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 * A poorly behaving BPF scheduler can trigger hard lockup by 201 * e.g. putting numerous affinitized tasks in a single queue and 202 * directing all CPUs at it. The following call can return true 203 * only once when sched_ext is enabled and will immediately 204 * abort the BPF scheduler and print out a warning message. 205 */ 206 if (scx_hardlockup(cpu)) 207 return; 208 209 /* Only print hardlockups once. */ 210 if (per_cpu(watchdog_hardlockup_warned, cpu)) 211 return; 212 213 /* 214 * Prevent multiple hard-lockup reports if one cpu is already 215 * engaged in dumping all cpu back traces. 216 */ 217 if (sysctl_hardlockup_all_cpu_backtrace) { 218 if (test_and_set_bit_lock(0, &hard_lockup_nmi_warn)) 219 return; 220 } 221 222 /* 223 * NOTE: we call printk_cpu_sync_get_irqsave() after printing 224 * the lockup message. While it would be nice to serialize 225 * that printout, we really want to make sure that if some 226 * other CPU somehow locked up while holding the lock associated 227 * with printk_cpu_sync_get_irqsave() that we can still at least 228 * get the message about the lockup out. 229 */ 230 pr_emerg("CPU%u: Watchdog detected hard LOCKUP on cpu %u\n", this_cpu, cpu); 231 printk_cpu_sync_get_irqsave(flags); 232 233 print_modules(); 234 print_irqtrace_events(current); 235 if (cpu == this_cpu) { 236 if (regs) 237 show_regs(regs); 238 else 239 dump_stack(); 240 printk_cpu_sync_put_irqrestore(flags); 241 } else { 242 printk_cpu_sync_put_irqrestore(flags); 243 trigger_single_cpu_backtrace(cpu); 244 } 245 246 if (sysctl_hardlockup_all_cpu_backtrace) { 247 trigger_allbutcpu_cpu_backtrace(cpu); 248 if (!hardlockup_panic) 249 clear_bit_unlock(0, &hard_lockup_nmi_warn); 250 } 251 252 if (hardlockup_panic) 253 nmi_panic(regs, "Hard LOCKUP"); 254 255 per_cpu(watchdog_hardlockup_warned, cpu) = true; 256 } else { 257 per_cpu(watchdog_hardlockup_warned, cpu) = false; 258 } 259 } 260 261 #else /* CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */ 262 263 static inline void watchdog_hardlockup_kick(void) { } 264 265 #endif /* !CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER */ 266 267 /* 268 * These functions can be overridden based on the configured hardlockdup detector. 269 * 270 * watchdog_hardlockup_enable/disable can be implemented to start and stop when 271 * softlockup watchdog start and stop. The detector must select the 272 * SOFTLOCKUP_DETECTOR Kconfig. 273 */ 274 void __weak watchdog_hardlockup_enable(unsigned int cpu) { } 275 276 void __weak watchdog_hardlockup_disable(unsigned int cpu) { } 277 278 /* 279 * Watchdog-detector specific API. 280 * 281 * Return 0 when hardlockup watchdog is available, negative value otherwise. 282 * Note that the negative value means that a delayed probe might 283 * succeed later. 284 */ 285 int __weak __init watchdog_hardlockup_probe(void) 286 { 287 return -ENODEV; 288 } 289 290 /** 291 * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration 292 * 293 * The reconfiguration steps are: 294 * watchdog_hardlockup_stop(); 295 * update_variables(); 296 * watchdog_hardlockup_start(); 297 */ 298 void __weak watchdog_hardlockup_stop(void) { } 299 300 /** 301 * watchdog_hardlockup_start - Start the watchdog after reconfiguration 302 * 303 * Counterpart to watchdog_hardlockup_stop(). 304 * 305 * The following variables have been updated in update_variables() and 306 * contain the currently valid configuration: 307 * - watchdog_enabled 308 * - watchdog_thresh 309 * - watchdog_cpumask 310 */ 311 void __weak watchdog_hardlockup_start(void) { } 312 313 /** 314 * lockup_detector_update_enable - Update the sysctl enable bit 315 * 316 * Caller needs to make sure that the hard watchdogs are off, so this 317 * can't race with watchdog_hardlockup_disable(). 318 */ 319 static void lockup_detector_update_enable(void) 320 { 321 watchdog_enabled = 0; 322 if (!watchdog_user_enabled) 323 return; 324 if (watchdog_hardlockup_available && watchdog_hardlockup_user_enabled) 325 watchdog_enabled |= WATCHDOG_HARDLOCKUP_ENABLED; 326 if (watchdog_softlockup_user_enabled) 327 watchdog_enabled |= WATCHDOG_SOFTOCKUP_ENABLED; 328 } 329 330 #ifdef CONFIG_SOFTLOCKUP_DETECTOR 331 332 /* 333 * Delay the soflockup report when running a known slow code. 334 * It does _not_ affect the timestamp of the last successdul reschedule. 