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 #define SOFTLOCKUP_RESET        ULONG_MAX
 168
 169 /* Global variables, exported for sysctl */
 170 unsigned int __read_mostly softlockup_panic =
 171                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 172
 173 static bool softlockup_threads_initialized __read_mostly;
 174 static u64 __read_mostly sample_period;
 175
 176 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 177 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 178 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 179 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 180 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 181 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 182 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 183 static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
 184 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 185 static unsigned long soft_lockup_nmi_warn;
 186
 187 static int __init softlockup_panic_setup(char *str)
 188 {
 189         softlockup_panic = simple_strtoul(str, NULL, 0);
 190         return 1;
 191 }
 192 __setup("softlockup_panic=", softlockup_panic_setup);
 193
 194 static int __init nowatchdog_setup(char *str)
 195 {
 196         watchdog_user_enabled = 0;
 197         return 1;
 198 }
 199 __setup("nowatchdog", nowatchdog_setup);
 200
 201 static int __init nosoftlockup_setup(char *str)
 202 {
 203         soft_watchdog_user_enabled = 0;
 204         return 1;
 205 }
 206 __setup("nosoftlockup", nosoftlockup_setup);
 207
 208 #ifdef CONFIG_SMP
 209 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 210
 211 static int __init softlockup_all_cpu_backtrace_setup(char *str)
 212 {
 213         sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
 214         return 1;
 215 }
 216 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
 217 #endif
 218
 219 static void __lockup_detector_cleanup(void);
 220
 221 /*
 222  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 223  * lockups can have false positives under extreme conditions. So we generally
 224  * want a higher threshold for soft lockups than for hard lockups. So we couple
 225  * the thresholds with a factor: we make the soft threshold twice the amount of
 226  * time the hard threshold is.
 227  */
 228 static int get_softlockup_thresh(void)
 229 {
 230         return watchdog_thresh * 2;
 231 }
 232
 233 /*
 234  * Returns seconds, approximately.  We don't need nanosecond
 235  * resolution, and we don't need to waste time with a big divide when
 236  * 2^30ns == 1.074s.
 237  */
 238 static unsigned long get_timestamp(void)
 239 {
 240         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 241 }
 242
 243 static void set_sample_period(void)
 244 {
 245         /*
 246          * convert watchdog_thresh from seconds to ns
 247          * the divide by 5 is to give hrtimer several chances (two
 248          * or three with the current relation between the soft
 249          * and hard thresholds) to increment before the
 250          * hardlockup detector generates a warning
 251          */
 252         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 253         watchdog_update_hrtimer_threshold(sample_period);
 254 }
 255
 256 /* Commands for resetting the watchdog */
 257 static void __touch_watchdog(void)
 258 {
 259         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 260 }
 261
 262 /**
 263  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 264  *
 265  * Call when the scheduler may have stalled for legitimate reasons
 266  * preventing the watchdog task from executing - e.g. the scheduler
 267  * entering idle state.  This should only be used for scheduler events.
 268  * Use touch_softlockup_watchdog() for everything else.
 269  */
 270 notrace void touch_softlockup_watchdog_sched(void)
 271 {
 272         /*
 273          * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 274          * gets zeroed here, so use the raw_ operation.
 275          */
 276         raw_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
 277 }
 278
 279 notrace void touch_softlockup_watchdog(void)
 280 {
 281         touch_softlockup_watchdog_sched();
 282         wq_watchdog_touch(raw_smp_processor_id());
 283 }
 284 EXPORT_SYMBOL(touch_softlockup_watchdog);
 285
 286 void touch_all_softlockup_watchdogs(void)
 287 {
 288         int cpu;
 289
 290         /*
 291          * watchdog_mutex cannpt be taken here, as this might be called
 292          * from (soft)interrupt context, so the access to
 293          * watchdog_allowed_cpumask might race with a concurrent update.
 294          *
 295          * The watchdog time stamp can race against a concurrent real
 296          * update as well, the only side effect might be a cycle delay for
 297          * the softlockup check.
