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 hard_lockup_nmi_warn;
  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                 unsigned long flags;
 155
 156                 /* Only print hardlockups once. */
 157                 if (per_cpu(watchdog_hardlockup_warned, cpu))
 158                         return;
 159
 160                 /*
 161                  * Prevent multiple hard-lockup reports if one cpu is already
 162                  * engaged in dumping all cpu back traces.
 163                  */
 164                 if (sysctl_hardlockup_all_cpu_backtrace) {
 165                         if (test_and_set_bit_lock(0, &hard_lockup_nmi_warn))
 166                                 return;
 167                 }
 168
 169                 /*
 170                  * NOTE: we call printk_cpu_sync_get_irqsave() after printing
 171                  * the lockup message. While it would be nice to serialize
 172                  * that printout, we really want to make sure that if some
 173                  * other CPU somehow locked up while holding the lock associated
 174                  * with printk_cpu_sync_get_irqsave() that we can still at least
 175                  * get the message about the lockup out.
 176                  */
 177                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu);
 178                 printk_cpu_sync_get_irqsave(flags);
 179
 180                 print_modules();
 181                 print_irqtrace_events(current);
 182                 if (cpu == this_cpu) {
 183                         if (regs)
 184                                 show_regs(regs);
 185                         else
 186                                 dump_stack();
 187                         printk_cpu_sync_put_irqrestore(flags);
 188                 } else {
 189                         printk_cpu_sync_put_irqrestore(flags);
 190                         trigger_single_cpu_backtrace(cpu);
 191                 }
 192
 193                 if (sysctl_hardlockup_all_cpu_backtrace) {
 194                         trigger_allbutcpu_cpu_backtrace(cpu);
 195                         if (!hardlockup_panic)
 196                                 clear_bit_unlock(0, &hard_lockup_nmi_warn);
 197                 }
 198
 199                 if (hardlockup_panic)
 200                         nmi_panic(regs, "Hard LOCKUP");
 201
 202                 per_cpu(watchdog_hardlockup_warned, cpu) = true;
 203         } else {
 204                 per_cpu(watchdog_hardlockup_warned, cpu) = false;
 205         }
 206 }
 207
 208 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 209
 210 static inline void watchdog_hardlockup_kick(void) { }
 211
 212 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 213
 214 /*
 215  * These functions can be overridden based on the configured hardlockdup detector.
 216  *
 217  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
 218  * softlockup watchdog start and stop. The detector must select the
 219  * SOFTLOCKUP_DETECTOR Kconfig.
 220  */
 221 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
 222
 223 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
 224
 225 /*
 226  * Watchdog-detector specific API.
 227  *
 228  * Return 0 when hardlockup watchdog is available, negative value otherwise.
 229  * Note that the negative value means that a delayed probe might
 230  * succeed later.
 231  */
 232 int __weak __init watchdog_hardlockup_probe(void)
 233 {
 234         return -ENODEV;
 235 }
 236
 237 /**
 238  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
 239  *
 240  * The reconfiguration steps are:
 241  * watchdog_hardlockup_stop();
 242  * update_variables();
 243  * watchdog_hardlockup_start();
 244  */
 245 void __weak watchdog_hardlockup_stop(void) { }
 246
 247 /**
 248  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
 249  *
 250  * Counterpart to watchdog_hardlockup_stop().
 251  *
 252  * The following variables have been updated in update_variables() and
 253  * contain the currently valid configuration:
 254  * - watchdog_enabled
 255  * - watchdog_thresh
 256  * - watchdog_cpumask
 257  */
 258 void __weak watchdog_hardlockup_start(void) { }
 259
 260 /**
 261  * lockup_detector_update_enable - Update the sysctl enable bit
 262  *
 263  * Caller needs to make sure that the hard watchdogs are off, so this
 264  * can't race with watchdog_hardlockup_disable().
 265  */
 266 static void lockup_detector_update_enable(void)
 267 {
 268         watchdog_enabled = 0;
 269         if (!watchdog_user_enabled)
 270                 return;
 271         if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
 272                 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
 273         if (watchdog_softlockup_user_enabled)
 274                 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
 275 }
 276
 277 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 278
 279 /*
 280  * Delay the soflockup report when running a known slow code.
