kernel/watchdog.c

   1 /*
   2  * Detect hard and soft lockups on a system
   3  *
   4  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   5  *
   6  * Note: Most of this code is borrowed heavily from the original softlockup
   7  * detector, so thanks to Ingo for the initial implementation.
   8  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
   9  * to those contributors as well.
  10  */
  11
  12 #define pr_fmt(fmt) "NMI watchdog: " fmt
  13
  14 #include <linux/mm.h>
  15 #include <linux/cpu.h>
  16 #include <linux/nmi.h>
  17 #include <linux/init.h>
  18 #include <linux/delay.h>
  19 #include <linux/freezer.h>
  20 #include <linux/kthread.h>
  21 #include <linux/lockdep.h>
  22 #include <linux/notifier.h>
  23 #include <linux/module.h>
  24 #include <linux/sysctl.h>
  25 #include <linux/smpboot.h>
  26 #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_enabled = 1;
  33 int __read_mostly watchdog_thresh = 10;
  34 static int __read_mostly watchdog_disabled;
  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 #endif
  49 #ifdef CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU
  50 static cpumask_t __read_mostly watchdog_cpus;
  51 #endif
  52 #ifdef CONFIG_HARDLOCKUP_DETECTOR_NMI
  53 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
  54 #endif
  55
  56 /* boot commands */
  57 /*
  58  * Should we panic when a soft-lockup or hard-lockup occurs:
  59  */
  60 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  61 static int hardlockup_panic =
  62                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  63
  64 static int __init hardlockup_panic_setup(char *str)
  65 {
  66         if (!strncmp(str, "panic", 5))
  67                 hardlockup_panic = 1;
  68         else if (!strncmp(str, "nopanic", 7))
  69                 hardlockup_panic = 0;
  70         else if (!strncmp(str, "0", 1))
  71                 watchdog_enabled = 0;
  72         return 1;
  73 }
  74 __setup("nmi_watchdog=", hardlockup_panic_setup);
  75 #endif
  76
  77 unsigned int __read_mostly softlockup_panic =
  78                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
  79
  80 static int __init softlockup_panic_setup(char *str)
  81 {
  82         softlockup_panic = simple_strtoul(str, NULL, 0);
  83
  84         return 1;
  85 }
  86 __setup("softlockup_panic=", softlockup_panic_setup);
  87
  88 static int __init nowatchdog_setup(char *str)
  89 {
  90         watchdog_enabled = 0;
  91         return 1;
  92 }
  93 __setup("nowatchdog", nowatchdog_setup);
  94
  95 /* deprecated */
  96 static int __init nosoftlockup_setup(char *str)
  97 {
  98         watchdog_enabled = 0;
  99         return 1;
 100 }
 101 __setup("nosoftlockup", nosoftlockup_setup);
 102 /*  */
 103
 104 /*
 105  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 106  * lockups can have false positives under extreme conditions. So we generally
 107  * want a higher threshold for soft lockups than for hard lockups. So we couple
 108  * the thresholds with a factor: we make the soft threshold twice the amount of
 109  * time the hard threshold is.
 110  */
 111 static int get_softlockup_thresh(void)
 112 {
 113         return watchdog_thresh * 2;
 114 }
 115
 116 /*
 117  * Returns seconds, approximately.  We don't need nanosecond
 118  * resolution, and we don't need to waste time with a big divide when
 119  * 2^30ns == 1.074s.
 120  */
 121 static unsigned long get_timestamp(void)
 122 {
 123         return local_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 124 }
 125
 126 static void set_sample_period(void)
 127 {
 128         /*
 129          * convert watchdog_thresh from seconds to ns
 130          * the divide by 5 is to give hrtimer several chances (two
 131          * or three with the current relation between the soft
 132          * and hard thresholds) to increment before the
 133          * hardlockup detector generates a warning
 134          */
 135         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 136 }
 137
 138 /* Commands for resetting the watchdog */
 139 static void __touch_watchdog(void)
 140 {
 141         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 142 }
 143
 144 void touch_softlockup_watchdog(void)
 145 {
 146         __this_cpu_write(watchdog_touch_ts, 0);
 147 }
 148 EXPORT_SYMBOL(touch_softlockup_watchdog);
 149
 150 void touch_all_softlockup_watchdogs(void)
 151 {
 152         int cpu;
 153
 154         /*
 155          * this is done lockless
 156          * do we care if a 0 races with a timestamp?
