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_HARDLOCKUP_DETECTOR_SPARC64)
  33 # define WATCHDOG_HARDLOCKUP_DEFAULT    1
  34 #else
  35 # define WATCHDOG_HARDLOCKUP_DEFAULT    0
  36 #endif
  37
  38 unsigned long __read_mostly watchdog_enabled;
  39 int __read_mostly watchdog_user_enabled = 1;
  40 static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
  41 static int __read_mostly watchdog_softlockup_user_enabled = 1;
  42 int __read_mostly watchdog_thresh = 10;
  43 static int __read_mostly watchdog_hardlockup_available;
  44
  45 struct cpumask watchdog_cpumask __read_mostly;
  46 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  47
  48 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  49
  50 # ifdef CONFIG_SMP
  51 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  52 # endif /* CONFIG_SMP */
  53
  54 /*
  55  * Should we panic when a soft-lockup or hard-lockup occurs:
  56  */
  57 unsigned int __read_mostly hardlockup_panic =
  58                         IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
  59 /*
  60  * We may not want to enable hard lockup detection by default in all cases,
  61  * for example when running the kernel as a guest on a hypervisor. In these
  62  * cases this function can be called to disable hard lockup detection. This
  63  * function should only be executed once by the boot processor before the
  64  * kernel command line parameters are parsed, because otherwise it is not
  65  * possible to override this in hardlockup_panic_setup().
  66  */
  67 void __init hardlockup_detector_disable(void)
  68 {
  69         watchdog_hardlockup_user_enabled = 0;
  70 }
  71
  72 static int __init hardlockup_panic_setup(char *str)
  73 {
  74         if (!strncmp(str, "panic", 5))
  75                 hardlockup_panic = 1;
  76         else if (!strncmp(str, "nopanic", 7))
  77                 hardlockup_panic = 0;
  78         else if (!strncmp(str, "0", 1))
  79                 watchdog_hardlockup_user_enabled = 0;
  80         else if (!strncmp(str, "1", 1))
  81                 watchdog_hardlockup_user_enabled = 1;
  82         return 1;
  83 }
  84 __setup("nmi_watchdog=", hardlockup_panic_setup);
  85
  86 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
  87
  88 #if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
  89
  90 static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
  91 static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
  92 static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
  93 static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
  94 static unsigned long watchdog_hardlockup_all_cpu_dumped;
  95
  96 notrace void arch_touch_nmi_watchdog(void)
  97 {
  98         /*
  99          * Using __raw here because some code paths have
 100          * preemption enabled.  If preemption is enabled
 101          * then interrupts should be enabled too, in which
 102          * case we shouldn't have to worry about the watchdog
 103          * going off.
 104          */
 105         raw_cpu_write(watchdog_hardlockup_touched, true);
 106 }
 107 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 108
 109 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
 110 {
 111         per_cpu(watchdog_hardlockup_touched, cpu) = true;
 112 }
 113
 114 static bool is_hardlockup(unsigned int cpu)
 115 {
 116         int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu));
 117
 118         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 119                 return true;
 120
 121         /*
 122          * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE
 123          * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is
 124          * written/read by a single CPU.