 281  * It does _not_ affect the timestamp of the last successdul reschedule.
 282  */
 283 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
 284
 285 #ifdef CONFIG_SMP
 286 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 287 #endif
 288
 289 static struct cpumask watchdog_allowed_mask __read_mostly;
 290
 291 /* Global variables, exported for sysctl */
 292 unsigned int __read_mostly softlockup_panic =
 293                         IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
 294
 295 static bool softlockup_initialized __read_mostly;
 296 static u64 __read_mostly sample_period;
 297
 298 /* Timestamp taken after the last successful reschedule. */
 299 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 300 /* Timestamp of the last softlockup report. */
 301 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
 302 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 303 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 304 static unsigned long soft_lockup_nmi_warn;
 305
 306 static int __init softlockup_panic_setup(char *str)
 307 {
 308         softlockup_panic = simple_strtoul(str, NULL, 0);
 309         return 1;
 310 }
 311 __setup("softlockup_panic=", softlockup_panic_setup);
 312
 313 static int __init nowatchdog_setup(char *str)
 314 {
 315         watchdog_user_enabled = 0;
 316         return 1;
 317 }
 318 __setup("nowatchdog", nowatchdog_setup);
 319
 320 static int __init nosoftlockup_setup(char *str)
 321 {
 322         watchdog_softlockup_user_enabled = 0;
 323         return 1;
 324 }
 325 __setup("nosoftlockup", nosoftlockup_setup);
 326
 327 static int __init watchdog_thresh_setup(char *str)
 328 {
 329         get_option(&str, &watchdog_thresh);
 330         return 1;
 331 }
 332 __setup("watchdog_thresh=", watchdog_thresh_setup);
 333
 334 static void __lockup_detector_cleanup(void);
 335
 336 /*
 337  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 338  * lockups can have false positives under extreme conditions. So we generally
 339  * want a higher threshold for soft lockups than for hard lockups. So we couple
 340  * the thresholds with a factor: we make the soft threshold twice the amount of
 341  * time the hard threshold is.
 342  */
 343 static int get_softlockup_thresh(void)
 344 {
 345         return watchdog_thresh * 2;
 346 }
 347
 348 /*
 349  * Returns seconds, approximately.  We don't need nanosecond
 350  * resolution, and we don't need to waste time with a big divide when
 351  * 2^30ns == 1.074s.
 352  */
 353 static unsigned long get_timestamp(void)
 354 {
 355         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 356 }
 357
 358 static void set_sample_period(void)
 359 {
 360         /*
 361          * convert watchdog_thresh from seconds to ns
 362          * the divide by 5 is to give hrtimer several chances (two
 363          * or three with the current relation between the soft
 364          * and hard thresholds) to increment before the
 365          * hardlockup detector generates a warning
 366          */
 367         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 368         watchdog_update_hrtimer_threshold(sample_period);
 369 }
 370
 371 static void update_report_ts(void)
 372 {
 373         __this_cpu_write(watchdog_report_ts, get_timestamp());
 374 }
 375
 376 /* Commands for resetting the watchdog */
 377 static void update_touch_ts(void)
 378 {
 379         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 380         update_report_ts();
 381 }
 382
 383 /**
 384  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 385  *
 386  * Call when the scheduler may have stalled for legitimate reasons
 387  * preventing the watchdog task from executing - e.g. the scheduler
 388  * entering idle state.  This should only be used for scheduler events.
 389  * Use touch_softlockup_watchdog() for everything else.
 390  */
 391 notrace void touch_softlockup_watchdog_sched(void)
 392 {
 393         /*
 394          * Preemption can be enabled.  It doesn't matter which CPU's watchdog
 395          * report period gets restarted here, so use the raw_ operation.
 396          */
 397         raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 398 }
 399
 400 notrace void touch_softlockup_watchdog(void)
 401 {
 402         touch_softlockup_watchdog_sched();
 403         wq_watchdog_touch(raw_smp_processor_id());
 404 }
 405 EXPORT_SYMBOL(touch_softlockup_watchdog);
 406
 407 void touch_all_softlockup_watchdogs(void)
 408 {
 409         int cpu;
 410
 411         /*
 412          * watchdog_mutex cannpt be taken here, as this might be called
 413          * from (soft)interrupt context, so the access to
 414          * watchdog_allowed_cpumask might race with a concurrent update.
