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/cpu.h>
  16 #include <linux/init.h>
  17 #include <linux/irq.h>
  18 #include <linux/irqdesc.h>
  19 #include <linux/kernel_stat.h>
  20 #include <linux/kvm_para.h>
  21 #include <linux/math64.h>
  22 #include <linux/mm.h>
  23 #include <linux/module.h>
  24 #include <linux/nmi.h>
  25 #include <linux/stop_machine.h>
  26 #include <linux/sysctl.h>
  27 #include <linux/tick.h>
  28
  29 #include <linux/sched/clock.h>
  30 #include <linux/sched/debug.h>
  31 #include <linux/sched/isolation.h>
  32
  33 #include <asm/irq_regs.h>
  34
  35 static DEFINE_MUTEX(watchdog_mutex);
  36
  37 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HARDLOCKUP_DETECTOR_SPARC64)
  38 # define WATCHDOG_HARDLOCKUP_DEFAULT    1
  39 #else
  40 # define WATCHDOG_HARDLOCKUP_DEFAULT    0
  41 #endif
  42
  43 #define NUM_SAMPLE_PERIODS      5
  44
  45 unsigned long __read_mostly watchdog_enabled;
  46 int __read_mostly watchdog_user_enabled = 1;
  47 static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT;
  48 static int __read_mostly watchdog_softlockup_user_enabled = 1;
  49 int __read_mostly watchdog_thresh = 10;
  50 static int __read_mostly watchdog_thresh_next;
  51 static int __read_mostly watchdog_hardlockup_available;
  52
  53 struct cpumask watchdog_cpumask __read_mostly;
  54 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  55
  56 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  57
  58 # ifdef CONFIG_SMP
  59 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  60 # endif /* CONFIG_SMP */
  61
  62 /*
  63  * Should we panic when a soft-lockup or hard-lockup occurs:
  64  */
  65 unsigned int __read_mostly hardlockup_panic =
  66                         IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
  67
  68 #ifdef CONFIG_SYSFS
  69
  70 static unsigned int hardlockup_count;
  71
  72 static ssize_t hardlockup_count_show(struct kobject *kobj, struct kobj_attribute *attr,
  73                                      char *page)
  74 {
  75         return sysfs_emit(page, "%u\n", hardlockup_count);
  76 }
  77
  78 static struct kobj_attribute hardlockup_count_attr = __ATTR_RO(hardlockup_count);
  79
  80 static __init int kernel_hardlockup_sysfs_init(void)
  81 {
  82         sysfs_add_file_to_group(kernel_kobj, &hardlockup_count_attr.attr, NULL);
  83         return 0;
  84 }
  85
  86 late_initcall(kernel_hardlockup_sysfs_init);
  87
  88 #endif // CONFIG_SYSFS
  89
  90 /*
  91  * We may not want to enable hard lockup detection by default in all cases,
  92  * for example when running the kernel as a guest on a hypervisor. In these
  93  * cases this function can be called to disable hard lockup detection. This
  94  * function should only be executed once by the boot processor before the
  95  * kernel command line parameters are parsed, because otherwise it is not
  96  * possible to override this in hardlockup_panic_setup().
  97  */
  98 void __init hardlockup_detector_disable(void)
  99 {
 100         watchdog_hardlockup_user_enabled = 0;
 101 }
 102
 103 static int __init hardlockup_panic_setup(char *str)
 104 {
 105 next:
 106         if (!strncmp(str, "panic", 5))
 107                 hardlockup_panic = 1;
 108         else if (!strncmp(str, "nopanic", 7))
 109                 hardlockup_panic = 0;
 110         else if (!strncmp(str, "0", 1))
 111                 watchdog_hardlockup_user_enabled = 0;
 112         else if (!strncmp(str, "1", 1))
 113                 watchdog_hardlockup_user_enabled = 1;
 114         else if (!strncmp(str, "r", 1))
 115                 hardlockup_config_perf_event(str + 1);
 116         while (*(str++)) {
 117                 if (*str == ',') {
 118                         str++;
 119                         goto next;
 120                 }
 121         }
 122         return 1;
 123 }
 124 __setup("nmi_watchdog=", hardlockup_panic_setup);
 125
 126 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 127
 128 #if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
 129
 130 static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts);
 131 static DEFINE_PER_CPU(int, hrtimer_interrupts_saved);
 132 static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned);
 133 static DEFINE_PER_CPU(bool, watchdog_hardlockup_touched);
 134 static unsigned long hard_lockup_nmi_warn;
 135
 136 notrace void arch_touch_nmi_watchdog(void)
 137 {
 138         /*
 139          * Using __raw here because some code paths have
 140          * preemption enabled.  If preemption is enabled
 141          * then interrupts should be enabled too, in which
 142          * case we shouldn't have to worry about the watchdog
 143          * going off.
 144          */
 145         raw_cpu_write(watchdog_hardlockup_touched, true);
 146 }
 147 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 148
 149 void watchdog_hardlockup_touch_cpu(unsigned int cpu)
 150 {
 151         per_cpu(watchdog_hardlockup_touched, cpu) = true;
 152 }
 153
 154 static bool is_hardlockup(unsigned int cpu)
 155 {
 156         int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu));
 157
 158         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 159                 return true;
 160
 161         /*
 162          * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE
 163          * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is
 164          * written/read by a single CPU.