335 */ 336 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX 337 338 #ifdef CONFIG_SMP 339 int __read_mostly sysctl_softlockup_all_cpu_backtrace; 340 #endif 341 342 static struct cpumask watchdog_allowed_mask __read_mostly; 343 344 /* Global variables, exported for sysctl */ 345 unsigned int __read_mostly softlockup_panic = 346 IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC); 347 348 static bool softlockup_initialized __read_mostly; 349 static u64 __read_mostly sample_period; 350 351 #ifdef CONFIG_SYSFS 352 353 static unsigned int softlockup_count; 354 355 static ssize_t softlockup_count_show(struct kobject *kobj, struct kobj_attribute *attr, 356 char *page) 357 { 358 return sysfs_emit(page, "%u\n", softlockup_count); 359 } 360 361 static struct kobj_attribute softlockup_count_attr = __ATTR_RO(softlockup_count); 362 363 static __init int kernel_softlockup_sysfs_init(void) 364 { 365 sysfs_add_file_to_group(kernel_kobj, &softlockup_count_attr.attr, NULL); 366 return 0; 367 } 368 369 late_initcall(kernel_softlockup_sysfs_init); 370 371 #endif // CONFIG_SYSFS 372 373 /* Timestamp taken after the last successful reschedule. */ 374 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); 375 /* Timestamp of the last softlockup report. */ 376 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts); 377 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); 378 static DEFINE_PER_CPU(bool, softlockup_touch_sync); 379 static unsigned long soft_lockup_nmi_warn; 380 381 static int __init softlockup_panic_setup(char *str) 382 { 383 softlockup_panic = simple_strtoul(str, NULL, 0); 384 return 1; 385 } 386 __setup("softlockup_panic=", softlockup_panic_setup); 387 388 static int __init nowatchdog_setup(char *str) 389 { 390 watchdog_user_enabled = 0; 391 return 1; 392 } 393 __setup("nowatchdog", nowatchdog_setup); 394 395 static int __init nosoftlockup_setup(char *str) 396 { 397 watchdog_softlockup_user_enabled = 0; 398 return 1; 399 } 400 __setup("nosoftlockup", nosoftlockup_setup); 401 402 static int __init watchdog_thresh_setup(char *str) 403 { 404 get_option(&str, &watchdog_thresh); 405 return 1; 406 } 407 __setup("watchdog_thresh=", watchdog_thresh_setup); 408 409 #ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM 410 enum stats_per_group { 411 STATS_SYSTEM, 412 STATS_SOFTIRQ, 413 STATS_HARDIRQ, 414 STATS_IDLE, 415 NUM_STATS_PER_GROUP, 416 }; 417 418 static const enum cpu_usage_stat tracked_stats[NUM_STATS_PER_GROUP] = { 419 CPUTIME_SYSTEM, 420 CPUTIME_SOFTIRQ, 421 CPUTIME_IRQ, 422 CPUTIME_IDLE, 423 }; 424 425 static DEFINE_PER_CPU(u16, cpustat_old[NUM_STATS_PER_GROUP]); 426 static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]); 427 static DEFINE_PER_CPU(u8, cpustat_tail); 428 429 /* 430 * We don't need nanosecond resolution. A granularity of 16ms is 431 * sufficient for our precision, allowing us to use u16 to store 432 * cpustats, which will roll over roughly every ~1000 seconds. 433 * 2^24 ~= 16 * 10^6 434 */ 435 static u16 get_16bit_precision(u64 data_ns) 436 { 437 /* 438 * 2^24ns ~= 16.8ms 439 * Round to the nearest multiple of 16.8 milliseconds. 440 */ 441 return (data_ns + (1 << 23)) >> 24LL; 442 } 443 444 static void update_cpustat(void) 445 { 446 int i; 447 u8 util; 448 u16 old_stat, new_stat; 449 struct kernel_cpustat kcpustat; 450 u64 *cpustat = kcpustat.cpustat; 451 u8 tail = __this_cpu_read(cpustat_tail); 452 u16 sample_period_16 = get_16bit_precision(sample_period); 453 454 kcpustat_cpu_fetch(&kcpustat, smp_processor_id()); 455 456 for (i = 0; i < NUM_STATS_PER_GROUP; i++) { 457 old_stat = __this_cpu_read(cpustat_old[i]); 458 new_stat = get_16bit_precision(cpustat[tracked_stats[i]]); 459 util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16); 460 /* 461 * Since we use 16-bit precision, the raw data will undergo 462 * integer division, which may sometimes result in data loss, 463 * and then result might exceed 100%. To avoid confusion, 464 * we enforce a 100% display cap when calculations exceed this threshold. 465 */ 466 if (util > 100) 467 util = 100; 468 __this_cpu_write(cpustat_util[tail][i], util); 469 __this_cpu_write(cpustat_old[i], new_stat); 470 } 471 472 __this_cpu_write(cpustat_tail, (tail + 1) % NUM_SAMPLE_PERIODS); 473 } 474 475 static void print_cpustat(void) 476 { 477 int i, group; 478 u8 tail = __this_cpu_read(cpustat_tail); 479 u64 sample_period_msecond = sample_period; 480 481 do_div(sample_period_msecond, NSEC_PER_MSEC); 482 483 /* 484 * Outputting the "watchdog" prefix on every line is redundant and not 485 * concise, and the original alarm information is sufficient for 486 * positioning in logs, hence here printk() is used instead of pr_crit(). 