 415          *
 416          * The watchdog time stamp can race against a concurrent real
 417          * update as well, the only side effect might be a cycle delay for
 418          * the softlockup check.
 419          */
 420         for_each_cpu(cpu, &watchdog_allowed_mask) {
 421                 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
 422                 wq_watchdog_touch(cpu);
 423         }
 424 }
 425
 426 void touch_softlockup_watchdog_sync(void)
 427 {
 428         __this_cpu_write(softlockup_touch_sync, true);
 429         __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 430 }
 431
 432 static int is_softlockup(unsigned long touch_ts,
 433                          unsigned long period_ts,
 434                          unsigned long now)
 435 {
 436         if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
 437                 /* Warn about unreasonable delays. */
 438                 if (time_after(now, period_ts + get_softlockup_thresh()))
 439                         return now - touch_ts;
 440         }
 441         return 0;
 442 }
 443
 444 /* watchdog detector functions */
 445 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 446 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 447
 448 /*
 449  * The watchdog feed function - touches the timestamp.
 450  *
 451  * It only runs once every sample_period seconds (4 seconds by
 452  * default) to reset the softlockup timestamp. If this gets delayed
 453  * for more than 2*watchdog_thresh seconds then the debug-printout
 454  * triggers in watchdog_timer_fn().
 455  */
 456 static int softlockup_fn(void *data)
 457 {
 458         update_touch_ts();
 459         complete(this_cpu_ptr(&softlockup_completion));
 460
 461         return 0;
 462 }
 463
 464 /* watchdog kicker functions */
 465 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 466 {
 467         unsigned long touch_ts, period_ts, now;
 468         struct pt_regs *regs = get_irq_regs();
 469         int duration;
 470         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 471         unsigned long flags;
 472
 473         if (!watchdog_enabled)
 474                 return HRTIMER_NORESTART;
 475
 476         watchdog_hardlockup_kick();
 477
 478         /* kick the softlockup detector */
 479         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
 480                 reinit_completion(this_cpu_ptr(&softlockup_completion));
 481                 stop_one_cpu_nowait(smp_processor_id(),
 482                                 softlockup_fn, NULL,
 483                                 this_cpu_ptr(&softlockup_stop_work));
 484         }
 485
 486         /* .. and repeat */
 487         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 488
 489         /*
 490          * Read the current timestamp first. It might become invalid anytime
 491          * when a virtual machine is stopped by the host or when the watchog
 492          * is touched from NMI.
 493          */
 494         now = get_timestamp();
 495         /*
 496          * If a virtual machine is stopped by the host it can look to
 497          * the watchdog like a soft lockup. This function touches the watchdog.
 498          */
 499         kvm_check_and_clear_guest_paused();
 500         /*
 501          * The stored timestamp is comparable with @now only when not touched.
 502          * It might get touched anytime from NMI. Make sure that is_softlockup()
 503          * uses the same (valid) value.
 504          */
 505         period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
 506
 507         /* Reset the interval when touched by known problematic code. */
 508         if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
 509                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 510                         /*
 511                          * If the time stamp was touched atomically
 512                          * make sure the scheduler tick is up to date.
 513                          */
 514                         __this_cpu_write(softlockup_touch_sync, false);
 515                         sched_clock_tick();
 516                 }
 517
 518                 update_report_ts();
 519                 return HRTIMER_RESTART;
 520         }
 521
 522         /* Check for a softlockup. */
 523         touch_ts = __this_cpu_read(watchdog_touch_ts);
 524         duration = is_softlockup(touch_ts, period_ts, now);
 525         if (unlikely(duration)) {
 526                 /*
 527                  * Prevent multiple soft-lockup reports if one cpu is already
 528                  * engaged in dumping all cpu back traces.
