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(bool, watchdog_nmi_touch);
  35 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  36 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  37 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  38 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
  39 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
  40 #ifdef CONFIG_PERF_EVENTS_NMI
  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_PERF_EVENTS_NMI
  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 = raw_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 void touch_nmi_watchdog(void)
 143 {
 144         __get_cpu_var(watchdog_nmi_touch) = true;
 145         touch_softlockup_watchdog();
 146 }
 147 EXPORT_SYMBOL(touch_nmi_watchdog);
 148
 149 void touch_softlockup_watchdog_sync(void)
 150 {
 151         __raw_get_cpu_var(softlockup_touch_sync) = true;
 152         __raw_get_cpu_var(watchdog_touch_ts) = 0;
 153 }
 154
 155 #ifdef CONFIG_PERF_EVENTS_NMI
 156 /* watchdog detector functions */
 157 static int is_hardlockup(int cpu)
 158 {
 159         unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
 160
 161         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 162                 return 1;
 163
 164         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 165         return 0;
 166 }
 167 #endif
 168
 169 static int is_softlockup(unsigned long touch_ts, int cpu)
 170 {
 171         unsigned long now = get_timestamp(cpu);
 172
 173         /* Warn about unreasonable delays: */
 174         if (time_after(now, touch_ts + softlockup_thresh))
 175                 return now - touch_ts;
 176
 177         return 0;
 178 }
 179
 180 static int
 181 watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
 182 {
 183         did_panic = 1;
 184
 185         return NOTIFY_DONE;
 186 }
 187
 188 static struct notifier_block panic_block = {
 189         .notifier_call = watchdog_panic,
 190 };
 191
 192 #ifdef CONFIG_PERF_EVENTS_NMI
 193 static struct perf_event_attr wd_hw_attr = {
 194         .type           = PERF_TYPE_HARDWARE,
 195         .config         = PERF_COUNT_HW_CPU_CYCLES,
 196         .size           = sizeof(struct perf_event_attr),
 197         .pinned         = 1,
 198         .disabled       = 1,
 199 };
 200
 201 /* Callback function for perf event subsystem */
 202 void watchdog_overflow_callback(struct perf_event *event, int nmi,
 203                  struct perf_sample_data *data,
 204                  struct pt_regs *regs)
 205 {
 206         int this_cpu = smp_processor_id();
 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(this_cpu)) {
 220                 /* only print hardlockups once */
 221                 if (__get_cpu_var(hard_watchdog_warn) == true)
 222                         return;
 223
 224                 if (hardlockup_panic)
 225                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 226                 else
 227                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 228
 229                 __get_cpu_var(hard_watchdog_warn) = true;
 230                 return;
 231         }
 232
 233         __get_cpu_var(hard_watchdog_warn) = false;
 234         return;
 235 }
 236 static void watchdog_interrupt_count(void)
 237 {
 238         __get_cpu_var(hrtimer_interrupts)++;
 239 }
 240 #else
 241 static inline void watchdog_interrupt_count(void) { return; }
 242 #endif /* CONFIG_PERF_EVENTS_NMI */
 243
 244 /* watchdog kicker functions */
 245 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 246 {
 247         int this_cpu = smp_processor_id();
 248         unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
 249         struct pt_regs *regs = get_irq_regs();
 250         int duration;
 251
 252         /* kick the hardlockup detector */
 253         watchdog_interrupt_count();
 254
 255         /* kick the softlockup detector */
 256         wake_up_process(__get_cpu_var(softlockup_watchdog));
 257
 258         /* .. and repeat */
 259         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 260
 261         if (touch_ts == 0) {
 262                 if (unlikely(per_cpu(softlockup_touch_sync, this_cpu))) {
 263                         /*
 264                          * If the time stamp was touched atomically
 265                          * make sure the scheduler tick is up to date.
