * be parked and the watchdog threads of other CPUs can still be runnable.
683  * Callers are expected to handle this special condition as appropriate in
684  * their context.
685  *
686  * This function may only be called in a context that is protected against
687  * races with CPU hotplug - for example, via get_online_cpus().
688  */
689 static int watchdog_park_threads(void)
690 {
691         int cpu, ret = 0;
692
693         for_each_watchdog_cpu(cpu) {
694                 ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
695                 if (ret)
696                         break;
697         }
698
699         return ret;
700 }
701
702 /*
703  * unpark all watchdog threads that are specified in 'watchdog_cpumask'
704  *
705  * This function may only be called in a context that is protected against
706  * races with CPU hotplug - for example, via get_online_cpus().
707  */
708 static void watchdog_unpark_threads(void)
709 {
710         int cpu;
711
712         for_each_watchdog_cpu(cpu)
713                 kthread_unpark(per_cpu(softlockup_watchdog, cpu));
714 }
715
716 /*
717  * Suspend the hard and soft lockup detector by parking the watchdog threads.
718  */
719 int lockup_detector_suspend(void)
720 {
721         int ret = 0;
722
723         get_online_cpus();
724         mutex_lock(&watchdog_proc_mutex);
725         /*
726          * Multiple suspend requests can be active in parallel (counted by
727          * the 'watchdog_suspended' variable). If the watchdog threads are
728          * running, the first caller takes care that they will be parked.
729          * The state of 'watchdog_running' cannot change while a suspend
730          * request is active (see related code in 'proc' handlers).
731          */
732         if (watchdog_running && !watchdog_suspended)
733                 ret = watchdog_park_threads();
734
735         if (ret == 0)
736                 watchdog_suspended++;
737         else {
738                 watchdog_disable_all_cpus();
739                 pr_err("Failed to suspend lockup detectors, disabled\n");
740                 watchdog_enabled = 0;
741         }
742
743         mutex_unlock(&watchdog_proc_mutex);
744
745         return ret;
746 }
747
748 /*
749  * Resume the hard and soft lockup detector by unparking the watchdog threads.
750  */
751 void lockup_detector_resume(void)
752 {
753         mutex_lock(&watchdog_proc_mutex);
754
755         watchdog_suspended--;
756         /*
757          * The watchdog threads are unparked if they were previously running
758          * and if there is no more active suspend request.
759          */
760         if (watchdog_running && !watchdog_suspended)
761                 watchdog_unpark_threads();
762
763         mutex_unlock(&watchdog_proc_mutex);
764         put_online_cpus();
765 }
766
767 static int update_watchdog_all_cpus(void)
768 {
769         int ret;
770
771         ret = watchdog_park_threads();
772         if (ret)
773                 return ret;
774
775         watchdog_unpark_threads();
776
777         return 0;
778 }
779
780 static int watchdog_enable_all_cpus(void)
781 {
782         int err = 0;
783
784         if (!watchdog_running) {
785                 err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
786                                                              &watchdog_cpumask);
787                 if (err)
788                         pr_err("Failed to create watchdog threads, disabled\n");
789                 else
790                         watchdog_running = 1;
791         } else {
792                 /*
793                  * Enable/disable the lockup detectors or
794                  * change the sample period 'on the fly'.
795                  */
796                 err = update_watchdog_all_cpus();
797
798                 if (err) {
799                         watchdog_disable_all_cpus();
800                         pr_err("Failed to update lockup detectors, disabled\n");
801                 }
802         }
803
804         if (err)
805                 watchdog_enabled = 0;
806
807         return err;
808 }
809
810 static void watchdog_disable_all_cpus(void)
811 {
812         if (watchdog_running) {
813                 watchdog_running = 0;
814                 smpboot_unregister_percpu_thread(&watchdog_threads);
815         }
816 }
817
818 #ifdef CONFIG_SYSCTL
819
820 /*
821  * Update the run state of the lockup detectors.
822  */
823 static int proc_watchdog_update(void)
824 {
825         int err = 0;
826
827         /*
828          * Watchdog threads won't be started if they are already active.
829          * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
830          * care of this. If those threads are already active, the sample
831          * period will be updated and the lockup detectors will be enabled
832          * or disabled 'on the fly'.
833          */
834         if (watchdog_enabled && watchdog_thresh)
835                 err = watchdog_enable_all_cpus();
836         else
837                 watchdog_disable_all_cpus();
838
839         return err;
840
841 }
842
843 /*
844  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
845  *
846  * caller             | table->data points to | 'which' contains the flag(s)
847  * -------------------|-----------------------|-----------------------------
848  * proc_watchdog      | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
849  *                    |                       | with SOFT_WATCHDOG_ENABLED
850  * -------------------|-----------------------|-----------------------------
851  * proc_nmi_watchdog  | nmi_watchdog_enabled  | NMI_WATCHDOG_ENABLED
852  * -------------------|-----------------------|-----------------------------
853  * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
854  */
855 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
856                                 void __user *buffer, size_t *lenp, loff_t *ppos)
857 {
858         int err, old, new;
859         int *watchdog_param = (int *)table->data;
860
861         get_online_cpus();
862         mutex_lock(&watchdog_proc_mutex);
863
864         if (watchdog_suspended) {
865                 /* no parameter changes allowed while watchdog is suspended */
866                 err = -EAGAIN;
867                 goto out;
868         }
869
870         /*
871          * If the parameter is being read return the state of the corresponding
872          * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
873          * run state of the lockup detectors.
