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/smpboot.h>
  22 #include <linux/sched/rt.h>
  23 #include <uapi/linux/sched/types.h>
  24 #include <linux/tick.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/sched/clock.h>
  27 #include <linux/sched/debug.h>
  28 #include <linux/sched/isolation.h>
  29
  30 #include <asm/irq_regs.h>
  31 #include <linux/kvm_para.h>
  32 #include <linux/kthread.h>
  33
  34 static DEFINE_MUTEX(watchdog_mutex);
  35
  36 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
  37 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
  38 # define NMI_WATCHDOG_DEFAULT   1
  39 #else
  40 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED)
  41 # define NMI_WATCHDOG_DEFAULT   0
  42 #endif
  43
  44 unsigned long __read_mostly watchdog_enabled;
  45 int __read_mostly watchdog_user_enabled = 1;
  46 int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
  47 int __read_mostly soft_watchdog_user_enabled = 1;
  48 int __read_mostly watchdog_thresh = 10;
  49 int __read_mostly nmi_watchdog_available;
  50
  51 struct cpumask watchdog_allowed_mask __read_mostly;
  52
  53 struct cpumask watchdog_cpumask __read_mostly;
  54 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  55
  56 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  57 /*
  58  * Should we panic when a soft-lockup or hard-lockup occurs:
  59  */
  60 unsigned int __read_mostly hardlockup_panic =
  61                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  62 /*
  63  * We may not want to enable hard lockup detection by default in all cases,
  64  * for example when running the kernel as a guest on a hypervisor. In these
  65  * cases this function can be called to disable hard lockup detection. This
  66  * function should only be executed once by the boot processor before the
  67  * kernel command line parameters are parsed, because otherwise it is not
  68  * possible to override this in hardlockup_panic_setup().
  69  */
  70 void __init hardlockup_detector_disable(void)
  71 {
  72         nmi_watchdog_user_enabled = 0;
  73 }
  74
  75 static int __init hardlockup_panic_setup(char *str)
  76 {
  77         if (!strncmp(str, "panic", 5))
  78                 hardlockup_panic = 1;
  79         else if (!strncmp(str, "nopanic", 7))
  80                 hardlockup_panic = 0;
  81         else if (!strncmp(str, "0", 1))
  82                 nmi_watchdog_user_enabled = 0;
  83         else if (!strncmp(str, "1", 1))
  84                 nmi_watchdog_user_enabled = 1;
  85         return 1;
  86 }
  87 __setup("nmi_watchdog=", hardlockup_panic_setup);
  88
  89 # ifdef CONFIG_SMP
  90 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  91
  92 static int __init hardlockup_all_cpu_backtrace_setup(char *str)
  93 {
  94         sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
  95         return 1;
  96 }
  97 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
  98 # endif /* CONFIG_SMP */
  99 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 100
 101 /*
 102  * These functions can be overridden if an architecture implements its
 103  * own hardlockup detector.
 104  *
 105  * watchdog_nmi_enable/disable can be implemented to start and stop when
 106  * softlockup watchdog threads start and stop. The arch must select the
 107  * SOFTLOCKUP_DETECTOR Kconfig.
 108  */
 109 int __weak watchdog_nmi_enable(unsigned int cpu)
 110 {
 111         hardlockup_detector_perf_enable();
 112         return 0;
 113 }
 114
 115 void __weak watchdog_nmi_disable(unsigned int cpu)
 116 {
 117         hardlockup_detector_perf_disable();
 118 }
 119
 120 /* Return 0, if a NMI watchdog is available. Error code otherwise */
 121 int __weak __init watchdog_nmi_probe(void)
 122 {
 123         return hardlockup_detector_perf_init();
 124 }
 125
 126 /**
 127  * watchdog_nmi_stop - Stop the watchdog for reconfiguration
 128  *
 129  * The reconfiguration steps are:
 130  * watchdog_nmi_stop();
 131  * update_variables();
 132  * watchdog_nmi_start();
 133  */
 134 void __weak watchdog_nmi_stop(void) { }
 135
 136 /**
 137  * watchdog_nmi_start - Start the watchdog after reconfiguration
 138  *
 139  * Counterpart to watchdog_nmi_stop().
