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 static int __read_mostly nmi_watchdog_available;
  46
  47 static 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(struct task_struct *, softlockup_task_ptr_saved);
 177 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 178 static unsigned long soft_lockup_nmi_warn;
 179
 180 static int __init softlockup_panic_setup(char *str)
 181 {
 182         softlockup_panic = simple_strtoul(str, NULL, 0);
 183         return 1;
 184 }
 185 __setup("softlockup_panic=", softlockup_panic_setup);
 186
 187 static int __init nowatchdog_setup(char *str)
 188 {
 189         watchdog_user_enabled = 0;
 190         return 1;
 191 }
 192 __setup("nowatchdog", nowatchdog_setup);
 193
 194 static int __init nosoftlockup_setup(char *str)
 195 {
 196         soft_watchdog_user_enabled = 0;
 197         return 1;
 198 }
 199 __setup("nosoftlockup", nosoftlockup_setup);
 200
 201 static int __init watchdog_thresh_setup(char *str)
 202 {
 203         get_option(&str, &watchdog_thresh);
 204         return 1;
 205 }
 206 __setup("watchdog_thresh=", watchdog_thresh_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, 0);
 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) = 0;
 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, 0);
 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 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 340 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 341
 342 /*
 343  * The watchdog thread function - touches the timestamp.
 344  *
 345  * It only runs once every sample_period seconds (4 seconds by
 346  * default) to reset the softlockup timestamp. If this gets delayed
 347  * for more than 2*watchdog_thresh seconds then the debug-printout
 348  * triggers in watchdog_timer_fn().
 349  */
 350 static int softlockup_fn(void *data)
 351 {
 352         __touch_watchdog();
 353         complete(this_cpu_ptr(&softlockup_completion));
 354
 355         return 0;
 356 }
 357
 358 /* watchdog kicker functions */
 359 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 360 {
 361         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 362         struct pt_regs *regs = get_irq_regs();
 363         int duration;
 364         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 365
 366         if (!watchdog_enabled)
 367                 return HRTIMER_NORESTART;
 368
 369         /* kick the hardlockup detector */
 370         watchdog_interrupt_count();
 371
 372         /* kick the softlockup detector */
 373         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
 374                 reinit_completion(this_cpu_ptr(&softlockup_completion));
 375                 stop_one_cpu_nowait(smp_processor_id(),
 376                                 softlockup_fn, NULL,
 377                                 this_cpu_ptr(&softlockup_stop_work));
 378         }
 379
 380         /* .. and repeat */
 381         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 382
 383         if (touch_ts == 0) {
 384                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 385                         /*
 386                          * If the time stamp was touched atomically
 387                          * make sure the scheduler tick is up to date.
 388                          */
 389                         __this_cpu_write(softlockup_touch_sync, false);
 390                         sched_clock_tick();
 391                 }
 392
 393                 /* Clear the guest paused flag on watchdog reset */
 394                 kvm_check_and_clear_guest_paused();
 395                 __touch_watchdog();
 396                 return HRTIMER_RESTART;
 397         }
 398
 399         /* check for a softlockup
 400          * This is done by making sure a high priority task is
 401          * being scheduled.  The task touches the watchdog to
 402          * indicate it is getting cpu time.  If it hasn't then
 403          * this is a good indication some task is hogging the cpu
 404          */
 405         duration = is_softlockup(touch_ts);
 406         if (unlikely(duration)) {
 407                 /*
 408                  * If a virtual machine is stopped by the host it can look to
 409                  * the watchdog like a soft lockup, check to see if the host
 410                  * stopped the vm before we issue the warning
 411                  */
 412                 if (kvm_check_and_clear_guest_paused())
 413                         return HRTIMER_RESTART;
 414
 415                 /* only warn once */
 416                 if (__this_cpu_read(soft_watchdog_warn) == true) {
 417                         /*
 418                          * When multiple processes are causing softlockups the
 419                          * softlockup detector only warns on the first one
 420                          * because the code relies on a full quiet cycle to
 421                          * re-arm.  The second process prevents the quiet cycle
 422                          * and never gets reported.  Use task pointers to detect
 423                          * this.
