kernel/watchdog.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Detect hard and soft lockups on a system
   4  *
   5  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   6  *
   7  * Note: Most of this code is borrowed heavily from the original softlockup
   8  * detector, so thanks to Ingo for the initial implementation.
   9  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
  10  * to those contributors as well.
  11  */
  12
  13 #define pr_fmt(fmt) "watchdog: " fmt
  14
  15 #include <linux/mm.h>
  16 #include <linux/cpu.h>
  17 #include <linux/nmi.h>
  18 #include <linux/init.h>
  19 #include <linux/module.h>
  20 #include <linux/sysctl.h>
  21 #include <linux/tick.h>
  22 #include <linux/sched/clock.h>
  23 #include <linux/sched/debug.h>
  24 #include <linux/sched/isolation.h>
  25 #include <linux/stop_machine.h>
  26
  27 #include <asm/irq_regs.h>
  28 #include <linux/kvm_para.h>
  29
  30 static DEFINE_MUTEX(watchdog_mutex);
  31
  32 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
  33 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
  34 # define NMI_WATCHDOG_DEFAULT   1
  35 #else
  36 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED)
  37 # define NMI_WATCHDOG_DEFAULT   0
  38 #endif
  39
  40 unsigned long __read_mostly watchdog_enabled;
  41 int __read_mostly watchdog_user_enabled = 1;
  42 int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
  43 int __read_mostly soft_watchdog_user_enabled = 1;
  44 int __read_mostly watchdog_thresh = 10;
  45 static int __read_mostly nmi_watchdog_available;
  46
  47 struct cpumask watchdog_cpumask __read_mostly;
  48 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  49
  50 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  51
  52 # ifdef CONFIG_SMP
  53 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  54 # endif /* CONFIG_SMP */
  55
  56 /*
  57  * Should we panic when a soft-lockup or hard-lockup occurs:
  58  */
  59 unsigned int __read_mostly hardlockup_panic =
  60                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  61 /*
  62  * We may not want to enable hard lockup detection by default in all cases,
  63  * for example when running the kernel as a guest on a hypervisor. In these
  64  * cases this function can be called to disable hard lockup detection. This
  65  * function should only be executed once by the boot processor before the
  66  * kernel command line parameters are parsed, because otherwise it is not
  67  * possible to override this in hardlockup_panic_setup().
  68  */
  69 void __init hardlockup_detector_disable(void)
  70 {
  71         nmi_watchdog_user_enabled = 0;
  72 }
  73
  74 static int __init hardlockup_panic_setup(char *str)
  75 {
  76         if (!strncmp(str, "panic", 5))
  77                 hardlockup_panic = 1;
  78         else if (!strncmp(str, "nopanic", 7))
  79                 hardlockup_panic = 0;
  80         else if (!strncmp(str, "0", 1))
  81                 nmi_watchdog_user_enabled = 0;
  82         else if (!strncmp(str, "1", 1))
  83                 nmi_watchdog_user_enabled = 1;
  84         return 1;
  85 }
  86 __setup("nmi_watchdog=", hardlockup_panic_setup);
  87
  88 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
  89
  90 /*
  91  * These functions can be overridden if an architecture implements its
  92  * own hardlockup detector.
  93  *
  94  * watchdog_nmi_enable/disable can be implemented to start and stop when
  95  * softlockup watchdog threads start and stop. The arch must select the
  96  * SOFTLOCKUP_DETECTOR Kconfig.