487 */ 488 printk(KERN_CRIT "CPU#%d Utilization every %llums during lockup:\n", 489 smp_processor_id(), sample_period_msecond); 490 491 for (i = 0; i < NUM_SAMPLE_PERIODS; i++) { 492 group = (tail + i) % NUM_SAMPLE_PERIODS; 493 printk(KERN_CRIT "\t#%d: %3u%% system,\t%3u%% softirq,\t" 494 "%3u%% hardirq,\t%3u%% idle\n", i + 1, 495 __this_cpu_read(cpustat_util[group][STATS_SYSTEM]), 496 __this_cpu_read(cpustat_util[group][STATS_SOFTIRQ]), 497 __this_cpu_read(cpustat_util[group][STATS_HARDIRQ]), 498 __this_cpu_read(cpustat_util[group][STATS_IDLE])); 499 } 500 } 501 502 #define HARDIRQ_PERCENT_THRESH 50 503 #define NUM_HARDIRQ_REPORT 5 504 struct irq_counts { 505 int irq; 506 u32 counts; 507 }; 508 509 static DEFINE_PER_CPU(bool, snapshot_taken); 510 511 /* Tabulate the most frequent interrupts. */ 512 static void tabulate_irq_count(struct irq_counts *irq_counts, int irq, u32 counts, int rank) 513 { 514 int i; 515 struct irq_counts new_count = {irq, counts}; 516 517 for (i = 0; i < rank; i++) { 518 if (counts > irq_counts[i].counts) 519 swap(new_count, irq_counts[i]); 520 } 521 } 522 523 /* 524 * If the hardirq time exceeds HARDIRQ_PERCENT_THRESH% of the sample_period, 525 * then the cause of softlockup might be interrupt storm. In this case, it 526 * would be useful to start interrupt counting. 527 */ 528 static bool need_counting_irqs(void) 529 { 530 u8 util; 531 int tail = __this_cpu_read(cpustat_tail); 532 533 tail = (tail + NUM_HARDIRQ_REPORT - 1) % NUM_HARDIRQ_REPORT; 534 util = __this_cpu_read(cpustat_util[tail][STATS_HARDIRQ]); 535 return util > HARDIRQ_PERCENT_THRESH; 536 } 537 538 static void start_counting_irqs(void) 539 { 540 if (!__this_cpu_read(snapshot_taken)) { 541 kstat_snapshot_irqs(); 542 __this_cpu_write(snapshot_taken, true); 543 } 544 } 545 546 static void stop_counting_irqs(void) 547 { 548 __this_cpu_write(snapshot_taken, false); 549 } 550 551 static void print_irq_counts(void) 552 { 553 unsigned int i, count; 554 struct irq_counts irq_counts_sorted[NUM_HARDIRQ_REPORT] = { 555 {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0} 556 }; 557 558 if (__this_cpu_read(snapshot_taken)) { 559 for_each_active_irq(i) { 560 count = kstat_get_irq_since_snapshot(i); 561 tabulate_irq_count(irq_counts_sorted, i, count, NUM_HARDIRQ_REPORT); 562 } 563 564 /* 565 * Outputting the "watchdog" prefix on every line is redundant and not 566 * concise, and the original alarm information is sufficient for 567 * positioning in logs, hence here printk() is used instead of pr_crit(). 568 */ 569 printk(KERN_CRIT "CPU#%d Detect HardIRQ Time exceeds %d%%. Most frequent HardIRQs:\n", 570 smp_processor_id(), HARDIRQ_PERCENT_THRESH); 571 572 for (i = 0; i < NUM_HARDIRQ_REPORT; i++) { 573 if (irq_counts_sorted[i].irq == -1) 574 break; 575 576 printk(KERN_CRIT "\t#%u: %-10u\tirq#%d\n", 577 i + 1, irq_counts_sorted[i].counts, 578 irq_counts_sorted[i].irq); 579 } 580 581 /* 582 * If the hardirq time is less than HARDIRQ_PERCENT_THRESH% in the last 583 * sample_period, then we suspect the interrupt storm might be subsiding. 584 */ 585 if (!need_counting_irqs()) 586 stop_counting_irqs(); 587 } 588 } 589 590 static void report_cpu_status(void) 591 { 592 print_cpustat(); 593 print_irq_counts(); 594 } 595 #else 596 static inline void update_cpustat(void) { } 597 static inline void report_cpu_status(void) { } 598 static inline bool need_counting_irqs(void) { return false; } 599 static inline void start_counting_irqs(void) { } 600 static inline void stop_counting_irqs(void) { } 601 #endif 602 603 /* 604 * Hard-lockup warnings should be triggered after just a few seconds. Soft- 605 * lockups can have false positives under extreme conditions. So we generally 606 * want a higher threshold for soft lockups than for hard lockups. So we couple 607 * the thresholds with a factor: we make the soft threshold twice the amount of 608 * time the hard threshold is. 609 */ 610 static int get_softlockup_thresh(void) 611 { 612 return watchdog_thresh * 2; 613 } 614 615 /* 616 * Returns