 157          * all it means is the softlock check starts one cycle later
 158          */
 159         for_each_online_cpu(cpu)
 160                 per_cpu(watchdog_touch_ts, cpu) = 0;
 161 }
 162
 163 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 164 void touch_nmi_watchdog(void)
 165 {
 166         if (watchdog_enabled) {
 167                 unsigned cpu;
 168
 169                 for_each_present_cpu(cpu) {
 170                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
 171                                 per_cpu(watchdog_nmi_touch, cpu) = true;
 172                 }
 173         }
 174         touch_softlockup_watchdog();
 175 }
 176 EXPORT_SYMBOL(touch_nmi_watchdog);
 177
 178 #endif
 179
 180 void touch_softlockup_watchdog_sync(void)
 181 {
 182         __raw_get_cpu_var(softlockup_touch_sync) = true;
 183         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 184 }
 185
 186 #ifdef CONFIG_HARDLOCKUP_DETECTOR_NMI
 187 /* watchdog detector functions */
 188 static int is_hardlockup(void)
 189 {
 190         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 191
 192         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 193                 return 1;
 194
 195         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 196         return 0;
 197 }
 198 #endif
 199
 200 #ifdef CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU
 201 static unsigned int watchdog_next_cpu(unsigned int cpu)
 202 {
 203         cpumask_t cpus = watchdog_cpus;
 204         unsigned int next_cpu;
 205
 206         next_cpu = cpumask_next(cpu, &cpus);
 207         if (next_cpu >= nr_cpu_ids)
 208                 next_cpu = cpumask_first(&cpus);
 209
 210         if (next_cpu == cpu)
 211                 return nr_cpu_ids;
 212
 213         return next_cpu;
 214 }
 215
 216 static int is_hardlockup_other_cpu(unsigned int cpu)
 217 {
 218         unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
 219
 220         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 221                 return 1;
 222
 223         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 224         return 0;
 225 }
 226
 227 static void watchdog_check_hardlockup_other_cpu(void)
 228 {
 229         unsigned int next_cpu;
 230
 231         /*
 232          * Test for hardlockups every 3 samples.  The sample period is
 233          *  watchdog_thresh * 2 / 5, so 3 samples gets us back to slightly over
 234          *  watchdog_thresh (over by 20%).
 235          */
 236         if (__this_cpu_read(hrtimer_interrupts) % 3 != 0)
 237                 return;
 238
 239         /* check for a hardlockup on the next cpu */
 240         next_cpu = watchdog_next_cpu(smp_processor_id());
 241         if (next_cpu >= nr_cpu_ids)
 242                 return;
 243
 244         smp_rmb();
 245
 246         if (per_cpu(watchdog_nmi_touch, next_cpu) == true) {
 247                 per_cpu(watchdog_nmi_touch, next_cpu) = false;
 248                 return;
 249         }
 250
 251         if (is_hardlockup_other_cpu(next_cpu)) {
 252                 /* only warn once */
 253                 if (per_cpu(hard_watchdog_warn, next_cpu) == true)
 254                         return;
 255
 256                 if (hardlockup_panic)
 257                         panic("Watchdog detected hard LOCKUP on cpu %u", next_cpu);
 258                 else
 259                         WARN(1, "Watchdog detected hard LOCKUP on cpu %u", next_cpu);
 260
 261                 per_cpu(hard_watchdog_warn, next_cpu) = true;
 262         } else {
 263                 per_cpu(hard_watchdog_warn, next_cpu) = false;
 264         }
 265 }
 266 #else
 267 static inline void watchdog_check_hardlockup_other_cpu(void) { return; }
 268 #endif
 269
 270 static int is_softlockup(unsigned long touch_ts)
 271 {
 272         unsigned long now = get_timestamp();
 273
 274         /* Warn about unreasonable delays: */
 275         if (time_after(now, touch_ts + get_softlockup_thresh()))
 276                 return now - touch_ts;
 277
 278         return 0;
 279 }
 280
 281 #ifdef CONFIG_HARDLOCKUP_DETECTOR_NMI
 282
 283 static struct perf_event_attr wd_hw_attr = {
 284         .type           = PERF_TYPE_HARDWARE,
 285         .config         = PERF_COUNT_HW_CPU_CYCLES,
 286         .size           = sizeof(struct perf_event_attr),
 287         .pinned         = 1,
 288         .disabled       = 1,
 289 };
 290
 291 /* Callback function for perf event subsystem */
 292 static void watchdog_overflow_callback(struct perf_event *event,
 293                  struct perf_sample_data *data,
 294                  struct pt_regs *regs)
 295 {
 296         /* Ensure the watchdog never gets throttled */
 297         event->hw.interrupts = 0;
 298
 299         if (__this_cpu_read(watchdog_nmi_touch) == true) {
 300                 __this_cpu_write(watchdog_nmi_touch, false);