  97  */
  98 int __weak watchdog_nmi_enable(unsigned int cpu)
  99 {
 100         hardlockup_detector_perf_enable();
 101         return 0;
 102 }
 103
 104 void __weak watchdog_nmi_disable(unsigned int cpu)
 105 {
 106         hardlockup_detector_perf_disable();
 107 }
 108
 109 /* Return 0, if a NMI watchdog is available. Error code otherwise */
 110 int __weak __init watchdog_nmi_probe(void)
 111 {
 112         return hardlockup_detector_perf_init();
 113 }
 114
 115 /**
 116  * watchdog_nmi_stop - Stop the watchdog for reconfiguration
 117  *
 118  * The reconfiguration steps are:
 119  * watchdog_nmi_stop();
 120  * update_variables();
 121  * watchdog_nmi_start();
 122  */
 123 void __weak watchdog_nmi_stop(void) { }
 124
 125 /**
 126  * watchdog_nmi_start - Start the watchdog after reconfiguration
 127  *
 128  * Counterpart to watchdog_nmi_stop().
 129  *
 130  * The following variables have been updated in update_variables() and
 131  * contain the currently valid configuration:
 132  * - watchdog_enabled
 133  * - watchdog_thresh
 134  * - watchdog_cpumask
 135  */
 136 void __weak watchdog_nmi_start(void) { }
 137
 138 /**
 139  * lockup_detector_update_enable - Update the sysctl enable bit
 140  *
 141  * Caller needs to make sure that the NMI/perf watchdogs are off, so this
 142  * can't race with watchdog_nmi_disable().
 143  */
 144 static void lockup_detector_update_enable(void)
 145 {
 146         watchdog_enabled = 0;
 147         if (!watchdog_user_enabled)
 148                 return;
 149         if (nmi_watchdog_available && nmi_watchdog_user_enabled)
 150                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
 151         if (soft_watchdog_user_enabled)
 152                 watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
 153 }
 154
 155 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 156
 157 #define SOFTLOCKUP_RESET        ULONG_MAX
 158
 159 #ifdef CONFIG_SMP
 160 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 161 #endif
 162
 163 static struct cpumask watchdog_allowed_mask __read_mostly;
 164
 165 /* Global variables, exported for sysctl */
 166 unsigned int __read_mostly softlockup_panic =
 167                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 168
 169 static bool softlockup_initialized __read_mostly;
 170 static u64 __read_mostly sample_period;
 171
 172 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 173 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 174 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 175 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 176 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 177 static unsigned long soft_lockup_nmi_warn;
 178
 179 static int __init nowatchdog_setup(char *str)
 180 {
 181         watchdog_user_enabled = 0;
 182         return 1;
 183 }
 184 __setup("nowatchdog", nowatchdog_setup);
 185
 186 static int __init nosoftlockup_setup(char *str)
 187 {
 188         soft_watchdog_user_enabled = 0;
 189         return 1;
 190 }
 191 __setup("nosoftlockup", nosoftlockup_setup);
 192
 193 static int __init watchdog_thresh_setup(char *str)
 194 {
 195         get_option(&str, &watchdog_thresh);
 196         return 1;
 197 }
 198 __setup("watchdog_thresh=", watchdog_thresh_setup);
 199
 200 static void __lockup_detector_cleanup(void);
 201
 202 /*
 203  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 204  * lockups can have false positives under extreme conditions. So we generally
 205  * want a higher threshold for soft lockups than for hard lockups. So we couple
 206  * the thresholds with a factor: we make the soft threshold twice the amount of
 207  * time the hard threshold is.
 208  */
 209 static int get_softlockup_thresh(void)
 210 {
 211         return watchdog_thresh * 2;
 212 }
 213
 214 /*
 215  * Returns seconds, approximately.  We don't need nanosecond
 216  * resolution, and we don't need to waste time with a big divide when
 217  * 2^30ns == 1.074s.
