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 __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_HARDLOCKUP_DETECTOR
  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 = 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         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 126 }
 127 EXPORT_SYMBOL(touch_softlockup_watchdog);
 128
 129 void touch_all_softlockup_watchdogs(void)
 130 {
 131         int cpu;
 132
 133         /*
 134          * this is done lockless
 135          * do we care if a 0 races with a timestamp?
 136          * all it means is the softlock check starts one cycle later
 137          */
 138         for_each_online_cpu(cpu)
 139                 per_cpu(watchdog_touch_ts, cpu) = 0;
 140 }
 141
 142 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 143 void touch_nmi_watchdog(void)
 144 {
 145         if (watchdog_enabled) {
 146                 unsigned cpu;
 147
 148                 for_each_present_cpu(cpu) {
 149                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
 150                                 per_cpu(watchdog_nmi_touch, cpu) = true;
 151                 }
 152         }
 153         touch_softlockup_watchdog();
 154 }
 155 EXPORT_SYMBOL(touch_nmi_watchdog);
 156
 157 #endif
 158
 159 void touch_softlockup_watchdog_sync(void)
 160 {
 161         __raw_get_cpu_var(softlockup_touch_sync) = true;
 162         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 163 }
 164
 165 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 166 /* watchdog detector functions */
 167 static int is_hardlockup(void)
 168 {
 169         unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
 170
 171         if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
 172                 return 1;
 173
 174         __get_cpu_var(hrtimer_interrupts_saved) = hrint;
 175         return 0;
 176 }
 177 #endif
 178
 179 static int is_softlockup(unsigned long touch_ts)
 180 {
 181         unsigned long now = get_timestamp(smp_processor_id());
 182
 183         /* Warn about unreasonable delays: */
 184         if (time_after(now, touch_ts + softlockup_thresh))
 185                 return now - touch_ts;
 186
 187         return 0;
 188 }
 189
 190 static int
 191 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
 192 {
 193         did_panic = 1;
 194
 195         return NOTIFY_DONE;
 196 }
 197
 198 static struct notifier_block panic_block = {
 199         .notifier_call = watchdog_panic,
 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 (__get_cpu_var(watchdog_nmi_touch) == true) {
 220                 __get_cpu_var(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 (__get_cpu_var(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                 __get_cpu_var(hard_watchdog_warn) = true;
 243                 return;
 244         }
 245
 246         __get_cpu_var(hard_watchdog_warn) = false;
 247         return;
 248 }
 249 static void watchdog_interrupt_count(void)
 250 {
 251         __get_cpu_var(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 = __get_cpu_var(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(__get_cpu_var(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(__get_cpu_var(softlockup_touch_sync))) {
 275                         /*
 276                          * If the time stamp was touched atomically
 277                          * make sure the scheduler tick is up to date.
 278                          */
 279                         __get_cpu_var(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 (__get_cpu_var(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                 __get_cpu_var(soft_watchdog_warn) = true;
 311         } else
 312                 __get_cpu_var(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         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();
 374         event = perf_event_create_kernel_counter(wd_attr, cpu, -1, 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         printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
 381         return -1;
 382
 383         /* success path */
 384 out_save:
 385         per_cpu(watchdog_ev, cpu) = event;
 386 out_enable:
 387         perf_event_enable(per_cpu(watchdog_ev, cpu));
 388 out:
 389         return 0;
 390 }
 391
 392 static void watchdog_nmi_disable(int cpu)
 393 {
 394         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 395
 396         if (event) {
 397                 perf_event_disable(event);
 398                 per_cpu(watchdog_ev, cpu) = NULL;
 399
 400                 /* should be in cleanup, but blocks oprofile */
 401                 perf_event_release_kernel(event);
 402         }
 403         return;
 404 }
 405 #else
 406 static int watchdog_nmi_enable(int cpu) { return 0; }
 407 static void watchdog_nmi_disable(int cpu) { return; }
 408 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 409
 410 /* prepare/enable/disable routines */
 411 static int watchdog_prepare_cpu(int cpu)
 412 {
 413         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 414