874          */
875         if (!write) {
876                 *watchdog_param = (watchdog_enabled & which) != 0;
877                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
878         } else {
879                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
880                 if (err)
881                         goto out;
882
883                 /*
884                  * There is a race window between fetching the current value
885                  * from 'watchdog_enabled' and storing the new value. During
886                  * this race window, watchdog_nmi_enable() can sneak in and
887                  * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
888                  * The 'cmpxchg' detects this race and the loop retries.
889                  */
890                 do {
891                         old = watchdog_enabled;
892                         /*
893                          * If the parameter value is not zero set the
894                          * corresponding bit(s), else clear it(them).
895                          */
896                         if (*watchdog_param)
897                                 new = old | which;
898                         else
899                                 new = old & ~which;
900                 } while (cmpxchg(&watchdog_enabled, old, new) != old);
901
902                 /*
903                  * Update the run state of the lockup detectors. There is _no_
904                  * need to check the value returned by proc_watchdog_update()
905                  * and to restore the previous value of 'watchdog_enabled' as
906                  * both lockup detectors are disabled if proc_watchdog_update()
907                  * returns an error.
908                  */
909                 if (old == new)
910                         goto out;
911
912                 err = proc_watchdog_update();
913         }
914 out:
915         mutex_unlock(&watchdog_proc_mutex);
916         put_online_cpus();
917         return err;
918 }
919
920 /*
921  * /proc/sys/kernel/watchdog
922  */
923 int proc_watchdog(struct ctl_table *table, int write,
924                   void __user *buffer, size_t *lenp, loff_t *ppos)
925 {
926         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
927                                     table, write, buffer, lenp, ppos);
928 }
929
930 /*
931  * /proc/sys/kernel/nmi_watchdog
932  */
933 int proc_nmi_watchdog(struct ctl_table *table, int write,
934                       void __user *buffer, size_t *lenp, loff_t *ppos)
935 {
936         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
937                                     table, write, buffer, lenp, ppos);
938 }
939
940 /*
941  * /proc/sys/kernel/soft_watchdog
942  */
943 int proc_soft_watchdog(struct ctl_table *table, int write,
944                         void __user *buffer, size_t *lenp, loff_t *ppos)
945 {
946         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
947                                     table, write, buffer, lenp, ppos);
948 }
949
950 /*
951  * /proc/sys/kernel/watchdog_thresh
952  */
953 int proc_watchdog_thresh(struct ctl_table *table, int write,
954                          void __user *buffer, size_t *lenp, loff_t *ppos)
955 {
956         int err, old, new;
957
958         get_online_cpus();
959         mutex_lock(&watchdog_proc_mutex);
960
961         if (watchdog_suspended) {
962                 /* no parameter changes allowed while watchdog is suspended */
963                 err = -EAGAIN;
964                 goto out;
965         }
966
967         old = ACCESS_ONCE(watchdog_thresh);
968         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
969
970         if (err || !write)
971                 goto out;
972
973         /*
974          * Update the sample period. Restore on failure.
975          */
976         new = ACCESS_ONCE(watchdog_thresh);
977         if (old == new)
978                 goto out;
979
980         set_sample_period();
981         err = proc_watchdog_update();
982         if (err) {
983                 watchdog_thresh = old;
984                 set_sample_period();
985         }
986 out:
987         mutex_unlock(&watchdog_proc_mutex);
988         put_online_cpus();
989         return err;
990 }
991
992 /*
993  * The cpumask is the mask of possible cpus that the watchdog can run
994  * on, not the mask of cpus it is actually running on.  This allows the
995  * user to specify a mask that will include cpus that have not yet
996  * been brought online, if desired.
997  */
998 int proc_watchdog_cpumask(struct ctl_table *table, int write,
999                           void __user *buffer, size_t *lenp, loff_t *ppos)
1000 {
1001         int err;
1002
1003         get_online_cpus();
1004         mutex_lock(&watchdog_proc_mutex);
1005
1006         if (watchdog_suspended) {
1007                 /* no parameter changes allowed while watchdog is suspended */
1008                 err = -EAGAIN;
1009                 goto out;
1010         }
1011
1012         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1013         if (!err && write) {
1014                 /* Remove impossible cpus to keep sysctl output cleaner. */
1015                 cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
1016                             cpu_possible_mask);
1017
1018                 if (watchdog_running) {
1019                         /*
1020                          * Failure would be due to being unable to allocate
1021                          * a temporary cpumask, so we are likely not in a
1022                          * position to do much else to make things better.
1023                          */
1024                         if (smpboot_update_cpumask_percpu_thread(
1025                                     &watchdog_threads, &watchdog_cpumask) != 0)
1026                                 pr_err("cpumask update failed\n");
1027                 }
1028         }
1029 out:
1030         mutex_unlock(&watchdog_proc_mutex);
1031         put_online_cpus();
1032         return err;
1033 }
1034
1035 #endif /* CONFIG_SYSCTL */
1036
1037 void __init lockup_detector_init(void)
1038 {
1039         set_sample_period();
1040
1041 #ifdef CONFIG_NO_HZ_FULL
1042         if (tick_nohz_full_enabled()) {
1043                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1044                 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
1045         } else
1046                 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1047 #else
1048         cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1049 #endif
1050
1051         if (watchdog_enabled)
1052                 watchdog_enable_all_cpus();
1053 }