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