 140  *
 141  * The following variables have been updated in update_variables() and
 142  * contain the currently valid configuration:
 143  * - watchdog_enabled
 144  * - watchdog_thresh
 145  * - watchdog_cpumask
 146  */
 147 void __weak watchdog_nmi_start(void) { }
 148
 149 /**
 150  * lockup_detector_update_enable - Update the sysctl enable bit
 151  *
 152  * Caller needs to make sure that the NMI/perf watchdogs are off, so this
 153  * can't race with watchdog_nmi_disable().
 154  */
 155 static void lockup_detector_update_enable(void)
 156 {
 157         watchdog_enabled = 0;
 158         if (!watchdog_user_enabled)
 159                 return;
 160         if (nmi_watchdog_available && nmi_watchdog_user_enabled)
 161                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
 162         if (soft_watchdog_user_enabled)
 163                 watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
 164 }
 165
 166 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 167
 168 /* Global variables, exported for sysctl */
 169 unsigned int __read_mostly softlockup_panic =
 170                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 171
 172 static bool softlockup_threads_initialized __read_mostly;
 173 static u64 __read_mostly sample_period;
 174
 175 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 176 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 177 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 178 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 179 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 180 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 181 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 182 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
 183 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 184 static unsigned long soft_lockup_nmi_warn;
 185
 186 static int __init softlockup_panic_setup(char *str)
 187 {
 188         softlockup_panic = simple_strtoul(str, NULL, 0);
 189         return 1;
 190 }
 191 __setup("softlockup_panic=", softlockup_panic_setup);
 192
 193 static int __init nowatchdog_setup(char *str)
 194 {
 195         watchdog_user_enabled = 0;
 196         return 1;
 197 }
 198 __setup("nowatchdog", nowatchdog_setup);
 199
 200 static int __init nosoftlockup_setup(char *str)
 201 {
 202         soft_watchdog_user_enabled = 0;
 203         return 1;
 204 }
 205 __setup("nosoftlockup", nosoftlockup_setup);
 206
 207 #ifdef CONFIG_SMP
 208 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 209
 210 static int __init softlockup_all_cpu_backtrace_setup(char *str)
 211 {
 212         sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
 213         return 1;
 214 }
 215 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
 216 #endif
 217
 218 static void __lockup_detector_cleanup(void);
 219
 220 /*
 221  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 222  * lockups can have false positives under extreme conditions. So we generally
 223  * want a higher threshold for soft lockups than for hard lockups. So we couple
 224  * the thresholds with a factor: we make the soft threshold twice the amount of
 225  * time the hard threshold is.
 226  */
 227 static int get_softlockup_thresh(void)
 228 {
 229         return watchdog_thresh * 2;
 230 }
 231
 232 /*
 233  * Returns seconds, approximately.  We don't need nanosecond
 234  * resolution, and we don't need to waste time with a big divide when
 235  * 2^30ns == 1.074s.
 236  */
 237 static unsigned long get_timestamp(void)
 238 {
 239         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 240 }
 241
 242 static void set_sample_period(void)
 243 {
 244         /*
 245          * convert watchdog_thresh from seconds to ns
 246          * the divide by 5 is to give hrtimer several chances (two
 247          * or three with the current relation between the soft
 248          * and hard thresholds) to increment before the
 249          * hardlockup detector generates a warning
 250          */
 251         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 252         watchdog_update_hrtimer_threshold(sample_period);
 253 }
 254
 255 /* Commands for resetting the watchdog */
 256 static void __touch_watchdog(void)
 257 {
 258         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 259 }
 260
 261 /**
 262  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 263  *
 264  * Call when the scheduler may have stalled for legitimate reasons
 265  * preventing the watchdog task from executing - e.g. the scheduler
 266  * entering idle state.  This should only be used for scheduler events.
