kernel/watchdog.c

   1 /*
   2  * Detect hard and soft lockups on a system
   3  *
   4  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   5  *
   6  * Note: Most of this code is borrowed heavily from the original softlockup
   7  * detector, so thanks to Ingo for the initial implementation.
   8  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
   9  * to those contributors as well.
  10  */
  11
  12 #define pr_fmt(fmt) "NMI watchdog: " fmt
  13
  14 #include <linux/mm.h>
  15 #include <linux/cpu.h>
  16 #include <linux/nmi.h>
  17 #include <linux/init.h>
  18 #include <linux/delay.h>
  19 #include <linux/freezer.h>
  20 #include <linux/kthread.h>
  21 #include <linux/lockdep.h>
  22 #include <linux/notifier.h>
  23 #include <linux/module.h>
  24 #include <linux/sysctl.h>
  25
  26 #include <asm/irq_regs.h>
  27 #include <linux/perf_event.h>
  28
  29 int watchdog_enabled = 1;
  30 int __read_mostly watchdog_thresh = 10;
  31
  32 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
  33 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  34 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  35 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  36 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
  37 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  38 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  39 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
  40 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
  41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
  42 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
  43 #endif
  44
  45 /* boot commands */
  46 /*
  47  * Should we panic when a soft-lockup or hard-lockup occurs:
  48  */
  49 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  50 static int hardlockup_panic =
  51                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  52
  53 static int __init hardlockup_panic_setup(char *str)
  54 {
  55         if (!strncmp(str, "panic", 5))
  56                 hardlockup_panic = 1;
  57         else if (!strncmp(str, "nopanic", 7))
  58                 hardlockup_panic = 0;
  59         else if (!strncmp(str, "0", 1))
  60                 watchdog_enabled = 0;
  61         return 1;
  62 }
  63 __setup("nmi_watchdog=", hardlockup_panic_setup);
  64 #endif
  65
  66 unsigned int __read_mostly softlockup_panic =
  67                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
  68
  69 static int __init softlockup_panic_setup(char *str)
  70 {
  71         softlockup_panic = simple_strtoul(str, NULL, 0);
  72
  73         return 1;
  74 }
  75 __setup("softlockup_panic=", softlockup_panic_setup);
  76
  77 static int __init nowatchdog_setup(char *str)
  78 {
  79         watchdog_enabled = 0;
  80         return 1;
  81 }
  82 __setup("nowatchdog", nowatchdog_setup);
  83
  84 /* deprecated */
  85 static int __init nosoftlockup_setup(char *str)
  86 {
  87         watchdog_enabled = 0;
  88         return 1;
  89 }
  90 __setup("nosoftlockup", nosoftlockup_setup);
  91 /*  */
  92
  93 /*
  94  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
  95  * lockups can have false positives under extreme conditions. So we generally
  96  * want a higher threshold for soft lockups than for hard lockups. So we couple
  97  * the thresholds with a factor: we make the soft threshold twice the amount of
  98  * time the hard threshold is.
  99  */
 100 static int get_softlockup_thresh(void)
 101 {
 102         return watchdog_thresh * 2;
 103 }
 104
 105 /*
 106  * Returns seconds, approximately.  We don't need nanosecond
 107  * resolution, and we don't need to waste time with a big divide when
 108  * 2^30ns == 1.074s.
 109  */
 110 static unsigned long get_timestamp(int this_cpu)
 111 {
 112         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
 113 }
 114
 115 static unsigned long get_sample_period(void)
 116 {
 117         /*
 118          * convert watchdog_thresh from seconds to ns
 119          * the divide by 5 is to give hrtimer several chances (two
 120          * or three with the current relation between the soft
 121          * and hard thresholds) to increment before the
 122          * hardlockup detector generates a warning
 123          */
 124         return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
 125 }
 126
 127 /* Commands for resetting the watchdog */
 128 static void __touch_watchdog(void)
 129 {
 130         int this_cpu = smp_processor_id();
 131
 132         __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
 133 }
 134
 135 void touch_softlockup_watchdog(void)
 136 {
 137         __this_cpu_write(watchdog_touch_ts, 0);
 138 }
 139 EXPORT_SYMBOL(touch_softlockup_watchdog);
 140
 141 void touch_all_softlockup_watchdogs(void)
 142 {
 143         int cpu;
 144
 145         /*
 146          * this is done lockless
 147          * do we care if a 0 races with a timestamp?
