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 void __weak hw_nmi_watchdog_set_attr(struct perf_event_attr *wd_attr) { }
 204
 205 static struct perf_event_attr wd_hw_attr = {
 206         .type           = PERF_TYPE_HARDWARE,
 207         .config         = PERF_COUNT_HW_CPU_CYCLES,
 208         .size           = sizeof(struct perf_event_attr),
 209         .pinned         = 1,
 210         .disabled       = 1,
 211 };
 212
 213 /* Callback function for perf event subsystem */
 214 static void watchdog_overflow_callback(struct perf_event *event, int nmi,
 215                  struct perf_sample_data *data,
 216                  struct pt_regs *regs)
 217 {
 218         /* Ensure the watchdog never gets throttled */
 219         event->hw.interrupts = 0;
 220
 221         if (__this_cpu_read(watchdog_nmi_touch) == true) {
 222                 __this_cpu_write(watchdog_nmi_touch, false);
 223                 return;
 224         }
 225
 226         /* check for a hardlockup
 227          * This is done by making sure our timer interrupt
 228          * is incrementing.  The timer interrupt should have
 229          * fired multiple times before we overflow'd.  If it hasn't
 230          * then this is a good indication the cpu is stuck
 231          */
 232         if (is_hardlockup()) {
 233                 int this_cpu = smp_processor_id();
 234
 235                 /* only print hardlockups once */
 236                 if (__this_cpu_read(hard_watchdog_warn) == true)
 237                         return;
 238
 239                 if (hardlockup_panic)
 240                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 241                 else
 242                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 243
 244                 __this_cpu_write(hard_watchdog_warn, true);
 245                 return;
 246         }
 247
 248         __this_cpu_write(hard_watchdog_warn, false);
 249         return;
 250 }
 251 static void watchdog_interrupt_count(void)
 252 {
 253         __this_cpu_inc(hrtimer_interrupts);
 254 }
 255 #else
 256 static inline void watchdog_interrupt_count(void) { return; }
 257 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 258
 259 /* watchdog kicker functions */
 260 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 261 {
 262         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 263         struct pt_regs *regs = get_irq_regs();
 264         int duration;
 265
 266         /* kick the hardlockup detector */
 267         watchdog_interrupt_count();
 268
 269         /* kick the softlockup detector */
 270         wake_up_process(__this_cpu_read(softlockup_watchdog));
 271
 272         /* .. and repeat */
 273         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 274
 275         if (touch_ts == 0) {
 276                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 277                         /*
 278                          * If the time stamp was touched atomically
 279                          * make sure the scheduler tick is up to date.
 280                          */
 281                         __this_cpu_write(softlockup_touch_sync, false);
 282                         sched_clock_tick();
 283                 }
 284                 __touch_watchdog();
 285                 return HRTIMER_RESTART;
 286         }
 287
 288         /* check for a softlockup
 289          * This is done by making sure a high priority task is
 290          * being scheduled.  The task touches the watchdog to
 291          * indicate it is getting cpu time.  If it hasn't then
 292          * this is a good indication some task is hogging the cpu
 293          */
 294         duration = is_softlockup(touch_ts);
 295         if (unlikely(duration)) {
 296                 /* only warn once */
 297                 if (__this_cpu_read(soft_watchdog_warn) == true)
 298                         return HRTIMER_RESTART;
 299
 300                 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 301                         smp_processor_id(), duration,
 302                         current->comm, task_pid_nr(current));
 303                 print_modules();
 304                 print_irqtrace_events(current);
 305                 if (regs)
 306                         show_regs(regs);
 307                 else
 308                         dump_stack();
 309
 310                 if (softlockup_panic)
 311                         panic("softlockup: hung tasks");
 312                 __this_cpu_write(soft_watchdog_warn, true);
 313         } else
 314                 __this_cpu_write(soft_watchdog_warn, false);
 315
 316         return HRTIMER_RESTART;
 317 }
 318
 319
 320 /*
 321  * The watchdog thread - touches the timestamp.
