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