kernel/watchdog.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Detect hard and soft lockups on a system
   4  *
   5  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   6  *
   7  * Note: Most of this code is borrowed heavily from the original softlockup
   8  * detector, so thanks to Ingo for the initial implementation.
   9  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
  10  * to those contributors as well.
  11  */
  12
  13 #define pr_fmt(fmt) "watchdog: " fmt
  14
  15 #include <linux/mm.h>
  16 #include <linux/cpu.h>
  17 #include <linux/nmi.h>
  18 #include <linux/init.h>
  19 #include <linux/module.h>
  20 #include <linux/sysctl.h>
  21 #include <linux/smpboot.h>
  22 #include <linux/sched/rt.h>
  23 #include <uapi/linux/sched/types.h>
  24 #include <linux/tick.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/sched/clock.h>
  27 #include <linux/sched/debug.h>
  28
  29 #include <asm/irq_regs.h>
  30 #include <linux/kvm_para.h>
  31 #include <linux/kthread.h>
  32
  33 static DEFINE_MUTEX(watchdog_mutex);
  34
  35 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
  36 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
  37 # define NMI_WATCHDOG_DEFAULT   1
  38 #else
  39 # define WATCHDOG_DEFAULT       (SOFT_WATCHDOG_ENABLED)
  40 # define NMI_WATCHDOG_DEFAULT   0
  41 #endif
  42
  43 unsigned long __read_mostly watchdog_enabled;
  44 int __read_mostly watchdog_user_enabled = 1;
  45 int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
  46 int __read_mostly soft_watchdog_user_enabled = 1;
  47 int __read_mostly watchdog_thresh = 10;
  48 int __read_mostly nmi_watchdog_available;
  49
  50 struct cpumask watchdog_allowed_mask __read_mostly;
  51
  52 struct cpumask watchdog_cpumask __read_mostly;
  53 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  54
  55 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  56 /*
  57  * Should we panic when a soft-lockup or hard-lockup occurs:
  58  */
  59 unsigned int __read_mostly hardlockup_panic =
  60                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  61 /*
  62  * We may not want to enable hard lockup detection by default in all cases,
  63  * for example when running the kernel as a guest on a hypervisor. In these
  64  * cases this function can be called to disable hard lockup detection. This
  65  * function should only be executed once by the boot processor before the
  66  * kernel command line parameters are parsed, because otherwise it is not
  67  * possible to override this in hardlockup_panic_setup().
  68  */
  69 void __init hardlockup_detector_disable(void)
  70 {
  71         nmi_watchdog_user_enabled = 0;
  72 }
  73
  74 static int __init hardlockup_panic_setup(char *str)
  75 {
  76         if (!strncmp(str, "panic", 5))
  77                 hardlockup_panic = 1;
  78         else if (!strncmp(str, "nopanic", 7))
  79                 hardlockup_panic = 0;
  80         else if (!strncmp(str, "0", 1))
  81                 nmi_watchdog_user_enabled = 0;
  82         else if (!strncmp(str, "1", 1))
  83                 nmi_watchdog_user_enabled = 1;
  84         return 1;
  85 }
  86 __setup("nmi_watchdog=", hardlockup_panic_setup);
  87
  88 # ifdef CONFIG_SMP
  89 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  90
  91 static int __init hardlockup_all_cpu_backtrace_setup(char *str)
  92 {
  93         sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
  94         return 1;
  95 }
  96 __setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
  97 # endif /* CONFIG_SMP */
  98 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
  99
 100 /*
 101  * These functions can be overridden if an architecture implements its
 102  * own hardlockup detector.
 103  *
 104  * watchdog_nmi_enable/disable can be implemented to start and stop when
 105  * softlockup watchdog threads start and stop. The arch must select the
 106  * SOFTLOCKUP_DETECTOR Kconfig.