 267  * Use touch_softlockup_watchdog() for everything else.
 268  */
 269 void touch_softlockup_watchdog_sched(void)
 270 {
 271         /*
 272          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 273          * gets zeroed here, so use the raw_ operation.
 274          */
 275         raw_cpu_write(watchdog_touch_ts, 0);
 276 }
 277
 278 void touch_softlockup_watchdog(void)
 279 {
 280         touch_softlockup_watchdog_sched();
 281         wq_watchdog_touch(raw_smp_processor_id());
 282 }
 283 EXPORT_SYMBOL(touch_softlockup_watchdog);
 284
 285 void touch_all_softlockup_watchdogs(void)
 286 {
 287         int cpu;
 288
 289         /*
 290          * watchdog_mutex cannpt be taken here, as this might be called
 291          * from (soft)interrupt context, so the access to
 292          * watchdog_allowed_cpumask might race with a concurrent update.
 293          *
 294          * The watchdog time stamp can race against a concurrent real
 295          * update as well, the only side effect might be a cycle delay for
 296          * the softlockup check.
 297          */
 298         for_each_cpu(cpu, &watchdog_allowed_mask)
 299                 per_cpu(watchdog_touch_ts, cpu) = 0;
 300         wq_watchdog_touch(-1);
 301 }
 302
 303 void touch_softlockup_watchdog_sync(void)
 304 {
 305         __this_cpu_write(softlockup_touch_sync, true);
 306         __this_cpu_write(watchdog_touch_ts, 0);
 307 }
 308
 309 static int is_softlockup(unsigned long touch_ts)
 310 {
 311         unsigned long now = get_timestamp();
 312
 313         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
 314                 /* Warn about unreasonable delays. */
 315                 if (time_after(now, touch_ts + get_softlockup_thresh()))
 316                         return now - touch_ts;
 317         }
 318         return 0;
 319 }
 320
 321 /* watchdog detector functions */
 322 bool is_hardlockup(void)
 323 {
 324         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 325
 326         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 327                 return true;
 328
 329         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 330         return false;
 331 }
 332
 333 static void watchdog_interrupt_count(void)
 334 {
 335         __this_cpu_inc(hrtimer_interrupts);
 336 }
 337
 338 /* watchdog kicker functions */
 339 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 340 {
 341         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 342         struct pt_regs *regs = get_irq_regs();
 343         int duration;
 344         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 345
 346         if (!watchdog_enabled)
 347                 return HRTIMER_NORESTART;
 348
 349         /* kick the hardlockup detector */
 350         watchdog_interrupt_count();
 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                         /*
 393                          * When multiple processes are causing softlockups the
 394                          * softlockup detector only warns on the first one
 395                          * because the code relies on a full quiet cycle to
 396                          * re-arm.  The second process prevents the quiet cycle
 397                          * and never gets reported.  Use task pointers to detect
 398                          * this.