 125          */
 126         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 127
 128         return false;
 129 }
 130
 131 static void watchdog_hardlockup_kick(void)
 132 {
 133         int new_interrupts;
 134
 135         new_interrupts = atomic_inc_return(this_cpu_ptr(&hrtimer_interrupts));
 136         watchdog_buddy_check_hardlockup(new_interrupts);
 137 }
 138
 139 void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
 140 {
 141         if (per_cpu(watchdog_hardlockup_touched, cpu)) {
 142                 per_cpu(watchdog_hardlockup_touched, cpu) = false;
 143                 return;
 144         }
 145
 146         /*
 147          * Check for a hardlockup by making sure the CPU's timer
 148          * interrupt is incrementing. The timer interrupt should have
 149          * fired multiple times before we overflow'd. If it hasn't
 150          * then this is a good indication the cpu is stuck
 151          */
 152         if (is_hardlockup(cpu)) {
 153                 unsigned int this_cpu = smp_processor_id();
 154
 155                 /* Only print hardlockups once. */
 156                 if (per_cpu(watchdog_hardlockup_warned, cpu))
 157                         return;
 158
 159                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
 160                 print_modules();
 161                 print_irqtrace_events(current);
 162                 if (cpu == this_cpu) {
 163                         if (regs)
 164                                 show_regs(regs);
 165                         else
 166                                 dump_stack();
 167                 } else {
 168                         trigger_single_cpu_backtrace(cpu);
 169                 }
 170
 171                 /*
 172                  * Perform multi-CPU dump only once to avoid multiple
 173                  * hardlockups generating interleaving traces
 174                  */
 175                 if (sysctl_hardlockup_all_cpu_backtrace &&
 176                     !test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped))
 177                         trigger_allbutcpu_cpu_backtrace(cpu);
 178
 179                 if (hardlockup_panic)
 180                         nmi_panic(regs, "Hard LOCKUP");
 181
 182                 per_cpu(watchdog_hardlockup_warned, cpu) = true;
 183         } else {
 184                 per_cpu(watchdog_hardlockup_warned, cpu) = false;
 185         }
 186 }
 187
 188 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 189
 190 static inline void watchdog_hardlockup_kick(void) { }
 191
 192 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 193
 194 /*
 195  * These functions can be overridden based on the configured hardlockdup detector.
 196  *
 197  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
 198  * softlockup watchdog start and stop. The detector must select the
 199  * SOFTLOCKUP_DETECTOR Kconfig.
 200  */
 201 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
 202
 203 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
 204
 205 /*
 206  * Watchdog-detector specific API.
 207  *
 208  * Return 0 when hardlockup watchdog is available, negative value otherwise.
 209  * Note that the negative value means that a delayed probe might
 210  * succeed later.
 211  */
 212 int __weak __init watchdog_hardlockup_probe(void)
 213 {
 214         return -ENODEV;
 215 }
 216
 217 /**
 218  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
 219  *
 220  * The reconfiguration steps are:
 221  * watchdog_hardlockup_stop();
 222  * update_variables();
 223  * watchdog_hardlockup_start();
 224  */
 225 void __weak watchdog_hardlockup_stop(void) { }
 226
 227 /**
 228  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
 229  *
 230  * Counterpart to watchdog_hardlockup_stop().
 231  *
 232  * The following variables have been updated in update_variables() and
 233  * contain the currently valid configuration:
 234  * - watchdog_enabled
 235  * - watchdog_thresh
 236  * - watchdog_cpumask
 237  */
 238 void __weak watchdog_hardlockup_start(void) { }
 239
 240 /**
 241  * lockup_detector_update_enable - Update the sysctl enable bit
 242  *
 243  * Caller needs to make sure that the hard watchdogs are off, so this
 244  * can't race with watchdog_hardlockup_disable().
 245  */
 246 static void lockup_detector_update_enable(void)
 247 {
 248         watchdog_enabled = 0;
 249         if (!watchdog_user_enabled)
 250                 return;
 251         if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
 252                 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
 253         if (watchdog_softlockup_user_enabled)
 254                 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
 255 }
 256
 257 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 258
 259 /*
 260  * Delay the soflockup report when running a known slow code.
 261  * It does _not_ affect the timestamp of the last successdul reschedule.