 165          */
 166         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 167
 168         return false;
 169 }
 170
 171 static void watchdog_hardlockup_kick(void)
 172 {
 173         int new_interrupts;
 174
 175         new_interrupts = atomic_inc_return(this_cpu_ptr(&hrtimer_interrupts));
 176         watchdog_buddy_check_hardlockup(new_interrupts);
 177 }
 178
 179 void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
 180 {
 181         if (per_cpu(watchdog_hardlockup_touched, cpu)) {
 182                 per_cpu(watchdog_hardlockup_touched, cpu) = false;
 183                 return;
 184         }
 185
 186         /*
 187          * Check for a hardlockup by making sure the CPU's timer
 188          * interrupt is incrementing. The timer interrupt should have
 189          * fired multiple times before we overflow'd. If it hasn't
 190          * then this is a good indication the cpu is stuck
 191          */
 192         if (is_hardlockup(cpu)) {
 193                 unsigned int this_cpu = smp_processor_id();
 194                 unsigned long flags;
 195
 196 #ifdef CONFIG_SYSFS
 197                 ++hardlockup_count;
 198 #endif
 199
 200                 /* Only print hardlockups once. */
 201                 if (per_cpu(watchdog_hardlockup_warned, cpu))
 202                         return;
 203
 204                 /*
 205                  * Prevent multiple hard-lockup reports if one cpu is already
 206                  * engaged in dumping all cpu back traces.
 207                  */
 208                 if (sysctl_hardlockup_all_cpu_backtrace) {
 209                         if (test_and_set_bit_lock(0, &hard_lockup_nmi_warn))
 210                                 return;
 211                 }
 212
 213                 /*
 214                  * NOTE: we call printk_cpu_sync_get_irqsave() after printing
 215                  * the lockup message. While it would be nice to serialize
 216                  * that printout, we really want to make sure that if some
 217                  * other CPU somehow locked up while holding the lock associated
 218                  * with printk_cpu_sync_get_irqsave() that we can still at least
 219                  * get the message about the lockup out.
 220                  */
 221                 pr_emerg("CPU%u: Watchdog detected hard LOCKUP on cpu %u\n", this_cpu, cpu);
 222                 printk_cpu_sync_get_irqsave(flags);
 223
 224                 print_modules();
 225                 print_irqtrace_events(current);
 226                 if (cpu == this_cpu) {
 227                         if (regs)
 228                                 show_regs(regs);
 229                         else
 230                                 dump_stack();
 231                         printk_cpu_sync_put_irqrestore(flags);
 232                 } else {
 233                         printk_cpu_sync_put_irqrestore(flags);
 234                         trigger_single_cpu_backtrace(cpu);
 235                 }
 236
 237                 if (sysctl_hardlockup_all_cpu_backtrace) {
 238                         trigger_allbutcpu_cpu_backtrace(cpu);
 239                         if (!hardlockup_panic)
 240                                 clear_bit_unlock(0, &hard_lockup_nmi_warn);
 241                 }
 242
 243                 if (hardlockup_panic)
 244                         nmi_panic(regs, "Hard LOCKUP");
 245
 246                 per_cpu(watchdog_hardlockup_warned, cpu) = true;
 247         } else {
 248                 per_cpu(watchdog_hardlockup_warned, cpu) = false;
 249         }
 250 }
 251
 252 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 253
 254 static inline void watchdog_hardlockup_kick(void) { }
 255
 256 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */
 257
 258 /*
 259  * These functions can be overridden based on the configured hardlockdup detector.
 260  *
 261  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
 262  * softlockup watchdog start and stop. The detector must select the
 263  * SOFTLOCKUP_DETECTOR Kconfig.
 264  */
 265 void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
 266
 267 void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
 268
 269 /*
 270  * Watchdog-detector specific API.
 271  *
 272  * Return 0 when hardlockup watchdog is available, negative value otherwise.
 273  * Note that the negative value means that a delayed probe might
 274  * succeed later.
 275  */
 276 int __weak __init watchdog_hardlockup_probe(void)
 277 {
 278         return -ENODEV;
 279 }
 280
 281 /**
 282  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
 283  *
 284  * The reconfiguration steps are:
 285  * watchdog_hardlockup_stop();
 286  * update_variables();
 287  * watchdog_hardlockup_start();
 288  */
 289 void __weak watchdog_hardlockup_stop(void) { }
 290
 291 /**
 292  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
 293  *
 294  * Counterpart to watchdog_hardlockup_stop().
 295  *
 296  * The following variables have been updated in update_variables() and
 297  * contain the currently valid configuration:
 298  * - watchdog_enabled
 299  * - watchdog_thresh
 300  * - watchdog_cpumask
 301  */
 302 void __weak watchdog_hardlockup_start(void) { }
 303
 304 /**
 305  * lockup_detector_update_enable - Update the sysctl enable bit
 306  *
 307  * Caller needs to make sure that the hard watchdogs are off, so this
 308  * can't race with watchdog_hardlockup_disable().
 309  */
 310 static void lockup_detector_update_enable(void)
 311 {
 312         watchdog_enabled = 0;
 313         if (!watchdog_user_enabled)
 314                 return;
 315         if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled)
 316                 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED;
 317         if (watchdog_softlockup_user_enabled)
 318                 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED;
 319 }
 320
 321 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 322
 323 /*
 324  * Delay the soflockup report when running a known slow code.
 325  * It does _not_ affect the timestamp of the last successdul reschedule.