 415         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 416         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 417         hrtimer->function = watchdog_timer_fn;
 418
 419         return 0;
 420 }
 421
 422 static int watchdog_enable(int cpu)
 423 {
 424         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 425
 426         /* enable the perf event */
 427         if (watchdog_nmi_enable(cpu) != 0)
 428                 return -1;
 429
 430         /* create the watchdog thread */
 431         if (!p) {
 432                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 433                 if (IS_ERR(p)) {
 434                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 435                         return -1;
 436                 }
 437                 kthread_bind(p, cpu);
 438                 per_cpu(watchdog_touch_ts, cpu) = 0;
 439                 per_cpu(softlockup_watchdog, cpu) = p;
 440                 wake_up_process(p);
 441         }
 442
 443         /* if any cpu succeeds, watchdog is considered enabled for the system */
 444         watchdog_enabled = 1;
 445
 446         return 0;
 447 }
 448
 449 static void watchdog_disable(int cpu)
 450 {
 451         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 452         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 453
 454         /*
 455          * cancel the timer first to stop incrementing the stats
 456          * and waking up the kthread
 457          */
 458         hrtimer_cancel(hrtimer);
 459
 460         /* disable the perf event */
 461         watchdog_nmi_disable(cpu);
 462
 463         /* stop the watchdog thread */
 464         if (p) {
 465                 per_cpu(softlockup_watchdog, cpu) = NULL;
 466                 kthread_stop(p);
 467         }
 468 }
 469
 470 static void watchdog_enable_all_cpus(void)
 471 {
 472         int cpu;
 473         int result = 0;
 474
 475         for_each_online_cpu(cpu)
 476                 result += watchdog_enable(cpu);
 477
 478         if (result)
 479                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 480
 481 }
 482
 483 static void watchdog_disable_all_cpus(void)
 484 {
 485         int cpu;
 486
 487         for_each_online_cpu(cpu)
 488                 watchdog_disable(cpu);
 489
 490         /* if all watchdogs are disabled, then they are disabled for the system */
 491         watchdog_enabled = 0;
 492 }
 493
 494
 495 /* sysctl functions */
 496 #ifdef CONFIG_SYSCTL
 497 /*
 498  * proc handler for /proc/sys/kernel/nmi_watchdog
 499  */
 500
 501 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 502                      void __user *buffer, size_t *length, loff_t *ppos)
 503 {
 504         proc_dointvec(table, write, buffer, length, ppos);
 505
 506         if (watchdog_enabled)
 507                 watchdog_enable_all_cpus();
 508         else
 509                 watchdog_disable_all_cpus();
 510         return 0;
 511 }
 512
 513 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 514                              void __user *buffer,
 515                              size_t *lenp, loff_t *ppos)
 516 {
 517         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 518 }
 519 #endif /* CONFIG_SYSCTL */
 520
 521
 522 /*
 523  * Create/destroy watchdog threads as CPUs come and go:
 524  */
 525 static int __cpuinit
 526 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 527 {
 528         int hotcpu = (unsigned long)hcpu;
 529
 530         switch (action) {
 531         case CPU_UP_PREPARE:
 532         case CPU_UP_PREPARE_FROZEN:
 533                 if (watchdog_prepare_cpu(hotcpu))
 534                         return NOTIFY_BAD;
 535                 break;
 536         case CPU_ONLINE:
 537         case CPU_ONLINE_FROZEN:
 538                 if (watchdog_enable(hotcpu))
 539                         return NOTIFY_BAD;
 540                 break;
 541 #ifdef CONFIG_HOTPLUG_CPU
 542         case CPU_UP_CANCELED:
 543         case CPU_UP_CANCELED_FROZEN:
 544                 watchdog_disable(hotcpu);
 545                 break;
 546         case CPU_DEAD:
 547         case CPU_DEAD_FROZEN:
 548                 watchdog_disable(hotcpu);
 549                 break;
 550 #endif /* CONFIG_HOTPLUG_CPU */
 551         }
 552         return NOTIFY_OK;
 553 }
 554
 555 static struct notifier_block __cpuinitdata cpu_nfb = {
 556         .notifier_call = cpu_callback
 557 };
 558
 559 static int __init spawn_watchdog_task(void)
 560 {
 561         void *cpu = (void *)(long)smp_processor_id();
 562         int err;
 563
 564         if (no_watchdog)
 565                 return 0;
 566
 567         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 568         WARN_ON(err == NOTIFY_BAD);
 569
 570         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 571         register_cpu_notifier(&cpu_nfb);
 572
 573         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
 574
 575         return 0;
 576 }
 577 early_initcall(spawn_watchdog_task);