 298          */
 299         for_each_cpu(cpu, &watchdog_allowed_mask)
 300                 per_cpu(watchdog_touch_ts, cpu) = SOFTLOCKUP_RESET;
 301         wq_watchdog_touch(-1);
 302 }
 303
 304 void touch_softlockup_watchdog_sync(void)
 305 {
 306         __this_cpu_write(softlockup_touch_sync, true);
 307         __this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
 308 }
 309
 310 static int is_softlockup(unsigned long touch_ts)
 311 {
 312         unsigned long now = get_timestamp();
 313
 314         if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
 315                 /* Warn about unreasonable delays. */
 316                 if (time_after(now, touch_ts + get_softlockup_thresh()))
 317                         return now - touch_ts;
 318         }
 319         return 0;
 320 }
 321
 322 /* watchdog detector functions */
 323 bool is_hardlockup(void)
 324 {
 325         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 326
 327         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 328                 return true;
 329
 330         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 331         return false;
 332 }
 333
 334 static void watchdog_interrupt_count(void)
 335 {
 336         __this_cpu_inc(hrtimer_interrupts);
 337 }
 338
 339 /* watchdog kicker functions */
 340 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 341 {
 342         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 343         struct pt_regs *regs = get_irq_regs();
 344         int duration;
 345         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 346
 347         if (!watchdog_enabled)
 348                 return HRTIMER_NORESTART;
 349
 350         /* kick the hardlockup detector */
 351         watchdog_interrupt_count();
 352
 353         /* kick the softlockup detector */
 354         wake_up_process(__this_cpu_read(softlockup_watchdog));
 355
 356         /* .. and repeat */
 357         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 358
 359         if (touch_ts == SOFTLOCKUP_RESET) {
 360                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 361                         /*
 362                          * If the time stamp was touched atomically
 363                          * make sure the scheduler tick is up to date.
 364                          */
 365                         __this_cpu_write(softlockup_touch_sync, false);
 366                         sched_clock_tick();
 367                 }
 368
 369                 /* Clear the guest paused flag on watchdog reset */
 370                 kvm_check_and_clear_guest_paused();
 371                 __touch_watchdog();
 372                 return HRTIMER_RESTART;
 373         }
 374
 375         /* check for a softlockup
 376          * This is done by making sure a high priority task is
 377          * being scheduled.  The task touches the watchdog to
 378          * indicate it is getting cpu time.  If it hasn't then
 379          * this is a good indication some task is hogging the cpu
 380          */
 381         duration = is_softlockup(touch_ts);
 382         if (unlikely(duration)) {
 383                 /*
 384                  * If a virtual machine is stopped by the host it can look to
 385                  * the watchdog like a soft lockup, check to see if the host
 386                  * stopped the vm before we issue the warning
 387                  */
 388                 if (kvm_check_and_clear_guest_paused())
 389                         return HRTIMER_RESTART;
 390
 391                 /* only warn once */
 392                 if (__this_cpu_read(soft_watchdog_warn) == true) {
 393                         /*
 394                          * When multiple processes are causing softlockups the
 395                          * softlockup detector only warns on the first one
 396                          * because the code relies on a full quiet cycle to
 397                          * re-arm.  The second process prevents the quiet cycle
 398                          * and never gets reported.  Use task pointers to detect
 399                          * this.