 148          * all it means is the softlock check starts one cycle later
 149          */
 150         for_each_online_cpu(cpu)
 151                 per_cpu(watchdog_touch_ts, cpu) = 0;
 152 }
 153
 154 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 155 void touch_nmi_watchdog(void)
 156 {
 157         if (watchdog_enabled) {
 158                 unsigned cpu;
 159
 160                 for_each_present_cpu(cpu) {
 161                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
 162                                 per_cpu(watchdog_nmi_touch, cpu) = true;
 163                 }
 164         }
 165         touch_softlockup_watchdog();
 166 }
 167 EXPORT_SYMBOL(touch_nmi_watchdog);
 168
 169 #endif
 170
 171 void touch_softlockup_watchdog_sync(void)
 172 {
 173         __raw_get_cpu_var(softlockup_touch_sync) = true;
 174         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 175 }
 176
 177 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 178 /* watchdog detector functions */
 179 static int is_hardlockup(void)
 180 {
 181         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 182
 183         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 184                 return 1;
 185
 186         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 187         return 0;
 188 }
 189 #endif
 190
 191 static int is_softlockup(unsigned long touch_ts)
 192 {
 193         unsigned long now = get_timestamp(smp_processor_id());
 194
 195         /* Warn about unreasonable delays: */
 196         if (time_after(now, touch_ts + get_softlockup_thresh()))
 197                 return now - touch_ts;
 198
 199         return 0;
 200 }
 201
 202 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 203
 204 static struct perf_event_attr wd_hw_attr = {
 205         .type           = PERF_TYPE_HARDWARE,
 206         .config         = PERF_COUNT_HW_CPU_CYCLES,
 207         .size           = sizeof(struct perf_event_attr),
 208         .pinned         = 1,
 209         .disabled       = 1,
 210 };
 211
 212 /* Callback function for perf event subsystem */
 213 static void watchdog_overflow_callback(struct perf_event *event,
 214                  struct perf_sample_data *data,
 215                  struct pt_regs *regs)
 216 {
 217         /* Ensure the watchdog never gets throttled */
 218         event->hw.interrupts = 0;
 219
 220         if (__this_cpu_read(watchdog_nmi_touch) == true) {
 221                 __this_cpu_write(watchdog_nmi_touch, false);
 222                 return;
 223         }
 224
 225         /* check for a hardlockup
 226          * This is done by making sure our timer interrupt
 227          * is incrementing.  The timer interrupt should have
 228          * fired multiple times before we overflow'd.  If it hasn't
 229          * then this is a good indication the cpu is stuck
 230          */
 231         if (is_hardlockup()) {
 232                 int this_cpu = smp_processor_id();
 233
 234                 /* only print hardlockups once */
 235                 if (__this_cpu_read(hard_watchdog_warn) == true)
 236                         return;
 237
 238                 if (hardlockup_panic)
 239                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 240                 else
 241                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 242
 243                 __this_cpu_write(hard_watchdog_warn, true);
 244                 return;
 245         }
 246
 247         __this_cpu_write(hard_watchdog_warn, false);
 248         return;
 249 }
 250 static void watchdog_interrupt_count(void)
 251 {
 252         __this_cpu_inc(hrtimer_interrupts);
 253 }
 254 #else
 255 static inline void watchdog_interrupt_count(void) { return; }
 256 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 257
 258 /* watchdog kicker functions */
 259 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 260 {
 261         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 262         struct pt_regs *regs = get_irq_regs();
 263         int duration;
 264
 265         /* kick the hardlockup detector */
 266         watchdog_interrupt_count();
 267
 268         /* kick the softlockup detector */
 269         wake_up_process(__this_cpu_read(softlockup_watchdog));
 270
 271         /* .. and repeat */
 272         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 273
 274         if (touch_ts == 0) {
 275                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 276                         /*
 277                          * If the time stamp was touched atomically
 278                          * make sure the scheduler tick is up to date.
 279                          */
 280                         __this_cpu_write(softlockup_touch_sync, false);
 281                         sched_clock_tick();
 282                 }
 283                 __touch_watchdog();
 284                 return HRTIMER_RESTART;
 285         }
 286
 287         /* check for a softlockup
 288          * This is done by making sure a high priority task is
 289          * being scheduled.  The task touches the watchdog to
 290          * indicate it is getting cpu time.  If it hasn't then
 291          * this is a good indication some task is hogging the cpu
 292          */
 293         duration = is_softlockup(touch_ts);
 294         if (unlikely(duration)) {
 295                 /* only warn once */
 296                 if (__this_cpu_read(soft_watchdog_warn) == true)
 297                         return HRTIMER_RESTART;
 298
 299                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 300                         smp_processor_id(), duration,
 301                         current->comm, task_pid_nr(current));
 302                 print_modules();
 303                 print_irqtrace_events(current);
 304                 if (regs)
 305                         show_regs(regs);
 306                 else
 307                         dump_stack();
 308
 309                 if (softlockup_panic)
 310                         panic("softlockup: hung tasks");
 311                 __this_cpu_write(soft_watchdog_warn, true);
 312         } else
 313                 __this_cpu_write(soft_watchdog_warn, false);
 314
 315         return HRTIMER_RESTART;
 316 }
 317
 318
 319 /*
 320  * The watchdog thread - touches the timestamp.
