linux/kernel/watchdog.c
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   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
  30int watchdog_enabled = 1;
  31int __read_mostly softlockup_thresh = 60;
  32
  33static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
  34static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  35static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  36static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  37static DEFINE_PER_CPU(bool, soft_watchdog_warn);
  38#ifdef CONFIG_HARDLOCKUP_DETECTOR
  39static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  40static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
  41static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
  42static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
  43static 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
  51static int hardlockup_panic =
  52                        CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  53
  54static 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
  67unsigned int __read_mostly softlockup_panic =
  68                        CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
  69
  70static 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
  78static int __init nowatchdog_setup(char *str)
  79{
  80        watchdog_enabled = 0;
  81        return 1;
  82}
  83__setup("nowatchdog", nowatchdog_setup);
  84
  85/* deprecated */
  86static int __init nosoftlockup_setup(char *str)
  87{
  88        watchdog_enabled = 0;
  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 */
 100static unsigned long get_timestamp(int this_cpu)
 101{
 102        return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
 103}
 104
 105static 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 */
 117static void __touch_watchdog(void)
 118{
 119        int this_cpu = smp_processor_id();
 120
 121        __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
 122}
 123
 124void touch_softlockup_watchdog(void)
 125{
 126        __this_cpu_write(watchdog_touch_ts, 0);
 127}
 128EXPORT_SYMBOL(touch_softlockup_watchdog);
 129
 130void 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
 144void 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}
 156EXPORT_SYMBOL(touch_nmi_watchdog);
 157
 158#endif
 159
 160void 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 */
 168static int is_hardlockup(void)
 169{
 170        unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 171
 172        if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 173                return 1;
 174
 175        __this_cpu_write(hrtimer_interrupts_saved, hrint);
 176        return 0;
 177}
 178#endif
 179
 180static 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
 192static 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 */
 201static 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 (__this_cpu_read(watchdog_nmi_touch) == true) {
 209                __this_cpu_write(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 (__this_cpu_read(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                __this_cpu_write(hard_watchdog_warn, true);
 232                return;
 233        }
 234
 235        __this_cpu_write(hard_watchdog_warn, false);
 236        return;
 237}
 238static void watchdog_interrupt_count(void)
 239{
 240        __this_cpu_inc(hrtimer_interrupts);
 241}
 242#else
 243static inline void watchdog_interrupt_count(void) { return; }
 244#endif /* CONFIG_HARDLOCKUP_DETECTOR */
 245
 246/* watchdog kicker functions */
 247static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 248{
 249        unsigned long touch_ts = __this_cpu_read(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(__this_cpu_read(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(__this_cpu_read(softlockup_touch_sync))) {
 264                        /*
 265                         * If the time stamp was touched atomically
 266                         * make sure the scheduler tick is up to date.
 267                         */
 268                        __this_cpu_write(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 (__this_cpu_read(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                __this_cpu_write(soft_watchdog_warn, true);
 300        } else
 301                __this_cpu_write(soft_watchdog_warn, false);
 302
 303        return HRTIMER_RESTART;
 304}
 305
 306
 307/*
 308 * The watchdog thread - touches the timestamp.
 309 */
 310static int watchdog(void *unused)
 311{
 312        static 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
 347static 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
 370        /* vary the KERN level based on the returned errno */
 371        if (PTR_ERR(event) == -EOPNOTSUPP)
 372                printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 373        else if (PTR_ERR(event) == -ENOENT)
 374                printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
 375        else
 376                printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
 377        return PTR_ERR(event);
 378
 379        /* success path */
 380out_save:
 381        per_cpu(watchdog_ev, cpu) = event;
 382out_enable:
 383        perf_event_enable(per_cpu(watchdog_ev, cpu));
 384out:
 385        return 0;
 386}
 387
 388static void watchdog_nmi_disable(int cpu)
 389{
 390        struct perf_event *event = per_cpu(watchdog_ev, cpu);
 391
 392        if (event) {
 393                perf_event_disable(event);
 394                per_cpu(watchdog_ev, cpu) = NULL;
 395
 396                /* should be in cleanup, but blocks oprofile */
 397                perf_event_release_kernel(event);
 398        }
 399        return;
 400}
 401#else
 402static int watchdog_nmi_enable(int cpu) { return 0; }
