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(bool, watchdog_nmi_touch);
  35 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  36 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  37 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  38 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  39 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
  40 #ifdef CONFIG_PERF_EVENTS_NMI
  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 __read_mostly did_panic;
  47 static int __initdata no_watchdog;
  48
  49
  50 /* boot commands */
  51 /*
  52  * Should we panic when a soft-lockup or hard-lockup occurs:
  53  */
  54 #ifdef CONFIG_PERF_EVENTS_NMI
  55 static int hardlockup_panic;
  56
  57 static int __init hardlockup_panic_setup(char *str)
  58 {
  59         if (!strncmp(str, "panic", 5))
  60                 hardlockup_panic = 1;
  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         no_watchdog = 1;
  80         return 1;
  81 }
  82 __setup("nowatchdog", nowatchdog_setup);
  83
  84 /* deprecated */
  85 static int __init nosoftlockup_setup(char *str)
  86 {
  87         no_watchdog = 1;
  88         return 1;
  89 }
  90 __setup("nosoftlockup", nosoftlockup_setup);
  91 /*  */
  92
  93
  94 /*
  95  * Returns seconds, approximately.  We don't need nanosecond
  96  * resolution, and we don't need to waste time with a big divide when
  97  * 2^30ns == 1.074s.
  98  */
  99 static unsigned long get_timestamp(int this_cpu)
 100 {
 101         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
 102 }
 103
 104 static unsigned long get_sample_period(void)
 105 {
 106         /*
 107          * convert softlockup_thresh from seconds to ns
 108          * the divide by 5 is to give hrtimer 5 chances to
 109          * increment before the hardlockup detector generates
 110          * a warning
 111          */
 112         return softlockup_thresh / 5 * NSEC_PER_SEC;
 113 }
 114
 115 /* Commands for resetting the watchdog */
 116 static void __touch_watchdog(void)
 117 {
 118         int this_cpu = raw_smp_processor_id();
 119
 120         __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
 121 }
 122
 123 void touch_softlockup_watchdog(void)
 124 {
 125         __get_cpu_var(watchdog_touch_ts) = 0;
 126 }
 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 void touch_nmi_watchdog(void)
 142 {
 143         __get_cpu_var(watchdog_nmi_touch) = true;
 144         touch_softlockup_watchdog();
 145 }
 146 EXPORT_SYMBOL(touch_nmi_watchdog);
 147
 148 void touch_softlockup_watchdog_sync(void)
 149 {
 150         __raw_get_cpu_var(softlockup_touch_sync) = true;
 151         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 152 }
 153
 154 #ifdef CONFIG_PERF_EVENTS_NMI
 155 /* watchdog detector functions */
 156 static int is_hardlockup(int cpu)
 157 {
 158         unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
 159
 160         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 161                 return 1;
 162
 163         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 164         return 0;
 165 }
 166 #endif
 167
 168 static int is_softlockup(unsigned long touch_ts, int cpu)
 169 {
 170         unsigned long now = get_timestamp(cpu);
 171
 172         /* Warn about unreasonable delays: */
 173         if (time_after(now, touch_ts + softlockup_thresh))
 174                 return now - touch_ts;
 175
 176         return 0;
 177 }
 178
 179 static int
 180 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
 181 {
 182         did_panic = 1;
 183
 184         return NOTIFY_DONE;
 185 }
 186
 187 static struct notifier_block panic_block = {
 188         .notifier_call = watchdog_panic,
 189 };
 190
 191 #ifdef CONFIG_PERF_EVENTS_NMI
 192 static struct perf_event_attr wd_hw_attr = {
 193         .type           = PERF_TYPE_HARDWARE,
 194         .config         = PERF_COUNT_HW_CPU_CYCLES,
 195         .size           = sizeof(struct perf_event_attr),
 196         .pinned         = 1,
 197         .disabled       = 1,
 198 };
 199
 200 /* Callback function for perf event subsystem */
 201 void watchdog_overflow_callback(struct perf_event *event, int nmi,
 202                  struct perf_sample_data *data,
 203                  struct pt_regs *regs)
 204 {
 205         int this_cpu = smp_processor_id();