 529                  */
 530                 if (softlockup_all_cpu_backtrace) {
 531                         if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
 532                                 return HRTIMER_RESTART;
 533                 }
 534
 535                 /* Start period for the next softlockup warning. */
 536                 update_report_ts();
 537
 538                 printk_cpu_sync_get_irqsave(flags);
 539                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 540                         smp_processor_id(), duration,
 541                         current->comm, task_pid_nr(current));
 542                 print_modules();
 543                 print_irqtrace_events(current);
 544                 if (regs)
 545                         show_regs(regs);
 546                 else
 547                         dump_stack();
 548                 printk_cpu_sync_put_irqrestore(flags);
 549
 550                 if (softlockup_all_cpu_backtrace) {
 551                         trigger_allbutcpu_cpu_backtrace(smp_processor_id());
 552                         if (!softlockup_panic)
 553                                 clear_bit_unlock(0, &soft_lockup_nmi_warn);
 554                 }
 555
 556                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 557                 if (softlockup_panic)
 558                         panic("softlockup: hung tasks");
 559         }
 560
 561         return HRTIMER_RESTART;
 562 }
 563
 564 static void watchdog_enable(unsigned int cpu)
 565 {
 566         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 567         struct completion *done = this_cpu_ptr(&softlockup_completion);
 568
 569         WARN_ON_ONCE(cpu != smp_processor_id());
 570
 571         init_completion(done);
 572         complete(done);
 573
 574         /*
 575          * Start the timer first to prevent the hardlockup watchdog triggering
 576          * before the timer has a chance to fire.
 577          */
 578         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 579         hrtimer->function = watchdog_timer_fn;
 580         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 581                       HRTIMER_MODE_REL_PINNED_HARD);
 582
 583         /* Initialize timestamp */
 584         update_touch_ts();
 585         /* Enable the hardlockup detector */
 586         if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
 587                 watchdog_hardlockup_enable(cpu);
 588 }
 589
 590 static void watchdog_disable(unsigned int cpu)
 591 {
 592         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 593
 594         WARN_ON_ONCE(cpu != smp_processor_id());
 595
 596         /*
 597          * Disable the hardlockup detector first. That prevents that a large
 598          * delay between disabling the timer and disabling the hardlockup
 599          * detector causes a false positive.
 600          */
 601         watchdog_hardlockup_disable(cpu);
 602         hrtimer_cancel(hrtimer);
 603         wait_for_completion(this_cpu_ptr(&softlockup_completion));
 604 }
 605
 606 static int softlockup_stop_fn(void *data)
 607 {
 608         watchdog_disable(smp_processor_id());
 609         return 0;
 610 }
 611
 612 static void softlockup_stop_all(void)
 613 {
 614         int cpu;
 615
 616         if (!softlockup_initialized)
 617                 return;
 618
 619         for_each_cpu(cpu, &watchdog_allowed_mask)
 620                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 621
 622         cpumask_clear(&watchdog_allowed_mask);
 623 }
 624
 625 static int softlockup_start_fn(void *data)
 626 {
 627         watchdog_enable(smp_processor_id());
 628         return 0;
 629 }
 630
 631 static void softlockup_start_all(void)
 632 {
 633         int cpu;
 634
 635         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 636         for_each_cpu(cpu, &watchdog_allowed_mask)
 637                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 638 }
 639
 640 int lockup_detector_online_cpu(unsigned int cpu)
 641 {
 642         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 643                 watchdog_enable(cpu);
 644         return 0;
 645 }
 646
 647 int lockup_detector_offline_cpu(unsigned int cpu)
 648 {
 649         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 650                 watchdog_disable(cpu);
 651         return 0;
 652 }
 653
 654 static void __lockup_detector_reconfigure(void)
 655 {
 656         cpus_read_lock();
 657         watchdog_hardlockup_stop();
 658
 659         softlockup_stop_all();
 660         set_sample_period();
 661         lockup_detector_update_enable();
 662         if (watchdog_enabled && watchdog_thresh)
 663                 softlockup_start_all();
 664
 665         watchdog_hardlockup_start();
 666         cpus_read_unlock();
 667         /*
 668          * Must be called outside the cpus locked section to prevent
 669          * recursive locking in the perf code.
 670          */
 671         __lockup_detector_cleanup();
 672 }
 673
 674 void lockup_detector_reconfigure(void)
 675 {
 676         mutex_lock(&watchdog_mutex);
 677         __lockup_detector_reconfigure();
 678         mutex_unlock(&watchdog_mutex);
 679 }
 680
 681 /*
 682  * Create the watchdog infrastructure and configure the detector(s).