seconds, approximately. We don't need nanosecond 617 * resolution, and we don't need to waste time with a big divide when 618 * 2^30ns == 1.074s. 619 */ 620 static unsigned long get_timestamp(void) 621 { 622 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */ 623 } 624 625 static void set_sample_period(void) 626 { 627 /* 628 * convert watchdog_thresh from seconds to ns 629 * the divide by 5 is to give hrtimer several chances (two 630 * or three with the current relation between the soft 631 * and hard thresholds) to increment before the 632 * hardlockup detector generates a warning 633 */ 634 sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / NUM_SAMPLE_PERIODS); 635 watchdog_update_hrtimer_threshold(sample_period); 636 } 637 638 static void update_report_ts(void) 639 { 640 __this_cpu_write(watchdog_report_ts, get_timestamp()); 641 } 642 643 /* Commands for resetting the watchdog */ 644 static void update_touch_ts(void) 645 { 646 __this_cpu_write(watchdog_touch_ts, get_timestamp()); 647 update_report_ts(); 648 } 649 650 /** 651 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls 652 * 653 * Call when the scheduler may have stalled for legitimate reasons 654 * preventing the watchdog task from executing - e.g. the scheduler 655 * entering idle state. This should only be used for scheduler events. 656 * Use touch_softlockup_watchdog() for everything else. 657 */ 658 notrace void touch_softlockup_watchdog_sched(void) 659 { 660 /* 661 * Preemption can be enabled. It doesn't matter which CPU's watchdog 662 * report period gets restarted here, so use the raw_ operation. 663 */ 664 raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT); 665 } 666 667 notrace void touch_softlockup_watchdog(void) 668 { 669 touch_softlockup_watchdog_sched(); 670 wq_watchdog_touch(raw_smp_processor_id()); 671 } 672 EXPORT_SYMBOL(touch_softlockup_watchdog); 673 674 void touch_all_softlockup_watchdogs(void) 675 { 676 int cpu; 677 678 /* 679 * watchdog_mutex cannpt be taken here, as this might be called 680 * from (soft)interrupt context, so the access to 681 * watchdog_allowed_cpumask might race with a concurrent update. 682 * 683 * The watchdog time stamp can race against a concurrent real 684 * update as well, the only side effect might be a cycle delay for 685 * the softlockup check. 686 */ 687 for_each_cpu(cpu, &watchdog_allowed_mask) { 688 per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT; 689 wq_watchdog_touch(cpu); 690 } 691 } 692 693 void touch_softlockup_watchdog_sync(void) 694 { 695 __this_cpu_write(softlockup_touch_sync, true); 696 __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT); 697 } 698 699 static int is_softlockup(unsigned long touch_ts, 700 unsigned long period_ts, 701 unsigned long now) 702 { 703 if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) { 704 /* 705 * If period_ts has not been updated during a sample_period, then 706 * in the subsequent few sample_periods, period_ts might also not 707 * be updated, which could indicate a potential softlockup. In 708 * this case, if we suspect the cause of the potential softlockup 709 * might be interrupt storm, then we need to count the interrupts 710 * to find which interrupt is storming. 711 */ 712 if (time_after_eq(now, period_ts + get_softlockup_thresh() / NUM_SAMPLE_PERIODS) && 713 need_counting_irqs()) 714 start_counting_irqs(); 715 716 /* 717 * A poorly behaving BPF scheduler can live-lock the system into 718 * soft lockups. Tell sched_ext to try ejecting the BPF 719 * scheduler when close to a soft lockup. 720 */ 721 if (time_after_eq(now, period_ts + get_softlockup_thresh() * 3 / 4)) 722 scx_softlockup(now - touch_ts); 723 724 /* Warn about unreasonable delays. */ 725 if (time_after(now, period_ts + get_softlockup_thresh())) 726 return now - touch_ts; 727 } 728 return 0; 729 } 730 731 /* watchdog detector functions */ 732 static DEFINE_PER_CPU(struct completion, softlockup_completion); 733 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work); 734 735 /* 736 * The watchdog feed function - touches the timestamp. 737 * 738 * It only runs once every sample_period seconds (4 seconds by 739 * default) to reset the softlockup timestamp. If this gets delayed 740 * for more than 2*watchdog_thresh seconds then the debug-printout 741 * triggers in watchdog_timer_fn(). 