 321  */
 322 static int watchdog(void *unused)
 323 {
 324         struct sched_param param = { .sched_priority = 0 };
 325         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 326
 327         /* initialize timestamp */
 328         __touch_watchdog();
 329
 330         /* kick off the timer for the hardlockup detector */
 331         /* done here because hrtimer_start can only pin to smp_processor_id() */
 332         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 333                       HRTIMER_MODE_REL_PINNED);
 334
 335         set_current_state(TASK_INTERRUPTIBLE);
 336         /*
 337          * Run briefly (kicked by the hrtimer callback function) once every
 338          * get_sample_period() seconds (4 seconds by default) to reset the
 339          * softlockup timestamp. If this gets delayed for more than
 340          * 2*watchdog_thresh seconds then the debug-printout triggers in
 341          * watchdog_timer_fn().
 342          */
 343         while (!kthread_should_stop()) {
 344                 __touch_watchdog();
 345                 schedule();
 346
 347                 if (kthread_should_stop())
 348                         break;
 349
 350                 set_current_state(TASK_INTERRUPTIBLE);
 351         }
 352         /*
 353          * Drop the policy/priority elevation during thread exit to avoid a
 354          * scheduling latency spike.
 355          */
 356         __set_current_state(TASK_RUNNING);
 357         sched_setscheduler(current, SCHED_NORMAL, &param);
 358         return 0;
 359 }
 360
 361
 362 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 363 static int watchdog_nmi_enable(int cpu)
 364 {
 365         struct perf_event_attr *wd_attr;
 366         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 367
 368         /* is it already setup and enabled? */
 369         if (event && event->state > PERF_EVENT_STATE_OFF)
 370                 goto out;
 371
 372         /* it is setup but not enabled */
 373         if (event != NULL)
 374                 goto out_enable;
 375
 376         wd_attr = &wd_hw_attr;
 377         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 378
 379         /* Try to register using hardware perf events */
 380         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 381         if (!IS_ERR(event)) {
 382                 pr_info("enabled, takes one hw-pmu counter.\n");
 383                 goto out_save;
 384         }
 385
 386
 387         /* vary the KERN level based on the returned errno */
 388         if (PTR_ERR(event) == -EOPNOTSUPP)
 389                 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 390         else if (PTR_ERR(event) == -ENOENT)
 391                 pr_warning("disabled (cpu%i): hardware events not enabled\n",
 392                          cpu);
 393         else
 394                 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 395                         cpu, PTR_ERR(event));
 396         return PTR_ERR(event);
 397
 398         /* success path */
 399 out_save:
 400         per_cpu(watchdog_ev, cpu) = event;
 401 out_enable:
 402         perf_event_enable(per_cpu(watchdog_ev, cpu));
 403 out:
 404         return 0;
 405 }
 406
 407 static void watchdog_nmi_disable(int cpu)
 408 {
 409         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 410
 411         if (event) {
 412                 perf_event_disable(event);
 413                 per_cpu(watchdog_ev, cpu) = NULL;
 414
 415                 /* should be in cleanup, but blocks oprofile */
 416                 perf_event_release_kernel(event);
 417         }
 418         return;
 419 }
 420 #else
 421 static int watchdog_nmi_enable(int cpu) { return 0; }
 422 static void watchdog_nmi_disable(int cpu) { return; }
 423 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 424
 425 /* prepare/enable/disable routines */
 426 static void watchdog_prepare_cpu(int cpu)
 427 {
 428         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 429
 430         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 431         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 432         hrtimer->function = watchdog_timer_fn;
 433 }
 434
 435 static int watchdog_enable(int cpu)
 436 {
 437         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 438         int err = 0;
 439
 440         /* enable the perf event */
 441         err = watchdog_nmi_enable(cpu);
 442
 443         /* Regardless of err above, fall through and start softlockup */
 444
 445         /* create the watchdog thread */
 446         if (!p) {
 447                 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 448                 p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
 449                 if (IS_ERR(p)) {