 218  */
 219 static unsigned long get_timestamp(void)
 220 {
 221         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 222 }
 223
 224 static void set_sample_period(void)
 225 {
 226         /*
 227          * convert watchdog_thresh from seconds to ns
 228          * the divide by 5 is to give hrtimer several chances (two
 229          * or three with the current relation between the soft
 230          * and hard thresholds) to increment before the
 231          * hardlockup detector generates a warning
 232          */
 233         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 234         watchdog_update_hrtimer_threshold(sample_period);
 235 }
 236
 237 /* Commands for resetting the watchdog */
 238 static void update_touch_ts(void)
 239 {
 240         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 241 }
 242
 243 /**
 244  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 245  *
 246  * Call when the scheduler may have stalled for legitimate reasons
 247  * preventing the watchdog task from executing - e.g. the scheduler
 248  * entering idle state.  This should only be used for scheduler events.
 249  * Use touch_softlockup_watchdog() for everything else.
 250  */
 251 notrace void touch_softlockup_watchdog_sched(void)
 252 {
 253         /*
 254          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 255          * gets zeroed here, so use the raw_ operation.
 256          */
 257         raw_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
 258 }
 259
 260 notrace void touch_softlockup_watchdog(void)
 261 {
 262         touch_softlockup_watchdog_sched();
 263         wq_watchdog_touch(raw_smp_processor_id());
 264 }
 265 EXPORT_SYMBOL(touch_softlockup_watchdog);
 266
 267 void touch_all_softlockup_watchdogs(void)
 268 {
 269         int cpu;
 270
 271         /*
 272          * watchdog_mutex cannpt be taken here, as this might be called
 273          * from (soft)interrupt context, so the access to
 274          * watchdog_allowed_cpumask might race with a concurrent update.
 275          *
 276          * The watchdog time stamp can race against a concurrent real
 277          * update as well, the only side effect might be a cycle delay for
 278          * the softlockup check.
 279          */
 280         for_each_cpu(cpu, &watchdog_allowed_mask)
 281                 per_cpu(watchdog_touch_ts, cpu) = SOFTLOCKUP_RESET;
 282         wq_watchdog_touch(-1);
 283 }
 284
 285 void touch_softlockup_watchdog_sync(void)
 286 {
 287         __this_cpu_write(softlockup_touch_sync, true);
 288         __this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
 289 }
 290
 291 static int is_softlockup(unsigned long touch_ts)
 292 {
 293         unsigned long now = get_timestamp();
 294
 295         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
 296                 /* Warn about unreasonable delays. */
 297                 if (time_after(now, touch_ts + get_softlockup_thresh()))
 298                         return now - touch_ts;
 299         }
 300         return 0;
 301 }
 302
 303 /* watchdog detector functions */
 304 bool is_hardlockup(void)
 305 {
 306         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 307
 308         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 309                 return true;
 310
 311         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 312         return false;
 313 }
 314
 315 static void watchdog_interrupt_count(void)
 316 {
 317         __this_cpu_inc(hrtimer_interrupts);
 318 }
 319
 320 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 321 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 322
 323 /*
 324  * The watchdog thread function - touches the timestamp.
 325  *
 326  * It only runs once every sample_period seconds (4 seconds by
 327  * default) to reset the softlockup timestamp. If this gets delayed
 328  * for more than 2*watchdog_thresh seconds then the debug-printout
 329  * triggers in watchdog_timer_fn().
 330  */
 331 static int softlockup_fn(void *data)
 332 {
 333         update_touch_ts();
 334         complete(this_cpu_ptr(&softlockup_completion));
 335
 336         return 0;
 337 }
 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         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 346
 347         if (!watchdog_enabled)
 348                 return HRTIMER_NORESTART;
 349
 350         /* kick the hardlockup detector */
 351         watchdog_interrupt_count();
 352
 353         /* kick the softlockup detector */
 354         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
 355                 reinit_completion(this_cpu_ptr(&softlockup_completion));
 356                 stop_one_cpu_nowait(smp_processor_id(),
 357                                 softlockup_fn, NULL,
 358                                 this_cpu_ptr(&softlockup_stop_work));
 359         }
 360
 361         /* .. and repeat */
 362         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 363
 364         if (touch_ts == SOFTLOCKUP_RESET) {
 365                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 366                         /*
 367                          * If the time stamp was touched atomically
 368                          * make sure the scheduler tick is up to date.