 107  */
 108 int __weak watchdog_nmi_enable(unsigned int cpu)
 109 {
 110         hardlockup_detector_perf_enable();
 111         return 0;
 112 }
 113
 114 void __weak watchdog_nmi_disable(unsigned int cpu)
 115 {
 116         hardlockup_detector_perf_disable();
 117 }
 118
 119 /* Return 0, if a NMI watchdog is available. Error code otherwise */
 120 int __weak __init watchdog_nmi_probe(void)
 121 {
 122         return hardlockup_detector_perf_init();
 123 }
 124
 125 /**
 126  * watchdog_nmi_stop - Stop the watchdog for reconfiguration
 127  *
 128  * The reconfiguration steps are:
 129  * watchdog_nmi_stop();
 130  * update_variables();
 131  * watchdog_nmi_start();
 132  */
 133 void __weak watchdog_nmi_stop(void) { }
 134
 135 /**
 136  * watchdog_nmi_start - Start the watchdog after reconfiguration
 137  *
 138  * Counterpart to watchdog_nmi_stop().
 139  *
 140  * The following variables have been updated in update_variables() and
 141  * contain the currently valid configuration:
 142  * - watchdog_enabled
 143  * - watchdog_thresh
 144  * - watchdog_cpumask
 145  */
 146 void __weak watchdog_nmi_start(void) { }
 147
 148 /**
 149  * lockup_detector_update_enable - Update the sysctl enable bit
 150  *
 151  * Caller needs to make sure that the NMI/perf watchdogs are off, so this
 152  * can't race with watchdog_nmi_disable().
 153  */
 154 static void lockup_detector_update_enable(void)
 155 {
 156         watchdog_enabled = 0;
 157         if (!watchdog_user_enabled)
 158                 return;
 159         if (nmi_watchdog_available && nmi_watchdog_user_enabled)
 160                 watchdog_enabled |= NMI_WATCHDOG_ENABLED;
 161         if (soft_watchdog_user_enabled)
 162                 watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
 163 }
 164
 165 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 166
 167 /* Global variables, exported for sysctl */
 168 unsigned int __read_mostly softlockup_panic =
 169                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 170
 171 static bool softlockup_threads_initialized __read_mostly;
 172 static u64 __read_mostly sample_period;
 173
 174 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 175 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 176 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 177 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 178 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 179 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 180 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 181 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
 182 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 183 static unsigned long soft_lockup_nmi_warn;
 184
 185 static int __init softlockup_panic_setup(char *str)
 186 {
 187         softlockup_panic = simple_strtoul(str, NULL, 0);
 188         return 1;
 189 }
 190 __setup("softlockup_panic=", softlockup_panic_setup);
 191
 192 static int __init nowatchdog_setup(char *str)
 193 {
 194         watchdog_user_enabled = 0;
 195         return 1;
 196 }
 197 __setup("nowatchdog", nowatchdog_setup);
 198
 199 static int __init nosoftlockup_setup(char *str)
 200 {
 201         soft_watchdog_user_enabled = 0;
 202         return 1;
 203 }
 204 __setup("nosoftlockup", nosoftlockup_setup);
 205
 206 #ifdef CONFIG_SMP
 207 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 208
 209 static int __init softlockup_all_cpu_backtrace_setup(char *str)
 210 {
 211         sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
 212         return 1;
 213 }
 214 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
 215 #endif
 216
 217 static void __lockup_detector_cleanup(void);
 218
 219 /*
 220  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 221  * lockups can have false positives under extreme conditions. So we generally
 222  * want a higher threshold for soft lockups than for hard lockups. So we couple
 223  * the thresholds with a factor: we make the soft threshold twice the amount of
 224  * time the hard threshold is.
 225  */
 226 static int get_softlockup_thresh(void)
 227 {
 228         return watchdog_thresh * 2;
 229 }
 230
 231 /*
 232  * Returns seconds, approximately.  We don't need nanosecond
 233  * resolution, and we don't need to waste time with a big divide when
 234  * 2^30ns == 1.074s.
 235  */
 236 static unsigned long get_timestamp(void)
 237 {
 238         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 239 }
 240
 241 static void set_sample_period(void)
 242 {
 243         /*
 244          * convert watchdog_thresh from seconds to ns
 245          * the divide by 5 is to give hrtimer several chances (two
 246          * or three with the current relation between the soft
 247          * and hard thresholds) to increment before the
 248          * hardlockup detector generates a warning
 249          */
 250         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 251         watchdog_update_hrtimer_threshold(sample_period);
 252 }
 253
 254 /* Commands for resetting the watchdog */
 255 static void __touch_watchdog(void)
 256 {
 257         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 258 }
 259
 260 /**
 261  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 262  *
 263  * Call when the scheduler may have stalled for legitimate reasons
 264  * preventing the watchdog task from executing - e.g. the scheduler
 265  * entering idle state.  This should only be used for scheduler events.