 400                          */
 401                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
 402                             current) {
 403                                 __this_cpu_write(soft_watchdog_warn, false);
 404                                 __touch_watchdog();
 405                         }
 406                         return HRTIMER_RESTART;
 407                 }
 408
 409                 if (softlockup_all_cpu_backtrace) {
 410                         /* Prevent multiple soft-lockup reports if one cpu is already
 411                          * engaged in dumping cpu back traces
 412                          */
 413                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
 414                                 /* Someone else will report us. Let's give up */
 415                                 __this_cpu_write(soft_watchdog_warn, true);
 416                                 return HRTIMER_RESTART;
 417                         }
 418                 }
 419
 420                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 421                         smp_processor_id(), duration,
 422                         current->comm, task_pid_nr(current));
 423                 __this_cpu_write(softlockup_task_ptr_saved, current);
 424                 print_modules();
 425                 print_irqtrace_events(current);
 426                 if (regs)
 427                         show_regs(regs);
 428                 else
 429                         dump_stack();
 430
 431                 if (softlockup_all_cpu_backtrace) {
 432                         /* Avoid generating two back traces for current
 433                          * given that one is already made above
 434                          */
 435                         trigger_allbutself_cpu_backtrace();
 436
 437                         clear_bit(0, &soft_lockup_nmi_warn);
 438                         /* Barrier to sync with other cpus */
 439                         smp_mb__after_atomic();
 440                 }
 441
 442                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 443                 if (softlockup_panic)
 444                         panic("softlockup: hung tasks");
 445                 __this_cpu_write(soft_watchdog_warn, true);
 446         } else
 447                 __this_cpu_write(soft_watchdog_warn, false);
 448
 449         return HRTIMER_RESTART;
 450 }
 451
 452 static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 453 {
 454         struct sched_param param = { .sched_priority = prio };
 455
 456         sched_setscheduler(current, policy, &param);
 457 }
 458
 459 static void watchdog_enable(unsigned int cpu)
 460 {
 461         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 462
 463         /*
 464          * Start the timer first to prevent the NMI watchdog triggering
 465          * before the timer has a chance to fire.
 466          */
 467         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 468         hrtimer->function = watchdog_timer_fn;
 469         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 470                       HRTIMER_MODE_REL_PINNED);
 471
 472         /* Initialize timestamp */
 473         __touch_watchdog();
 474         /* Enable the perf event */
 475         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
 476                 watchdog_nmi_enable(cpu);
 477
 478         watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
 479 }
 480
 481 static void watchdog_disable(unsigned int cpu)
 482 {
 483         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 484
 485         watchdog_set_prio(SCHED_NORMAL, 0);
 486         /*
 487          * Disable the perf event first. That prevents that a large delay
 488          * between disabling the timer and disabling the perf event causes
 489          * the perf NMI to detect a false positive.
 490          */
 491         watchdog_nmi_disable(cpu);
 492         hrtimer_cancel(hrtimer);
 493 }
 494
 495 static void watchdog_cleanup(unsigned int cpu, bool online)
 496 {
 497         watchdog_disable(cpu);
 498 }
 499
 500 static int watchdog_should_run(unsigned int cpu)
 501 {
 502         return __this_cpu_read(hrtimer_interrupts) !=
 503                 __this_cpu_read(soft_lockup_hrtimer_cnt);
 504 }
 505
 506 /*
 507  * The watchdog thread function - touches the timestamp.
 508  *
 509  * It only runs once every sample_period seconds (4 seconds by
 510  * default) to reset the softlockup timestamp. If this gets delayed
 511  * for more than 2*watchdog_thresh seconds then the debug-printout
 512  * triggers in watchdog_timer_fn().
 513  */
 514 static void watchdog(unsigned int cpu)
 515 {
 516         __this_cpu_write(soft_lockup_hrtimer_cnt,
 517                          __this_cpu_read(hrtimer_interrupts));
 518         __touch_watchdog();
 519 }
 520
 521 static struct smp_hotplug_thread watchdog_threads = {
 522         .store                  = &softlockup_watchdog,
 523         .thread_should_run      = watchdog_should_run,
 524         .thread_fn              = watchdog,
 525         .thread_comm            = "watchdog/%u",
 526         .setup                  = watchdog_enable,
 527         .cleanup                = watchdog_cleanup,
 528         .park                   = watchdog_disable,
 529         .unpark                 = watchdog_enable,
 530 };
 531
 532 static void softlockup_update_smpboot_threads(void)
 533 {
 534         lockdep_assert_held(&watchdog_mutex);
 535
 536         if (!softlockup_threads_initialized)
 537                 return;
 538
 539         smpboot_update_cpumask_percpu_thread(&watchdog_threads,
 540                                              &watchdog_allowed_mask);
 541 }
 542
 543 /* Temporarily park all watchdog threads */
 544 static void softlockup_park_all_threads(void)
 545 {
 546         cpumask_clear(&watchdog_allowed_mask);
 547         softlockup_update_smpboot_threads();
 548 }
 549
 550 /* Unpark enabled threads */
 551 static void softlockup_unpark_threads(void)
 552 {
 553         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 554         softlockup_update_smpboot_threads();
 555 }
 556
 557 static void lockup_detector_reconfigure(void)
 558 {
 559         cpus_read_lock();
 560         watchdog_nmi_stop();
 561         softlockup_park_all_threads();
 562         set_sample_period();
 563         lockup_detector_update_enable();
 564         if (watchdog_enabled && watchdog_thresh)
 565                 softlockup_unpark_threads();
 566         watchdog_nmi_start();
 567         cpus_read_unlock();
 568         /*
 569          * Must be called outside the cpus locked section to prevent
 570          * recursive locking in the perf code.