 262  */
 263 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
 264
 265 #ifdef CONFIG_SMP
 266 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 267 #endif
 268
 269 static struct cpumask watchdog_allowed_mask __read_mostly;
 270
 271 /* Global variables, exported for sysctl */
 272 unsigned int __read_mostly softlockup_panic =
 273                         IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
 274
 275 static bool softlockup_initialized __read_mostly;
 276 static u64 __read_mostly sample_period;
 277
 278 /* Timestamp taken after the last successful reschedule. */
 279 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 280 /* Timestamp of the last softlockup report. */
 281 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
 282 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 283 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 284 static unsigned long soft_lockup_nmi_warn;
 285
 286 static int __init softlockup_panic_setup(char *str)
 287 {
 288         softlockup_panic = simple_strtoul(str, NULL, 0);
 289         return 1;
 290 }
 291 __setup("softlockup_panic=", softlockup_panic_setup);
 292
 293 static int __init nowatchdog_setup(char *str)
 294 {
 295         watchdog_user_enabled = 0;
 296         return 1;
 297 }
 298 __setup("nowatchdog", nowatchdog_setup);
 299
 300 static int __init nosoftlockup_setup(char *str)
 301 {
 302         watchdog_softlockup_user_enabled = 0;
 303         return 1;
 304 }
 305 __setup("nosoftlockup", nosoftlockup_setup);
 306
 307 static int __init watchdog_thresh_setup(char *str)
 308 {
 309         get_option(&str, &watchdog_thresh);
 310         return 1;
 311 }
 312 __setup("watchdog_thresh=", watchdog_thresh_setup);
 313
 314 static void __lockup_detector_cleanup(void);
 315
 316 /*
 317  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 318  * lockups can have false positives under extreme conditions. So we generally
 319  * want a higher threshold for soft lockups than for hard lockups. So we couple
 320  * the thresholds with a factor: we make the soft threshold twice the amount of
 321  * time the hard threshold is.
 322  */
 323 static int get_softlockup_thresh(void)
 324 {
 325         return watchdog_thresh * 2;
 326 }
 327
 328 /*
 329  * Returns seconds, approximately.  We don't need nanosecond
 330  * resolution, and we don't need to waste time with a big divide when
 331  * 2^30ns == 1.074s.
 332  */
 333 static unsigned long get_timestamp(void)
 334 {
 335         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 336 }
 337
 338 static void set_sample_period(void)
 339 {
 340         /*
 341          * convert watchdog_thresh from seconds to ns
 342          * the divide by 5 is to give hrtimer several chances (two
 343          * or three with the current relation between the soft
 344          * and hard thresholds) to increment before the
 345          * hardlockup detector generates a warning
 346          */
 347         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 348         watchdog_update_hrtimer_threshold(sample_period);
 349 }
 350
 351 static void update_report_ts(void)
 352 {
 353         __this_cpu_write(watchdog_report_ts, get_timestamp());
 354 }
 355
 356 /* Commands for resetting the watchdog */
 357 static void update_touch_ts(void)
 358 {
 359         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 360         update_report_ts();
 361 }
 362
 363 /**
 364  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 365  *
 366  * Call when the scheduler may have stalled for legitimate reasons
 367  * preventing the watchdog task from executing - e.g. the scheduler
 368  * entering idle state.  This should only be used for scheduler events.
 369  * Use touch_softlockup_watchdog() for everything else.
 370  */
 371 notrace void touch_softlockup_watchdog_sched(void)
 372 {
 373         /*
 374          * Preemption can be enabled.  It doesn't matter which CPU's watchdog
 375          * report period gets restarted here, so use the raw_ operation.
 376          */
 377         raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 378 }
 379
 380 notrace void touch_softlockup_watchdog(void)
 381 {
 382         touch_softlockup_watchdog_sched();
 383         wq_watchdog_touch(raw_smp_processor_id());
 384 }
 385 EXPORT_SYMBOL(touch_softlockup_watchdog);
 386
 387 void touch_all_softlockup_watchdogs(void)
 388 {
 389         int cpu;
 390
 391         /*
 392          * watchdog_mutex cannpt be taken here, as this might be called
 393          * from (soft)interrupt context, so the access to
 394          * watchdog_allowed_cpumask might race with a concurrent update.
 395          *
 396          * The watchdog time stamp can race against a concurrent real
 397          * update as well, the only side effect might be a cycle delay for
 398          * the softlockup check.
