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 = 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 #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(int cpu)
 161 {
 162         unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
 163
 164         if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
 165                 return 1;
 166
 167         per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
 168         return 0;
 169 }
 170 #endif
 171
 172 static int is_softlockup(unsigned long touch_ts, int cpu)
 173 {
 174         unsigned long now = get_timestamp(cpu);
 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         int this_cpu = smp_processor_id();
 210
 211         if (__get_cpu_var(watchdog_nmi_touch) == true) {
 212                 __get_cpu_var(watchdog_nmi_touch) = false;
 213                 return;
 214         }
 215
 216         /* check for a hardlockup
 217          * This is done by making sure our timer interrupt
 218          * is incrementing.  The timer interrupt should have
 219          * fired multiple times before we overflow'd.  If it hasn't
 220          * then this is a good indication the cpu is stuck
 221          */
 222         if (is_hardlockup(this_cpu)) {
 223                 /* only print hardlockups once */
 224                 if (__get_cpu_var(hard_watchdog_warn) == true)
 225                         return;
 226
 227                 if (hardlockup_panic)
 228                         panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 229                 else
 230                         WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 231
 232                 __get_cpu_var(hard_watchdog_warn) = true;
 233                 return;
 234         }
 235
 236         __get_cpu_var(hard_watchdog_warn) = false;
 237         return;
 238 }
 239 static void watchdog_interrupt_count(void)
 240 {
 241         __get_cpu_var(hrtimer_interrupts)++;
 242 }
 243 #else
 244 static inline void watchdog_interrupt_count(void) { return; }
 245 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 246
 247 /* watchdog kicker functions */
 248 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 249 {
 250         int this_cpu = smp_processor_id();
 251         unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
 252         struct pt_regs *regs = get_irq_regs();
 253         int duration;
 254
 255         /* kick the hardlockup detector */
 256         watchdog_interrupt_count();
 257
 258         /* kick the softlockup detector */
 259         wake_up_process(__get_cpu_var(softlockup_watchdog));
 260
 261         /* .. and repeat */
 262         hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 263
 264         if (touch_ts == 0) {
 265                 if (unlikely(per_cpu(softlockup_touch_sync, this_cpu))) {
 266                         /*
 267                          * If the time stamp was touched atomically
 268                          * make sure the scheduler tick is up to date.
 269                          */
 270                         per_cpu(softlockup_touch_sync, this_cpu) = false;
 271                         sched_clock_tick();
 272                 }
 273                 __touch_watchdog();
 274                 return HRTIMER_RESTART;
 275         }
 276
 277         /* check for a softlockup
 278          * This is done by making sure a high priority task is
 279          * being scheduled.  The task touches the watchdog to
 280          * indicate it is getting cpu time.  If it hasn't then
 281          * this is a good indication some task is hogging the cpu
 282          */
 283         duration = is_softlockup(touch_ts, this_cpu);
 284         if (unlikely(duration)) {
 285                 /* only warn once */
 286                 if (__get_cpu_var(soft_watchdog_warn) == true)
 287                         return HRTIMER_RESTART;
 288
 289                 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 290                         this_cpu, duration,
 291                         current->comm, task_pid_nr(current));
 292                 print_modules();
 293                 print_irqtrace_events(current);
 294                 if (regs)
 295                         show_regs(regs);
 296                 else
 297                         dump_stack();
 298
 299                 if (softlockup_panic)
 300                         panic("softlockup: hung tasks");
 301                 __get_cpu_var(soft_watchdog_warn) = true;
 302         } else
 303                 __get_cpu_var(soft_watchdog_warn) = false;
 304
 305         return HRTIMER_RESTART;
 306 }
 307
 308
 309 /*
 310  * The watchdog thread - touches the timestamp.
 311  */
 312 static int watchdog(void *__bind_cpu)
 313 {
 314         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 315         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
 316
 317         sched_setscheduler(current, SCHED_FIFO, &param);
 318
 319         /* initialize timestamp */
 320         __touch_watchdog();
 321
 322         /* kick off the timer for the hardlockup detector */
 323         /* done here because hrtimer_start can only pin to smp_processor_id() */
 324         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
 325                       HRTIMER_MODE_REL_PINNED);
 326
 327         set_current_state(TASK_INTERRUPTIBLE);
 328         /*
 329          * Run briefly once per second to reset the softlockup timestamp.
 330          * If this gets delayed for more than 60 seconds then the
 331          * debug-printout triggers in softlockup_tick().