 399                          */
 400                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
 401                             current) {
 402                                 __this_cpu_write(soft_watchdog_warn, false);
 403                                 __touch_watchdog();
 404                         }
 405                         return HRTIMER_RESTART;
 406                 }
 407
 408                 if (softlockup_all_cpu_backtrace) {
 409                         /* Prevent multiple soft-lockup reports if one cpu is already
 410                          * engaged in dumping cpu back traces
 411                          */
 412                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
 413                                 /* Someone else will report us. Let's give up */
 414                                 __this_cpu_write(soft_watchdog_warn, true);
 415                                 return HRTIMER_RESTART;
 416                         }
 417                 }
 418
 419                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 420                         smp_processor_id(), duration,
 421                         current->comm, task_pid_nr(current));
 422                 __this_cpu_write(softlockup_task_ptr_saved, current);
 423                 print_modules();
 424                 print_irqtrace_events(current);
 425                 if (regs)
 426                         show_regs(regs);
 427                 else
 428                         dump_stack();
 429
 430                 if (softlockup_all_cpu_backtrace) {
 431                         /* Avoid generating two back traces for current
 432                          * given that one is already made above
 433                          */
 434                         trigger_allbutself_cpu_backtrace();
 435
 436                         clear_bit(0, &soft_lockup_nmi_warn);
 437                         /* Barrier to sync with other cpus */
 438                         smp_mb__after_atomic();
 439                 }
 440
 441                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 442                 if (softlockup_panic)
 443                         panic("softlockup: hung tasks");
 444                 __this_cpu_write(soft_watchdog_warn, true);
 445         } else
 446                 __this_cpu_write(soft_watchdog_warn, false);
 447
 448         return HRTIMER_RESTART;
 449 }
 450
 451 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 452 {
 453         struct sched_param param = { .sched_priority = prio };
 454
 455         sched_setscheduler(current, policy, &param);
 456 }
 457
 458 static void watchdog_enable(unsigned int cpu)
 459 {
 460         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 461
 462         /*
 463          * Start the timer first to prevent the NMI watchdog triggering
 464          * before the timer has a chance to fire.
 465          */
 466         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 467         hrtimer->function = watchdog_timer_fn;
 468         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 469                       HRTIMER_MODE_REL_PINNED);
 470
 471         /* Initialize timestamp */
 472         __touch_watchdog();
 473         /* Enable the perf event */
 474         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
 475                 watchdog_nmi_enable(cpu);
 476
 477         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
 478 }
 479
 480 static void watchdog_disable(unsigned int cpu)
 481 {
 482         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 483
 484         watchdog_set_prio(SCHED_NORMAL, 0);
 485         /*
 486          * Disable the perf event first. That prevents that a large delay
 487          * between disabling the timer and disabling the perf event causes
 488          * the perf NMI to detect a false positive.
 489          */
 490         watchdog_nmi_disable(cpu);
 491         hrtimer_cancel(hrtimer);
 492 }
 493
 494 static void watchdog_cleanup(unsigned int cpu, bool online)
 495 {
 496         watchdog_disable(cpu);
 497 }
 498
 499 static int watchdog_should_run(unsigned int cpu)
 500 {
 501         return __this_cpu_read(hrtimer_interrupts) !=
 502                 __this_cpu_read(soft_lockup_hrtimer_cnt);
 503 }
 504
 505 /*
 506  * The watchdog thread function - touches the timestamp.
 507  *
 508  * It only runs once every sample_period seconds (4 seconds by
 509  * default) to reset the softlockup timestamp. If this gets delayed
 510  * for more than 2*watchdog_thresh seconds then the debug-printout
 511  * triggers in watchdog_timer_fn().
 512  */
 513 static void watchdog(unsigned int cpu)
 514 {
 515         __this_cpu_write(soft_lockup_hrtimer_cnt,
 516                          __this_cpu_read(hrtimer_interrupts));
 517         __touch_watchdog();
 518 }
 519
 520 static struct smp_hotplug_thread watchdog_threads = {
 521         .store                  = &softlockup_watchdog,
 522         .thread_should_run      = watchdog_should_run,
 523         .thread_fn              = watchdog,
 524         .thread_comm            = "watchdog/%u",
 525         .setup                  = watchdog_enable,
 526         .cleanup                = watchdog_cleanup,
 527         .park                   = watchdog_disable,
 528         .unpark                 = watchdog_enable,
 529 };
 530
 531 static void softlockup_update_smpboot_threads(void)
 532 {
 533         lockdep_assert_held(&watchdog_mutex);
 534
 535         if (!softlockup_threads_initialized)
 536                 return;
 537
 538         smpboot_update_cpumask_percpu_thread(&watchdog_threads,
 539                                              &watchdog_allowed_mask);
 540 }
 541
 542 /* Temporarily park all watchdog threads */
 543 static void softlockup_park_all_threads(void)
 544 {
 545         cpumask_clear(&watchdog_allowed_mask);
 546         softlockup_update_smpboot_threads();
 547 }
 548
 549 /* Unpark enabled threads */
 550 static void softlockup_unpark_threads(void)
 551 {
 552         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 553         softlockup_update_smpboot_threads();
 554 }
 555
 556 static void lockup_detector_reconfigure(void)
 557 {
 558         cpus_read_lock();
 559         watchdog_nmi_stop();
 560         softlockup_park_all_threads();
 561         set_sample_period();
 562         lockup_detector_update_enable();
 563         if (watchdog_enabled && watchdog_thresh)
 564                 softlockup_unpark_threads();
 565         watchdog_nmi_start();
 566         cpus_read_unlock();
 567         /*
 568          * Must be called outside the cpus locked section to prevent
 569          * recursive locking in the perf code.