 301                 return;
 302         }
 303
 304         /* check for a hardlockup
 305          * This is done by making sure our timer interrupt
 306          * is incrementing.  The timer interrupt should have
 307          * fired multiple times before we overflow'd.  If it hasn't
 308          * then this is a good indication the cpu is stuck
 309          */
 310         if (is_hardlockup()) {
 311                 int this_cpu = smp_processor_id();
 312
 313                 /* only print hardlockups once */
 314                 if (__this_cpu_read(hard_watchdog_warn) == true)
 315                         return;
 316
 317                 if (hardlockup_panic)
 318                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 319                 else
 320                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 321
 322                 __this_cpu_write(hard_watchdog_warn, true);
 323                 return;
 324         }
 325
 326         __this_cpu_write(hard_watchdog_warn, false);
 327         return;
 328 }
 329 #endif /* CONFIG_HARDLOCKUP_DETECTOR_NMI */
 330
 331 static void watchdog_interrupt_count(void)
 332 {
 333         __this_cpu_inc(hrtimer_interrupts);
 334 }
 335
 336 static int watchdog_nmi_enable(unsigned int cpu);
 337 static void watchdog_nmi_disable(unsigned int cpu);
 338
 339 /* watchdog kicker functions */
 340 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 341 {
 342         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 343         struct pt_regs *regs = get_irq_regs();
 344         int duration;
 345
 346         /* kick the hardlockup detector */
 347         watchdog_interrupt_count();
 348
 349         /* test for hardlockups on the next cpu */
 350         watchdog_check_hardlockup_other_cpu();
 351
 352         /* kick the softlockup detector */
 353         wake_up_process(__this_cpu_read(softlockup_watchdog));
 354
 355         /* .. and repeat */
 356         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 357
 358         if (touch_ts == 0) {
 359                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 360                         /*
 361                          * If the time stamp was touched atomically
 362                          * make sure the scheduler tick is up to date.
 363                          */
 364                         __this_cpu_write(softlockup_touch_sync, false);
 365                         sched_clock_tick();
 366                 }
 367
 368                 /* Clear the guest paused flag on watchdog reset */
 369                 kvm_check_and_clear_guest_paused();
 370                 __touch_watchdog();
 371                 return HRTIMER_RESTART;
 372         }
 373
 374         /* check for a softlockup
 375          * This is done by making sure a high priority task is
 376          * being scheduled.  The task touches the watchdog to
 377          * indicate it is getting cpu time.  If it hasn't then
 378          * this is a good indication some task is hogging the cpu
 379          */
 380         duration = is_softlockup(touch_ts);
 381         if (unlikely(duration)) {
 382                 /*
 383                  * If a virtual machine is stopped by the host it can look to
 384                  * the watchdog like a soft lockup, check to see if the host
 385                  * stopped the vm before we issue the warning
 386                  */
 387                 if (kvm_check_and_clear_guest_paused())
 388                         return HRTIMER_RESTART;
 389
 390                 /* only warn once */
 391                 if (__this_cpu_read(soft_watchdog_warn) == true)
 392                         return HRTIMER_RESTART;
 393
 394                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 395                         smp_processor_id(), duration,
 396                         current->comm, task_pid_nr(current));
 397                 print_modules();
 398                 print_irqtrace_events(current);
 399                 if (regs)
 400                         show_regs(regs);
 401                 else
 402                         dump_stack();
 403
 404                 if (softlockup_panic)
 405                         panic("softlockup: hung tasks");
 406                 __this_cpu_write(soft_watchdog_warn, true);
 407         } else
 408                 __this_cpu_write(soft_watchdog_warn, false);
 409
 410         return HRTIMER_RESTART;
 411 }
 412
 413 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 414 {
 415         struct sched_param param = { .sched_priority = prio };
 416
 417         sched_setscheduler(current, policy, &param);
 418 }
 419
 420 static void watchdog_enable(unsigned int cpu)
 421 {
 422         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 423
 424         /* kick off the timer for the hardlockup detector */