 326  */
 327 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
 328
 329 #ifdef CONFIG_SMP
 330 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 331 #endif
 332
 333 static struct cpumask watchdog_allowed_mask __read_mostly;
 334
 335 /* Global variables, exported for sysctl */
 336 unsigned int __read_mostly softlockup_panic =
 337                         IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
 338
 339 static bool softlockup_initialized __read_mostly;
 340 static u64 __read_mostly sample_period;
 341
 342 #ifdef CONFIG_SYSFS
 343
 344 static unsigned int softlockup_count;
 345
 346 static ssize_t softlockup_count_show(struct kobject *kobj, struct kobj_attribute *attr,
 347                                      char *page)
 348 {
 349         return sysfs_emit(page, "%u\n", softlockup_count);
 350 }
 351
 352 static struct kobj_attribute softlockup_count_attr = __ATTR_RO(softlockup_count);
 353
 354 static __init int kernel_softlockup_sysfs_init(void)
 355 {
 356         sysfs_add_file_to_group(kernel_kobj, &softlockup_count_attr.attr, NULL);
 357         return 0;
 358 }
 359
 360 late_initcall(kernel_softlockup_sysfs_init);
 361
 362 #endif // CONFIG_SYSFS
 363
 364 /* Timestamp taken after the last successful reschedule. */
 365 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 366 /* Timestamp of the last softlockup report. */
 367 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
 368 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 369 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 370 static unsigned long soft_lockup_nmi_warn;
 371
 372 static int __init softlockup_panic_setup(char *str)
 373 {
 374         softlockup_panic = simple_strtoul(str, NULL, 0);
 375         return 1;
 376 }
 377 __setup("softlockup_panic=", softlockup_panic_setup);
 378
 379 static int __init nowatchdog_setup(char *str)
 380 {
 381         watchdog_user_enabled = 0;
 382         return 1;
 383 }
 384 __setup("nowatchdog", nowatchdog_setup);
 385
 386 static int __init nosoftlockup_setup(char *str)
 387 {
 388         watchdog_softlockup_user_enabled = 0;
 389         return 1;
 390 }
 391 __setup("nosoftlockup", nosoftlockup_setup);
 392
 393 static int __init watchdog_thresh_setup(char *str)
 394 {
 395         get_option(&str, &watchdog_thresh);
 396         return 1;
 397 }
 398 __setup("watchdog_thresh=", watchdog_thresh_setup);
 399
 400 #ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
 401 enum stats_per_group {
 402         STATS_SYSTEM,
 403         STATS_SOFTIRQ,
 404         STATS_HARDIRQ,
 405         STATS_IDLE,
 406         NUM_STATS_PER_GROUP,
 407 };
 408
 409 static const enum cpu_usage_stat tracked_stats[NUM_STATS_PER_GROUP] = {
 410         CPUTIME_SYSTEM,
 411         CPUTIME_SOFTIRQ,
 412         CPUTIME_IRQ,
 413         CPUTIME_IDLE,
 414 };
 415
 416 static DEFINE_PER_CPU(u16, cpustat_old[NUM_STATS_PER_GROUP]);
 417 static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]);
 418 static DEFINE_PER_CPU(u8, cpustat_tail);
 419
 420 /*
 421  * We don't need nanosecond resolution. A granularity of 16ms is
 422  * sufficient for our precision, allowing us to use u16 to store
 423  * cpustats, which will roll over roughly every ~1000 seconds.
 424  * 2^24 ~= 16 * 10^6
 425  */
 426 static u16 get_16bit_precision(u64 data_ns)
 427 {
 428         return data_ns >> 24LL; /* 2^24ns ~= 16.8ms */
 429 }
 430
 431 static void update_cpustat(void)
 432 {
 433         int i;
 434         u8 util;
 435         u16 old_stat, new_stat;
 436         struct kernel_cpustat kcpustat;
 437         u64 *cpustat = kcpustat.cpustat;
 438         u8 tail = __this_cpu_read(cpustat_tail);
 439         u16 sample_period_16 = get_16bit_precision(sample_period);
 440
 441         kcpustat_cpu_fetch(&kcpustat, smp_processor_id());
 442
 443         for (i = 0; i < NUM_STATS_PER_GROUP; i++) {
 444                 old_stat = __this_cpu_read(cpustat_old[i]);
 445                 new_stat = get_16bit_precision(cpustat[tracked_stats[i]]);
 446                 util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16);
 447                 __this_cpu_write(cpustat_util[tail][i], util);
 448                 __this_cpu_write(cpustat_old[i], new_stat);
 449         }
 450
 451         __this_cpu_write(cpustat_tail, (tail + 1) % NUM_SAMPLE_PERIODS);
 452 }
 453
 454 static void print_cpustat(void)
 455 {
 456         int i, group;
 457         u8 tail = __this_cpu_read(cpustat_tail);
 458         u64 sample_period_second = sample_period;
 459
 460         do_div(sample_period_second, NSEC_PER_SEC);
 461
 462         /*
 463          * Outputting the "watchdog" prefix on every line is redundant and not
 464          * concise, and the original alarm information is sufficient for
 465          * positioning in logs, hence here printk() is used instead of pr_crit().
 466          */
 467         printk(KERN_CRIT "CPU#%d Utilization every %llus during lockup:\n",
 468                smp_processor_id(), sample_period_second);
 469
 470         for (i = 0; i < NUM_SAMPLE_PERIODS; i++) {
 471                 group = (tail + i) % NUM_SAMPLE_PERIODS;
 472                 printk(KERN_CRIT "\t#%d: %3u%% system,\t%3u%% softirq,\t"
 473                         "%3u%% hardirq,\t%3u%% idle\n", i + 1,
 474                         __this_cpu_read(cpustat_util[group][STATS_SYSTEM]),
 475                         __this_cpu_read(cpustat_util[group][STATS_SOFTIRQ]),
 476                         __this_cpu_read(cpustat_util[group][STATS_HARDIRQ]),
 477                         __this_cpu_read(cpustat_util[group][STATS_IDLE]));
 478         }
 479 }
 480
 481 #define HARDIRQ_PERCENT_THRESH          50
 482 #define NUM_HARDIRQ_REPORT              5
 483 struct irq_counts {
 484         int irq;
 485         u32 counts;
 486 };
 487
 488 static DEFINE_PER_CPU(bool, snapshot_taken);
 489
 490 /* Tabulate the most frequent interrupts. */
 491 static void tabulate_irq_count(struct irq_counts *irq_counts, int irq, u32 counts, int rank)
 492 {
 493         int i;
 494         struct irq_counts new_count = {irq, counts};
 495
 496         for (i = 0; i < rank; i++) {
 497                 if (counts > irq_counts[i].counts)
 498                         swap(new_count, irq_counts[i]);
 499         }
 500 }
 501
 502 /*
 503  * If the hardirq time exceeds HARDIRQ_PERCENT_THRESH% of the sample_period,
 504  * then the cause of softlockup might be interrupt storm. In this case, it
 505  * would be useful to start interrupt counting.