742 */ 743 static int softlockup_fn(void *data) 744 { 745 update_touch_ts(); 746 stop_counting_irqs(); 747 complete(this_cpu_ptr(&softlockup_completion)); 748 749 return 0; 750 } 751 752 /* watchdog kicker functions */ 753 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 754 { 755 unsigned long touch_ts, period_ts, now; 756 struct pt_regs *regs = get_irq_regs(); 757 int duration; 758 int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace; 759 unsigned long flags; 760 761 if (!watchdog_enabled) 762 return HRTIMER_NORESTART; 763 764 /* 765 * pass the buddy check if a panic is in process 766 */ 767 if (panic_in_progress()) 768 return HRTIMER_NORESTART; 769 770 watchdog_hardlockup_kick(); 771 772 /* kick the softlockup detector */ 773 if (completion_done(this_cpu_ptr(&softlockup_completion))) { 774 reinit_completion(this_cpu_ptr(&softlockup_completion)); 775 stop_one_cpu_nowait(smp_processor_id(), 776 softlockup_fn, NULL, 777 this_cpu_ptr(&softlockup_stop_work)); 778 } 779 780 /* .. and repeat */ 781 hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); 782 783 /* 784 * Read the current timestamp first. It might become invalid anytime 785 * when a virtual machine is stopped by the host or when the watchog 786 * is touched from NMI. 787 */ 788 now = get_timestamp(); 789 /* 790 * If a virtual machine is stopped by the host it can look to 791 * the watchdog like a soft lockup. This function touches the watchdog. 792 */ 793 kvm_check_and_clear_guest_paused(); 794 /* 795 * The stored timestamp is comparable with @now only when not touched. 796 * It might get touched anytime from NMI. Make sure that is_softlockup() 797 * uses the same (valid) value. 798 */ 799 period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts)); 800 801 update_cpustat(); 802 803 /* Reset the interval when touched by known problematic code. */ 804 if (period_ts == SOFTLOCKUP_DELAY_REPORT) { 805 if (unlikely(__this_cpu_read(softlockup_touch_sync))) { 806 /* 807 * If the time stamp was touched atomically 808 * make sure the scheduler tick is up to date. 809 */ 810 __this_cpu_write(softlockup_touch_sync, false); 811 sched_clock_tick(); 812 } 813 814 update_report_ts(); 815 return HRTIMER_RESTART; 816 } 817 818 /* Check for a softlockup. */ 819 touch_ts = __this_cpu_read(watchdog_touch_ts); 820 duration = is_softlockup(touch_ts, period_ts, now); 821 if (unlikely(duration)) { 822 #ifdef CONFIG_SYSFS 823 ++softlockup_count; 824 #endif 825 826 /* 827 * Prevent multiple soft-lockup reports if one cpu is already 828 * engaged in dumping all cpu back traces. 829 */ 830 if (softlockup_all_cpu_backtrace) { 831 if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn)) 832 return HRTIMER_RESTART; 833 } 834 835 /* Start period for the next softlockup warning. */ 836 update_report_ts(); 837 838 printk_cpu_sync_get_irqsave(flags); 839 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", 840 smp_processor_id(), duration, 841 current->comm, task_pid_nr(current)); 842 report_cpu_status(); 843 print_modules(); 844 print_irqtrace_events(current); 845 if (regs) 846 show_regs(regs); 847 else 848 dump_stack(); 849 printk_cpu_sync_put_irqrestore(flags); 850 851 if (softlockup_all_cpu_backtrace) { 852 trigger_allbutcpu_cpu_backtrace(smp_processor_id()); 853 if (!softlockup_panic) 854 clear_bit_unlock(0, &soft_lockup_nmi_warn); 855 } 856 857 add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); 858 if (softlockup_panic) 859 panic("softlockup: hung tasks"); 860 } 861 862 return HRTIMER_RESTART; 863 } 864 865 static void watchdog_enable(unsigned int cpu) 866 { 867 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); 868 struct completion *done = this_cpu_ptr(&softlockup_completion); 869 870 WARN_ON_ONCE(cpu != smp_processor_id()); 871 872 init_completion(done); 873 complete(done); 874 875 /* 876 * Start the timer first to prevent the hardlockup watchdog triggering 877 * before the timer has a chance to fire. 878 */ 879 hrtimer_setup(hrtimer, watchdog_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); 880 hrtimer_start(hrtimer, ns_to_ktime(sample_period), 881 HRTIMER_MODE_REL_PINNED_HARD); 882 883 /* Initialize timestamp */ 884 update_touch_ts(); 885 /* Enable the hardlockup detector */ 886 if (watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED) 887 watchdog_hardlockup_enable(cpu); 888 } 889 890 static void watchdog_disable(unsigned int cpu) 891 { 892 struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer); 893 894 WARN_ON_ONCE(cpu != smp_processor_id()); 895 896 /* 897 * Disable the hardlockup detector first. That prevents that a large 898 * delay between disabling the timer and disabling the hardlockup 899 * detector causes a false positive. 