 425         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 426         hrtimer->function = watchdog_timer_fn;
 427
 428         if (!watchdog_enabled) {
 429                 kthread_park(current);
 430                 return;
 431         }
 432
 433         /* Enable the perf event */
 434         watchdog_nmi_enable(cpu);
 435
 436         /* done here because hrtimer_start can only pin to smp_processor_id() */
 437         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 438                       HRTIMER_MODE_REL_PINNED);
 439
 440         /* initialize timestamp */
 441         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
 442         __touch_watchdog();
 443 }
 444
 445 static void watchdog_disable(unsigned int cpu)
 446 {
 447         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 448
 449         watchdog_set_prio(SCHED_NORMAL, 0);
 450         hrtimer_cancel(hrtimer);
 451         /* disable the perf event */
 452         watchdog_nmi_disable(cpu);
 453 }
 454
 455 static int watchdog_should_run(unsigned int cpu)
 456 {
 457         return __this_cpu_read(hrtimer_interrupts) !=
 458                 __this_cpu_read(soft_lockup_hrtimer_cnt);
 459 }
 460
 461 /*
 462  * The watchdog thread function - touches the timestamp.
 463  *
 464  * It only runs once every sample_period seconds (4 seconds by
 465  * default) to reset the softlockup timestamp. If this gets delayed
 466  * for more than 2*watchdog_thresh seconds then the debug-printout
 467  * triggers in watchdog_timer_fn().
 468  */
 469 static void watchdog(unsigned int cpu)
 470 {
 471         __this_cpu_write(soft_lockup_hrtimer_cnt,
 472                          __this_cpu_read(hrtimer_interrupts));
 473         __touch_watchdog();
 474 }
 475
 476 #ifdef CONFIG_HARDLOCKUP_DETECTOR_NMI
 477 /*
 478  * People like the simple clean cpu node info on boot.
 479  * Reduce the watchdog noise by only printing messages
 480  * that are different from what cpu0 displayed.
 481  */
 482 static unsigned long cpu0_err;
 483
 484 static int watchdog_nmi_enable(unsigned int cpu)
 485 {
 486         struct perf_event_attr *wd_attr;
 487         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 488
 489         /* is it already setup and enabled? */
 490         if (event && event->state > PERF_EVENT_STATE_OFF)
 491                 goto out;
 492
 493         /* it is setup but not enabled */
 494         if (event != NULL)
 495                 goto out_enable;
 496
 497         wd_attr = &wd_hw_attr;
 498         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 499
 500         /* Try to register using hardware perf events */
 501         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 502
 503         /* save cpu0 error for future comparision */
 504         if (cpu == 0 && IS_ERR(event))
 505                 cpu0_err = PTR_ERR(event);
 506
 507         if (!IS_ERR(event)) {
 508                 /* only print for cpu0 or different than cpu0 */
 509                 if (cpu == 0 || cpu0_err)
 510                         pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
 511                 goto out_save;
 512         }
 513
 514         /* skip displaying the same error again */
 515         if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
 516                 return PTR_ERR(event);
 517
 518         /* vary the KERN level based on the returned errno */
 519         if (PTR_ERR(event) == -EOPNOTSUPP)
 520                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 521         else if (PTR_ERR(event) == -ENOENT)
 522                 pr_warning("disabled (cpu%i): hardware events not enabled\n",
 523                          cpu);
 524         else
 525                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 526                         cpu, PTR_ERR(event));
 527         return PTR_ERR(event);
 528
 529         /* success path */
 530 out_save:
 531         per_cpu(watchdog_ev, cpu) = event;
 532 out_enable:
 533         perf_event_enable(per_cpu(watchdog_ev, cpu));
 534 out:
 535         return 0;
 536 }
 537
 538 static void watchdog_nmi_disable(unsigned int cpu)
 539 {
 540         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 541
 542         if (event) {
 543                 perf_event_disable(event);
 544                 per_cpu(watchdog_ev, cpu) = NULL;
 545
 546                 /* should be in cleanup, but blocks oprofile */
 547                 perf_event_release_kernel(event);
 548         }
 549         return;
 550 }
 551 #else
 552 #ifdef CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU
 553 static int watchdog_nmi_enable(unsigned int cpu)
 554 {
 555         /*
 556          * The new cpu will be marked online before the first hrtimer interrupt
 557          * runs on it.  If another cpu tests for a hardlockup on the new cpu
 558          * before it has run its first hrtimer, it will get a false positive.