 322  */
 323 static int watchdog(void *unused)
 324 {
 325         static struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 326         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 327
 328         sched_setscheduler(current, SCHED_FIFO, &param);
 329
 330         /* initialize timestamp */
 331         __touch_watchdog();
 332
 333         /* kick off the timer for the hardlockup detector */
 334         /* done here because hrtimer_start can only pin to smp_processor_id() */
 335         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 336                       HRTIMER_MODE_REL_PINNED);
 337
 338         set_current_state(TASK_INTERRUPTIBLE);
 339         /*
 340          * Run briefly once per second to reset the softlockup timestamp.
 341          * If this gets delayed for more than 60 seconds then the
 342          * debug-printout triggers in watchdog_timer_fn().
 343          */
 344         while (!kthread_should_stop()) {
 345                 __touch_watchdog();
 346                 schedule();
 347
 348                 if (kthread_should_stop())
 349                         break;
 350
 351                 set_current_state(TASK_INTERRUPTIBLE);
 352         }
 353         __set_current_state(TASK_RUNNING);
 354
 355         return 0;
 356 }
 357
 358
 359 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 360 static int watchdog_nmi_enable(int cpu)
 361 {
 362         struct perf_event_attr *wd_attr;
 363         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 364
 365         /* is it already setup and enabled? */
 366         if (event && event->state > PERF_EVENT_STATE_OFF)
 367                 goto out;
 368
 369         /* it is setup but not enabled */
 370         if (event != NULL)
 371                 goto out_enable;
 372
 373         wd_attr = &wd_hw_attr;
 374         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 375         hw_nmi_watchdog_set_attr(wd_attr);
 376
 377         /* Try to register using hardware perf events */
 378         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback);
 379         if (!IS_ERR(event)) {
 380                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
 381                 goto out_save;
 382         }
 383
 384
 385         /* vary the KERN level based on the returned errno */
 386         if (PTR_ERR(event) == -EOPNOTSUPP)
 387                 printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 388         else if (PTR_ERR(event) == -ENOENT)
 389                 printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
 390         else
 391                 printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
 392         return PTR_ERR(event);
 393
 394         /* success path */
 395 out_save:
 396         per_cpu(watchdog_ev, cpu) = event;
 397 out_enable:
 398         perf_event_enable(per_cpu(watchdog_ev, cpu));
 399 out:
 400         return 0;
 401 }
 402
 403 static void watchdog_nmi_disable(int cpu)
 404 {
 405         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 406
 407         if (event) {
 408                 perf_event_disable(event);
 409                 per_cpu(watchdog_ev, cpu) = NULL;
 410
 411                 /* should be in cleanup, but blocks oprofile */
 412                 perf_event_release_kernel(event);
 413         }
 414         return;
 415 }
 416 #else
 417 static int watchdog_nmi_enable(int cpu) { return 0; }
 418 static void watchdog_nmi_disable(int cpu) { return; }
 419 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 420
 421 /* prepare/enable/disable routines */
 422 static void watchdog_prepare_cpu(int cpu)
 423 {
 424         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 425
 426         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 427         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 428         hrtimer->function = watchdog_timer_fn;
 429 }
 430
 431 static int watchdog_enable(int cpu)
 432 {
 433         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 434         int err = 0;
 435
 436         /* enable the perf event */
 437         err = watchdog_nmi_enable(cpu);
 438
 439         /* Regardless of err above, fall through and start softlockup */
 440
 441         /* create the watchdog thread */
 442         if (!p) {
 443                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 444                 if (IS_ERR(p)) {
 445                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 446                         if (!err) {