 399          */
 400         for_each_cpu(cpu, &watchdog_allowed_mask) {
 401                 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
 402                 wq_watchdog_touch(cpu);
 403         }
 404 }
 405
 406 void touch_softlockup_watchdog_sync(void)
 407 {
 408         __this_cpu_write(softlockup_touch_sync, true);
 409         __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 410 }
 411
 412 static int is_softlockup(unsigned long touch_ts,
 413                          unsigned long period_ts,
 414                          unsigned long now)
 415 {
 416         if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
 417                 /* Warn about unreasonable delays. */
 418                 if (time_after(now, period_ts + get_softlockup_thresh()))
 419                         return now - touch_ts;
 420         }
 421         return 0;
 422 }
 423
 424 /* watchdog detector functions */
 425 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 426 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 427
 428 /*
 429  * The watchdog feed function - touches the timestamp.
 430  *
 431  * It only runs once every sample_period seconds (4 seconds by
 432  * default) to reset the softlockup timestamp. If this gets delayed
 433  * for more than 2*watchdog_thresh seconds then the debug-printout
 434  * triggers in watchdog_timer_fn().
 435  */
 436 static int softlockup_fn(void *data)
 437 {
 438         update_touch_ts();
 439         complete(this_cpu_ptr(&softlockup_completion));
 440
 441         return 0;
 442 }
 443
 444 /* watchdog kicker functions */
 445 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 446 {
 447         unsigned long touch_ts, period_ts, now;
 448         struct pt_regs *regs = get_irq_regs();
 449         int duration;
 450         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 451
 452         if (!watchdog_enabled)
 453                 return HRTIMER_NORESTART;
 454
 455         watchdog_hardlockup_kick();
 456
 457         /* kick the softlockup detector */
 458         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
 459                 reinit_completion(this_cpu_ptr(&softlockup_completion));
 460                 stop_one_cpu_nowait(smp_processor_id(),
 461                                 softlockup_fn, NULL,
 462                                 this_cpu_ptr(&softlockup_stop_work));
 463         }
 464
 465         /* .. and repeat */
 466         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 467
 468         /*
 469          * Read the current timestamp first. It might become invalid anytime
 470          * when a virtual machine is stopped by the host or when the watchog
 471          * is touched from NMI.
 472          */
 473         now = get_timestamp();
 474         /*
 475          * If a virtual machine is stopped by the host it can look to
 476          * the watchdog like a soft lockup. This function touches the watchdog.
 477          */
 478         kvm_check_and_clear_guest_paused();
 479         /*
 480          * The stored timestamp is comparable with @now only when not touched.
 481          * It might get touched anytime from NMI. Make sure that is_softlockup()
 482          * uses the same (valid) value.
 483          */
 484         period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
 485
 486         /* Reset the interval when touched by known problematic code. */
 487         if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
 488                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 489                         /*
 490                          * If the time stamp was touched atomically
 491                          * make sure the scheduler tick is up to date.
 492                          */
 493                         __this_cpu_write(softlockup_touch_sync, false);
 494                         sched_clock_tick();
 495                 }
 496
 497                 update_report_ts();
 498                 return HRTIMER_RESTART;
 499         }
 500
 501         /* Check for a softlockup. */
 502         touch_ts = __this_cpu_read(watchdog_touch_ts);
 503         duration = is_softlockup(touch_ts, period_ts, now);
 504         if (unlikely(duration)) {
 505                 /*
 506                  * Prevent multiple soft-lockup reports if one cpu is already
 507                  * engaged in dumping all cpu back traces.
 508                  */
 509                 if (softlockup_all_cpu_backtrace) {
 510                         if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
 511                                 return HRTIMER_RESTART;
 512                 }
 513
 514                 /* Start period for the next softlockup warning. */
 515                 update_report_ts();
 516
 517                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 518                         smp_processor_id(), duration,
 519                         current->comm, task_pid_nr(current));
 520                 print_modules();
 521                 print_irqtrace_events(current);
 522                 if (regs)
 523                         show_regs(regs);
 524                 else
 525                         dump_stack();
 526
 527                 if (softlockup_all_cpu_backtrace) {
 528                         trigger_allbutcpu_cpu_backtrace(smp_processor_id());
 529                         clear_bit_unlock(0, &soft_lockup_nmi_warn);
 530                 }
 531
 532                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 533                 if (softlockup_panic)
 534                         panic("softlockup: hung tasks");
 535         }
 536
 537         return HRTIMER_RESTART;
 538 }
 539
 540 static void watchdog_enable(unsigned int cpu)
 541 {
 542         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 543         struct completion *done = this_cpu_ptr(&softlockup_completion);
 544
 545         WARN_ON_ONCE(cpu != smp_processor_id());
 546
 547         init_completion(done);
 548         complete(done);
 549
 550         /*
 551          * Start the timer first to prevent the hardlockup watchdog triggering
 552          * before the timer has a chance to fire.