 559          * Touch the watchdog on the new cpu to delay the first check for at
 560          * least 3 sampling periods to guarantee one hrtimer has run on the new
 561          * cpu.
 562          */
 563         per_cpu(watchdog_nmi_touch, cpu) = true;
 564         smp_wmb();
 565         cpumask_set_cpu(cpu, &watchdog_cpus);
 566         return 0;
 567 }
 568
 569 static void watchdog_nmi_disable(unsigned int cpu)
 570 {
 571         unsigned int next_cpu = watchdog_next_cpu(cpu);
 572
 573         /*
 574          * Offlining this cpu will cause the cpu before this one to start
 575          * checking the one after this one.  If this cpu just finished checking
 576          * the next cpu and updating hrtimer_interrupts_saved, and then the
 577          * previous cpu checks it within one sample period, it will trigger a
 578          * false positive.  Touch the watchdog on the next cpu to prevent it.
 579          */
 580         if (next_cpu < nr_cpu_ids)
 581                 per_cpu(watchdog_nmi_touch, next_cpu) = true;
 582         smp_wmb();
 583         cpumask_clear_cpu(cpu, &watchdog_cpus);
 584 }
 585 #else
 586 static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
 587 static void watchdog_nmi_disable(unsigned int cpu) { return; }
 588 #endif /* CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU */
 589 #endif /* CONFIG_HARDLOCKUP_DETECTOR_NMI */
 590
 591 /* prepare/enable/disable routines */
 592 /* sysctl functions */
 593 #ifdef CONFIG_SYSCTL
 594 static void watchdog_enable_all_cpus(void)
 595 {
 596         unsigned int cpu;
 597
 598         if (watchdog_disabled) {
 599                 watchdog_disabled = 0;
 600                 for_each_online_cpu(cpu)
 601                         kthread_unpark(per_cpu(softlockup_watchdog, cpu));
 602         }
 603 }
 604
 605 static void watchdog_disable_all_cpus(void)
 606 {
 607         unsigned int cpu;
 608
 609         if (!watchdog_disabled) {
 610                 watchdog_disabled = 1;
 611                 for_each_online_cpu(cpu)
 612                         kthread_park(per_cpu(softlockup_watchdog, cpu));
 613         }
 614 }
 615
 616 /*
 617  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
 618  */
 619
 620 int proc_dowatchdog(struct ctl_table *table, int write,
 621                     void __user *buffer, size_t *lenp, loff_t *ppos)
 622 {
 623         int ret;
 624
 625         if (watchdog_disabled < 0)
 626                 return -ENODEV;
 627
 628         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 629         if (ret || !write)
 630                 return ret;
 631
 632         set_sample_period();
 633         /*
 634          * Watchdog threads shouldn't be enabled if they are
 635          * disabled. The 'watchdog_disabled' variable check in
 636          * watchdog_*_all_cpus() function takes care of this.
 637          */
 638         if (watchdog_enabled && watchdog_thresh)
 639                 watchdog_enable_all_cpus();
 640         else
 641                 watchdog_disable_all_cpus();
 642
 643         return ret;
 644 }
 645 #endif /* CONFIG_SYSCTL */
 646
 647 static struct smp_hotplug_thread watchdog_threads = {
 648         .store                  = &softlockup_watchdog,
 649         .thread_should_run      = watchdog_should_run,
 650         .thread_fn              = watchdog,
 651         .thread_comm            = "watchdog/%u",
 652         .setup                  = watchdog_enable,
 653         .park                   = watchdog_disable,
 654         .unpark                 = watchdog_enable,
 655 };
 656
 657 void __init lockup_detector_init(void)
 658 {
 659         set_sample_period();
 660         if (smpboot_register_percpu_thread(&watchdog_threads)) {
 661                 pr_err("Failed to create watchdog threads, disabled\n");
 662                 watchdog_disabled = -ENODEV;
 663         }
 664 }