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   1 /*
   2  *  NMI watchdog support on APIC systems
   3  *
   4  *  Started by Ingo Molnar <mingo@redhat.com>
   5  *
   6  *  Fixes:
   7  *  Mikael Pettersson   : AMD K7 support for local APIC NMI watchdog.
   8  *  Mikael Pettersson   : Power Management for local APIC NMI watchdog.
   9  *  Mikael Pettersson   : Pentium 4 support for local APIC NMI watchdog.
  10  *  Pavel Machek and
  11  *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
  12  */
  13
  14 #include <asm/apic.h>
  15
  16 #include <linux/nmi.h>
  17 #include <linux/mm.h>
  18 #include <linux/delay.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/module.h>
  21 #include <linux/sysdev.h>
  22 #include <linux/sysctl.h>
  23 #include <linux/percpu.h>
  24 #include <linux/kprobes.h>
  25 #include <linux/cpumask.h>
  26 #include <linux/kernel_stat.h>
  27 #include <linux/kdebug.h>
  28 #include <linux/smp.h>
  29
  30 #include <asm/i8259.h>
  31 #include <asm/io_apic.h>
  32 #include <asm/proto.h>
  33 #include <asm/timer.h>
  34
  35 #include <asm/mce.h>
  36
  37 #include <asm/mach_traps.h>
  38
  39 int unknown_nmi_panic;
  40 int nmi_watchdog_enabled;
  41
  42 static cpumask_t backtrace_mask __read_mostly;
  43
  44 /* nmi_active:
  45  * >0: the lapic NMI watchdog is active, but can be disabled
  46  * <0: the lapic NMI watchdog has not been set up, and cannot
  47  *     be enabled
  48  *  0: the lapic NMI watchdog is disabled, but can be enabled
  49  */
  50 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  51 EXPORT_SYMBOL(nmi_active);
  52
  53 unsigned int nmi_watchdog = NMI_NONE;
  54 EXPORT_SYMBOL(nmi_watchdog);
  55
  56 static int panic_on_timeout;
  57
  58 static unsigned int nmi_hz = HZ;
  59 static DEFINE_PER_CPU(short, wd_enabled);
  60 static int endflag __initdata;
  61
  62 static inline unsigned int get_nmi_count(int cpu)
  63 {
  64         return per_cpu(irq_stat, cpu).__nmi_count;
  65 }
  66
  67 static inline int mce_in_progress(void)
  68 {
  69 #if defined(CONFIG_X86_MCE)
  70         return atomic_read(&mce_entry) > 0;
  71 #endif
  72         return 0;
  73 }
  74
  75 /*
  76  * Take the local apic timer and PIT/HPET into account. We don't
  77  * know which one is active, when we have highres/dyntick on
  78  */
  79 static inline unsigned int get_timer_irqs(int cpu)
  80 {
  81         return per_cpu(irq_stat, cpu).apic_timer_irqs +
  82                 per_cpu(irq_stat, cpu).irq0_irqs;
  83 }
  84
  85 #ifdef CONFIG_SMP
  86 /*
  87  * The performance counters used by NMI_LOCAL_APIC don't trigger when
  88  * the CPU is idle. To make sure the NMI watchdog really ticks on all
  89  * CPUs during the test make them busy.
  90  */
  91 static __init void nmi_cpu_busy(void *data)
  92 {
  93         local_irq_enable_in_hardirq();
  94         /*
  95          * Intentionally don't use cpu_relax here. This is
  96          * to make sure that the performance counter really ticks,
  97          * even if there is a simulator or similar that catches the
  98          * pause instruction. On a real HT machine this is fine because
  99          * all other CPUs are busy with "useless" delay loops and don't
 100          * care if they get somewhat less cycles.