 266  * Use touch_softlockup_watchdog() for everything else.
 267  */
 268 void touch_softlockup_watchdog_sched(void)
 269 {
 270         /*
 271          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 272          * gets zeroed here, so use the raw_ operation.
 273          */
 274         raw_cpu_write(watchdog_touch_ts, 0);
 275 }
 276
 277 void touch_softlockup_watchdog(void)
 278 {
 279         touch_softlockup_watchdog_sched();
 280         wq_watchdog_touch(raw_smp_processor_id());
 281 }
 282 EXPORT_SYMBOL(touch_softlockup_watchdog);
 283
 284 void touch_all_softlockup_watchdogs(void)
 285 {
 286         int cpu;
 287
 288         /*
 289          * watchdog_mutex cannpt be taken here, as this might be called
 290          * from (soft)interrupt context, so the access to
 291          * watchdog_allowed_cpumask might race with a concurrent update.
 292          *
 293          * The watchdog time stamp can race against a concurrent real
 294          * update as well, the only side effect might be a cycle delay for
 295          * the softlockup check.
 296          */
 297         for_each_cpu(cpu, &watchdog_allowed_mask)
 298                 per_cpu(watchdog_touch_ts, cpu) = 0;
 299         wq_watchdog_touch(-1);
 300 }
 301
 302 void touch_softlockup_watchdog_sync(void)
 303 {
 304         __this_cpu_write(softlockup_touch_sync, true);
 305         __this_cpu_write(watchdog_touch_ts, 0);
 306 }
 307
 308 static int is_softlockup(unsigned long touch_ts)
 309 {
 310         unsigned long now = get_timestamp();
 311
 312         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
 313                 /* Warn about unreasonable delays. */
 314                 if (time_after(now, touch_ts + get_softlockup_thresh()))
 315                         return now - touch_ts;
 316         }
 317         return 0;
 318 }
 319
 320 /* watchdog detector functions */
 321 bool is_hardlockup(void)
 322 {
 323         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 324
 325         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 326                 return true;
 327
 328         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 329         return false;
 330 }
 331
 332 static void watchdog_interrupt_count(void)
 333 {
 334         __this_cpu_inc(hrtimer_interrupts);
 335 }
 336
 337 /* watchdog kicker functions */
 338 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 339 {
 340         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 341         struct pt_regs *regs = get_irq_regs();
 342         int duration;
 343         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 344
 345         if (!watchdog_enabled)
 346                 return HRTIMER_NORESTART;
 347
 348         /* kick the hardlockup detector */
 349         watchdog_interrupt_count();
 350
 351         /* kick the softlockup detector */
 352         wake_up_process(__this_cpu_read(softlockup_watchdog));
 353
 354         /* .. and repeat */
 355         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 356
 357         if (touch_ts == 0) {
 358                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 359                         /*
 360                          * If the time stamp was touched atomically
 361                          * make sure the scheduler tick is up to date.
 362                          */
 363                         __this_cpu_write(softlockup_touch_sync, false);
 364                         sched_clock_tick();
 365                 }
 366
 367                 /* Clear the guest paused flag on watchdog reset */
 368                 kvm_check_and_clear_guest_paused();
 369                 __touch_watchdog();
 370                 return HRTIMER_RESTART;
 371         }
 372
 373         /* check for a softlockup
 374          * This is done by making sure a high priority task is
 375          * being scheduled.  The task touches the watchdog to
 376          * indicate it is getting cpu time.  If it hasn't then
 377          * this is a good indication some task is hogging the cpu
 378          */
 379         duration = is_softlockup(touch_ts);
 380         if (unlikely(duration)) {
 381                 /*
 382                  * If a virtual machine is stopped by the host it can look to
 383                  * the watchdog like a soft lockup, check to see if the host
 384                  * stopped the vm before we issue the warning
 385                  */
 386                 if (kvm_check_and_clear_guest_paused())
 387                         return HRTIMER_RESTART;
 388
 389                 /* only warn once */
 390                 if (__this_cpu_read(soft_watchdog_warn) == true) {
 391                         /*
 392                          * When multiple processes are causing softlockups the
 393                          * softlockup detector only warns on the first one
 394                          * because the code relies on a full quiet cycle to
 395                          * re-arm.  The second process prevents the quiet cycle
 396                          * and never gets reported.  Use task pointers to detect
 397                          * this.