 506  */
 507 static bool need_counting_irqs(void)
 508 {
 509         u8 util;
 510         int tail = __this_cpu_read(cpustat_tail);
 511
 512         tail = (tail + NUM_HARDIRQ_REPORT - 1) % NUM_HARDIRQ_REPORT;
 513         util = __this_cpu_read(cpustat_util[tail][STATS_HARDIRQ]);
 514         return util > HARDIRQ_PERCENT_THRESH;
 515 }
 516
 517 static void start_counting_irqs(void)
 518 {
 519         if (!__this_cpu_read(snapshot_taken)) {
 520                 kstat_snapshot_irqs();
 521                 __this_cpu_write(snapshot_taken, true);
 522         }
 523 }
 524
 525 static void stop_counting_irqs(void)
 526 {
 527         __this_cpu_write(snapshot_taken, false);
 528 }
 529
 530 static void print_irq_counts(void)
 531 {
 532         unsigned int i, count;
 533         struct irq_counts irq_counts_sorted[NUM_HARDIRQ_REPORT] = {
 534                 {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}
 535         };
 536
 537         if (__this_cpu_read(snapshot_taken)) {
 538                 for_each_active_irq(i) {
 539                         count = kstat_get_irq_since_snapshot(i);
 540                         tabulate_irq_count(irq_counts_sorted, i, count, NUM_HARDIRQ_REPORT);
 541                 }
 542
 543                 /*
 544                  * Outputting the "watchdog" prefix on every line is redundant and not
 545                  * concise, and the original alarm information is sufficient for
 546                  * positioning in logs, hence here printk() is used instead of pr_crit().
 547                  */
 548                 printk(KERN_CRIT "CPU#%d Detect HardIRQ Time exceeds %d%%. Most frequent HardIRQs:\n",
 549                        smp_processor_id(), HARDIRQ_PERCENT_THRESH);
 550
 551                 for (i = 0; i < NUM_HARDIRQ_REPORT; i++) {
 552                         if (irq_counts_sorted[i].irq == -1)
 553                                 break;
 554
 555                         printk(KERN_CRIT "\t#%u: %-10u\tirq#%d\n",
 556                                i + 1, irq_counts_sorted[i].counts,
 557                                irq_counts_sorted[i].irq);
 558                 }
 559
 560                 /*
 561                  * If the hardirq time is less than HARDIRQ_PERCENT_THRESH% in the last
 562                  * sample_period, then we suspect the interrupt storm might be subsiding.
 563                  */
 564                 if (!need_counting_irqs())
 565                         stop_counting_irqs();
 566         }
 567 }
 568
 569 static void report_cpu_status(void)
 570 {
 571         print_cpustat();
 572         print_irq_counts();
 573 }
 574 #else
 575 static inline void update_cpustat(void) { }
 576 static inline void report_cpu_status(void) { }
 577 static inline bool need_counting_irqs(void) { return false; }
 578 static inline void start_counting_irqs(void) { }
 579 static inline void stop_counting_irqs(void) { }
 580 #endif
 581
 582 /*
 583  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 584  * lockups can have false positives under extreme conditions. So we generally
 585  * want a higher threshold for soft lockups than for hard lockups. So we couple
 586  * the thresholds with a factor: we make the soft threshold twice the amount of
 587  * time the hard threshold is.
 588  */
 589 static int get_softlockup_thresh(void)
 590 {
 591         return watchdog_thresh * 2;
 592 }
 593
 594 /*
 595  * Returns seconds, approximately.  We don't need nanosecond
 596  * resolution, and we don't need to waste time with a big divide when
 597  * 2^30ns == 1.074s.
 598  */
 599 static unsigned long get_timestamp(void)
 600 {
 601         return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 602 }
 603
 604 static void set_sample_period(void)
 605 {
 606         /*
 607          * convert watchdog_thresh from seconds to ns
 608          * the divide by 5 is to give hrtimer several chances (two
 609          * or three with the current relation between the soft
 610          * and hard thresholds) to increment before the
 611          * hardlockup detector generates a warning
 612          */
 613         sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / NUM_SAMPLE_PERIODS);
 614         watchdog_update_hrtimer_threshold(sample_period);
 615 }
 616
 617 static void update_report_ts(void)
 618 {
 619         __this_cpu_write(watchdog_report_ts, get_timestamp());
 620 }
 621
 622 /* Commands for resetting the watchdog */
 623 static void update_touch_ts(void)
 624 {
 625         __this_cpu_write(watchdog_touch_ts, get_timestamp());
 626         update_report_ts();
 627 }
 628
 629 /**
 630  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 631  *
 632  * Call when the scheduler may have stalled for legitimate reasons
 633  * preventing the watchdog task from executing - e.g. the scheduler
 634  * entering idle state.  This should only be used for scheduler events.
 635  * Use touch_softlockup_watchdog() for everything else.
 636  */
 637 notrace void touch_softlockup_watchdog_sched(void)
 638 {
 639         /*
 640          * Preemption can be enabled.  It doesn't matter which CPU's watchdog
 641          * report period gets restarted here, so use the raw_ operation.
