kernel/watchdog.c

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