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