 553          */
 554         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 555         hrtimer->function = watchdog_timer_fn;
 556         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 557                       HRTIMER_MODE_REL_PINNED_HARD);
 558
 559         /* Initialize timestamp */
 560         update_touch_ts();
 561         /* Enable the hardlockup detector */
 562         if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
 563                 watchdog_hardlockup_enable(cpu);
 564 }
 565
 566 static void watchdog_disable(unsigned int cpu)
 567 {
 568         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 569
 570         WARN_ON_ONCE(cpu != smp_processor_id());
 571
 572         /*
 573          * Disable the hardlockup detector first. That prevents that a large
 574          * delay between disabling the timer and disabling the hardlockup
 575          * detector causes a false positive.
 576          */
 577         watchdog_hardlockup_disable(cpu);
 578         hrtimer_cancel(hrtimer);
 579         wait_for_completion(this_cpu_ptr(&softlockup_completion));
 580 }
 581
 582 static int softlockup_stop_fn(void *data)
 583 {
 584         watchdog_disable(smp_processor_id());
 585         return 0;
 586 }
 587
 588 static void softlockup_stop_all(void)
 589 {
 590         int cpu;
 591
 592         if (!softlockup_initialized)
 593                 return;
 594
 595         for_each_cpu(cpu, &watchdog_allowed_mask)
 596                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 597
 598         cpumask_clear(&watchdog_allowed_mask);
 599 }
 600
 601 static int softlockup_start_fn(void *data)
 602 {
 603         watchdog_enable(smp_processor_id());
 604         return 0;
 605 }
 606
 607 static void softlockup_start_all(void)
 608 {
 609         int cpu;
 610
 611         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 612         for_each_cpu(cpu, &watchdog_allowed_mask)
 613                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 614 }
 615
 616 int lockup_detector_online_cpu(unsigned int cpu)
 617 {
 618         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 619                 watchdog_enable(cpu);
 620         return 0;
 621 }
 622
 623 int lockup_detector_offline_cpu(unsigned int cpu)
 624 {
 625         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 626                 watchdog_disable(cpu);
 627         return 0;
 628 }
 629
 630 static void __lockup_detector_reconfigure(void)
 631 {
 632         cpus_read_lock();
 633         watchdog_hardlockup_stop();
 634
 635         softlockup_stop_all();
 636         set_sample_period();
 637         lockup_detector_update_enable();
 638         if (watchdog_enabled && watchdog_thresh)
 639                 softlockup_start_all();
 640
 641         watchdog_hardlockup_start();
 642         cpus_read_unlock();
 643         /*
 644          * Must be called outside the cpus locked section to prevent
 645          * recursive locking in the perf code.
 646          */
 647         __lockup_detector_cleanup();
 648 }
 649
 650 void lockup_detector_reconfigure(void)
 651 {
 652         mutex_lock(&watchdog_mutex);
 653         __lockup_detector_reconfigure();
 654         mutex_unlock(&watchdog_mutex);
 655 }
 656
 657 /*
 658  * Create the watchdog infrastructure and configure the detector(s).
 659  */
 660 static __init void lockup_detector_setup(void)
 661 {
 662         /*
 663          * If sysctl is off and watchdog got disabled on the command line,
 664          * nothing to do here.