900 */ 901 watchdog_hardlockup_disable(cpu); 902 hrtimer_cancel(hrtimer); 903 wait_for_completion(this_cpu_ptr(&softlockup_completion)); 904 } 905 906 static int softlockup_stop_fn(void *data) 907 { 908 watchdog_disable(smp_processor_id()); 909 return 0; 910 } 911 912 static void softlockup_stop_all(void) 913 { 914 int cpu; 915 916 if (!softlockup_initialized) 917 return; 918 919 for_each_cpu(cpu, &watchdog_allowed_mask) 920 smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false); 921 922 cpumask_clear(&watchdog_allowed_mask); 923 } 924 925 static int softlockup_start_fn(void *data) 926 { 927 watchdog_enable(smp_processor_id()); 928 return 0; 929 } 930 931 static void softlockup_start_all(void) 932 { 933 int cpu; 934 935 cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask); 936 for_each_cpu(cpu, &watchdog_allowed_mask) 937 smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false); 938 } 939 940 int lockup_detector_online_cpu(unsigned int cpu) 941 { 942 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask)) 943 watchdog_enable(cpu); 944 return 0; 945 } 946 947 int lockup_detector_offline_cpu(unsigned int cpu) 948 { 949 if (cpumask_test_cpu(cpu, &watchdog_allowed_mask)) 950 watchdog_disable(cpu); 951 return 0; 952 } 953 954 static void __lockup_detector_reconfigure(bool thresh_changed) 955 { 956 cpus_read_lock(); 957 watchdog_hardlockup_stop(); 958 959 softlockup_stop_all(); 960 /* 961 * To prevent watchdog_timer_fn from using the old interval and 962 * the new watchdog_thresh at the same time, which could lead to 963 * false softlockup reports, it is necessary to update the 964 * watchdog_thresh after the softlockup is completed. 965 */ 966 if (thresh_changed) 967 watchdog_thresh = READ_ONCE(watchdog_thresh_next); 968 set_sample_period(); 969 lockup_detector_update_enable(); 970 if (watchdog_enabled && watchdog_thresh) 971 softlockup_start_all(); 972 973 watchdog_hardlockup_start(); 974 cpus_read_unlock(); 975 } 976 977 void lockup_detector_reconfigure(void) 978 { 979 mutex_lock(&watchdog_mutex); 980 __lockup_detector_reconfigure(false); 981 mutex_unlock(&watchdog_mutex); 982 } 983 984 /* 985 * Create the watchdog infrastructure and configure the detector(s). 986 */ 987 static __init void lockup_detector_setup(void) 988 { 989 /* 990 * If sysctl is off and watchdog got disabled on the command line, 991 * nothing to do here. 992 */ 993 lockup_detector_update_enable(); 994 995 if (!IS_ENABLED(CONFIG_SYSCTL) && 996 !(watchdog_enabled && watchdog_thresh)) 997 return; 998 999 mutex_lock(&watchdog_mutex); 1000 __lockup_detector_reconfigure(false); 1001 softlockup_initialized = true; 1002 mutex_unlock(&watchdog_mutex); 1003 } 1004 1005 #else /* CONFIG_SOFTLOCKUP_DETECTOR */ 1006 static void __lockup_detector_reconfigure(bool thresh_changed) 1007 { 1008 cpus_read_lock(); 1009 watchdog_hardlockup_stop(); 1010 if (thresh_changed) 1011 watchdog_thresh = READ_ONCE(watchdog_thresh_next); 1012 lockup_detector_update_enable(); 1013 watchdog_hardlockup_start(); 1014 cpus_read_unlock(); 1015 } 1016 void lockup_detector_reconfigure(void) 1017 { 1018 __lockup_detector_reconfigure(false); 1019 } 1020 static inline void lockup_detector_setup(void) 1021 { 1022 __lockup_detector_reconfigure(false); 1023 } 1024 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ 1025 1026 /** 1027 * lockup_detector_soft_poweroff - Interface to stop lockup detector(s) 1028 * 1029 * Special interface for parisc. It prevents lockup detector warnings from 1030 * the default pm_poweroff() function which busy loops forever. 