 571          */
 572         __lockup_detector_cleanup();
 573 }
 574
 575 /*
 576  * Create the watchdog thread infrastructure and configure the detector(s).
 577  *
 578  * The threads are not unparked as watchdog_allowed_mask is empty.  When
 579  * the threads are sucessfully initialized, take the proper locks and
 580  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
 581  */
 582 static __init void lockup_detector_setup(void)
 583 {
 584         int ret;
 585
 586         /*
 587          * If sysctl is off and watchdog got disabled on the command line,
 588          * nothing to do here.
 589          */
 590         lockup_detector_update_enable();
 591
 592         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 593             !(watchdog_enabled && watchdog_thresh))
 594                 return;
 595
 596         ret = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
 597                                                      &watchdog_allowed_mask);
 598         if (ret) {
 599                 pr_err("Failed to initialize soft lockup detector threads\n");
 600                 return;
 601         }
 602
 603         mutex_lock(&watchdog_mutex);
 604         softlockup_threads_initialized = true;
 605         lockup_detector_reconfigure();
 606         mutex_unlock(&watchdog_mutex);
 607 }
 608
 609 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 610 static inline int watchdog_park_threads(void) { return 0; }
 611 static inline void watchdog_unpark_threads(void) { }
 612 static inline int watchdog_enable_all_cpus(void) { return 0; }
 613 static inline void watchdog_disable_all_cpus(void) { }
 614 static void lockup_detector_reconfigure(void)
 615 {
 616         cpus_read_lock();
 617         watchdog_nmi_stop();
 618         lockup_detector_update_enable();
 619         watchdog_nmi_start();
 620         cpus_read_unlock();
 621 }
 622 static inline void lockup_detector_setup(void)
 623 {
 624         lockup_detector_reconfigure();
 625 }
 626 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 627
 628 static void __lockup_detector_cleanup(void)
 629 {
 630         lockdep_assert_held(&watchdog_mutex);
 631         hardlockup_detector_perf_cleanup();
 632 }
 633
 634 /**
 635  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
 636  *
 637  * Caller must not hold the cpu hotplug rwsem.
 638  */
 639 void lockup_detector_cleanup(void)
 640 {
 641         mutex_lock(&watchdog_mutex);
 642         __lockup_detector_cleanup();
 643         mutex_unlock(&watchdog_mutex);
 644 }
 645
 646 /**
 647  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
 648  *
 649  * Special interface for parisc. It prevents lockup detector warnings from
 650  * the default pm_poweroff() function which busy loops forever.
