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  * Note: Most of this code is borrowed heavily from the original softlockup
   7  * detector, so thanks to Ingo for the initial implementation.
   8  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
   9  * to those contributors as well.
  10  */
  11
  12 #include <linux/mm.h>
  13 #include <linux/cpu.h>
  14 #include <linux/nmi.h>
  15 #include <linux/init.h>
  16 #include <linux/delay.h>
  17 #include <linux/freezer.h>
  18 #include <linux/kthread.h>
  19 #include <linux/lockdep.h>
  20 #include <linux/notifier.h>
  21 #include <linux/module.h>
  22 #include <linux/sysctl.h>
  23
  24 #include <asm/irq_regs.h>
  25 #include <linux/perf_event.h>
  26
  27 int watchdog_enabled = 1;
  28 int __read_mostly watchdog_thresh = 10;
  29
  30 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
  31 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  32 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  33 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  34 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
  35 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  36 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  37 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
  38 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
  39 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
  40 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
  41 #endif
  42
  43 /* boot commands */
  44 /*
  45  * Should we panic when a soft-lockup or hard-lockup occurs:
  46  */
  47 #ifdef CONFIG_HARDLOCKUP_DETECTOR
  48 static int hardlockup_panic =
  49                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
  50
  51 static int __init hardlockup_panic_setup(char *str)
  52 {
  53         if (!strncmp(str, "panic", 5))
  54                 hardlockup_panic = 1;
  55         else if (!strncmp(str, "nopanic", 7))
  56                 hardlockup_panic = 0;
  57         else if (!strncmp(str, "0", 1))
  58                 watchdog_enabled = 0;
  59         return 1;
  60 }
  61 __setup("nmi_watchdog=", hardlockup_panic_setup);
  62 #endif
  63
  64 unsigned int __read_mostly softlockup_panic =
  65                         CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
  66
  67 static int __init softlockup_panic_setup(char *str)
  68 {
  69         softlockup_panic = simple_strtoul(str, NULL, 0);
  70
  71         return 1;
  72 }
  73 __setup("softlockup_panic=", softlockup_panic_setup);
  74
  75 static int __init nowatchdog_setup(char *str)
  76 {
  77         watchdog_enabled = 0;
  78         return 1;
  79 }
  80 __setup("nowatchdog", nowatchdog_setup);
  81
  82 /* deprecated */
  83 static int __init nosoftlockup_setup(char *str)
  84 {
  85         watchdog_enabled = 0;
  86         return 1;
  87 }
  88 __setup("nosoftlockup", nosoftlockup_setup);
  89 /*  */
  90
  91 /*
  92  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
  93  * lockups can have false positives under extreme conditions. So we generally
  94  * want a higher threshold for soft lockups than for hard lockups. So we couple
  95  * the thresholds with a factor: we make the soft threshold twice the amount of
  96  * time the hard threshold is.
  97  */
  98 static int get_softlockup_thresh(void)
  99 {
 100         return watchdog_thresh * 2;
 101 }
 102
 103 /*
 104  * Returns seconds, approximately.  We don't need nanosecond
 105  * resolution, and we don't need to waste time with a big divide when
 106  * 2^30ns == 1.074s.
 107  */
 108 static unsigned long get_timestamp(int this_cpu)
 109 {
 110         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
 111 }
 112
 113 static unsigned long get_sample_period(void)
 114 {
 115         /*
 116          * convert watchdog_thresh from seconds to ns
 117          * the divide by 5 is to give hrtimer several chances (two
 118          * or three with the current relation between the soft
 119          * and hard thresholds) to increment before the
 120          * hardlockup detector generates a warning
 121          */
 122         return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
 123 }
 124
 125 /* Commands for resetting the watchdog */
 126 static void __touch_watchdog(void)
 127 {
 128         int this_cpu = smp_processor_id();
 129
 130         __this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
 131 }
 132
 133 void touch_softlockup_watchdog(void)
 134 {
 135         __this_cpu_write(watchdog_touch_ts, 0);
 136 }
 137 EXPORT_SYMBOL(touch_softlockup_watchdog);
 138
 139 void touch_all_softlockup_watchdogs(void)
 140 {
 141         int cpu;
 142
 143         /*
 144          * this is done lockless
 145          * do we care if a 0 races with a timestamp?