 369                          */
 370                         __this_cpu_write(softlockup_touch_sync, false);
 371                         sched_clock_tick();
 372                 }
 373
 374                 /* Clear the guest paused flag on watchdog reset */
 375                 kvm_check_and_clear_guest_paused();
 376                 update_touch_ts();
 377                 return HRTIMER_RESTART;
 378         }
 379
 380         /* check for a softlockup
 381          * This is done by making sure a high priority task is
 382          * being scheduled.  The task touches the watchdog to
 383          * indicate it is getting cpu time.  If it hasn't then
 384          * this is a good indication some task is hogging the cpu
 385          */
 386         duration = is_softlockup(touch_ts);
 387         if (unlikely(duration)) {
 388                 /*
 389                  * If a virtual machine is stopped by the host it can look to
 390                  * the watchdog like a soft lockup, check to see if the host
 391                  * stopped the vm before we issue the warning
 392                  */
 393                 if (kvm_check_and_clear_guest_paused())
 394                         return HRTIMER_RESTART;
 395
 396                 /*
 397                  * Prevent multiple soft-lockup reports if one cpu is already
 398                  * engaged in dumping all cpu back traces.
 399                  */
 400                 if (softlockup_all_cpu_backtrace) {
 401                         if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
 402                                 return HRTIMER_RESTART;
 403                 }
 404
 405                 /* Start period for the next softlockup warning. */
 406                 update_touch_ts();
 407
 408                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 409                         smp_processor_id(), duration,
 410                         current->comm, task_pid_nr(current));
 411                 print_modules();
 412                 print_irqtrace_events(current);
 413                 if (regs)
 414                         show_regs(regs);
 415                 else
 416                         dump_stack();
 417
 418                 if (softlockup_all_cpu_backtrace) {
 419                         trigger_allbutself_cpu_backtrace();
 420                         clear_bit_unlock(0, &soft_lockup_nmi_warn);
 421                 }
 422
 423                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 424                 if (softlockup_panic)
 425                         panic("softlockup: hung tasks");
 426         }
 427
 428         return HRTIMER_RESTART;
 429 }
 430
 431 static void watchdog_enable(unsigned int cpu)
 432 {
 433         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 434         struct completion *done = this_cpu_ptr(&softlockup_completion);
 435
 436         WARN_ON_ONCE(cpu != smp_processor_id());
 437
 438         init_completion(done);
 439         complete(done);
 440
 441         /*
 442          * Start the timer first to prevent the NMI watchdog triggering
 443          * before the timer has a chance to fire.
 444          */
 445         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 446         hrtimer->function = watchdog_timer_fn;
 447         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 448                       HRTIMER_MODE_REL_PINNED_HARD);
 449
 450         /* Initialize timestamp */
 451         update_touch_ts();
 452         /* Enable the perf event */
 453         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
 454                 watchdog_nmi_enable(cpu);
 455 }
 456
 457 static void watchdog_disable(unsigned int cpu)
 458 {
 459         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 460
 461         WARN_ON_ONCE(cpu != smp_processor_id());
 462
 463         /*
 464          * Disable the perf event first. That prevents that a large delay
 465          * between disabling the timer and disabling the perf event causes
 466          * the perf NMI to detect a false positive.