 332          */
 333         while (!kthread_should_stop()) {
 334                 __touch_watchdog();
 335                 schedule();
 336
 337                 if (kthread_should_stop())
 338                         break;
 339
 340                 set_current_state(TASK_INTERRUPTIBLE);
 341         }
 342         __set_current_state(TASK_RUNNING);
 343
 344         return 0;
 345 }
 346
 347
 348 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 349 static int watchdog_nmi_enable(int cpu)
 350 {
 351         struct perf_event_attr *wd_attr;
 352         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 353
 354         /* is it already setup and enabled? */
 355         if (event && event->state > PERF_EVENT_STATE_OFF)
 356                 goto out;
 357
 358         /* it is setup but not enabled */
 359         if (event != NULL)
 360                 goto out_enable;
 361
 362         /* Try to register using hardware perf events */
 363         wd_attr = &wd_hw_attr;
 364         wd_attr->sample_period = hw_nmi_get_sample_period();
 365         event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
 366         if (!IS_ERR(event)) {
 367                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
 368                 goto out_save;
 369         }
 370
 371         printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
 372         return -1;
 373
 374         /* success path */
 375 out_save:
 376         per_cpu(watchdog_ev, cpu) = event;
 377 out_enable:
 378         perf_event_enable(per_cpu(watchdog_ev, cpu));
 379 out:
 380         return 0;
 381 }
 382
 383 static void watchdog_nmi_disable(int cpu)
 384 {
 385         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 386
 387         if (event) {
 388                 perf_event_disable(event);
 389                 per_cpu(watchdog_ev, cpu) = NULL;
 390
 391                 /* should be in cleanup, but blocks oprofile */
 392                 perf_event_release_kernel(event);
 393         }
 394         return;
 395 }
 396 #else
 397 static int watchdog_nmi_enable(int cpu) { return 0; }
 398 static void watchdog_nmi_disable(int cpu) { return; }
 399 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 400
 401 /* prepare/enable/disable routines */
 402 static int watchdog_prepare_cpu(int cpu)
 403 {
 404         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 405
 406         WARN_ON(per_cpu(softlockup_watchdog, cpu));
 407         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 408         hrtimer->function = watchdog_timer_fn;
 409
 410         return 0;
 411 }
 412
 413 static int watchdog_enable(int cpu)
 414 {
 415         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 416
 417         /* enable the perf event */
 418         if (watchdog_nmi_enable(cpu) != 0)
 419                 return -1;
 420
 421         /* create the watchdog thread */
 422         if (!p) {
 423                 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
 424                 if (IS_ERR(p)) {
 425                         printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
 426                         return -1;
 427                 }
 428                 kthread_bind(p, cpu);
 429                 per_cpu(watchdog_touch_ts, cpu) = 0;
 430                 per_cpu(softlockup_watchdog, cpu) = p;
 431                 wake_up_process(p);
 432         }
 433
 434         return 0;
 435 }
 436
 437 static void watchdog_disable(int cpu)
 438 {
 439         struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
 440         struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
 441
 442         /*
 443          * cancel the timer first to stop incrementing the stats
 444          * and waking up the kthread
 445          */
 446         hrtimer_cancel(hrtimer);
 447
 448         /* disable the perf event */
 449         watchdog_nmi_disable(cpu);
 450
 451         /* stop the watchdog thread */
 452         if (p) {
 453                 per_cpu(softlockup_watchdog, cpu) = NULL;
 454                 kthread_stop(p);
 455         }
 456
 457         /* if any cpu succeeds, watchdog is considered enabled for the system */
 458         watchdog_enabled = 1;
 459 }
 460
 461 static void watchdog_enable_all_cpus(void)
 462 {
 463         int cpu;
 464         int result;
 465
 466         for_each_online_cpu(cpu)
 467                 result += watchdog_enable(cpu);
 468
 469         if (result)
 470                 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
 471
 472 }
 473
 474 static void watchdog_disable_all_cpus(void)
 475 {
 476         int cpu;
 477
 478         for_each_online_cpu(cpu)
 479                 watchdog_disable(cpu);
 480
 481         /* if all watchdogs are disabled, then they are disabled for the system */
 482         watchdog_enabled = 0;
 483 }
 484
 485
 486 /* sysctl functions */
 487 #ifdef CONFIG_SYSCTL
 488 /*
 489  * proc handler for /proc/sys/kernel/nmi_watchdog
 490  */
 491
 492 int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 493                      void __user *buffer, size_t *length, loff_t *ppos)
 494 {
 495         proc_dointvec(table, write, buffer, length, ppos);
 496
 497         if (watchdog_enabled)
 498                 watchdog_enable_all_cpus();
 499         else
 500                 watchdog_disable_all_cpus();
 501         return 0;
 502 }
 503
 504 int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 505                              void __user *buffer,
 506                              size_t *lenp, loff_t *ppos)
 507 {
 508         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 509 }
 510 #endif /* CONFIG_SYSCTL */
 511
 512
 513 /*
 514  * Create/destroy watchdog threads as CPUs come and go:
 515  */
 516 static int __cpuinit
 517 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 518 {
 519         int hotcpu = (unsigned long)hcpu;
 520
 521         switch (action) {
 522         case CPU_UP_PREPARE:
 523         case CPU_UP_PREPARE_FROZEN:
 524                 if (watchdog_prepare_cpu(hotcpu))
 525                         return NOTIFY_BAD;
 526                 break;
 527         case CPU_ONLINE:
 528         case CPU_ONLINE_FROZEN:
 529                 if (watchdog_enable(hotcpu))
 530                         return NOTIFY_BAD;
 531                 break;
 532 #ifdef CONFIG_HOTPLUG_CPU
 533         case CPU_UP_CANCELED:
 534         case CPU_UP_CANCELED_FROZEN:
 535                 watchdog_disable(hotcpu);
 536                 break;
 537         case CPU_DEAD:
 538         case CPU_DEAD_FROZEN:
 539                 watchdog_disable(hotcpu);
 540                 break;
 541 #endif /* CONFIG_HOTPLUG_CPU */
 542         }
 543         return NOTIFY_OK;
 544 }
 545
 546 static struct notifier_block __cpuinitdata cpu_nfb = {
 547         .notifier_call = cpu_callback
 548 };
 549
 550 static int __init spawn_watchdog_task(void)
 551 {
 552         void *cpu = (void *)(long)smp_processor_id();
 553         int err;
 554
 555         if (no_watchdog)
 556                 return 0;
 557
 558         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 559         WARN_ON(err == NOTIFY_BAD);
 560
 561         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 562         register_cpu_notifier(&cpu_nfb);
 563
 564         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
 565
 566         return 0;
 567 }
 568 early_initcall(spawn_watchdog_task);