 206
 207         if (__get_cpu_var(watchdog_nmi_touch) == true) {
 208                 __get_cpu_var(watchdog_nmi_touch) = false;
 209                 return;
 210         }
 211
 212         /* check for a hardlockup
 213          * This is done by making sure our timer interrupt
 214          * is incrementing.  The timer interrupt should have
 215          * fired multiple times before we overflow'd.  If it hasn't
 216          * then this is a good indication the cpu is stuck
 217          */
 218         if (is_hardlockup(this_cpu)) {
 219                 /* only print hardlockups once */
 220                 if (__get_cpu_var(hard_watchdog_warn) == true)
 221                         return;
 222
 223                 if (hardlockup_panic)
 224                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 225                 else
 226                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 227
 228                 __get_cpu_var(hard_watchdog_warn) = true;
 229                 return;
 230         }
 231
 232         __get_cpu_var(hard_watchdog_warn) = false;
 233         return;
 234 }
 235 static void watchdog_interrupt_count(void)
 236 {
 237         __get_cpu_var(hrtimer_interrupts)++;
 238 }
 239 #else
 240 static inline void watchdog_interrupt_count(void) { return; }
 241 #endif /* CONFIG_PERF_EVENTS_NMI */
 242
 243 /* watchdog kicker functions */
 244 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 245 {
 246         int this_cpu = smp_processor_id();
 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(per_cpu(softlockup_touch_sync, this_cpu))) {
 262                         /*
 263                          * If the time stamp was touched atomically
 264                          * make sure the scheduler tick is up to date.
 265                          */
 266                         per_cpu(softlockup_touch_sync, this_cpu) = 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, this_cpu);
 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                         this_cpu, 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 *__bind_cpu)
 309 {
 310         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 311         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
 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 softlockup_tick().
 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_PERF_EVENTS_NMI
 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, -1, 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 failed to create perf event on cpu%i: %p\n", cpu, event);
 368         return -1;
 369
 370         /* success path */
 371 out_save:
 372         per_cpu(watchdog_ev, cpu) = event;
 373 out_enable:
 374         perf_event_enable(per_cpu(watchdog_ev, cpu));
 375 out:
 376         return 0;
 377 }
 378
 379 static void watchdog_nmi_disable(int cpu)
 380 {
 381         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 382
 383         if (event) {
 384                 perf_event_disable(event);
 385                 per_cpu(watchdog_ev, cpu) = NULL;
 386
 387                 /* should be in cleanup, but blocks oprofile */
 388                 perf_event_release_kernel(event);
 389         }
 390         return;
 391 }
 392 #else
 393 static int watchdog_nmi_enable(int cpu) { return 0; }
 394 static void watchdog_nmi_disable(int cpu) { return; }
 395 #endif /* CONFIG_PERF_EVENTS_NMI */
 396
 397 /* prepare/enable/disable routines */
 398 static int watchdog_prepare_cpu(int cpu)
 399 {
 400         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 401
 402         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 403         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 404         hrtimer->function = watchdog_timer_fn;
 405
 406         return 0;
 407 }
 408
 409 static int watchdog_enable(int cpu)
 410 {
 411         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 412
 413         /* enable the perf event */
 414         if (watchdog_nmi_enable(cpu) != 0)
 415                 return -1;
 416
 417         /* create the watchdog thread */
 418         if (!p) {
 419                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 420                 if (IS_ERR(p)) {
 421                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 422                         return -1;