 642          */
 643         raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 644 }
 645
 646 notrace void touch_softlockup_watchdog(void)
 647 {
 648         touch_softlockup_watchdog_sched();
 649         wq_watchdog_touch(raw_smp_processor_id());
 650 }
 651 EXPORT_SYMBOL(touch_softlockup_watchdog);
 652
 653 void touch_all_softlockup_watchdogs(void)
 654 {
 655         int cpu;
 656
 657         /*
 658          * watchdog_mutex cannpt be taken here, as this might be called
 659          * from (soft)interrupt context, so the access to
 660          * watchdog_allowed_cpumask might race with a concurrent update.
 661          *
 662          * The watchdog time stamp can race against a concurrent real
 663          * update as well, the only side effect might be a cycle delay for
 664          * the softlockup check.
 665          */
 666         for_each_cpu(cpu, &watchdog_allowed_mask) {
 667                 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
 668                 wq_watchdog_touch(cpu);
 669         }
 670 }
 671
 672 void touch_softlockup_watchdog_sync(void)
 673 {
 674         __this_cpu_write(softlockup_touch_sync, true);
 675         __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 676 }
 677
 678 static int is_softlockup(unsigned long touch_ts,
 679                          unsigned long period_ts,
 680                          unsigned long now)
 681 {
 682         if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) {
 683                 /*
 684                  * If period_ts has not been updated during a sample_period, then
 685                  * in the subsequent few sample_periods, period_ts might also not
 686                  * be updated, which could indicate a potential softlockup. In
 687                  * this case, if we suspect the cause of the potential softlockup
 688                  * might be interrupt storm, then we need to count the interrupts
 689                  * to find which interrupt is storming.
 690                  */
 691                 if (time_after_eq(now, period_ts + get_softlockup_thresh() / NUM_SAMPLE_PERIODS) &&
 692                     need_counting_irqs())
 693                         start_counting_irqs();
 694
 695                 /*
 696                  * A poorly behaving BPF scheduler can live-lock the system into
 697                  * soft lockups. Tell sched_ext to try ejecting the BPF
 698                  * scheduler when close to a soft lockup.
 699                  */
 700                 if (time_after_eq(now, period_ts + get_softlockup_thresh() * 3 / 4))
 701                         scx_softlockup(now - touch_ts);
 702
 703                 /* Warn about unreasonable delays. */
 704                 if (time_after(now, period_ts + get_softlockup_thresh()))
 705                         return now - touch_ts;
 706         }
 707         return 0;
 708 }
 709
 710 /* watchdog detector functions */
 711 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 712 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 713
 714 /*
 715  * The watchdog feed function - touches the timestamp.
 716  *
 717  * It only runs once every sample_period seconds (4 seconds by
 718  * default) to reset the softlockup timestamp. If this gets delayed
 719  * for more than 2*watchdog_thresh seconds then the debug-printout
 720  * triggers in watchdog_timer_fn().
 721  */
 722 static int softlockup_fn(void *data)
 723 {
 724         update_touch_ts();
 725         stop_counting_irqs();
 726         complete(this_cpu_ptr(&softlockup_completion));
 727
 728         return 0;
 729 }
 730
 731 /* watchdog kicker functions */
 732 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 733 {
 734         unsigned long touch_ts, period_ts, now;
 735         struct pt_regs *regs = get_irq_regs();
 736         int duration;
 737         int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 738         unsigned long flags;
 739
 740         if (!watchdog_enabled)
 741                 return HRTIMER_NORESTART;
 742
 743         watchdog_hardlockup_kick();
 744
 745         /* kick the softlockup detector */
 746         if (completion_done(this_cpu_ptr(&softlockup_completion))) {
 747                 reinit_completion(this_cpu_ptr(&softlockup_completion));
 748                 stop_one_cpu_nowait(smp_processor_id(),
 749                                 softlockup_fn, NULL,
 750                                 this_cpu_ptr(&softlockup_stop_work));
 751         }
 752
 753         /* .. and repeat */
 754         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 755
 756         /*
 757          * Read the current timestamp first. It might become invalid anytime
 758          * when a virtual machine is stopped by the host or when the watchog
 759          * is touched from NMI.
 760          */
 761         now = get_timestamp();
 762         /*
 763          * If a virtual machine is stopped by the host it can look to
 764          * the watchdog like a soft lockup. This function touches the watchdog.
 765          */
 766         kvm_check_and_clear_guest_paused();
 767         /*
 768          * The stored timestamp is comparable with @now only when not touched.
 769          * It might get touched anytime from NMI. Make sure that is_softlockup()
 770          * uses the same (valid) value.
 771          */
 772         period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
 773
 774         update_cpustat();
 775
 776         /* Reset the interval when touched by known problematic code. */
 777         if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
 778                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 779                         /*
 780                          * If the time stamp was touched atomically
 781                          * make sure the scheduler tick is up to date.
 782                          */
 783                         __this_cpu_write(softlockup_touch_sync, false);
 784                         sched_clock_tick();
 785                 }
 786
 787                 update_report_ts();
 788                 return HRTIMER_RESTART;
 789         }
 790
 791         /* Check for a softlockup. */
 792         touch_ts = __this_cpu_read(watchdog_touch_ts);
 793         duration = is_softlockup(touch_ts, period_ts, now);
 794         if (unlikely(duration)) {
 795 #ifdef CONFIG_SYSFS
 796                 ++softlockup_count;
 797 #endif
 798
 799                 /*
 800                  * Prevent multiple soft-lockup reports if one cpu is already
 801                  * engaged in dumping all cpu back traces.
