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