 146          * all it means is the softlock check starts one cycle later
 147          */
 148         for_each_online_cpu(cpu)
 149                 per_cpu(watchdog_touch_ts, cpu) = 0;
 150 }
 151
 152 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 153 void touch_nmi_watchdog(void)
 154 {
 155         if (watchdog_enabled) {
 156                 unsigned cpu;
 157
 158                 for_each_present_cpu(cpu) {
 159                         if (per_cpu(watchdog_nmi_touch, cpu) != true)
 160                                 per_cpu(watchdog_nmi_touch, cpu) = true;
 161                 }
 162         }
 163         touch_softlockup_watchdog();
 164 }
 165 EXPORT_SYMBOL(touch_nmi_watchdog);
 166
 167 #endif
 168
 169 void touch_softlockup_watchdog_sync(void)
 170 {
 171         __raw_get_cpu_var(softlockup_touch_sync) = true;
 172         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 173 }
 174
 175 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 176 /* watchdog detector functions */
 177 static int is_hardlockup(void)
 178 {
 179         unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 180
 181         if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 182                 return 1;
 183
 184         __this_cpu_write(hrtimer_interrupts_saved, hrint);
 185         return 0;
 186 }
 187 #endif
 188
 189 static int is_softlockup(unsigned long touch_ts)
 190 {
 191         unsigned long now = get_timestamp(smp_processor_id());
 192
 193         /* Warn about unreasonable delays: */
 194         if (time_after(now, touch_ts + get_softlockup_thresh()))
 195                 return now - touch_ts;
 196
 197         return 0;
 198 }
 199
 200 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 201
 202 static struct perf_event_attr wd_hw_attr = {
 203         .type           = PERF_TYPE_HARDWARE,
 204         .config         = PERF_COUNT_HW_CPU_CYCLES,
 205         .size           = sizeof(struct perf_event_attr),
 206         .pinned         = 1,
 207         .disabled       = 1,
 208 };
 209
 210 /* Callback function for perf event subsystem */
 211 static void watchdog_overflow_callback(struct perf_event *event,
 212                  struct perf_sample_data *data,
 213                  struct pt_regs *regs)
 214 {
 215         /* Ensure the watchdog never gets throttled */
 216         event->hw.interrupts = 0;
 217
 218         if (__this_cpu_read(watchdog_nmi_touch) == true) {
 219                 __this_cpu_write(watchdog_nmi_touch, false);
 220                 return;
 221         }
 222
 223         /* check for a hardlockup
 224          * This is done by making sure our timer interrupt
 225          * is incrementing.  The timer interrupt should have
 226          * fired multiple times before we overflow'd.  If it hasn't
 227          * then this is a good indication the cpu is stuck
 228          */
 229         if (is_hardlockup()) {
 230                 int this_cpu = smp_processor_id();
 231
 232                 /* only print hardlockups once */
 233                 if (__this_cpu_read(hard_watchdog_warn) == true)
 234                         return;
 235
 236                 if (hardlockup_panic)
 237                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 238                 else
 239                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 240
 241                 __this_cpu_write(hard_watchdog_warn, true);
 242                 return;
 243         }
 244
 245         __this_cpu_write(hard_watchdog_warn, false);
 246         return;
 247 }
 248 static void watchdog_interrupt_count(void)
 249 {
 250         __this_cpu_inc(hrtimer_interrupts);
 251 }
 252 #else
 253 static inline void watchdog_interrupt_count(void) { return; }
 254 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 255
 256 /* watchdog kicker functions */
 257 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 258 {
 259         unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 260         struct pt_regs *regs = get_irq_regs();
 261         int duration;
 262
 263         /* kick the hardlockup detector */
 264         watchdog_interrupt_count();
 265
 266         /* kick the softlockup detector */
 267         wake_up_process(__this_cpu_read(softlockup_watchdog));
 268
 269         /* .. and repeat */
 270         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 271
 272         if (touch_ts == 0) {
 273                 if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 274                         /*
 275                          * If the time stamp was touched atomically
 276                          * make sure the scheduler tick is up to date.