 802                  */
 803                 if (softlockup_all_cpu_backtrace) {
 804                         if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
 805                                 return HRTIMER_RESTART;
 806                 }
 807
 808                 /* Start period for the next softlockup warning. */
 809                 update_report_ts();
 810
 811                 printk_cpu_sync_get_irqsave(flags);
 812                 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 813                         smp_processor_id(), duration,
 814                         current->comm, task_pid_nr(current));
 815                 report_cpu_status();
 816                 print_modules();
 817                 print_irqtrace_events(current);
 818                 if (regs)
 819                         show_regs(regs);
 820                 else
 821                         dump_stack();
 822                 printk_cpu_sync_put_irqrestore(flags);
 823
 824                 if (softlockup_all_cpu_backtrace) {
 825                         trigger_allbutcpu_cpu_backtrace(smp_processor_id());
 826                         if (!softlockup_panic)
 827                                 clear_bit_unlock(0, &soft_lockup_nmi_warn);
 828                 }
 829
 830                 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 831                 if (softlockup_panic)
 832                         panic("softlockup: hung tasks");
 833         }
 834
 835         return HRTIMER_RESTART;
 836 }
 837
 838 static void watchdog_enable(unsigned int cpu)
 839 {
 840         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 841         struct completion *done = this_cpu_ptr(&softlockup_completion);
 842
 843         WARN_ON_ONCE(cpu != smp_processor_id());
 844
 845         init_completion(done);
 846         complete(done);
 847
 848         /*
 849          * Start the timer first to prevent the hardlockup watchdog triggering
 850          * before the timer has a chance to fire.
 851          */
 852         hrtimer_setup(hrtimer, watchdog_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
 853         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 854                       HRTIMER_MODE_REL_PINNED_HARD);
 855
 856         /* Initialize timestamp */
 857         update_touch_ts();
 858         /* Enable the hardlockup detector */
 859         if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)
 860                 watchdog_hardlockup_enable(cpu);
 861 }
 862
 863 static void watchdog_disable(unsigned int cpu)
 864 {
 865         struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 866
 867         WARN_ON_ONCE(cpu != smp_processor_id());
 868
 869         /*
 870          * Disable the hardlockup detector first. That prevents that a large
 871          * delay between disabling the timer and disabling the hardlockup
 872          * detector causes a false positive.
 873          */
 874         watchdog_hardlockup_disable(cpu);
 875         hrtimer_cancel(hrtimer);
 876         wait_for_completion(this_cpu_ptr(&softlockup_completion));
 877 }
 878
 879 static int softlockup_stop_fn(void *data)
 880 {
 881         watchdog_disable(smp_processor_id());
 882         return 0;
 883 }
 884
 885 static void softlockup_stop_all(void)
 886 {
 887         int cpu;
 888
 889         if (!softlockup_initialized)
 890                 return;
 891
 892         for_each_cpu(cpu, &watchdog_allowed_mask)
 893                 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 894
 895         cpumask_clear(&watchdog_allowed_mask);
 896 }
 897
 898 static int softlockup_start_fn(void *data)
 899 {
 900         watchdog_enable(smp_processor_id());
 901         return 0;
 902 }
 903
 904 static void softlockup_start_all(void)
 905 {
 906         int cpu;
 907
 908         cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
 909         for_each_cpu(cpu, &watchdog_allowed_mask)
 910                 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 911 }
 912
 913 int lockup_detector_online_cpu(unsigned int cpu)
 914 {
 915         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 916                 watchdog_enable(cpu);
 917         return 0;
 918 }
 919
 920 int lockup_detector_offline_cpu(unsigned int cpu)
 921 {
 922         if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
 923                 watchdog_disable(cpu);
 924         return 0;
 925 }
 926
 927 static void __lockup_detector_reconfigure(bool thresh_changed)
 928 {
 929         cpus_read_lock();
 930         watchdog_hardlockup_stop();
 931
 932         softlockup_stop_all();
 933         /*
 934          * To prevent watchdog_timer_fn from using the old interval and
 935          * the new watchdog_thresh at the same time, which could lead to
 936          * false softlockup reports, it is necessary to update the
 937          * watchdog_thresh after the softlockup is completed.
 938          */
 939         if (thresh_changed)
 940                 watchdog_thresh = READ_ONCE(watchdog_thresh_next);
 941         set_sample_period();
 942         lockup_detector_update_enable();
 943         if (watchdog_enabled && watchdog_thresh)
 944                 softlockup_start_all();
 945
 946         watchdog_hardlockup_start();
 947         cpus_read_unlock();
 948 }
 949
 950 void lockup_detector_reconfigure(void)
 951 {
 952         mutex_lock(&watchdog_mutex);
 953         __lockup_detector_reconfigure(false);
 954         mutex_unlock(&watchdog_mutex);
 955 }
 956
 957 /*
 958  * Create the watchdog infrastructure and configure the detector(s).
 959  */
 960 static __init void lockup_detector_setup(void)
 961 {
 962         /*
 963          * If sysctl is off and watchdog got disabled on the command line,
 964          * nothing to do here.
 965          */
 966         lockup_detector_update_enable();
 967
 968         if (!IS_ENABLED(CONFIG_SYSCTL) &&
 969             !(watchdog_enabled && watchdog_thresh))
 970                 return;
 971
 972         mutex_lock(&watchdog_mutex);
 973         __lockup_detector_reconfigure(false);
 974         softlockup_initialized = true;
 975         mutex_unlock(&watchdog_mutex);
 976 }
 977
 978 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 979 static void __lockup_detector_reconfigure(bool thresh_changed)
 980 {
 981         cpus_read_lock();
 982         watchdog_hardlockup_stop();
 983         if (thresh_changed)
 984                 watchdog_thresh = READ_ONCE(watchdog_thresh_next);
 985         lockup_detector_update_enable();
 986         watchdog_hardlockup_start();
 987         cpus_read_unlock();
 988 }
 989 void lockup_detector_reconfigure(void)
 990 {
 991         __lockup_detector_reconfigure(false);
 992 }
 993 static inline void lockup_detector_setup(void)
 994 {
 995         __lockup_detector_reconfigure(false);
 996 }
 997 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 998
 999 /**
1000  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
1001  *
1002  * Special interface for parisc. It prevents lockup detector warnings from
1003  * the default pm_poweroff() function which busy loops forever.
