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