1031 */ 1032 void lockup_detector_soft_poweroff(void) 1033 { 1034 watchdog_enabled = 0; 1035 } 1036 1037 #ifdef CONFIG_SYSCTL 1038 1039 /* Propagate any changes to the watchdog infrastructure */ 1040 static void proc_watchdog_update(bool thresh_changed) 1041 { 1042 /* Remove impossible cpus to keep sysctl output clean. */ 1043 cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); 1044 __lockup_detector_reconfigure(thresh_changed); 1045 } 1046 1047 /* 1048 * common function for watchdog, nmi_watchdog and soft_watchdog parameter 1049 * 1050 * caller | table->data points to | 'which' 1051 * -------------------|----------------------------------|------------------------------- 1052 * proc_watchdog | watchdog_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED | 1053 * | | WATCHDOG_SOFTOCKUP_ENABLED 1054 * -------------------|----------------------------------|------------------------------- 1055 * proc_nmi_watchdog | watchdog_hardlockup_user_enabled | WATCHDOG_HARDLOCKUP_ENABLED 1056 * -------------------|----------------------------------|------------------------------- 1057 * proc_soft_watchdog | watchdog_softlockup_user_enabled | WATCHDOG_SOFTOCKUP_ENABLED 1058 */ 1059 static int proc_watchdog_common(int which, const struct ctl_table *table, int write, 1060 void *buffer, size_t *lenp, loff_t *ppos) 1061 { 1062 int err, old, *param = table->data; 1063 1064 mutex_lock(&watchdog_mutex); 1065 1066 old = *param; 1067 if (!write) { 1068 /* 1069 * On read synchronize the userspace interface. This is a 1070 * racy snapshot. 1071 */ 1072 *param = (watchdog_enabled & which) != 0; 1073 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 1074 *param = old; 1075 } else { 1076 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 1077 if (!err && old != READ_ONCE(*param)) 1078 proc_watchdog_update(false); 1079 } 1080 mutex_unlock(&watchdog_mutex); 1081 return err; 1082 } 1083 1084 /* 1085 * /proc/sys/kernel/watchdog 1086 */ 1087 static int proc_watchdog(const struct ctl_table *table, int write, 1088 void *buffer, size_t *lenp, loff_t *ppos) 1089 { 1090 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED | 1091 WATCHDOG_SOFTOCKUP_ENABLED, 1092 table, write, buffer, lenp, ppos); 1093 } 1094 1095 /* 1096 * /proc/sys/kernel/nmi_watchdog 1097 */ 1098 static int proc_nmi_watchdog(const struct ctl_table *table, int write, 1099 void *buffer, size_t *lenp, loff_t *ppos) 1100 { 1101 if (!watchdog_hardlockup_available && write) 1102 return -ENOTSUPP; 1103 return proc_watchdog_common(WATCHDOG_HARDLOCKUP_ENABLED, 1104 table, write, buffer, lenp, ppos); 1105 } 1106 1107 #ifdef CONFIG_SOFTLOCKUP_DETECTOR 1108 /* 1109 * /proc/sys/kernel/soft_watchdog 1110 */ 1111 static int proc_soft_watchdog(const struct ctl_table *table, int write, 1112 void *buffer, size_t *lenp, loff_t *ppos) 1113 { 1114 return proc_watchdog_common(WATCHDOG_SOFTOCKUP_ENABLED, 1115 table, write, buffer, lenp, ppos); 1116 } 1117 #endif 1118 1119 /* 1120 * /proc/sys/kernel/watchdog_thresh 1121 */ 1122 static int proc_watchdog_thresh(const struct ctl_table *table, int write, 1123 void *buffer, size_t *lenp, loff_t *ppos) 1124 { 1125 int err, old; 1126 1127 mutex_lock(&watchdog_mutex); 1128 1129 watchdog_thresh_next = READ_ONCE(watchdog_thresh); 1130 1131 old = watchdog_thresh_next; 1132 err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 1133 1134 if (!err && write && old != READ_ONCE(watchdog_thresh_next)) 1135 proc_watchdog_update(true); 1136 1137 mutex_unlock(&watchdog_mutex); 1138 return err; 1139 } 1140 1141 /* 1142 * The cpumask is the mask of possible cpus that the watchdog can run 1143 * on, not the mask of cpus it is actually running on. This allows the 1144 * user to specify a mask that will include cpus that have not yet 1145 * been brought online, if desired. 1146 */ 1147 static int proc_watchdog_cpumask(const struct ctl_table *table, int write, 1148 void *buffer, size_t *lenp, loff_t *ppos) 1149 { 1150 int err; 1151 1152 mutex_lock(&watchdog_mutex); 1153 1154 err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); 1155 if (!err && write) 1156 proc_watchdog_update(false); 1157 1158 mutex_unlock(&watchdog_mutex); 1159 return err; 1160 } 1161 1162 static const int sixty = 60; 1163 1164 static const struct ctl_table watchdog_sysctls[] = { 1165 { 1166 .procname = "watchdog", 1167 .data = &watchdog_user_enabled, 1168 .maxlen = sizeof(int), 1169 .mode = 0644, 1170 .proc_handler = proc_watchdog, 1171 .extra1 = SYSCTL_ZERO, 1172 .extra2 = SYSCTL_ONE, 1173 }, 1174 { 1175 .procname = "watchdog_thresh", 1176 .data = &watchdog_thresh_next, 1177 .maxlen = sizeof(int), 1178 .mode = 0644, 1179 .proc_handler = proc_watchdog_thresh, 1180 .extra1 = SYSCTL_ZERO, 1181 .extra2 = (void *)&sixty, 1182 }, 1183 { 1184 .procname = "watchdog_cpumask", 1185 .data = &watchdog_cpumask_bits, 1186 .maxlen = NR_CPUS, 1187 .mode = 