 467          */
 468         watchdog_nmi_disable(cpu);
 469         hrtimer_cancel(hrtimer);
 470         wait_for_completion(this_cpu_ptr(&softlockup_completion));
 471 }
 472
 473 static int softlockup_stop_fn(void *data)
 474 {
 475         watchdog_disable(smp_processor_id());
 476         return 0;
 477 }
 478
 479 static void softlockup_stop_all(void)
 480 {
 481         int cpu;
 482
 483         if (!softlockup_initialized)
 484                 return;
 485
 486         for_each_cpu(cpu, &watchdog_allowed_mask)
 487                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 488
 489         cpumask_clear(&watchdog_allowed_mask);
 490 }
 491
 492 static int softlockup_start_fn(void *data)
 493 {
 494         watchdog_enable(smp_processor_id());
 495         return 0;
 496 }
 497
 498 static void softlockup_start_all(void)
 499 {
 500         int cpu;
 501
 502         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 503         for_each_cpu(cpu, &watchdog_allowed_mask)
 504                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 505 }
 506
 507 int lockup_detector_online_cpu(unsigned int cpu)
 508 {
 509         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 510                 watchdog_enable(cpu);
 511         return 0;
 512 }
 513
 514 int lockup_detector_offline_cpu(unsigned int cpu)
 515 {
 516         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 517                 watchdog_disable(cpu);
 518         return 0;
 519 }
 520
 521 static void lockup_detector_reconfigure(void)
 522 {
 523         cpus_read_lock();
 524         watchdog_nmi_stop();
 525
 526         softlockup_stop_all();
 527         set_sample_period();
 528         lockup_detector_update_enable();
 529         if (watchdog_enabled && watchdog_thresh)
 530                 softlockup_start_all();
 531
 532         watchdog_nmi_start();
 533         cpus_read_unlock();
 534         /*
 535          * Must be called outside the cpus locked section to prevent
 536          * recursive locking in the perf code.
 537          */
 538         __lockup_detector_cleanup();
 539 }
 540
 541 /*
 542  * Create the watchdog thread infrastructure and configure the detector(s).
 543  *
 544  * The threads are not unparked as watchdog_allowed_mask is empty.  When
 545  * the threads are successfully initialized, take the proper locks and
 546  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
 547  */
 548 static __init void lockup_detector_setup(void)
 549 {
 550         /*
 551          * If sysctl is off and watchdog got disabled on the command line,
 552          * nothing to do here.
 553          */
 554         lockup_detector_update_enable();
 555
 556         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 557             !(watchdog_enabled && watchdog_thresh))
 558                 return;
 559
 560         mutex_lock(&watchdog_mutex);
 561         lockup_detector_reconfigure();
 562         softlockup_initialized = true;
 563         mutex_unlock(&watchdog_mutex);
 564 }
 565
 566 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 567 static void lockup_detector_reconfigure(void)
 568 {
 569         cpus_read_lock();
 570         watchdog_nmi_stop();
 571         lockup_detector_update_enable();
 572         watchdog_nmi_start();
 573         cpus_read_unlock();
 574 }
 575 static inline void lockup_detector_setup(void)
 576 {
 577         lockup_detector_reconfigure();
 578 }
 579 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 580
 581 static void __lockup_detector_cleanup(void)
 582 {
 583         lockdep_assert_held(&watchdog_mutex);
 584         hardlockup_detector_perf_cleanup();
 585 }
 586
 587 /**
 588  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 589  *
 590  * Caller must not hold the cpu hotplug rwsem.
 591  */
 592 void lockup_detector_cleanup(void)
 593 {
 594         mutex_lock(&watchdog_mutex);
 595         __lockup_detector_cleanup();
 596         mutex_unlock(&watchdog_mutex);
 597 }
 598
 599 /**
 600  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 601  *
 602  * Special interface for parisc. It prevents lockup detector warnings from
 603  * the default pm_poweroff() function which busy loops forever.
