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         __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         __get_cpu_var(watchdog_nmi_touch) = true;
 146         touch_softlockup_watchdog();
 147 }
 148 EXPORT_SYMBOL(touch_nmi_watchdog);
 149
 150 #endif
 151
 152 void touch_softlockup_watchdog_sync(void)
 153 {
 154         __raw_get_cpu_var(softlockup_touch_sync) = true;
 155         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 156 }
 157
 158 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 159 /* watchdog detector functions */
 160 static int is_hardlockup(void)
 161 {
 162         unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
 163
 164         if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
 165                 return 1;
 166
 167         __get_cpu_var(hrtimer_interrupts_saved) = hrint;
 168         return 0;
 169 }
 170 #endif
 171
 172 static int is_softlockup(unsigned long touch_ts)
 173 {
 174         unsigned long now = get_timestamp(smp_processor_id());
 175
 176         /* Warn about unreasonable delays: */
 177         if (time_after(now, touch_ts + softlockup_thresh))
 178                 return now - touch_ts;
 179
 180         return 0;
 181 }
 182
 183 static int
 184 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
 185 {
 186         did_panic = 1;
 187
 188         return NOTIFY_DONE;
 189 }
 190
 191 static struct notifier_block panic_block = {
 192         .notifier_call = watchdog_panic,
 193 };
 194
 195 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 196 static struct perf_event_attr wd_hw_attr = {
 197         .type           = PERF_TYPE_HARDWARE,
 198         .config         = PERF_COUNT_HW_CPU_CYCLES,
 199         .size           = sizeof(struct perf_event_attr),
 200         .pinned         = 1,
 201         .disabled       = 1,
 202 };
 203
 204 /* Callback function for perf event subsystem */
 205 void watchdog_overflow_callback(struct perf_event *event, int nmi,
 206                  struct perf_sample_data *data,
 207                  struct pt_regs *regs)
 208 {
 209         /* Ensure the watchdog never gets throttled */
 210         event->hw.interrupts = 0;
 211
 212         if (__get_cpu_var(watchdog_nmi_touch) == true) {
 213                 __get_cpu_var(watchdog_nmi_touch) = false;
 214                 return;
 215         }
 216
 217         /* check for a hardlockup
 218          * This is done by making sure our timer interrupt
 219          * is incrementing.  The timer interrupt should have
 220          * fired multiple times before we overflow'd.  If it hasn't
 221          * then this is a good indication the cpu is stuck
 222          */
 223         if (is_hardlockup()) {
 224                 int this_cpu = smp_processor_id();
 225
 226                 /* only print hardlockups once */
 227                 if (__get_cpu_var(hard_watchdog_warn) == true)
 228                         return;
 229
 230                 if (hardlockup_panic)
 231                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 232                 else
 233                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 234
 235                 __get_cpu_var(hard_watchdog_warn) = true;
 236                 return;
 237         }
 238
 239         __get_cpu_var(hard_watchdog_warn) = false;
 240         return;
 241 }
 242 static void watchdog_interrupt_count(void)
 243 {
 244         __get_cpu_var(hrtimer_interrupts)++;
 245 }
 246 #else
 247 static inline void watchdog_interrupt_count(void) { return; }
 248 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 249
 250 /* watchdog kicker functions */
 251 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 252 {
 253         unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
 254         struct pt_regs *regs = get_irq_regs();
 255         int duration;
 256
 257         /* kick the hardlockup detector */
 258         watchdog_interrupt_count();
 259
 260         /* kick the softlockup detector */
 261         wake_up_process(__get_cpu_var(softlockup_watchdog));
 262
 263         /* .. and repeat */
 264         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 265
 266         if (touch_ts == 0) {
 267                 if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
 268                         /*
 269                          * If the time stamp was touched atomically
 270                          * make sure the scheduler tick is up to date.