 665          */
 666         lockup_detector_update_enable();
 667
 668         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 669             !(watchdog_enabled && watchdog_thresh))
 670                 return;
 671
 672         mutex_lock(&watchdog_mutex);
 673         __lockup_detector_reconfigure();
 674         softlockup_initialized = true;
 675         mutex_unlock(&watchdog_mutex);
 676 }
 677
 678 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 679 static void __lockup_detector_reconfigure(void)
 680 {
 681         cpus_read_lock();
 682         watchdog_hardlockup_stop();
 683         lockup_detector_update_enable();
 684         watchdog_hardlockup_start();
 685         cpus_read_unlock();
 686 }
 687 void lockup_detector_reconfigure(void)
 688 {
 689         __lockup_detector_reconfigure();
 690 }
 691 static inline void lockup_detector_setup(void)
 692 {
 693         __lockup_detector_reconfigure();
 694 }
 695 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 696
 697 static void __lockup_detector_cleanup(void)
 698 {
 699         lockdep_assert_held(&watchdog_mutex);
 700         hardlockup_detector_perf_cleanup();
 701 }
 702
 703 /**
 704  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 705  *
 706  * Caller must not hold the cpu hotplug rwsem.
 707  */
 708 void lockup_detector_cleanup(void)
 709 {
 710         mutex_lock(&watchdog_mutex);
 711         __lockup_detector_cleanup();
 712         mutex_unlock(&watchdog_mutex);
 713 }
 714
 715 /**
 716  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 717  *
 718  * Special interface for parisc. It prevents lockup detector warnings from
 719  * the default pm_poweroff() function which busy loops forever.
 720  */
 721 void lockup_detector_soft_poweroff(void)
 722 {
 723         watchdog_enabled = 0;
 724 }
 725
 726 #ifdef CONFIG_SYSCTL
 727
 728 /* Propagate any changes to the watchdog infrastructure */
 729 static void proc_watchdog_update(void)
 730 {
 731         /* Remove impossible cpus to keep sysctl output clean. */
 732         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 733         __lockup_detector_reconfigure();
 734 }
 735
 736 /*
 737  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 738  *
 739  * caller             | table->data points to            | 'which'
 740  * -------------------|----------------------------------|-------------------------------
 741  * proc_watchdog      | watchdog_user_enabled            | WATCHDOG_HARDLOCKUP_ENABLED |
 742  *                    |                                  | WATCHDOG_SOFTOCKUP_ENABLED
 743  * -------------------|----------------------------------|-------------------------------
 744  * proc_nmi_watchdog  | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
 745  * -------------------|----------------------------------|-------------------------------
 746  * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
 747  */
 748 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 749                                 void *buffer, size_t *lenp, loff_t *ppos)
 750 {
 751         int err, old, *param = table->data;
 752
 753         mutex_lock(&watchdog_mutex);
 754
 755         if (!write) {
 756                 /*
 757                  * On read synchronize the userspace interface. This is a
 758                  * racy snapshot.
 759                  */
 760                 *param = (watchdog_enabled & which) != 0;
 761                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 762         } else {
 763                 old = READ_ONCE(*param);
 764                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 765                 if (!err && old != READ_ONCE(*param))
 766                         proc_watchdog_update();
 767         }
 768         mutex_unlock(&watchdog_mutex);
 769         return err;
 770 }
 771
 772 /*
 773  * /proc/sys/kernel/watchdog
 774  */
 775 int proc_watchdog(struct ctl_table *table, int write,
 776                   void *buffer, size_t *lenp, loff_t *ppos)
 777 {
 778         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
 779                                     WATCHDOG_SOFTOCKUP_ENABLED,
 780                                     table, write, buffer, lenp, ppos);
 781 }
 782
 783 /*
 784  * /proc/sys/kernel/nmi_watchdog
 785  */
 786 int proc_nmi_watchdog(struct ctl_table *table, int write,
 787                       void *buffer, size_t *lenp, loff_t *ppos)
 788 {
 789         if (!watchdog_hardlockup_available && write)
 790                 return -ENOTSUPP;
 791         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
 792                                     table, write, buffer, lenp, ppos);
 793 }
 794
 795 /*
 796  * /proc/sys/kernel/soft_watchdog
 797  */
 798 int proc_soft_watchdog(struct ctl_table *table, int write,
 799                         void *buffer, size_t *lenp, loff_t *ppos)
 800 {
 801         return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
 802                                     table, write, buffer, lenp, ppos);
 803 }
 804
 805 /*
 806  * /proc/sys/kernel/watchdog_thresh
 807  */
 808 int proc_watchdog_thresh(struct ctl_table *table, int write,
 809                          void *buffer, size_t *lenp, loff_t *ppos)
 810 {
 811         int err, old;
 812
 813         mutex_lock(&watchdog_mutex);
 814
 815         old = READ_ONCE(watchdog_thresh);
 816         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 817
 818         if (!err && write && old != READ_ONCE(watchdog_thresh))
 819                 proc_watchdog_update();
 820
 821         mutex_unlock(&watchdog_mutex);
 822         return err;
 823 }
 824
 825 /*
 826  * The cpumask is the mask of possible cpus that the watchdog can run
 827  * on, not the mask of cpus it is actually running on.  This allows the
 828  * user to specify a mask that will include cpus that have not yet
 829  * been brought online, if desired.