 570          */
 571         __lockup_detector_cleanup();
 572 }
 573
 574 /*
 575  * Create the watchdog thread infrastructure and configure the detector(s).
 576  *
 577  * The threads are not unparked as watchdog_allowed_mask is empty.  When
 578  * the threads are sucessfully initialized, take the proper locks and
 579  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
 580  */
 581 static __init void lockup_detector_setup(void)
 582 {
 583         int ret;
 584
 585         /*
 586          * If sysctl is off and watchdog got disabled on the command line,
 587          * nothing to do here.
 588          */
 589         lockup_detector_update_enable();
 590
 591         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 592             !(watchdog_enabled && watchdog_thresh))
 593                 return;
 594
 595         ret = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
 596                                                      &watchdog_allowed_mask);
 597         if (ret) {
 598                 pr_err("Failed to initialize soft lockup detector threads\n");
 599                 return;
 600         }
 601
 602         mutex_lock(&watchdog_mutex);
 603         softlockup_threads_initialized = true;
 604         lockup_detector_reconfigure();
 605         mutex_unlock(&watchdog_mutex);
 606 }
 607
 608 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 609 static inline int watchdog_park_threads(void) { return 0; }
 610 static inline void watchdog_unpark_threads(void) { }
 611 static inline int watchdog_enable_all_cpus(void) { return 0; }
 612 static inline void watchdog_disable_all_cpus(void) { }
 613 static void lockup_detector_reconfigure(void)
 614 {
 615         cpus_read_lock();
 616         watchdog_nmi_stop();
 617         lockup_detector_update_enable();
 618         watchdog_nmi_start();
 619         cpus_read_unlock();
 620 }
 621 static inline void lockup_detector_setup(void)
 622 {
 623         lockup_detector_reconfigure();
 624 }
 625 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 626
 627 static void __lockup_detector_cleanup(void)
 628 {
 629         lockdep_assert_held(&watchdog_mutex);
 630         hardlockup_detector_perf_cleanup();
 631 }
 632
 633 /**
 634  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 635  *
 636  * Caller must not hold the cpu hotplug rwsem.
 637  */
 638 void lockup_detector_cleanup(void)
 639 {
 640         mutex_lock(&watchdog_mutex);
 641         __lockup_detector_cleanup();
 642         mutex_unlock(&watchdog_mutex);
 643 }
 644
 645 /**
 646  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 647  *
 648  * Special interface for parisc. It prevents lockup detector warnings from
 649  * the default pm_poweroff() function which busy loops forever.