 423                 }
 424                 kthread_bind(p, cpu);
 425                 per_cpu(watchdog_touch_ts, cpu) = 0;
 426                 per_cpu(softlockup_watchdog, cpu) = p;
 427                 wake_up_process(p);
 428         }
 429
 430         return 0;
 431 }
 432
 433 static void watchdog_disable(int cpu)
 434 {
 435         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 436         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 437
 438         /*
 439          * cancel the timer first to stop incrementing the stats
 440          * and waking up the kthread
 441          */
 442         hrtimer_cancel(hrtimer);
 443
 444         /* disable the perf event */
 445         watchdog_nmi_disable(cpu);
 446
 447         /* stop the watchdog thread */
 448         if (p) {
 449                 per_cpu(softlockup_watchdog, cpu) = NULL;
 450                 kthread_stop(p);
 451         }
 452
 453         /* if any cpu succeeds, watchdog is considered enabled for the system */
 454         watchdog_enabled = 1;
 455 }
 456
 457 static void watchdog_enable_all_cpus(void)
 458 {
 459         int cpu;
 460         int result;
 461
 462         for_each_online_cpu(cpu)
 463                 result += watchdog_enable(cpu);
 464
 465         if (result)
 466                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 467
 468 }
 469
 470 static void watchdog_disable_all_cpus(void)
 471 {
 472         int cpu;
 473
 474         for_each_online_cpu(cpu)
 475                 watchdog_disable(cpu);
 476
 477         /* if all watchdogs are disabled, then they are disabled for the system */
 478         watchdog_enabled = 0;
 479 }
 480
 481
 482 /* sysctl functions */
 483 #ifdef CONFIG_SYSCTL
 484 /*
 485  * proc handler for /proc/sys/kernel/nmi_watchdog
 486  */
 487
 488 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 489                      void __user *buffer, size_t *length, loff_t *ppos)
 490 {
 491         proc_dointvec(table, write, buffer, length, ppos);
 492
 493         if (watchdog_enabled)
 494                 watchdog_enable_all_cpus();
 495         else
 496                 watchdog_disable_all_cpus();
 497         return 0;
 498 }
 499
 500 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 501                              void __user *buffer,
 502                              size_t *lenp, loff_t *ppos)
 503 {
 504         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 505 }
 506 #endif /* CONFIG_SYSCTL */
 507
 508
 509 /*
 510  * Create/destroy watchdog threads as CPUs come and go:
 511  */
 512 static int __cpuinit
 513 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 514 {
 515         int hotcpu = (unsigned long)hcpu;
 516
 517         switch (action) {
 518         case CPU_UP_PREPARE:
 519         case CPU_UP_PREPARE_FROZEN:
 520                 if (watchdog_prepare_cpu(hotcpu))
 521                         return NOTIFY_BAD;
 522                 break;
 523         case CPU_ONLINE:
 524         case CPU_ONLINE_FROZEN:
 525                 if (watchdog_enable(hotcpu))
 526                         return NOTIFY_BAD;
 527                 break;
 528 #ifdef CONFIG_HOTPLUG_CPU
 529         case CPU_UP_CANCELED:
 530         case CPU_UP_CANCELED_FROZEN:
 531                 watchdog_disable(hotcpu);
 532                 break;
 533         case CPU_DEAD:
 534         case CPU_DEAD_FROZEN:
 535                 watchdog_disable(hotcpu);
 536                 break;
 537 #endif /* CONFIG_HOTPLUG_CPU */
 538         }
 539         return NOTIFY_OK;
 540 }
 541
 542 static struct notifier_block __cpuinitdata cpu_nfb = {
 543         .notifier_call = cpu_callback
 544 };
 545
 546 static int __init spawn_watchdog_task(void)
 547 {
 548         void *cpu = (void *)(long)smp_processor_id();
 549         int err;
 550
 551         if (no_watchdog)
 552                 return 0;
 553
 554         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 555         WARN_ON(err == NOTIFY_BAD);
 556
 557         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 558         register_cpu_notifier(&cpu_nfb);
 559
 560         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
 561
 562         return 0;
 563 }
 564 early_initcall(spawn_watchdog_task);