 683  */
 684 static __init void lockup_detector_setup(void)
 685 {
 686         /*
 687          * If sysctl is off and watchdog got disabled on the command line,
 688          * nothing to do here.
 689          */
 690         lockup_detector_update_enable();
 691
 692         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 693             !(watchdog_enabled && watchdog_thresh))
 694                 return;
 695
 696         mutex_lock(&watchdog_mutex);
 697         __lockup_detector_reconfigure();
 698         softlockup_initialized = true;
 699         mutex_unlock(&watchdog_mutex);
 700 }
 701
 702 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 703 static void __lockup_detector_reconfigure(void)
 704 {
 705         cpus_read_lock();
 706         watchdog_hardlockup_stop();
 707         lockup_detector_update_enable();
 708         watchdog_hardlockup_start();
 709         cpus_read_unlock();
 710 }
 711 void lockup_detector_reconfigure(void)
 712 {
 713         __lockup_detector_reconfigure();
 714 }
 715 static inline void lockup_detector_setup(void)
 716 {
 717         __lockup_detector_reconfigure();
 718 }
 719 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 720
 721 static void __lockup_detector_cleanup(void)
 722 {
 723         lockdep_assert_held(&watchdog_mutex);
 724         hardlockup_detector_perf_cleanup();
 725 }
 726
 727 /**
 728  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 729  *
 730  * Caller must not hold the cpu hotplug rwsem.
 731  */
 732 void lockup_detector_cleanup(void)
 733 {
 734         mutex_lock(&watchdog_mutex);
 735         __lockup_detector_cleanup();
 736         mutex_unlock(&watchdog_mutex);
 737 }
 738
 739 /**
 740  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 741  *
 742  * Special interface for parisc. It prevents lockup detector warnings from
 743  * the default pm_poweroff() function which busy loops forever.
 744  */
 745 void lockup_detector_soft_poweroff(void)
 746 {
 747         watchdog_enabled = 0;
 748 }
 749
 750 #ifdef CONFIG_SYSCTL
 751
 752 /* Propagate any changes to the watchdog infrastructure */
 753 static void proc_watchdog_update(void)
 754 {
 755         /* Remove impossible cpus to keep sysctl output clean. */
 756         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 757         __lockup_detector_reconfigure();
 758 }
 759
 760 /*
 761  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 762  *
 763  * caller             | table->data points to            | 'which'
 764  * -------------------|----------------------------------|-------------------------------
 765  * proc_watchdog      | watchdog_user_enabled            | WATCHDOG_HARDLOCKUP_ENABLED |
 766  *                    |                                  | WATCHDOG_SOFTOCKUP_ENABLED
 767  * -------------------|----------------------------------|-------------------------------
 768  * proc_nmi_watchdog  | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
 769  * -------------------|----------------------------------|-------------------------------
 770  * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
 771  */
 772 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 773                                 void *buffer, size_t *lenp, loff_t *ppos)
 774 {
 775         int err, old, *param = table->data;
 776
 777         mutex_lock(&watchdog_mutex);
 778
 779         if (!write) {
 780                 /*
 781                  * On read synchronize the userspace interface. This is a
 782                  * racy snapshot.