 650  */
 651 void lockup_detector_soft_poweroff(void)
 652 {
 653         watchdog_enabled = 0;
 654 }
 655
 656 #ifdef CONFIG_SYSCTL
 657
 658 /* Propagate any changes to the watchdog threads */
 659 static void proc_watchdog_update(void)
 660 {
 661         /* Remove impossible cpus to keep sysctl output clean. */
 662         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 663         lockup_detector_reconfigure();
 664 }
 665
 666 /*
 667  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 668  *
 669  * caller             | table->data points to      | 'which'
 670  * -------------------|----------------------------|--------------------------
 671  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
 672  *                    |                            | SOFT_WATCHDOG_ENABLED
 673  * -------------------|----------------------------|--------------------------
 674  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
 675  * -------------------|----------------------------|--------------------------
 676  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
 677  */
 678 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 679                                 void __user *buffer, size_t *lenp, loff_t *ppos)
 680 {
 681         int err, old, *param = table->data;
 682
 683         mutex_lock(&watchdog_mutex);
 684
 685         if (!write) {
 686                 /*
 687                  * On read synchronize the userspace interface. This is a
 688                  * racy snapshot.
 689                  */
 690                 *param = (watchdog_enabled & which) != 0;
 691                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 692         } else {
 693                 old = READ_ONCE(*param);
 694                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 695                 if (!err && old != READ_ONCE(*param))
 696                         proc_watchdog_update();
 697         }
 698         mutex_unlock(&watchdog_mutex);
 699         return err;
 700 }
 701
 702 /*
 703  * /proc/sys/kernel/watchdog
 704  */
 705 int proc_watchdog(struct ctl_table *table, int write,
 706                   void __user *buffer, size_t *lenp, loff_t *ppos)
 707 {
 708         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
 709                                     table, write, buffer, lenp, ppos);
 710 }
 711
 712 /*
 713  * /proc/sys/kernel/nmi_watchdog
 714  */
 715 int proc_nmi_watchdog(struct ctl_table *table, int write,
 716                       void __user *buffer, size_t *lenp, loff_t *ppos)
 717 {
 718         if (!nmi_watchdog_available && write)
 719                 return -ENOTSUPP;
 720         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
 721                                     table, write, buffer, lenp, ppos);
 722 }
 723
 724 /*
 725  * /proc/sys/kernel/soft_watchdog
 726  */
 727 int proc_soft_watchdog(struct ctl_table *table, int write,
 728                         void __user *buffer, size_t *lenp, loff_t *ppos)
 729 {
 730         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
 731                                     table, write, buffer, lenp, ppos);
 732 }
 733
 734 /*
 735  * /proc/sys/kernel/watchdog_thresh
 736  */
 737 int proc_watchdog_thresh(struct ctl_table *table, int write,
 738                          void __user *buffer, size_t *lenp, loff_t *ppos)
 739 {
 740         int err, old;
 741
 742         mutex_lock(&watchdog_mutex);
 743
 744         old = READ_ONCE(watchdog_thresh);
 745         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 746
 747         if (!err && write && old != READ_ONCE(watchdog_thresh))
 748                 proc_watchdog_update();
 749
 750         mutex_unlock(&watchdog_mutex);
 751         return err;
 752 }
 753
 754 /*
 755  * The cpumask is the mask of possible cpus that the watchdog can run
 756  * on, not the mask of cpus it is actually running on.  This allows the
 757  * user to specify a mask that will include cpus that have not yet
 758  * been brought online, if desired.
 759  */
 760 int proc_watchdog_cpumask(struct ctl_table *table, int write,
 761                           void __user *buffer, size_t *lenp, loff_t *ppos)
 762 {
 763         int err;
 764
 765         mutex_lock(&watchdog_mutex);
 766
 767         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 768         if (!err && write)
 769                 proc_watchdog_update();
 770
 771         mutex_unlock(&watchdog_mutex);
 772         return err;
 773 }
 774 #endif /* CONFIG_SYSCTL */
 775
 776 void __init lockup_detector_init(void)
 777 {
 778         if (tick_nohz_full_enabled())
 779                 pr_info("Disabling watchdog on nohz_full cores by default\n");
 780
 781         cpumask_copy(&watchdog_cpumask,
 782                      housekeeping_cpumask(HK_FLAG_TIMER));
 783
 784         if (!watchdog_nmi_probe())
 785                 nmi_watchdog_available = true;
 786         lockup_detector_setup();
 787 }