 398                          */
 399                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
 400                             current) {
 401                                 __this_cpu_write(soft_watchdog_warn, false);
 402                                 __touch_watchdog();
 403                         }
 404                         return HRTIMER_RESTART;
 405                 }
 406
 407                 if (softlockup_all_cpu_backtrace) {
 408                         /* Prevent multiple soft-lockup reports if one cpu is already
 409                          * engaged in dumping cpu back traces
 410                          */
 411                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
 412                                 /* Someone else will report us. Let's give up */
 413                                 __this_cpu_write(soft_watchdog_warn, true);
 414                                 return HRTIMER_RESTART;
 415                         }
 416                 }
 417
 418                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 419                         smp_processor_id(), duration,
 420                         current->comm, task_pid_nr(current));
 421                 __this_cpu_write(softlockup_task_ptr_saved, current);
 422                 print_modules();
 423                 print_irqtrace_events(current);
 424                 if (regs)
 425                         show_regs(regs);
 426                 else
 427                         dump_stack();
 428
 429                 if (softlockup_all_cpu_backtrace) {
 430                         /* Avoid generating two back traces for current
 431                          * given that one is already made above
 432                          */
 433                         trigger_allbutself_cpu_backtrace();
 434
 435                         clear_bit(0, &soft_lockup_nmi_warn);
 436                         /* Barrier to sync with other cpus */
 437                         smp_mb__after_atomic();
 438                 }
 439
 440                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 441                 if (softlockup_panic)
 442                         panic("softlockup: hung tasks");
 443                 __this_cpu_write(soft_watchdog_warn, true);
 444         } else
 445                 __this_cpu_write(soft_watchdog_warn, false);
 446
 447         return HRTIMER_RESTART;
 448 }
 449
 450 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 451 {
 452         struct sched_param param = { .sched_priority = prio };
 453
 454         sched_setscheduler(current, policy, &param);
 455 }
 456
 457 static void watchdog_enable(unsigned int cpu)
 458 {
 459         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 460
 461         /*
 462          * Start the timer first to prevent the NMI watchdog triggering
 463          * before the timer has a chance to fire.
 464          */
 465         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 466         hrtimer->function = watchdog_timer_fn;
 467         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 468                       HRTIMER_MODE_REL_PINNED);
 469
 470         /* Initialize timestamp */
 471         __touch_watchdog();
 472         /* Enable the perf event */
 473         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
 474                 watchdog_nmi_enable(cpu);
 475
 476         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
 477 }
 478
 479 static void watchdog_disable(unsigned int cpu)
 480 {
 481         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 482
 483         watchdog_set_prio(SCHED_NORMAL, 0);
 484         /*
 485          * Disable the perf event first. That prevents that a large delay
 486          * between disabling the timer and disabling the perf event causes
 487          * the perf NMI to detect a false positive.
 488          */
 489         watchdog_nmi_disable(cpu);
 490         hrtimer_cancel(hrtimer);
 491 }
 492
 493 static void watchdog_cleanup(unsigned int cpu, bool online)
 494 {
 495         watchdog_disable(cpu);
 496 }
 497
 498 static int watchdog_should_run(unsigned int cpu)
 499 {
 500         return __this_cpu_read(hrtimer_interrupts) !=
 501                 __this_cpu_read(soft_lockup_hrtimer_cnt);
 502 }
 503
 504 /*
 505  * The watchdog thread function - touches the timestamp.
 506  *
 507  * It only runs once every sample_period seconds (4 seconds by
 508  * default) to reset the softlockup timestamp. If this gets delayed
 509  * for more than 2*watchdog_thresh seconds then the debug-printout
 510  * triggers in watchdog_timer_fn().