 604  */
 605 void lockup_detector_soft_poweroff(void)
 606 {
 607         watchdog_enabled = 0;
 608 }
 609
 610 #ifdef CONFIG_SYSCTL
 611
 612 /* Propagate any changes to the watchdog threads */
 613 static void proc_watchdog_update(void)
 614 {
 615         /* Remove impossible cpus to keep sysctl output clean. */
 616         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 617         lockup_detector_reconfigure();
 618 }
 619
 620 /*
 621  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 622  *
 623  * caller             | table->data points to      | 'which'
 624  * -------------------|----------------------------|--------------------------
 625  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
 626  *                    |                            | SOFT_WATCHDOG_ENABLED
 627  * -------------------|----------------------------|--------------------------
 628  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
 629  * -------------------|----------------------------|--------------------------
 630  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
 631  */
 632 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 633                                 void *buffer, size_t *lenp, loff_t *ppos)
 634 {
 635         int err, old, *param = table->data;
 636
 637         mutex_lock(&watchdog_mutex);
 638
 639         if (!write) {
 640                 /*
 641                  * On read synchronize the userspace interface. This is a
 642                  * racy snapshot.
 643                  */
 644                 *param = (watchdog_enabled & which) != 0;
 645                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 646         } else {
 647                 old = READ_ONCE(*param);
 648                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 649                 if (!err && old != READ_ONCE(*param))
 650                         proc_watchdog_update();
 651         }
 652         mutex_unlock(&watchdog_mutex);
 653         return err;
 654 }
 655
 656 /*
 657  * /proc/sys/kernel/watchdog
 658  */
 659 int proc_watchdog(struct ctl_table *table, int write,
 660                   void *buffer, size_t *lenp, loff_t *ppos)
 661 {
 662         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
 663                                     table, write, buffer, lenp, ppos);
 664 }
 665
 666 /*
 667  * /proc/sys/kernel/nmi_watchdog
 668  */
 669 int proc_nmi_watchdog(struct ctl_table *table, int write,
 670                       void *buffer, size_t *lenp, loff_t *ppos)
 671 {
 672         if (!nmi_watchdog_available && write)
 673                 return -ENOTSUPP;
 674         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
 675                                     table, write, buffer, lenp, ppos);
 676 }
 677
 678 /*
 679  * /proc/sys/kernel/soft_watchdog
 680  */
 681 int proc_soft_watchdog(struct ctl_table *table, int write,
 682                         void *buffer, size_t *lenp, loff_t *ppos)
 683 {
 684         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
 685                                     table, write, buffer, lenp, ppos);
 686 }
 687
 688 /*
 689  * /proc/sys/kernel/watchdog_thresh
 690  */
 691 int proc_watchdog_thresh(struct ctl_table *table, int write,
 692                          void *buffer, size_t *lenp, loff_t *ppos)
 693 {
 694         int err, old;
 695
 696         mutex_lock(&watchdog_mutex);
 697
 698         old = READ_ONCE(watchdog_thresh);
 699         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 700
 701         if (!err && write && old != READ_ONCE(watchdog_thresh))
 702                 proc_watchdog_update();
 703
 704         mutex_unlock(&watchdog_mutex);
 705         return err;
 706 }
 707
 708 /*
 709  * The cpumask is the mask of possible cpus that the watchdog can run
 710  * on, not the mask of cpus it is actually running on.  This allows the
 711  * user to specify a mask that will include cpus that have not yet
 712  * been brought online, if desired.
 713  */
 714 int proc_watchdog_cpumask(struct ctl_table *table, int write,
 715                           void *buffer, size_t *lenp, loff_t *ppos)
 716 {
 717         int err;
 718
 719         mutex_lock(&watchdog_mutex);
 720
 721         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 722         if (!err && write)
 723                 proc_watchdog_update();
 724
 725         mutex_unlock(&watchdog_mutex);
 726         return err;
 727 }
 728 #endif /* CONFIG_SYSCTL */
 729
 730 void __init lockup_detector_init(void)
 731 {
 732         if (tick_nohz_full_enabled())
 733                 pr_info("Disabling watchdog on nohz_full cores by default\n");
 734
 735         cpumask_copy(&watchdog_cpumask,
 736                      housekeeping_cpumask(HK_FLAG_TIMER));
 737
 738         if (!watchdog_nmi_probe())
 739                 nmi_watchdog_available = true;
 740         lockup_detector_setup();
 741 }