 447                                 /* if hardlockup hasn't already set this */
 448                                 err = PTR_ERR(p);
 449                                 /* and disable the perf event */
 450                                 watchdog_nmi_disable(cpu);
 451                         }
 452                         goto out;
 453                 }
 454                 kthread_bind(p, cpu);
 455                 per_cpu(watchdog_touch_ts, cpu) = 0;
 456                 per_cpu(softlockup_watchdog, cpu) = p;
 457                 wake_up_process(p);
 458         }
 459
 460 out:
 461         return err;
 462 }
 463
 464 static void watchdog_disable(int cpu)
 465 {
 466         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 467         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 468
 469         /*
 470          * cancel the timer first to stop incrementing the stats
 471          * and waking up the kthread
 472          */
 473         hrtimer_cancel(hrtimer);
 474
 475         /* disable the perf event */
 476         watchdog_nmi_disable(cpu);
 477
 478         /* stop the watchdog thread */
 479         if (p) {
 480                 per_cpu(softlockup_watchdog, cpu) = NULL;
 481                 kthread_stop(p);
 482         }
 483 }
 484
 485 static void watchdog_enable_all_cpus(void)
 486 {
 487         int cpu;
 488
 489         watchdog_enabled = 0;
 490
 491         for_each_online_cpu(cpu)
 492                 if (!watchdog_enable(cpu))
 493                         /* if any cpu succeeds, watchdog is considered
 494                            enabled for the system */
 495                         watchdog_enabled = 1;
 496
 497         if (!watchdog_enabled)
 498                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 499
 500 }
 501
 502 static void watchdog_disable_all_cpus(void)
 503 {
 504         int cpu;
 505
 506         for_each_online_cpu(cpu)
 507                 watchdog_disable(cpu);
 508
 509         /* if all watchdogs are disabled, then they are disabled for the system */
 510         watchdog_enabled = 0;
 511 }
 512
 513
 514 /* sysctl functions */
 515 #ifdef CONFIG_SYSCTL
 516 /*
 517  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
 518  */
 519
 520 int proc_dowatchdog(struct ctl_table *table, int write,
 521                     void __user *buffer, size_t *lenp, loff_t *ppos)
 522 {
 523         int ret;
 524
 525         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 526         if (ret || !write)
 527                 goto out;
 528
 529         if (watchdog_enabled && watchdog_thresh)
 530                 watchdog_enable_all_cpus();
 531         else
 532                 watchdog_disable_all_cpus();
 533
 534 out:
 535         return ret;
 536 }
 537 #endif /* CONFIG_SYSCTL */
 538
 539
 540 /*
 541  * Create/destroy watchdog threads as CPUs come and go:
 542  */
 543 static int __cpuinit
 544 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 545 {
 546         int hotcpu = (unsigned long)hcpu;
 547
 548         switch (action) {
 549         case CPU_UP_PREPARE:
 550         case CPU_UP_PREPARE_FROZEN:
 551                 watchdog_prepare_cpu(hotcpu);
 552                 break;
 553         case CPU_ONLINE:
 554         case CPU_ONLINE_FROZEN:
 555                 if (watchdog_enabled)
 556                         watchdog_enable(hotcpu);
 557                 break;
 558 #ifdef CONFIG_HOTPLUG_CPU
 559         case CPU_UP_CANCELED:
 560         case CPU_UP_CANCELED_FROZEN:
 561                 watchdog_disable(hotcpu);
 562                 break;
 563         case CPU_DEAD:
 564         case CPU_DEAD_FROZEN:
 565                 watchdog_disable(hotcpu);
 566                 break;
 567 #endif /* CONFIG_HOTPLUG_CPU */
 568         }
 569
 570         /*
 571          * hardlockup and softlockup are not important enough
 572          * to block cpu bring up.  Just always succeed and
 573          * rely on printk output to flag problems.
 574          */
 575         return NOTIFY_OK;
 576 }
 577
 578 static struct notifier_block __cpuinitdata cpu_nfb = {
 579         .notifier_call = cpu_callback
 580 };
 581
 582 void __init lockup_detector_init(void)
 583 {
 584         void *cpu = (void *)(long)smp_processor_id();
 585         int err;
 586
 587         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 588         WARN_ON(notifier_to_errno(err));
 589
 590         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 591         register_cpu_notifier(&cpu_nfb);
 592
 593         return;
 594 }