 271                          */
 272                         __get_cpu_var(softlockup_touch_sync) = false;
 273                         sched_clock_tick();
 274                 }
 275                 __touch_watchdog();
 276                 return HRTIMER_RESTART;
 277         }
 278
 279         /* check for a softlockup
 280          * This is done by making sure a high priority task is
 281          * being scheduled.  The task touches the watchdog to
 282          * indicate it is getting cpu time.  If it hasn't then
 283          * this is a good indication some task is hogging the cpu
 284          */
 285         duration = is_softlockup(touch_ts);
 286         if (unlikely(duration)) {
 287                 /* only warn once */
 288                 if (__get_cpu_var(soft_watchdog_warn) == true)
 289                         return HRTIMER_RESTART;
 290
 291                 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 292                         smp_processor_id(), duration,
 293                         current->comm, task_pid_nr(current));
 294                 print_modules();
 295                 print_irqtrace_events(current);
 296                 if (regs)
 297                         show_regs(regs);
 298                 else
 299                         dump_stack();
 300
 301                 if (softlockup_panic)
 302                         panic("softlockup: hung tasks");
 303                 __get_cpu_var(soft_watchdog_warn) = true;
 304         } else
 305                 __get_cpu_var(soft_watchdog_warn) = false;
 306
 307         return HRTIMER_RESTART;
 308 }
 309
 310
 311 /*
 312  * The watchdog thread - touches the timestamp.
 313  */
 314 static int watchdog(void *unused)
 315 {
 316         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 317         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 318
 319         sched_setscheduler(current, SCHED_FIFO, &param);
 320
 321         /* initialize timestamp */
 322         __touch_watchdog();
 323
 324         /* kick off the timer for the hardlockup detector */
 325         /* done here because hrtimer_start can only pin to smp_processor_id() */
 326         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 327                       HRTIMER_MODE_REL_PINNED);
 328
 329         set_current_state(TASK_INTERRUPTIBLE);
 330         /*
 331          * Run briefly once per second to reset the softlockup timestamp.
 332          * If this gets delayed for more than 60 seconds then the
 333          * debug-printout triggers in watchdog_timer_fn().
 334          */
 335         while (!kthread_should_stop()) {
 336                 __touch_watchdog();
 337                 schedule();
 338
 339                 if (kthread_should_stop())
 340                         break;
 341
 342                 set_current_state(TASK_INTERRUPTIBLE);
 343         }
 344         __set_current_state(TASK_RUNNING);
 345
 346         return 0;
 347 }
 348
 349
 350 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 351 static int watchdog_nmi_enable(int cpu)
 352 {
 353         struct perf_event_attr *wd_attr;
 354         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 355
 356         /* is it already setup and enabled? */
 357         if (event && event->state > PERF_EVENT_STATE_OFF)
 358                 goto out;
 359
 360         /* it is setup but not enabled */
 361         if (event != NULL)
 362                 goto out_enable;
 363
 364         /* Try to register using hardware perf events */
 365         wd_attr = &wd_hw_attr;
 366         wd_attr->sample_period = hw_nmi_get_sample_period();
 367         event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
 368         if (!IS_ERR(event)) {
 369                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
 370                 goto out_save;
 371         }
 372
 373         printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
 374         return -1;
 375
 376         /* success path */
 377 out_save:
 378         per_cpu(watchdog_ev, cpu) = event;
 379 out_enable:
 380         perf_event_enable(per_cpu(watchdog_ev, cpu));
 381 out:
 382         return 0;
 383 }
 384
 385 static void watchdog_nmi_disable(int cpu)
 386 {
 387         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 388
 389         if (event) {
 390                 perf_event_disable(event);
 391                 per_cpu(watchdog_ev, cpu) = NULL;
 392
 393                 /* should be in cleanup, but blocks oprofile */
 394                 perf_event_release_kernel(event);
 395         }
 396         return;
 397 }
 398 #else
 399 static int watchdog_nmi_enable(int cpu) { return 0; }
 400 static void watchdog_nmi_disable(int cpu) { return; }
 401 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 402