1004  */
1005 void lockup_detector_soft_poweroff(void)
1006 {
1007         watchdog_enabled = 0;
1008 }
1009
1010 #ifdef CONFIG_SYSCTL
1011
1012 /* Propagate any changes to the watchdog infrastructure */
1013 static void proc_watchdog_update(bool thresh_changed)
1014 {
1015         /* Remove impossible cpus to keep sysctl output clean. */
1016         cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
1017         __lockup_detector_reconfigure(thresh_changed);
1018 }
1019
1020 /*
1021  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
1022  *
1023  * caller             | table->data points to            | 'which'
1024  * -------------------|----------------------------------|-------------------------------
1025  * proc_watchdog      | watchdog_user_enabled            | WATCHDOG_HARDLOCKUP_ENABLED |
1026  *                    |                                  | WATCHDOG_SOFTOCKUP_ENABLED
1027  * -------------------|----------------------------------|-------------------------------
1028  * proc_nmi_watchdog  | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED
1029  * -------------------|----------------------------------|-------------------------------
1030  * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED
1031  */
1032 static int proc_watchdog_common(int which, const struct ctl_table *table, int write,
1033                                 void *buffer, size_t *lenp, loff_t *ppos)
1034 {
1035         int err, old, *param = table->data;
1036
1037         mutex_lock(&watchdog_mutex);
1038
1039         old = *param;
1040         if (!write) {
1041                 /*
1042                  * On read synchronize the userspace interface. This is a
1043                  * racy snapshot.
1044                  */
1045                 *param = (watchdog_enabled & which) != 0;
1046                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1047                 *param = old;
1048         } else {
1049                 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1050                 if (!err && old != READ_ONCE(*param))
1051                         proc_watchdog_update(false);
1052         }
1053         mutex_unlock(&watchdog_mutex);
1054         return err;
1055 }
1056
1057 /*
1058  * /proc/sys/kernel/watchdog
1059  */
1060 static int proc_watchdog(const struct ctl_table *table, int write,
1061                          void *buffer, size_t *lenp, loff_t *ppos)
1062 {
1063         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED |
1064                                     WATCHDOG_SOFTOCKUP_ENABLED,
1065                                     table, write, buffer, lenp, ppos);
1066 }
1067
1068 /*
1069  * /proc/sys/kernel/nmi_watchdog
1070  */
1071 static int proc_nmi_watchdog(const struct ctl_table *table, int write,
1072                              void *buffer, size_t *lenp, loff_t *ppos)
1073 {
1074         if (!watchdog_hardlockup_available && write)
1075                 return -ENOTSUPP;
1076         return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED,
1077                                     table, write, buffer, lenp, ppos);
1078 }
1079
1080 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
1081 /*
1082  * /proc/sys/kernel/soft_watchdog
1083  */
1084 static int proc_soft_watchdog(const struct ctl_table *table, int write,
1085                               void *buffer, size_t *lenp, loff_t *ppos)
1086 {
1087         return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED,
1088                                     table, write, buffer, lenp, ppos);
1089 }
1090 #endif
1091
1092 /*
1093  * /proc/sys/kernel/watchdog_thresh
1094  */
1095 static int proc_watchdog_thresh(const struct ctl_table *table, int write,
1096                                 void *buffer, size_t *lenp, loff_t *ppos)
1097 {
1098         int err, old;
1099
1100         mutex_lock(&watchdog_mutex);
1101
1102         watchdog_thresh_next = READ_ONCE(watchdog_thresh);
1103
1104         old = watchdog_thresh_next;
1105         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
1106
1107         if (!err && write && old != READ_ONCE(watchdog_thresh_next))
1108                 proc_watchdog_update(true);
1109
1110         mutex_unlock(&watchdog_mutex);
1111         return err;
1112 }
1113
1114 /*
1115  * The cpumask is the mask of possible cpus that the watchdog can run
1116  * on, not the mask of cpus it is actually running on.  This allows the
1117  * user to specify a mask that will include cpus that have not yet
1118  * been brought online, if desired.