 783                  */
 784                 *param = (watchdog_enabled & which) != 0;
 785                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 786         } else {
 787                 old = READ_ONCE(*param);
 788                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 789                 if (!err && old != READ_ONCE(*param))
 790                         proc_watchdog_update();
 791         }
 792         mutex_unlock(&watchdog_mutex);
 793         return err;
 794 }
 795
 796 /*
 797  * /proc/sys/kernel/watchdog
 798  */
 799 static int proc_watchdog(struct ctl_table *table, int write,
 800                          void *buffer, size_t *lenp, loff_t *ppos)
 801 {
 802         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
 803                                     WATCHDOG_SOFTOCKUP_ENABLED,
 804                                     table, write, buffer, lenp, ppos);
 805 }
 806
 807 /*
 808  * /proc/sys/kernel/nmi_watchdog
 809  */
 810 static int proc_nmi_watchdog(struct ctl_table *table, int write,
 811                              void *buffer, size_t *lenp, loff_t *ppos)
 812 {
 813         if (!watchdog_hardlockup_available && write)
 814                 return -ENOTSUPP;
 815         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
 816                                     table, write, buffer, lenp, ppos);
 817 }
 818
 819 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 820 /*
 821  * /proc/sys/kernel/soft_watchdog
 822  */
 823 static int proc_soft_watchdog(struct ctl_table *table, int write,
 824                               void *buffer, size_t *lenp, loff_t *ppos)
 825 {
 826         return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
 827                                     table, write, buffer, lenp, ppos);
 828 }
 829 #endif
 830
 831 /*
 832  * /proc/sys/kernel/watchdog_thresh
 833  */
 834 static int proc_watchdog_thresh(struct ctl_table *table, int write,
 835                                 void *buffer, size_t *lenp, loff_t *ppos)
 836 {
 837         int err, old;
 838
 839         mutex_lock(&watchdog_mutex);
 840
 841         old = READ_ONCE(watchdog_thresh);
 842         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 843
 844         if (!err && write && old != READ_ONCE(watchdog_thresh))
 845                 proc_watchdog_update();
 846
 847         mutex_unlock(&watchdog_mutex);
 848         return err;
 849 }
 850
 851 /*
 852  * The cpumask is the mask of possible cpus that the watchdog can run
 853  * on, not the mask of cpus it is actually running on.  This allows the
 854  * user to specify a mask that will include cpus that have not yet
 855  * been brought online, if desired.
 856  */
 857 static int proc_watchdog_cpumask(struct ctl_table *table, int write,
 858                                  void *buffer, size_t *lenp, loff_t *ppos)
 859 {
 860         int err;
 861
 862         mutex_lock(&watchdog_mutex);
 863
 864         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 865         if (!err && write)
 866                 proc_watchdog_update();
 867
 868         mutex_unlock(&watchdog_mutex);
 869         return err;
 870 }
 871
 872 static const int sixty = 60;
 873
 874 static struct ctl_table watchdog_sysctls[] = {
 875         {
 876                 .procname       = "watchdog",
 877                 .data           = &watchdog_user_enabled,
 878                 .maxlen         = sizeof(int),
 879                 .mode           = 0644,
 880                 .proc_handler   = proc_watchdog,
 881                 .extra1         = SYSCTL_ZERO,
 882                 .extra2         = SYSCTL_ONE,
 883         },
 884         {
 885                 .procname       = "watchdog_thresh",
 886                 .data           = &watchdog_thresh,
 887                 .maxlen         = sizeof(int),
 888                 .mode           = 0644,
 889                 .proc_handler   = proc_watchdog_thresh,
 890                 .extra1         = SYSCTL_ZERO,
 891                 .extra2         = (void *)&sixty,
 892         },
 893         {
 894                 .procname       = "watchdog_cpumask",
 895                 .data           = &watchdog_cpumask_bits,
 896                 .maxlen         = NR_CPUS,
 897                 .mode           = 0644,
 898                 .proc_handler   = proc_watchdog_cpumask,
 899         },
 900 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 901         {
 902                 .procname       = "soft_watchdog",
 903                 .data           = &watchdog_softlockup_user_enabled,
 904                 .maxlen         = sizeof(int),
 905                 .mode           = 0644,
 906                 .proc_handler   = proc_soft_watchdog,
 907                 .extra1         = SYSCTL_ZERO,
 908                 .extra2         = SYSCTL_ONE,
 909         },
 910         {
 911                 .procname       = "softlockup_panic",
 912                 .data           = &softlockup_panic,
 913                 .maxlen         = sizeof(int),