 403 /* prepare/enable/disable routines */
 404 static int watchdog_prepare_cpu(int cpu)
 405 {
 406         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 407
 408         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 409         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 410         hrtimer->function = watchdog_timer_fn;
 411
 412         return 0;
 413 }
 414
 415 static int watchdog_enable(int cpu)
 416 {
 417         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 418
 419         /* enable the perf event */
 420         if (watchdog_nmi_enable(cpu) != 0)
 421                 return -1;
 422
 423         /* create the watchdog thread */
 424         if (!p) {
 425                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 426                 if (IS_ERR(p)) {
 427                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 428                         return -1;
 429                 }
 430                 kthread_bind(p, cpu);
 431                 per_cpu(watchdog_touch_ts, cpu) = 0;
 432                 per_cpu(softlockup_watchdog, cpu) = p;
 433                 wake_up_process(p);
 434         }
 435
 436         return 0;
 437 }
 438
 439 static void watchdog_disable(int cpu)
 440 {
 441         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 442         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 443
 444         /*
 445          * cancel the timer first to stop incrementing the stats
 446          * and waking up the kthread
 447          */
 448         hrtimer_cancel(hrtimer);
 449
 450         /* disable the perf event */
 451         watchdog_nmi_disable(cpu);
 452
 453         /* stop the watchdog thread */
 454         if (p) {
 455                 per_cpu(softlockup_watchdog, cpu) = NULL;
 456                 kthread_stop(p);
 457         }
 458
 459         /* if any cpu succeeds, watchdog is considered enabled for the system */
 460         watchdog_enabled = 1;
 461 }
 462
 463 static void watchdog_enable_all_cpus(void)
 464 {
 465         int cpu;
 466         int result = 0;
 467
 468         for_each_online_cpu(cpu)
 469                 result += watchdog_enable(cpu);
 470
 471         if (result)
 472                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 473
 474 }
 475
 476 static void watchdog_disable_all_cpus(void)
 477 {
 478         int cpu;
 479
 480         for_each_online_cpu(cpu)
 481                 watchdog_disable(cpu);
 482
 483         /* if all watchdogs are disabled, then they are disabled for the system */
 484         watchdog_enabled = 0;
 485 }
 486
 487
 488 /* sysctl functions */
 489 #ifdef CONFIG_SYSCTL
 490 /*
 491  * proc handler for /proc/sys/kernel/nmi_watchdog
 492  */
 493
 494 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 495                      void __user *buffer, size_t *length, loff_t *ppos)
 496 {
 497         proc_dointvec(table, write, buffer, length, ppos);
 498
 499         if (watchdog_enabled)
 500                 watchdog_enable_all_cpus();
 501         else
 502                 watchdog_disable_all_cpus();
 503         return 0;
 504 }
 505
 506 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 507                              void __user *buffer,
 508                              size_t *lenp, loff_t *ppos)
 509 {
 510         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 511 }
 512 #endif /* CONFIG_SYSCTL */
 513
 514
 515 /*
 516  * Create/destroy watchdog threads as CPUs come and go:
 517  */
 518 static int __cpuinit
 519 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 520 {
 521         int hotcpu = (unsigned long)hcpu;
 522
 523         switch (action) {
 524         case CPU_UP_PREPARE:
 525         case CPU_UP_PREPARE_FROZEN:
 526                 if (watchdog_prepare_cpu(hotcpu))
 527                         return NOTIFY_BAD;
 528                 break;
 529         case CPU_ONLINE:
 530         case CPU_ONLINE_FROZEN:
 531                 if (watchdog_enable(hotcpu))
 532                         return NOTIFY_BAD;
 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 NOTIFY_OK;
 546 }
 547
 548 static struct notifier_block __cpuinitdata cpu_nfb = {
 549         .notifier_call = cpu_callback
 550 };
 551
 552 static int __init spawn_watchdog_task(void)
 553 {
 554         void *cpu = (void *)(long)smp_processor_id();
 555         int err;
 556
 557         if (no_watchdog)
 558                 return 0;
 559
 560         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 561         WARN_ON(err == NOTIFY_BAD);
 562
 563         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 564         register_cpu_notifier(&cpu_nfb);
 565
 566         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
 567
 568         return 0;
 569 }
 570 early_initcall(spawn_watchdog_task);