 511  */
 512 static void watchdog(unsigned int cpu)
 513 {
 514         __this_cpu_write(soft_lockup_hrtimer_cnt,
 515                          __this_cpu_read(hrtimer_interrupts));
 516         __touch_watchdog();
 517 }
 518
 519 static struct smp_hotplug_thread watchdog_threads = {
 520         .store                  = &softlockup_watchdog,
 521         .thread_should_run      = watchdog_should_run,
 522         .thread_fn              = watchdog,
 523         .thread_comm            = "watchdog/%u",
 524         .setup                  = watchdog_enable,
 525         .cleanup                = watchdog_cleanup,
 526         .park                   = watchdog_disable,
 527         .unpark                 = watchdog_enable,
 528 };
 529
 530 static void softlockup_update_smpboot_threads(void)
 531 {
 532         lockdep_assert_held(&watchdog_mutex);
 533
 534         if (!softlockup_threads_initialized)
 535                 return;
 536
 537         smpboot_update_cpumask_percpu_thread(&watchdog_threads,
 538                                              &watchdog_allowed_mask);
 539 }
 540
 541 /* Temporarily park all watchdog threads */
 542 static void softlockup_park_all_threads(void)
 543 {
 544         cpumask_clear(&watchdog_allowed_mask);
 545         softlockup_update_smpboot_threads();
 546 }
 547
 548 /* Unpark enabled threads */
 549 static void softlockup_unpark_threads(void)
 550 {
 551         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 552         softlockup_update_smpboot_threads();
 553 }
 554
 555 static void lockup_detector_reconfigure(void)
 556 {
 557         cpus_read_lock();
 558         watchdog_nmi_stop();
 559         softlockup_park_all_threads();
 560         set_sample_period();
 561         lockup_detector_update_enable();
 562         if (watchdog_enabled && watchdog_thresh)
 563                 softlockup_unpark_threads();
 564         watchdog_nmi_start();
 565         cpus_read_unlock();
 566         /*
 567          * Must be called outside the cpus locked section to prevent
 568          * recursive locking in the perf code.
 569          */
 570         __lockup_detector_cleanup();
 571 }
 572
 573 /*
 574  * Create the watchdog thread infrastructure and configure the detector(s).
 575  *
 576  * The threads are not unparked as watchdog_allowed_mask is empty.  When
 577  * the threads are sucessfully initialized, take the proper locks and
 578  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
 579  */
 580 static __init void lockup_detector_setup(void)
 581 {
 582         int ret;
 583
 584         /*
 585          * If sysctl is off and watchdog got disabled on the command line,
 586          * nothing to do here.
 587          */
 588         lockup_detector_update_enable();
 589
 590         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 591             !(watchdog_enabled && watchdog_thresh))
 592                 return;
 593
 594         ret = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
 595                                                      &watchdog_allowed_mask);
 596         if (ret) {
 597                 pr_err("Failed to initialize soft lockup detector threads\n");
 598                 return;
 599         }
 600
 601         mutex_lock(&watchdog_mutex);
 602         softlockup_threads_initialized = true;
 603         lockup_detector_reconfigure();
 604         mutex_unlock(&watchdog_mutex);
 605 }
 606
 607 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 608 static inline int watchdog_park_threads(void) { return 0; }
 609 static inline void watchdog_unpark_threads(void) { }
 610 static inline int watchdog_enable_all_cpus(void) { return 0; }
 611 static inline void watchdog_disable_all_cpus(void) { }
 612 static void lockup_detector_reconfigure(void)
 613 {
 614         cpus_read_lock();
 615         watchdog_nmi_stop();
 616         lockup_detector_update_enable();
 617         watchdog_nmi_start();
 618         cpus_read_unlock();
 619 }
 620 static inline void lockup_detector_setup(void)
 621 {
 622         lockup_detector_reconfigure();
 623 }
 624 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 625
 626 static void __lockup_detector_cleanup(void)
 627 {
 628         lockdep_assert_held(&watchdog_mutex);
 629         hardlockup_detector_perf_cleanup();
 630 }
 631
 632 /**
 633  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 634  *
 635  * Caller must not hold the cpu hotplug rwsem.
 636  */
 637 void lockup_detector_cleanup(void)
 638 {
 639         mutex_lock(&watchdog_mutex);
 640         __lockup_detector_cleanup();
 641         mutex_unlock(&watchdog_mutex);
 642 }
 643
 644 /**
 645  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 646  *
 647  * Special interface for parisc. It prevents lockup detector warnings from
 648  * the default pm_poweroff() function which busy loops forever.