 450                         pr_err("softlockup watchdog for %i failed\n", cpu);
 451                         if (!err) {
 452                                 /* if hardlockup hasn't already set this */
 453                                 err = PTR_ERR(p);
 454                                 /* and disable the perf event */
 455                                 watchdog_nmi_disable(cpu);
 456                         }
 457                         goto out;
 458                 }
 459                 sched_setscheduler(p, SCHED_FIFO, &param);
 460                 kthread_bind(p, cpu);
 461                 per_cpu(watchdog_touch_ts, cpu) = 0;
 462                 per_cpu(softlockup_watchdog, cpu) = p;
 463                 wake_up_process(p);
 464         }
 465
 466 out:
 467         return err;
 468 }
 469
 470 static void watchdog_disable(int cpu)
 471 {
 472         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 473         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 474
 475         /*
 476          * cancel the timer first to stop incrementing the stats
 477          * and waking up the kthread
 478          */
 479         hrtimer_cancel(hrtimer);
 480
 481         /* disable the perf event */
 482         watchdog_nmi_disable(cpu);
 483
 484         /* stop the watchdog thread */
 485         if (p) {
 486                 per_cpu(softlockup_watchdog, cpu) = NULL;
 487                 kthread_stop(p);
 488         }
 489 }
 490
 491 /* sysctl functions */
 492 #ifdef CONFIG_SYSCTL
 493 static void watchdog_enable_all_cpus(void)
 494 {
 495         int cpu;
 496
 497         watchdog_enabled = 0;
 498
 499         for_each_online_cpu(cpu)
 500                 if (!watchdog_enable(cpu))
 501                         /* if any cpu succeeds, watchdog is considered
 502                            enabled for the system */
 503                         watchdog_enabled = 1;
 504
 505         if (!watchdog_enabled)
 506                 pr_err("failed to be enabled on some cpus\n");
 507
 508 }
 509
 510 static void watchdog_disable_all_cpus(void)
 511 {
 512         int cpu;
 513
 514         for_each_online_cpu(cpu)
 515                 watchdog_disable(cpu);
 516
 517         /* if all watchdogs are disabled, then they are disabled for the system */
 518         watchdog_enabled = 0;
 519 }
 520
 521
 522 /*
 523  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
 524  */
 525
 526 int proc_dowatchdog(struct ctl_table *table, int write,
 527                     void __user *buffer, size_t *lenp, loff_t *ppos)
 528 {
 529         int ret;
 530
 531         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 532         if (ret || !write)
 533                 goto out;
 534
 535         if (watchdog_enabled && watchdog_thresh)
 536                 watchdog_enable_all_cpus();
 537         else
 538                 watchdog_disable_all_cpus();
 539
 540 out:
 541         return ret;
 542 }
 543 #endif /* CONFIG_SYSCTL */
 544
 545
 546 /*
 547  * Create/destroy watchdog threads as CPUs come and go:
 548  */
 549 static int __cpuinit
 550 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 551 {
 552         int hotcpu = (unsigned long)hcpu;
 553
 554         switch (action) {
 555         case CPU_UP_PREPARE:
 556         case CPU_UP_PREPARE_FROZEN:
 557                 watchdog_prepare_cpu(hotcpu);
 558                 break;
 559         case CPU_ONLINE:
 560         case CPU_ONLINE_FROZEN:
 561                 if (watchdog_enabled)
 562                         watchdog_enable(hotcpu);
 563                 break;
 564 #ifdef CONFIG_HOTPLUG_CPU
 565         case CPU_UP_CANCELED:
 566         case CPU_UP_CANCELED_FROZEN:
 567                 watchdog_disable(hotcpu);
 568                 break;
 569         case CPU_DEAD:
 570         case CPU_DEAD_FROZEN:
 571                 watchdog_disable(hotcpu);
 572                 break;
 573 #endif /* CONFIG_HOTPLUG_CPU */
 574         }
 575
 576         /*
 577          * hardlockup and softlockup are not important enough
 578          * to block cpu bring up.  Just always succeed and
 579          * rely on printk output to flag problems.
 580          */
 581         return NOTIFY_OK;
 582 }
 583
 584 static struct notifier_block __cpuinitdata cpu_nfb = {
 585         .notifier_call = cpu_callback
 586 };
 587
 588 void __init lockup_detector_init(void)
 589 {
 590         void *cpu = (void *)(long)smp_processor_id();
 591         int err;
 592
 593         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 594         WARN_ON(notifier_to_errno(err));
 595
 596         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 597         register_cpu_notifier(&cpu_nfb);
 598
 599         return;
 600 }