 266                          */
 267                         per_cpu(softlockup_touch_sync, this_cpu) = false;
 268                         sched_clock_tick();
 269                 }
 270                 __touch_watchdog();
 271                 return HRTIMER_RESTART;
 272         }
 273
 274         /* check for a softlockup
 275          * This is done by making sure a high priority task is
 276          * being scheduled.  The task touches the watchdog to
 277          * indicate it is getting cpu time.  If it hasn't then
 278          * this is a good indication some task is hogging the cpu
 279          */
 280         duration = is_softlockup(touch_ts, this_cpu);
 281         if (unlikely(duration)) {
 282                 /* only warn once */
 283                 if (__get_cpu_var(soft_watchdog_warn) == true)
 284                         return HRTIMER_RESTART;
 285
 286                 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 287                         this_cpu, duration,
 288                         current->comm, task_pid_nr(current));
 289                 print_modules();
 290                 print_irqtrace_events(current);
 291                 if (regs)
 292                         show_regs(regs);
 293                 else
 294                         dump_stack();
 295
 296                 if (softlockup_panic)
 297                         panic("softlockup: hung tasks");
 298                 __get_cpu_var(soft_watchdog_warn) = true;
 299         } else
 300                 __get_cpu_var(soft_watchdog_warn) = false;
 301
 302         return HRTIMER_RESTART;
 303 }
 304
 305
 306 /*
 307  * The watchdog thread - touches the timestamp.
 308  */
 309 static int watchdog(void *__bind_cpu)
 310 {
 311         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 312         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
 313
 314         sched_setscheduler(current, SCHED_FIFO, &param);
 315
 316         /* initialize timestamp */
 317         __touch_watchdog();
 318
 319         /* kick off the timer for the hardlockup detector */
 320         /* done here because hrtimer_start can only pin to smp_processor_id() */
 321         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 322                       HRTIMER_MODE_REL_PINNED);
 323
 324         set_current_state(TASK_INTERRUPTIBLE);
 325         /*
 326          * Run briefly once per second to reset the softlockup timestamp.
 327          * If this gets delayed for more than 60 seconds then the
 328          * debug-printout triggers in softlockup_tick().
 329          */
 330         while (!kthread_should_stop()) {
 331                 __touch_watchdog();
 332                 schedule();
 333
 334                 if (kthread_should_stop())
 335                         break;
 336
 337                 set_current_state(TASK_INTERRUPTIBLE);
 338         }
 339         __set_current_state(TASK_RUNNING);
 340
 341         return 0;
 342 }
 343
 344
 345 #ifdef CONFIG_PERF_EVENTS_NMI
 346 static int watchdog_nmi_enable(int cpu)
 347 {
 348         struct perf_event_attr *wd_attr;
 349         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 350
 351         /* is it already setup and enabled? */
 352         if (event && event->state > PERF_EVENT_STATE_OFF)
 353                 goto out;
 354
 355         /* it is setup but not enabled */
 356         if (event != NULL)
 357                 goto out_enable;
 358
 359         /* Try to register using hardware perf events */
 360         wd_attr = &wd_hw_attr;
 361         wd_attr->sample_period = hw_nmi_get_sample_period();
 362         event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
 363         if (!IS_ERR(event)) {
 364                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
 365                 goto out_save;
 366         }
 367
 368         printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
 369         return -1;
 370
 371         /* success path */
 372 out_save:
 373         per_cpu(watchdog_ev, cpu) = event;
 374 out_enable:
 375         perf_event_enable(per_cpu(watchdog_ev, cpu));
 376 out:
 377         return 0;
 378 }
 379
 380 static void watchdog_nmi_disable(int cpu)
 381 {
 382         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 383
 384         if (event) {
 385                 perf_event_disable(event);
 386                 per_cpu(watchdog_ev, cpu) = NULL;
 387
 388                 /* should be in cleanup, but blocks oprofile */
 389                 perf_event_release_kernel(event);
 390         }
 391         return;
 392 }
 393 #else
 394 static int watchdog_nmi_enable(int cpu) { return 0; }
 395 static void watchdog_nmi_disable(int cpu) { return; }
 396 #endif /* CONFIG_PERF_EVENTS_NMI */
 397
 398 /* prepare/enable/disable routines */
 399 static int watchdog_prepare_cpu(int cpu)
 400 {
 401         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 402