1119  */
1120 static int proc_watchdog_cpumask(const struct ctl_table *table, int write,
1121                                  void *buffer, size_t *lenp, loff_t *ppos)
1122 {
1123         int err;
1124
1125         mutex_lock(&watchdog_mutex);
1126
1127         err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1128         if (!err && write)
1129                 proc_watchdog_update(false);
1130
1131         mutex_unlock(&watchdog_mutex);
1132         return err;
1133 }
1134
1135 static const int sixty = 60;
1136
1137 static const struct ctl_table watchdog_sysctls[] = {
1138         {
1139                 .procname       = "watchdog",
1140                 .data           = &watchdog_user_enabled,
1141                 .maxlen         = sizeof(int),
1142                 .mode           = 0644,
1143                 .proc_handler   = proc_watchdog,
1144                 .extra1         = SYSCTL_ZERO,
1145                 .extra2         = SYSCTL_ONE,
1146         },
1147         {
1148                 .procname       = "watchdog_thresh",
1149                 .data           = &watchdog_thresh_next,
1150                 .maxlen         = sizeof(int),
1151                 .mode           = 0644,
1152                 .proc_handler   = proc_watchdog_thresh,
1153                 .extra1         = SYSCTL_ZERO,
1154                 .extra2         = (void *)&sixty,
1155         },
1156         {
1157                 .procname       = "watchdog_cpumask",
1158                 .data           = &watchdog_cpumask_bits,
1159                 .maxlen         = NR_CPUS,
1160                 .mode           = 0644,
1161                 .proc_handler   = proc_watchdog_cpumask,
1162         },
1163 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
1164         {
1165                 .procname       = "soft_watchdog",
1166                 .data           = &watchdog_softlockup_user_enabled,
1167                 .maxlen         = sizeof(int),
1168                 .mode           = 0644,
1169                 .proc_handler   = proc_soft_watchdog,
1170                 .extra1         = SYSCTL_ZERO,
1171                 .extra2         = SYSCTL_ONE,
1172         },
1173         {
1174                 .procname       = "softlockup_panic",
1175                 .data           = &softlockup_panic,
1176                 .maxlen         = sizeof(int),
1177                 .mode           = 0644,
1178                 .proc_handler   = proc_dointvec_minmax,
1179                 .extra1         = SYSCTL_ZERO,
1180                 .extra2         = SYSCTL_ONE,
1181         },
1182 #ifdef CONFIG_SMP
1183         {
1184                 .procname       = "softlockup_all_cpu_backtrace",
1185                 .data           = &sysctl_softlockup_all_cpu_backtrace,
1186                 .maxlen         = sizeof(int),
1187                 .mode           = 0644,
1188                 .proc_handler   = proc_dointvec_minmax,
1189                 .extra1         = SYSCTL_ZERO,
1190                 .extra2         = SYSCTL_ONE,
1191         },
1192 #endif /* CONFIG_SMP */
1193 #endif
1194 #ifdef CONFIG_HARDLOCKUP_DETECTOR
1195         {
1196                 .procname       = "hardlockup_panic",
1197                 .data           = &hardlockup_panic,
1198                 .maxlen         = sizeof(int),
1199                 .mode           = 0644,
1200                 .proc_handler   = proc_dointvec_minmax,
1201                 .extra1         = SYSCTL_ZERO,
1202                 .extra2         = SYSCTL_ONE,
1203         },
1204 #ifdef CONFIG_SMP
1205         {
1206                 .procname       = "hardlockup_all_cpu_backtrace",
1207                 .data           = &sysctl_hardlockup_all_cpu_backtrace,
1208                 .maxlen         = sizeof(int),
1209                 .mode           = 0644,
1210                 .proc_handler   = proc_dointvec_minmax,
1211                 .extra1         = SYSCTL_ZERO,
1212                 .extra2         = SYSCTL_ONE,
1213         },
1214 #endif /* CONFIG_SMP */
1215 #endif
1216 };
1217
1218 static struct ctl_table watchdog_hardlockup_sysctl[] = {
1219         {
1220                 .procname       = "nmi_watchdog",
1221                 .data           = &watchdog_hardlockup_user_enabled,
1222                 .maxlen         = sizeof(int),
1223                 .mode           = 0444,
1224                 .proc_handler   = proc_nmi_watchdog,
1225                 .extra1         = SYSCTL_ZERO,
1226                 .extra2         = SYSCTL_ONE,
1227         },
1228 };
1229
1230 static void __init watchdog_sysctl_init(void)
1231 {
1232         register_sysctl_init("kernel", watchdog_sysctls);
1233
1234         if (watchdog_hardlockup_available)
1235                 watchdog_hardlockup_sysctl[0].mode = 0644;
1236         register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
1237 }
1238
1239 #else
1240 #define watchdog_sysctl_init() do { } while (0)
1241 #endif /* CONFIG_SYSCTL */
1242
1243 static void __init lockup_detector_delay_init(struct work_struct *work);
1244 static bool allow_lockup_detector_init_retry __initdata;
1245
1246 static struct work_struct detector_work __initdata =
1247                 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
1248
1249 static void __init lockup_detector_delay_init(struct work_struct *work)
1250 {
1251         int ret;
1252
1253         ret = watchdog_hardlockup_probe();
1254         if (ret) {
1255                 if (ret == -ENODEV)
1256                         pr_info("NMI not fully supported\n");
1257                 else
1258                         pr_info("Delayed init of the lockup detector failed: %d\n", ret);
1259                 pr_info("Hard watchdog permanently disabled\n");
1260                 return;
1261         }
1262
1263         allow_lockup_detector_init_retry = false;
1264
1265         watchdog_hardlockup_available = true;
1266         lockup_detector_setup();
1267 }
1268
1269 /*
1270  * lockup_detector_retry_init - retry init lockup detector if possible.
1271  *
1272  * Retry hardlockup detector init. It is useful when it requires some
1273  * functionality that has to be initialized later on a particular
1274  * platform.
1275  */
1276 void __init lockup_detector_retry_init(void)
1277 {
1278         /* Must be called before late init calls */
1279         if (!allow_lockup_detector_init_retry)
1280                 return;
1281
1282         schedule_work(&detector_work);
1283 }
1284
1285 /*
1286  * Ensure that optional delayed hardlockup init is proceed before
1287  * the init code and memory is freed.
1288  */
1289 static int __init lockup_detector_check(void)
1290 {
1291         /* Prevent any later retry. */
1292         allow_lockup_detector_init_retry = false;
1293
1294         /* Make sure no work is pending. */
1295         flush_work(&detector_work);
1296
1297         watchdog_sysctl_init();
1298
1299         return 0;
1300
1301 }
1302 late_initcall_sync(lockup_detector_check);
1303
1304 void __init lockup_detector_init(void)
1305 {
1306         if (tick_nohz_full_enabled())
1307                 pr_info("Disabling watchdog on nohz_full cores by default\n");
1308
1309         cpumask_copy(&watchdog_cpumask,
1310                      housekeeping_cpumask(HK_TYPE_TIMER));
1311
1312         if (!watchdog_hardlockup_probe())
1313                 watchdog_hardlockup_available = true;
1314         else
1315                 allow_lockup_detector_init_retry = true;
1316
1317         lockup_detector_setup();
1318 }