 424                          */
 425                         if (__this_cpu_read(softlockup_task_ptr_saved) !=
 426                             current) {
 427                                 __this_cpu_write(soft_watchdog_warn, false);
 428                                 __touch_watchdog();
 429                         }
 430                         return HRTIMER_RESTART;
 431                 }
 432
 433                 if (softlockup_all_cpu_backtrace) {
 434                         /* Prevent multiple soft-lockup reports if one cpu is already
 435                          * engaged in dumping cpu back traces
 436                          */
 437                         if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
 438                                 /* Someone else will report us. Let's give up */
 439                                 __this_cpu_write(soft_watchdog_warn, true);
 440                                 return HRTIMER_RESTART;
 441                         }
 442                 }
 443
 444                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 445                         smp_processor_id(), duration,
 446                         current->comm, task_pid_nr(current));
 447                 __this_cpu_write(softlockup_task_ptr_saved, current);
 448                 print_modules();
 449                 print_irqtrace_events(current);
 450                 if (regs)
 451                         show_regs(regs);
 452                 else
 453                         dump_stack();
 454
 455                 if (softlockup_all_cpu_backtrace) {
 456                         /* Avoid generating two back traces for current
 457                          * given that one is already made above
 458                          */
 459                         trigger_allbutself_cpu_backtrace();
 460
 461                         clear_bit(0, &soft_lockup_nmi_warn);
 462                         /* Barrier to sync with other cpus */
 463                         smp_mb__after_atomic();
 464                 }
 465
 466                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 467                 if (softlockup_panic)
 468                         panic("softlockup: hung tasks");
 469                 __this_cpu_write(soft_watchdog_warn, true);
 470         } else
 471                 __this_cpu_write(soft_watchdog_warn, false);
 472
 473         return HRTIMER_RESTART;
 474 }
 475
 476 static void watchdog_enable(unsigned int cpu)
 477 {
 478         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 479         struct completion *done = this_cpu_ptr(&softlockup_completion);
 480
 481         WARN_ON_ONCE(cpu != smp_processor_id());
 482
 483         init_completion(done);
 484         complete(done);
 485
 486         /*
 487          * Start the timer first to prevent the NMI watchdog triggering
 488          * before the timer has a chance to fire.
 489          */
 490         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 491         hrtimer->function = watchdog_timer_fn;
 492         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 493                       HRTIMER_MODE_REL_PINNED_HARD);
 494
 495         /* Initialize timestamp */
 496         __touch_watchdog();
 497         /* Enable the perf event */
 498         if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
 499                 watchdog_nmi_enable(cpu);
 500 }
 501
 502 static void watchdog_disable(unsigned int cpu)
 503 {
 504         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 505
 506         WARN_ON_ONCE(cpu != smp_processor_id());
 507
 508         /*
 509          * Disable the perf event first. That prevents that a large delay
 510          * between disabling the timer and disabling the perf event causes
 511          * the perf NMI to detect a false positive.
 512          */
 513         watchdog_nmi_disable(cpu);
 514         hrtimer_cancel(hrtimer);
 515         wait_for_completion(this_cpu_ptr(&softlockup_completion));
 516 }
 517
 518 static int softlockup_stop_fn(void *data)
 519 {
 520         watchdog_disable(smp_processor_id());
 521         return 0;
 522 }
 523
 524 static void softlockup_stop_all(void)
 525 {
 526         int cpu;
 527
 528         if (!softlockup_initialized)
 529                 return;
 530
 531         for_each_cpu(cpu, &watchdog_allowed_mask)
 532                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 533
 534         cpumask_clear(&watchdog_allowed_mask);
 535 }
 536
 537 static int softlockup_start_fn(void *data)
 538 {
 539         watchdog_enable(smp_processor_id());
 540         return 0;
 541 }
 542
 543 static void softlockup_start_all(void)
 544 {
 545         int cpu;
 546
 547         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 548         for_each_cpu(cpu, &watchdog_allowed_mask)
 549                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 550 }
 551
 552 int lockup_detector_online_cpu(unsigned int cpu)
 553 {
 554         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 555                 watchdog_enable(cpu);
 556         return 0;
 557 }
 558
 559 int lockup_detector_offline_cpu(unsigned int cpu)
 560 {
 561         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 562                 watchdog_disable(cpu);
 563         return 0;
 564 }
 565
 566 static void lockup_detector_reconfigure(void)
 567 {
 568         cpus_read_lock();
 569         watchdog_nmi_stop();
 570
 571         softlockup_stop_all();
 572         set_sample_period();
 573         lockup_detector_update_enable();
 574         if (watchdog_enabled && watchdog_thresh)
 575                 softlockup_start_all();
 576
 577         watchdog_nmi_start();
 578         cpus_read_unlock();
 579         /*
 580          * Must be called outside the cpus locked section to prevent
 581          * recursive locking in the perf code.
 582          */
 583         __lockup_detector_cleanup();
 584 }
 585
 586 /*
 587  * Create the watchdog thread infrastructure and configure the detector(s).
 588  *
 589  * The threads are not unparked as watchdog_allowed_mask is empty.  When
 590  * the threads are successfully initialized, take the proper locks and
 591  * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
 592  */
 593 static __init void lockup_detector_setup(void)
 594 {
 595         /*
 596          * If sysctl is off and watchdog got disabled on the command line,
 597          * nothing to do here.
 598          */
 599         lockup_detector_update_enable();
 600
 601         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 602             !(watchdog_enabled && watchdog_thresh))
 603                 return;
 604
 605         mutex_lock(&watchdog_mutex);
 606         lockup_detector_reconfigure();
 607         softlockup_initialized = true;
 608         mutex_unlock(&watchdog_mutex);
 609 }
 610
 611 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 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         if (tick_nohz_full_enabled())
 778                 pr_info("Disabling watchdog on nohz_full cores by default\n");
 779
 780         cpumask_copy(&watchdog_cpumask,
 781                      housekeeping_cpumask(HK_FLAG_TIMER));
 782
 783         if (!watchdog_nmi_probe())
 784                 nmi_watchdog_available = true;
 785         lockup_detector_setup();
 786 }