 403         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 404         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 405         hrtimer->function = watchdog_timer_fn;
 406
 407         return 0;
 408 }
 409
 410 static int watchdog_enable(int cpu)
 411 {
 412         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 413
 414         /* enable the perf event */
 415         if (watchdog_nmi_enable(cpu) != 0)
 416                 return -1;
 417
 418         /* create the watchdog thread */
 419         if (!p) {
 420                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 421                 if (IS_ERR(p)) {
 422                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 423                         return -1;
 424                 }
 425                 kthread_bind(p, cpu);
 426                 per_cpu(watchdog_touch_ts, cpu) = 0;
 427                 per_cpu(softlockup_watchdog, cpu) = p;
 428                 wake_up_process(p);
 429         }
 430
 431         return 0;
 432 }
 433
 434 static void watchdog_disable(int cpu)
 435 {
 436         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 437         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 438
 439         /*
 440          * cancel the timer first to stop incrementing the stats
 441          * and waking up the kthread
 442          */
 443         hrtimer_cancel(hrtimer);
 444
 445         /* disable the perf event */
 446         watchdog_nmi_disable(cpu);
 447
 448         /* stop the watchdog thread */
 449         if (p) {
 450                 per_cpu(softlockup_watchdog, cpu) = NULL;
 451                 kthread_stop(p);
 452         }
 453
 454         /* if any cpu succeeds, watchdog is considered enabled for the system */
 455         watchdog_enabled = 1;
 456 }
 457
 458 static void watchdog_enable_all_cpus(void)
 459 {
 460         int cpu;
 461         int result;
 462
 463         for_each_online_cpu(cpu)
 464                 result += watchdog_enable(cpu);
 465
 466         if (result)
 467                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 468
 469 }
 470
 471 static void watchdog_disable_all_cpus(void)
 472 {
 473         int cpu;
 474
 475         for_each_online_cpu(cpu)
 476                 watchdog_disable(cpu);
 477
 478         /* if all watchdogs are disabled, then they are disabled for the system */
 479         watchdog_enabled = 0;
 480 }
 481
 482
 483 /* sysctl functions */
 484 #ifdef CONFIG_SYSCTL
 485 /*
 486  * proc handler for /proc/sys/kernel/nmi_watchdog
 487  */
 488
 489 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 490                      void __user *buffer, size_t *length, loff_t *ppos)
 491 {
 492         proc_dointvec(table, write, buffer, length, ppos);
 493
 494         if (watchdog_enabled)
 495                 watchdog_enable_all_cpus();
 496         else
 497                 watchdog_disable_all_cpus();
 498         return 0;
 499 }
 500
 501 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 502                              void __user *buffer,
 503                              size_t *lenp, loff_t *ppos)
 504 {
 505         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 506 }
 507 #endif /* CONFIG_SYSCTL */
 508
 509
 510 /*
 511  * Create/destroy watchdog threads as CPUs come and go:
 512  */
 513 static int __cpuinit
 514 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 515 {
 516         int hotcpu = (unsigned long)hcpu;
 517
 518         switch (action) {
 519         case CPU_UP_PREPARE:
 520         case CPU_UP_PREPARE_FROZEN:
 521                 if (watchdog_prepare_cpu(hotcpu))
 522                         return NOTIFY_BAD;
 523                 break;
 524         case CPU_ONLINE:
 525         case CPU_ONLINE_FROZEN:
 526                 if (watchdog_enable(hotcpu))
 527                         return NOTIFY_BAD;
 528                 break;
 529 #ifdef CONFIG_HOTPLUG_CPU
 530         case CPU_UP_CANCELED:
 531         case CPU_UP_CANCELED_FROZEN:
 532                 watchdog_disable(hotcpu);
 533                 break;
 534         case CPU_DEAD:
 535         case CPU_DEAD_FROZEN:
 536                 watchdog_disable(hotcpu);
 537                 break;
 538 #endif /* CONFIG_HOTPLUG_CPU */
 539         }
 540         return NOTIFY_OK;
 541 }
 542
 543 static struct notifier_block __cpuinitdata cpu_nfb = {
 544         .notifier_call = cpu_callback
 545 };
 546
 547 static int __init spawn_watchdog_task(void)
 548 {
 549         void *cpu = (void *)(long)smp_processor_id();
 550         int err;
 551
 552         if (no_watchdog)
 553                 return 0;
 554
 555         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 556         WARN_ON(err == NOTIFY_BAD);
 557
 558         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 559         register_cpu_notifier(&cpu_nfb);
 560
 561         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
 562
 563         return 0;
 564 }
 565 early_initcall(spawn_watchdog_task);