 914                 .mode           = 0644,
 915                 .proc_handler   = proc_dointvec_minmax,
 916                 .extra1         = SYSCTL_ZERO,
 917                 .extra2         = SYSCTL_ONE,
 918         },
 919 #ifdef CONFIG_SMP
 920         {
 921                 .procname       = "softlockup_all_cpu_backtrace",
 922                 .data           = &sysctl_softlockup_all_cpu_backtrace,
 923                 .maxlen         = sizeof(int),
 924                 .mode           = 0644,
 925                 .proc_handler   = proc_dointvec_minmax,
 926                 .extra1         = SYSCTL_ZERO,
 927                 .extra2         = SYSCTL_ONE,
 928         },
 929 #endif /* CONFIG_SMP */
 930 #endif
 931 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 932         {
 933                 .procname       = "hardlockup_panic",
 934                 .data           = &hardlockup_panic,
 935                 .maxlen         = sizeof(int),
 936                 .mode           = 0644,
 937                 .proc_handler   = proc_dointvec_minmax,
 938                 .extra1         = SYSCTL_ZERO,
 939                 .extra2         = SYSCTL_ONE,
 940         },
 941 #ifdef CONFIG_SMP
 942         {
 943                 .procname       = "hardlockup_all_cpu_backtrace",
 944                 .data           = &sysctl_hardlockup_all_cpu_backtrace,
 945                 .maxlen         = sizeof(int),
 946                 .mode           = 0644,
 947                 .proc_handler   = proc_dointvec_minmax,
 948                 .extra1         = SYSCTL_ZERO,
 949                 .extra2         = SYSCTL_ONE,
 950         },
 951 #endif /* CONFIG_SMP */
 952 #endif
 953         {}
 954 };
 955
 956 static struct ctl_table watchdog_hardlockup_sysctl[] = {
 957         {
 958                 .procname       = "nmi_watchdog",
 959                 .data           = &watchdog_hardlockup_user_enabled,
 960                 .maxlen         = sizeof(int),
 961                 .mode           = 0444,
 962                 .proc_handler   = proc_nmi_watchdog,
 963                 .extra1         = SYSCTL_ZERO,
 964                 .extra2         = SYSCTL_ONE,
 965         },
 966         {}
 967 };
 968
 969 static void __init watchdog_sysctl_init(void)
 970 {
 971         register_sysctl_init("kernel", watchdog_sysctls);
 972
 973         if (watchdog_hardlockup_available)
 974                 watchdog_hardlockup_sysctl[0].mode = 0644;
 975         register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
 976 }
 977
 978 #else
 979 #define watchdog_sysctl_init() do { } while (0)
 980 #endif /* CONFIG_SYSCTL */
 981
 982 static void __init lockup_detector_delay_init(struct work_struct *work);
 983 static bool allow_lockup_detector_init_retry __initdata;
 984
 985 static struct work_struct detector_work __initdata =
 986                 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
 987
 988 static void __init lockup_detector_delay_init(struct work_struct *work)
 989 {
 990         int ret;
 991
 992         ret = watchdog_hardlockup_probe();
 993         if (ret) {
 994                 pr_info("Delayed init of the lockup detector failed: %d\n", ret);
 995                 pr_info("Hard watchdog permanently disabled\n");
 996                 return;
 997         }
 998
 999         allow_lockup_detector_init_retry = false;
1000
1001         watchdog_hardlockup_available = true;
1002         lockup_detector_setup();
1003 }
1004
1005 /*
1006  * lockup_detector_retry_init - retry init lockup detector if possible.
1007  *
1008  * Retry hardlockup detector init. It is useful when it requires some
1009  * functionality that has to be initialized later on a particular
1010  * platform.
1011  */
1012 void __init lockup_detector_retry_init(void)
1013 {
1014         /* Must be called before late init calls */
1015         if (!allow_lockup_detector_init_retry)
1016                 return;
1017
1018         schedule_work(&detector_work);
1019 }
1020
1021 /*
1022  * Ensure that optional delayed hardlockup init is proceed before
1023  * the init code and memory is freed.
1024  */
1025 static int __init lockup_detector_check(void)
1026 {
1027         /* Prevent any later retry. */
1028         allow_lockup_detector_init_retry = false;
1029
1030         /* Make sure no work is pending. */
1031         flush_work(&detector_work);
1032
1033         watchdog_sysctl_init();
1034
1035         return 0;
1036
1037 }
1038 late_initcall_sync(lockup_detector_check);
1039
1040 void __init lockup_detector_init(void)
1041 {
1042         if (tick_nohz_full_enabled())
1043                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1044
1045         cpumask_copy(&watchdog_cpumask,
1046                      housekeeping_cpumask(HK_TYPE_TIMER));
1047
1048         if (!watchdog_hardlockup_probe())
1049                 watchdog_hardlockup_available = true;
1050         else
1051                 allow_lockup_detector_init_retry = true;
1052
1053         lockup_detector_setup();
1054 }