 830  */
 831 int proc_watchdog_cpumask(struct ctl_table *table, int write,
 832                           void *buffer, size_t *lenp, loff_t *ppos)
 833 {
 834         int err;
 835
 836         mutex_lock(&watchdog_mutex);
 837
 838         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 839         if (!err && write)
 840                 proc_watchdog_update();
 841
 842         mutex_unlock(&watchdog_mutex);
 843         return err;
 844 }
 845
 846 static const int sixty = 60;
 847
 848 static struct ctl_table watchdog_sysctls[] = {
 849         {
 850                 .procname       = "watchdog",
 851                 .data           = &watchdog_user_enabled,
 852                 .maxlen         = sizeof(int),
 853                 .mode           = 0644,
 854                 .proc_handler   = proc_watchdog,
 855                 .extra1         = SYSCTL_ZERO,
 856                 .extra2         = SYSCTL_ONE,
 857         },
 858         {
 859                 .procname       = "watchdog_thresh",
 860                 .data           = &watchdog_thresh,
 861                 .maxlen         = sizeof(int),
 862                 .mode           = 0644,
 863                 .proc_handler   = proc_watchdog_thresh,
 864                 .extra1         = SYSCTL_ZERO,
 865                 .extra2         = (void *)&sixty,
 866         },
 867         {
 868                 .procname       = "watchdog_cpumask",
 869                 .data           = &watchdog_cpumask_bits,
 870                 .maxlen         = NR_CPUS,
 871                 .mode           = 0644,
 872                 .proc_handler   = proc_watchdog_cpumask,
 873         },
 874 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 875         {
 876                 .procname       = "soft_watchdog",
 877                 .data           = &watchdog_softlockup_user_enabled,
 878                 .maxlen         = sizeof(int),
 879                 .mode           = 0644,
 880                 .proc_handler   = proc_soft_watchdog,
 881                 .extra1         = SYSCTL_ZERO,
 882                 .extra2         = SYSCTL_ONE,
 883         },
 884         {
 885                 .procname       = "softlockup_panic",
 886                 .data           = &softlockup_panic,
 887                 .maxlen         = sizeof(int),
 888                 .mode           = 0644,
 889                 .proc_handler   = proc_dointvec_minmax,
 890                 .extra1         = SYSCTL_ZERO,
 891                 .extra2         = SYSCTL_ONE,
 892         },
 893 #ifdef CONFIG_SMP
 894         {
 895                 .procname       = "softlockup_all_cpu_backtrace",
 896                 .data           = &sysctl_softlockup_all_cpu_backtrace,
 897                 .maxlen         = sizeof(int),
 898                 .mode           = 0644,
 899                 .proc_handler   = proc_dointvec_minmax,
 900                 .extra1         = SYSCTL_ZERO,
 901                 .extra2         = SYSCTL_ONE,
 902         },
 903 #endif /* CONFIG_SMP */
 904 #endif
 905 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 906         {
 907                 .procname       = "hardlockup_panic",
 908                 .data           = &hardlockup_panic,
 909                 .maxlen         = sizeof(int),
 910                 .mode           = 0644,
 911                 .proc_handler   = proc_dointvec_minmax,
 912                 .extra1         = SYSCTL_ZERO,
 913                 .extra2         = SYSCTL_ONE,
 914         },
 915 #ifdef CONFIG_SMP
 916         {
 917                 .procname       = "hardlockup_all_cpu_backtrace",
 918                 .data           = &sysctl_hardlockup_all_cpu_backtrace,