 403static void watchdog_nmi_disable(int cpu) { return; }
 404#endif /* CONFIG_HARDLOCKUP_DETECTOR */
 405
 406/* prepare/enable/disable routines */
 407static int watchdog_prepare_cpu(int cpu)
 408{
 409        struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 410
 411        WARN_ON(per_cpu(softlockup_watchdog, cpu));
 412        hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 413        hrtimer->function = watchdog_timer_fn;
 414
 415        return 0;
 416}
 417
 418static int watchdog_enable(int cpu)
 419{
 420        struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 421        int err = 0;
 422
 423        /* enable the perf event */
 424        err = watchdog_nmi_enable(cpu);
 425
 426        /* Regardless of err above, fall through and start softlockup */
 427
 428        /* create the watchdog thread */
 429        if (!p) {
 430                p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 431                if (IS_ERR(p)) {
 432                        printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 433                        if (!err) {
 434                                /* if hardlockup hasn't already set this */
 435                                err = PTR_ERR(p);
 436                                /* and disable the perf event */
 437                                watchdog_nmi_disable(cpu);
 438                        }
 439                        goto out;
 440                }
 441                kthread_bind(p, cpu);
 442                per_cpu(watchdog_touch_ts, cpu) = 0;
 443                per_cpu(softlockup_watchdog, cpu) = p;
 444                wake_up_process(p);
 445        }
 446
 447out:
 448        return err;
 449}
 450
 451static void watchdog_disable(int cpu)
 452{
 453        struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 454        struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 455
 456        /*
 457         * cancel the timer first to stop incrementing the stats
 458         * and waking up the kthread
 459         */
 460        hrtimer_cancel(hrtimer);
 461
 462        /* disable the perf event */
 463        watchdog_nmi_disable(cpu);
 464
 465        /* stop the watchdog thread */
 466        if (p) {
 467                per_cpu(softlockup_watchdog, cpu) = NULL;
 468                kthread_stop(p);
 469        }
 470}
 471
 472static void watchdog_enable_all_cpus(void)
 473{
 474        int cpu;
 475
 476        watchdog_enabled = 0;
 477
 478        for_each_online_cpu(cpu)
 479                if (!watchdog_enable(cpu))
 480                        /* if any cpu succeeds, watchdog is considered
 481                           enabled for the system */
 482                        watchdog_enabled = 1;
 483
 484        if (!watchdog_enabled)
 485                printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 486
 487}
 488
 489static void watchdog_disable_all_cpus(void)
 490{
 491        int cpu;
 492
 493        for_each_online_cpu(cpu)
 494                watchdog_disable(cpu);
 495
 496        /* if all watchdogs are disabled, then they are disabled for the system */
 497        watchdog_enabled = 0;
 498}
 499
 500
 501/* sysctl functions */
 502#ifdef CONFIG_SYSCTL
 503/*
 504 * proc handler for /proc/sys/kernel/nmi_watchdog
 505 */
 506
 507int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 508                     void __user *buffer, size_t *length, loff_t *ppos)
 509{
 510        proc_dointvec(table, write, buffer, length, ppos);
 511
 512        if (write) {
 513                if (watchdog_enabled)
 514                        watchdog_enable_all_cpus();
 515                else
 516                        watchdog_disable_all_cpus();
 517        }
 518        return 0;
 519}
 520
 521int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 522                             void __user *buffer,
 523                             size_t *lenp, loff_t *ppos)
 524{
 525        return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 526}
 527#endif /* CONFIG_SYSCTL */
 528
 529
 530/*
 531 * Create/destroy watchdog threads as CPUs come and go:
 532 */
 533static int __cpuinit
 534cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 535{
 536        int hotcpu = (unsigned long)hcpu;
 537        int err = 0;
 538
 539        switch (action) {
 540        case CPU_UP_PREPARE:
 541        case CPU_UP_PREPARE_FROZEN:
 542                err = watchdog_prepare_cpu(hotcpu);
 543                break;
 544        case CPU_ONLINE:
 545        case CPU_ONLINE_FROZEN:
 546                if (watchdog_enabled)
 547                        err = watchdog_enable(hotcpu);
 548                break;
 549#ifdef CONFIG_HOTPLUG_CPU
 550        case CPU_UP_CANCELED:
 551        case CPU_UP_CANCELED_FROZEN:
 552                watchdog_disable(hotcpu);
 553                break;
 554        case CPU_DEAD:
 555        case CPU_DEAD_FROZEN:
 556                watchdog_disable(hotcpu);
 557                break;
 558#endif /* CONFIG_HOTPLUG_CPU */
 559        }
 560
 561        /*
 562         * hardlockup and softlockup are not important enough
 563         * to block cpu bring up.  Just always succeed and
 564         * rely on printk output to flag problems.
 565         */
 566        return NOTIFY_OK;
 567}
 568
 569static struct notifier_block __cpuinitdata cpu_nfb = {
 570        .notifier_call = cpu_callback
 571};
 572
 573void __init lockup_detector_init(void)
 574{
 575        void *cpu = (void *)(long)smp_processor_id();
 576        int err;
 577
 578        err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 579        WARN_ON(notifier_to_errno(err));
 580
 581        cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 582        register_cpu_notifier(&cpu_nfb);
 583
 584        return;
 585}
 586