 277                          */
 278                         __this_cpu_write(softlockup_touch_sync, false);
 279                         sched_clock_tick();
 280                 }
 281                 __touch_watchdog();
 282                 return HRTIMER_RESTART;
 283         }
 284
 285         /* check for a softlockup
 286          * This is done by making sure a high priority task is
 287          * being scheduled.  The task touches the watchdog to
 288          * indicate it is getting cpu time.  If it hasn't then
 289          * this is a good indication some task is hogging the cpu
 290          */
 291         duration = is_softlockup(touch_ts);
 292         if (unlikely(duration)) {
 293                 /* only warn once */
 294                 if (__this_cpu_read(soft_watchdog_warn) == true)
 295                         return HRTIMER_RESTART;
 296
 297                 printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 298                         smp_processor_id(), duration,
 299                         current->comm, task_pid_nr(current));
 300                 print_modules();
 301                 print_irqtrace_events(current);
 302                 if (regs)
 303                         show_regs(regs);
 304                 else
 305                         dump_stack();
 306
 307                 if (softlockup_panic)
 308                         panic("softlockup: hung tasks");
 309                 __this_cpu_write(soft_watchdog_warn, true);
 310         } else
 311                 __this_cpu_write(soft_watchdog_warn, false);
 312
 313         return HRTIMER_RESTART;
 314 }
 315
 316
 317 /*
 318  * The watchdog thread - touches the timestamp.
 319  */
 320 static int watchdog(void *unused)
 321 {
 322         struct sched_param param = { .sched_priority = 0 };
 323         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 324
 325         /* initialize timestamp */
 326         __touch_watchdog();
 327
 328         /* kick off the timer for the hardlockup detector */
 329         /* done here because hrtimer_start can only pin to smp_processor_id() */
 330         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 331                       HRTIMER_MODE_REL_PINNED);
 332
 333         set_current_state(TASK_INTERRUPTIBLE);
 334         /*
 335          * Run briefly (kicked by the hrtimer callback function) once every
 336          * get_sample_period() seconds (4 seconds by default) to reset the
 337          * softlockup timestamp. If this gets delayed for more than
 338          * 2*watchdog_thresh seconds then the debug-printout triggers in
 339          * watchdog_timer_fn().
 340          */
 341         while (!kthread_should_stop()) {
 342                 __touch_watchdog();
 343                 schedule();
 344
 345                 if (kthread_should_stop())
 346                         break;
 347
 348                 set_current_state(TASK_INTERRUPTIBLE);
 349         }
 350         __set_current_state(TASK_RUNNING);
 351         sched_setscheduler(current, SCHED_NORMAL, &param);
 352         return 0;
 353 }
 354
 355
 356 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 357 static int watchdog_nmi_enable(int cpu)
 358 {
 359         struct perf_event_attr *wd_attr;
 360         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 361
 362         /* is it already setup and enabled? */
 363         if (event && event->state > PERF_EVENT_STATE_OFF)
 364                 goto out;
 365
 366         /* it is setup but not enabled */
 367         if (event != NULL)
 368                 goto out_enable;
 369
 370         wd_attr = &wd_hw_attr;
 371         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 372
 373         /* Try to register using hardware perf events */
 374         event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 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
 381         /* vary the KERN level based on the returned errno */
 382         if (PTR_ERR(event) == -EOPNOTSUPP)
 383                 printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 384         else if (PTR_ERR(event) == -ENOENT)
 385                 printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
 386         else
 387                 printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
 388         return PTR_ERR(event);
 389
 390         /* success path */
 391 out_save:
 392         per_cpu(watchdog_ev, cpu) = event;
 393 out_enable:
 394         perf_event_enable(per_cpu(watchdog_ev, cpu));
 395 out:
 396         return 0;
 397 }
 398
 399 static void watchdog_nmi_disable(int cpu)
 400 {
 401         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 402
 403         if (event) {
 404                 perf_event_disable(event);
 405                 per_cpu(watchdog_ev, cpu) = NULL;
 406
 407                 /* should be in cleanup, but blocks oprofile */
 408                 perf_event_release_kernel(event);
 409         }
 410         return;
 411 }
 412 #else
 413 static int watchdog_nmi_enable(int cpu) { return 0; }
 414 static void watchdog_nmi_disable(int cpu) { return; }
 415 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 416
 417 /* prepare/enable/disable routines */
 418 static void watchdog_prepare_cpu(int cpu)
 419 {
 420         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 421