 649  */
 650 void lockup_detector_soft_poweroff(void)
 651 {
 652         watchdog_enabled = 0;
 653 }
 654
 655 #ifdef CONFIG_SYSCTL
 656
 657 /* Propagate any changes to the watchdog threads */
 658 static void proc_watchdog_update(void)
 659 {
 660         /* Remove impossible cpus to keep sysctl output clean. */
 661         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 662         lockup_detector_reconfigure();
 663 }
 664
 665 /*
 666  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 667  *
 668  * caller             | table->data points to      | 'which'
 669  * -------------------|----------------------------|--------------------------
 670  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
 671  *                    |                            | SOFT_WATCHDOG_ENABLED
 672  * -------------------|----------------------------|--------------------------
 673  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
 674  * -------------------|----------------------------|--------------------------
 675  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
 676  */
 677 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 678                                 void __user *buffer, size_t *lenp, loff_t *ppos)
 679 {
 680         int err, old, *param = table->data;
 681
 682         mutex_lock(&watchdog_mutex);
 683
 684         if (!write) {
 685                 /*
 686                  * On read synchronize the userspace interface. This is a
 687                  * racy snapshot.
 688                  */
 689                 *param = (watchdog_enabled & which) != 0;
 690                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 691         } else {
 692                 old = READ_ONCE(*param);
 693                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 694                 if (!err && old != READ_ONCE(*param))
 695                         proc_watchdog_update();
 696         }
 697         mutex_unlock(&watchdog_mutex);
 698         return err;
 699 }
 700
 701 /*
 702  * /proc/sys/kernel/watchdog
 703  */
 704 int proc_watchdog(struct ctl_table *table, int write,
 705                   void __user *buffer, size_t *lenp, loff_t *ppos)
 706 {
 707         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
 708                                     table, write, buffer, lenp, ppos);
 709 }
 710
 711 /*
 712  * /proc/sys/kernel/nmi_watchdog
 713  */
 714 int proc_nmi_watchdog(struct ctl_table *table, int write,
 715                       void __user *buffer, size_t *lenp, loff_t *ppos)
 716 {
 717         if (!nmi_watchdog_available && write)
 718                 return -ENOTSUPP;
 719         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
 720                                     table, write, buffer, lenp, ppos);
 721 }
 722
 723 /*
 724  * /proc/sys/kernel/soft_watchdog
 725  */
 726 int proc_soft_watchdog(struct ctl_table *table, int write,
 727                         void __user *buffer, size_t *lenp, loff_t *ppos)
 728 {
 729         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
 730                                     table, write, buffer, lenp, ppos);
 731 }
 732
 733 /*
 734  * /proc/sys/kernel/watchdog_thresh
 735  */
 736 int proc_watchdog_thresh(struct ctl_table *table, int write,
 737                          void __user *buffer, size_t *lenp, loff_t *ppos)
 738 {
 739         int err, old;
 740
 741         mutex_lock(&watchdog_mutex);
 742
 743         old = READ_ONCE(watchdog_thresh);
 744         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 745
 746         if (!err && write && old != READ_ONCE(watchdog_thresh))
 747                 proc_watchdog_update();
 748
 749         mutex_unlock(&watchdog_mutex);
 750         return err;
 751 }
 752
 753 /*
 754  * The cpumask is the mask of possible cpus that the watchdog can run
 755  * on, not the mask of cpus it is actually running on.  This allows the
 756  * user to specify a mask that will include cpus that have not yet
 757  * been brought online, if desired.
 758  */
 759 int proc_watchdog_cpumask(struct ctl_table *table, int write,
 760                           void __user *buffer, size_t *lenp, loff_t *ppos)
 761 {
 762         int err;
 763
 764         mutex_lock(&watchdog_mutex);
 765
 766         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 767         if (!err && write)
 768                 proc_watchdog_update();
 769
 770         mutex_unlock(&watchdog_mutex);
 771         return err;
 772 }
 773 #endif /* CONFIG_SYSCTL */
 774
 775 void __init lockup_detector_init(void)
 776 {
 777 #ifdef CONFIG_NO_HZ_FULL
 778         if (tick_nohz_full_enabled()) {
 779                 pr_info("Disabling watchdog on nohz_full cores by default\n");
 780                 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
 781         } else
 782                 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
 783 #else
 784         cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
 785 #endif
 786
 787         if (!watchdog_nmi_probe())
 788                 nmi_watchdog_available = true;
 789         lockup_detector_setup();
 790 }