 919                 .maxlen         = sizeof(int),
 920                 .mode           = 0644,
 921                 .proc_handler   = proc_dointvec_minmax,
 922                 .extra1         = SYSCTL_ZERO,
 923                 .extra2         = SYSCTL_ONE,
 924         },
 925 #endif /* CONFIG_SMP */
 926 #endif
 927         {}
 928 };
 929
 930 static struct ctl_table watchdog_hardlockup_sysctl[] = {
 931         {
 932                 .procname       = "nmi_watchdog",
 933                 .data           = &watchdog_hardlockup_user_enabled,
 934                 .maxlen         = sizeof(int),
 935                 .mode           = 0444,
 936                 .proc_handler   = proc_nmi_watchdog,
 937                 .extra1         = SYSCTL_ZERO,
 938                 .extra2         = SYSCTL_ONE,
 939         },
 940         {}
 941 };
 942
 943 static void __init watchdog_sysctl_init(void)
 944 {
 945         register_sysctl_init("kernel", watchdog_sysctls);
 946
 947         if (watchdog_hardlockup_available)
 948                 watchdog_hardlockup_sysctl[0].mode = 0644;
 949         register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
 950 }
 951
 952 #else
 953 #define watchdog_sysctl_init() do { } while (0)
 954 #endif /* CONFIG_SYSCTL */
 955
 956 static void __init lockup_detector_delay_init(struct work_struct *work);
 957 static bool allow_lockup_detector_init_retry __initdata;
 958
 959 static struct work_struct detector_work __initdata =
 960                 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
 961
 962 static void __init lockup_detector_delay_init(struct work_struct *work)
 963 {
 964         int ret;
 965
 966         ret = watchdog_hardlockup_probe();
 967         if (ret) {
 968                 pr_info("Delayed init of the lockup detector failed: %d\n", ret);
 969                 pr_info("Hard watchdog permanently disabled\n");
 970                 return;
 971         }
 972
 973         allow_lockup_detector_init_retry = false;
 974
 975         watchdog_hardlockup_available = true;
 976         lockup_detector_setup();
 977 }
 978
 979 /*
 980  * lockup_detector_retry_init - retry init lockup detector if possible.
 981  *
 982  * Retry hardlockup detector init. It is useful when it requires some
 983  * functionality that has to be initialized later on a particular
 984  * platform.
 985  */
 986 void __init lockup_detector_retry_init(void)
 987 {
 988         /* Must be called before late init calls */
 989         if (!allow_lockup_detector_init_retry)
 990                 return;
 991
 992         schedule_work(&detector_work);
 993 }
 994
 995 /*
 996  * Ensure that optional delayed hardlockup init is proceed before
 997  * the init code and memory is freed.
 998  */
 999 static int __init lockup_detector_check(void)
1000 {
1001         /* Prevent any later retry. */
1002         allow_lockup_detector_init_retry = false;
1003
1004         /* Make sure no work is pending. */
1005         flush_work(&detector_work);
1006
1007         watchdog_sysctl_init();
1008
1009         return 0;
1010
1011 }
1012 late_initcall_sync(lockup_detector_check);
1013
1014 void __init lockup_detector_init(void)
1015 {
1016         if (tick_nohz_full_enabled())
1017                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1018
1019         cpumask_copy(&watchdog_cpumask,
1020                      housekeeping_cpumask(HK_TYPE_TIMER));
1021
1022         if (!watchdog_hardlockup_probe())
1023                 watchdog_hardlockup_available = true;
1024         else
1025                 allow_lockup_detector_init_retry = true;
1026
1027         lockup_detector_setup();
1028 }