 422         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 423         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 424         hrtimer->function = watchdog_timer_fn;
 425 }
 426
 427 static int watchdog_enable(int cpu)
 428 {
 429         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 430         int err = 0;
 431
 432         /* enable the perf event */
 433         err = watchdog_nmi_enable(cpu);
 434
 435         /* Regardless of err above, fall through and start softlockup */
 436
 437         /* create the watchdog thread */
 438         if (!p) {
 439                 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 440                 p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
 441                 if (IS_ERR(p)) {
 442                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 443                         if (!err) {
 444                                 /* if hardlockup hasn't already set this */
 445                                 err = PTR_ERR(p);
 446                                 /* and disable the perf event */
 447                                 watchdog_nmi_disable(cpu);
 448                         }
 449                         goto out;
 450                 }
 451                 sched_setscheduler(p, SCHED_FIFO, &param);
 452                 kthread_bind(p, cpu);
 453                 per_cpu(watchdog_touch_ts, cpu) = 0;
 454                 per_cpu(softlockup_watchdog, cpu) = p;
 455                 wake_up_process(p);
 456         }
 457
 458 out:
 459         return err;
 460 }
 461
 462 static void watchdog_disable(int cpu)
 463 {
 464         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 465         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 466
 467         /*
 468          * cancel the timer first to stop incrementing the stats
 469          * and waking up the kthread
 470          */
 471         hrtimer_cancel(hrtimer);
 472
 473         /* disable the perf event */
 474         watchdog_nmi_disable(cpu);
 475
 476         /* stop the watchdog thread */
 477         if (p) {
 478                 per_cpu(softlockup_watchdog, cpu) = NULL;
 479                 kthread_stop(p);
 480         }
 481 }
 482
 483 /* sysctl functions */
 484 #ifdef CONFIG_SYSCTL
 485 static void watchdog_enable_all_cpus(void)
 486 {
 487         int cpu;
 488
 489         watchdog_enabled = 0;
 490
 491         for_each_online_cpu(cpu)
 492                 if (!watchdog_enable(cpu))
 493                         /* if any cpu succeeds, watchdog is considered
 494                            enabled for the system */
 495                         watchdog_enabled = 1;
 496
 497         if (!watchdog_enabled)
 498                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 499
 500 }
 501
 502 static void watchdog_disable_all_cpus(void)
 503 {
 504         int cpu;
 505
 506         for_each_online_cpu(cpu)
 507                 watchdog_disable(cpu);
 508
 509         /* if all watchdogs are disabled, then they are disabled for the system */
 510         watchdog_enabled = 0;
 511 }
 512
 513
 514 /*
 515  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
 516  */
 517
 518 int proc_dowatchdog(struct ctl_table *table, int write,
 519                     void __user *buffer, size_t *lenp, loff_t *ppos)
 520 {
 521         int ret;
 522
 523         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 524         if (ret || !write)
 525                 goto out;
 526
 527         if (watchdog_enabled && watchdog_thresh)
 528                 watchdog_enable_all_cpus();
 529         else
 530                 watchdog_disable_all_cpus();
 531
 532 out:
 533         return ret;
 534 }
 535 #endif /* CONFIG_SYSCTL */
 536
 537
 538 /*
 539  * Create/destroy watchdog threads as CPUs come and go:
 540  */
 541 static int __cpuinit
 542 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 543 {
 544         int hotcpu = (unsigned long)hcpu;
 545
 546         switch (action) {
 547         case CPU_UP_PREPARE:
 548         case CPU_UP_PREPARE_FROZEN:
 549                 watchdog_prepare_cpu(hotcpu);
 550                 break;
 551         case CPU_ONLINE:
 552         case CPU_ONLINE_FROZEN:
 553                 if (watchdog_enabled)
 554                         watchdog_enable(hotcpu);
 555                 break;
 556 #ifdef CONFIG_HOTPLUG_CPU
 557         case CPU_UP_CANCELED:
 558         case CPU_UP_CANCELED_FROZEN:
 559                 watchdog_disable(hotcpu);
 560                 break;
 561         case CPU_DEAD:
 562         case CPU_DEAD_FROZEN:
 563                 watchdog_disable(hotcpu);
 564                 break;
 565 #endif /* CONFIG_HOTPLUG_CPU */
 566         }
 567
 568         /*
 569          * hardlockup and softlockup are not important enough
 570          * to block cpu bring up.  Just always succeed and
 571          * rely on printk output to flag problems.
 572          */
 573         return NOTIFY_OK;
 574 }
 575
 576 static struct notifier_block __cpuinitdata cpu_nfb = {
 577         .notifier_call = cpu_callback
 578 };
 579
 580 void __init lockup_detector_init(void)
 581 {
 582         void *cpu = (void *)(long)smp_processor_id();
 583         int err;
 584
 585         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 586         WARN_ON(notifier_to_errno(err));
 587
 588         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 589         register_cpu_notifier(&cpu_nfb);
 590
 591         return;
 592 }