 651  */
 652 void lockup_detector_soft_poweroff(void)
 653 {
 654         watchdog_enabled = 0;
 655 }
 656
 657 #ifdef CONFIG_SYSCTL
 658
 659 /* Propagate any changes to the watchdog threads */
 660 static void proc_watchdog_update(void)
 661 {
 662         /* Remove impossible cpus to keep sysctl output clean. */
 663         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
 664         lockup_detector_reconfigure();
 665 }
 666
 667 /*
 668  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 669  *
 670  * caller             | table->data points to      | 'which'
 671  * -------------------|----------------------------|--------------------------
 672  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
 673  *                    |                            | SOFT_WATCHDOG_ENABLED
 674  * -------------------|----------------------------|--------------------------
 675  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
 676  * -------------------|----------------------------|--------------------------
 677  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
 678  */
 679 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 680                                 void __user *buffer, size_t *lenp, loff_t *ppos)
 681 {
 682         int err, old, *param = table->data;
 683
 684         mutex_lock(&watchdog_mutex);
 685
 686         if (!write) {
 687                 /*
 688                  * On read synchronize the userspace interface. This is a
 689                  * racy snapshot.
 690                  */
 691                 *param = (watchdog_enabled & which) != 0;
 692                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 693         } else {
 694                 old = READ_ONCE(*param);
 695                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 696                 if (!err && old != READ_ONCE(*param))
 697                         proc_watchdog_update();
 698         }
 699         mutex_unlock(&watchdog_mutex);
 700         return err;
 701 }
 702
 703 /*
 704  * /proc/sys/kernel/watchdog
 705  */
 706 int proc_watchdog(struct ctl_table *table, int write,
 707                   void __user *buffer, size_t *lenp, loff_t *ppos)
 708 {
 709         return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
 710                                     table, write, buffer, lenp, ppos);
 711 }
 712
 713 /*
 714  * /proc/sys/kernel/nmi_watchdog
 715  */
 716 int proc_nmi_watchdog(struct ctl_table *table, int write,
 717                       void __user *buffer, size_t *lenp, loff_t *ppos)
 718 {
 719         if (!nmi_watchdog_available && write)
 720                 return -ENOTSUPP;
 721         return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
 722                                     table, write, buffer, lenp, ppos);
 723 }
 724
 725 /*
 726  * /proc/sys/kernel/soft_watchdog
 727  */
 728 int proc_soft_watchdog(struct ctl_table *table, int write,
 729                         void __user *buffer, size_t *lenp, loff_t *ppos)
 730 {
 731         return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
 732                                     table, write, buffer, lenp, ppos);
 733 }
 734
 735 /*
 736  * /proc/sys/kernel/watchdog_thresh
 737  */
 738 int proc_watchdog_thresh(struct ctl_table *table, int write,
 739                          void __user *buffer, size_t *lenp, loff_t *ppos)
 740 {
 741         int err, old;
 742
 743         mutex_lock(&watchdog_mutex);
 744
 745         old = READ_ONCE(watchdog_thresh);
 746         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 747
 748         if (!err && write && old != READ_ONCE(watchdog_thresh))
 749                 proc_watchdog_update();
 750
 751         mutex_unlock(&watchdog_mutex);
 752         return err;
 753 }
 754
 755 /*
 756  * The cpumask is the mask of possible cpus that the watchdog can run
 757  * on, not the mask of cpus it is actually running on.  This allows the
 758  * user to specify a mask that will include cpus that have not yet
 759  * been brought online, if desired.
 760  */
 761 int proc_watchdog_cpumask(struct ctl_table *table, int write,
 762                           void __user *buffer, size_t *lenp, loff_t *ppos)
 763 {
 764         int err;
 765
 766         mutex_lock(&watchdog_mutex);
 767
 768         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
 769         if (!err && write)
 770                 proc_watchdog_update();
 771
 772         mutex_unlock(&watchdog_mutex);
 773         return err;
 774 }
 775 #endif /* CONFIG_SYSCTL */
 776
 777 void __init lockup_detector_init(void)
 778 {
 779 #ifdef CONFIG_NO_HZ_FULL
 780         if (tick_nohz_full_enabled()) {
 781                 pr_info("Disabling watchdog on nohz_full cores by default\n");
 782                 cpumask_copy(&watchdog_cpumask, housekeeping_mask);
 783         } else
 784                 cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
 785 #else
 786         cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
 787 #endif
 788
 789         if (!watchdog_nmi_probe())
 790                 nmi_watchdog_available = true;
 791         lockup_detector_setup();
 792 }