0644, 1188 .proc_handler = proc_watchdog_cpumask, 1189 }, 1190 #ifdef CONFIG_SOFTLOCKUP_DETECTOR 1191 { 1192 .procname = "soft_watchdog", 1193 .data = &watchdog_softlockup_user_enabled, 1194 .maxlen = sizeof(int), 1195 .mode = 0644, 1196 .proc_handler = proc_soft_watchdog, 1197 .extra1 = SYSCTL_ZERO, 1198 .extra2 = SYSCTL_ONE, 1199 }, 1200 { 1201 .procname = "softlockup_panic", 1202 .data = &softlockup_panic, 1203 .maxlen = sizeof(int), 1204 .mode = 0644, 1205 .proc_handler = proc_dointvec_minmax, 1206 .extra1 = SYSCTL_ZERO, 1207 .extra2 = SYSCTL_ONE, 1208 }, 1209 #ifdef CONFIG_SMP 1210 { 1211 .procname = "softlockup_all_cpu_backtrace", 1212 .data = &sysctl_softlockup_all_cpu_backtrace, 1213 .maxlen = sizeof(int), 1214 .mode = 0644, 1215 .proc_handler = proc_dointvec_minmax, 1216 .extra1 = SYSCTL_ZERO, 1217 .extra2 = SYSCTL_ONE, 1218 }, 1219 #endif /* CONFIG_SMP */ 1220 #endif 1221 #ifdef CONFIG_HARDLOCKUP_DETECTOR 1222 { 1223 .procname = "hardlockup_panic", 1224 .data = &hardlockup_panic, 1225 .maxlen = sizeof(int), 1226 .mode = 0644, 1227 .proc_handler = proc_dointvec_minmax, 1228 .extra1 = SYSCTL_ZERO, 1229 .extra2 = SYSCTL_ONE, 1230 }, 1231 #ifdef CONFIG_SMP 1232 { 1233 .procname = "hardlockup_all_cpu_backtrace", 1234 .data = &sysctl_hardlockup_all_cpu_backtrace, 1235 .maxlen = sizeof(int), 1236 .mode = 0644, 1237 .proc_handler = proc_dointvec_minmax, 1238 .extra1 = SYSCTL_ZERO, 1239 .extra2 = SYSCTL_ONE, 1240 }, 1241 #endif /* CONFIG_SMP */ 1242 #endif 1243 }; 1244 1245 static struct ctl_table watchdog_hardlockup_sysctl[] = { 1246 { 1247 .procname = "nmi_watchdog", 1248 .data = &watchdog_hardlockup_user_enabled, 1249 .maxlen = sizeof(int), 1250 .mode = 0444, 1251 .proc_handler = proc_nmi_watchdog, 1252 .extra1 = SYSCTL_ZERO, 1253 .extra2 = SYSCTL_ONE, 1254 }, 1255 }; 1256 1257 static void __init watchdog_sysctl_init(void) 1258 { 1259 register_sysctl_init("kernel", watchdog_sysctls); 1260 1261 if (watchdog_hardlockup_available) 1262 watchdog_hardlockup_sysctl[0].mode = 0644; 1263 register_sysctl_init("kernel", watchdog_hardlockup_sysctl); 1264 } 1265 1266 #else 1267 #define watchdog_sysctl_init() do { } while (0) 1268 #endif /* CONFIG_SYSCTL */ 1269 1270 static void __init lockup_detector_delay_init(struct work_struct *work); 1271 static bool allow_lockup_detector_init_retry __initdata; 1272 1273 static struct work_struct detector_work __initdata = 1274 __WORK_INITIALIZER(detector_work, lockup_detector_delay_init); 1275 1276 static void __init lockup_detector_delay_init(struct work_struct *work) 1277 { 1278 int ret; 1279 1280 ret = watchdog_hardlockup_probe(); 1281 if (ret) { 1282 if (ret == -ENODEV) 1283 pr_info("NMI not fully supported\n"); 1284 else 1285 pr_info("Delayed init of the lockup detector failed: %d\n", ret); 1286 pr_info("Hard watchdog permanently disabled\n"); 1287 return; 1288 } 1289 1290 allow_lockup_detector_init_retry = false; 1291 1292 watchdog_hardlockup_available = true; 1293 lockup_detector_setup(); 1294 } 1295 1296 /* 1297 * lockup_detector_retry_init - retry init lockup detector if possible. 1298 * 1299 * Retry hardlockup detector init. It is useful when it requires some 1300 * functionality that has to be initialized later on a particular 1301 * platform. 1302 */ 1303 void __init lockup_detector_retry_init(void) 1304 { 1305 /* Must be called before late init calls */ 1306 if (!allow_lockup_detector_init_retry) 1307 return; 1308 1309 schedule_work(&detector_work); 1310 } 1311 1312 /* 1313 * Ensure that optional delayed hardlockup init is proceed before 1314 * the init code and memory is freed. 1315 */ 1316 static int __init lockup_detector_check(void) 1317 { 1318 /* Prevent any later retry. */ 1319 allow_lockup_detector_init_retry = false; 1320 1321 /* Make sure no work is pending. */ 1322 flush_work(&detector_work); 1323 1324 watchdog_sysctl_init(); 1325 1326 return 0; 1327 1328 } 1329 late_initcall_sync(lockup_detector_check); 1330 1331 void __init lockup_detector_init(void) 1332 { 1333 if (tick_nohz_full_enabled()) 1334 pr_info("Disabling watchdog on nohz_full cores by default\n"); 1335 1336 cpumask_copy(&watchdog_cpumask, 1337 housekeeping_cpumask(HK_TYPE_TIMER)); 1338 1339 if (!watchdog_hardlockup_probe()) 1340 watchdog_hardlockup_available = true; 1341 else 1342 allow_lockup_detector_init_retry = true; 1343 1344 lockup_detector_setup(); 1345 } 1346