 101          */
 102         while (endflag == 0)
 103                 mb();
 104 }
 105 #endif
 106
 107 static void report_broken_nmi(int cpu, unsigned int *prev_nmi_count)
 108 {
 109         printk(KERN_CONT "\n");
 110
 111         printk(KERN_WARNING
 112                 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 113                         cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
 114
 115         printk(KERN_WARNING
 116                 "Please report this to bugzilla.kernel.org,\n");
 117         printk(KERN_WARNING
 118                 "and attach the output of the 'dmesg' command.\n");
 119
 120         per_cpu(wd_enabled, cpu) = 0;
 121         atomic_dec(&nmi_active);
 122 }
 123
 124 static void __acpi_nmi_disable(void *__unused)
 125 {
 126         apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
 127 }
 128
 129 int __init check_nmi_watchdog(void)
 130 {
 131         unsigned int *prev_nmi_count;
 132         int cpu;
 133
 134         if (!nmi_watchdog_active() || !atomic_read(&nmi_active))
 135                 return 0;
 136
 137         prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
 138         if (!prev_nmi_count)
 139                 goto error;
 140
 141         printk(KERN_INFO "Testing NMI watchdog ... ");
 142
 143 #ifdef CONFIG_SMP
 144         if (nmi_watchdog == NMI_LOCAL_APIC)
 145                 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
 146 #endif
 147
 148         for_each_possible_cpu(cpu)
 149                 prev_nmi_count[cpu] = get_nmi_count(cpu);
 150         local_irq_enable();
 151         mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 152
 153         for_each_online_cpu(cpu) {
 154                 if (!per_cpu(wd_enabled, cpu))
 155                         continue;
 156                 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 157                         report_broken_nmi(cpu, prev_nmi_count);
 158         }
 159         endflag = 1;
 160         if (!atomic_read(&nmi_active)) {
 161                 kfree(prev_nmi_count);
 162                 atomic_set(&nmi_active, -1);
 163                 goto error;
 164         }
 165         printk("OK.\n");
 166
 167         /*
 168          * now that we know it works we can reduce NMI frequency to
 169          * something more reasonable; makes a difference in some configs
 170          */
 171         if (nmi_watchdog == NMI_LOCAL_APIC)
 172                 nmi_hz = lapic_adjust_nmi_hz(1);
 173
 174         kfree(prev_nmi_count);
 175         return 0;
 176 error:
 177         if (nmi_watchdog == NMI_IO_APIC) {
 178                 if (!timer_through_8259)
 179                         disable_8259A_irq(0);
 180                 on_each_cpu(__acpi_nmi_disable, NULL, 1);
 181         }
 182
 183 #ifdef CONFIG_X86_32
 184         timer_ack = 0;
 185 #endif
 186         return -1;
 187 }
 188
 189 static int __init setup_nmi_watchdog(char *str)
 190 {
 191         unsigned int nmi;
 192
 193         if (!strncmp(str, "panic", 5)) {
 194                 panic_on_timeout = 1;
 195                 str = strchr(str, ',');
 196                 if (!str)
 197                         return 1;
 198                 ++str;
 199         }
 200
 201         if (!strncmp(str, "lapic", 5))
 202                 nmi_watchdog = NMI_LOCAL_APIC;
 203         else if (!strncmp(str, "ioapic", 6))
 204                 nmi_watchdog = NMI_IO_APIC;
 205         else {
 206                 get_option(&str, &nmi);
 207                 if (nmi >= NMI_INVALID)
 208                         return 0;
 209                 nmi_watchdog = nmi;
 210         }
 211
 212         return 1;
 213 }
 214 __setup("nmi_watchdog=", setup_nmi_watchdog);
 215
 216 /*
 217  * Suspend/resume support
 218  */
 219 #ifdef CONFIG_PM
 220
 221 static int nmi_pm_active; /* nmi_active before suspend */
 222
 223 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 224 {
 225         /* only CPU0 goes here, other CPUs should be offline */
 226         nmi_pm_active = atomic_read(&nmi_active);
 227         stop_apic_nmi_watchdog(NULL);
 228         BUG_ON(atomic_read(&nmi_active) != 0);
 229         return 0;
 230 }
 231
 232 static int lapic_nmi_resume(struct sys_device *dev)
 233 {
 234         /* only CPU0 goes here, other CPUs should be offline */
 235         if (nmi_pm_active > 0) {
 236                 setup_apic_nmi_watchdog(NULL);
 237                 touch_nmi_watchdog();
 238         }
 239         return 0;
 240 }
 241
 242 static struct sysdev_class nmi_sysclass = {
 243         .name           = "lapic_nmi",
 244         .resume         = lapic_nmi_resume,
 245         .suspend        = lapic_nmi_suspend,
 246 };
 247
 248 static struct sys_device device_lapic_nmi = {
 249         .id     = 0,
 250         .cls    = &nmi_sysclass,
 251 };
 252
 253 static int __init init_lapic_nmi_sysfs(void)
 254 {
 255         int error;
 256
 257         /*
 258          * should really be a BUG_ON but b/c this is an
 259          * init call, it just doesn't work.  -dcz
 260          */
 261         if (nmi_watchdog != NMI_LOCAL_APIC)
 262                 return 0;
 263
 264         if (atomic_read(&nmi_active) < 0)
 265                 return 0;
 266
 267         error = sysdev_class_register(&nmi_sysclass);
 268         if (!error)
 269                 error = sysdev_register(&device_lapic_nmi);
 270         return error;
 271 }
 272
 273 /* must come after the local APIC's device_initcall() */
 274 late_initcall(init_lapic_nmi_sysfs);
 275
 276 #endif  /* CONFIG_PM */
 277
 278 static void __acpi_nmi_enable(void *__unused)
 279 {
 280         apic_write(APIC_LVT0, APIC_DM_NMI);
 281 }
 282
 283 /*
 284  * Enable timer based NMIs on all CPUs:
 285  */
 286 void acpi_nmi_enable(void)
 287 {
 288         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 289                 on_each_cpu(__acpi_nmi_enable, NULL, 1);
 290 }
 291
 292 /*
 293  * Disable timer based NMIs on all CPUs:
 294  */
 295 void acpi_nmi_disable(void)
 296 {
 297         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 298                 on_each_cpu(__acpi_nmi_disable, NULL, 1);
 299 }
 300
 301 /*
 302  * This function is called as soon the LAPIC NMI watchdog driver has everything
 303  * in place and it's ready to check if the NMIs belong to the NMI watchdog
 304  */
 305 void cpu_nmi_set_wd_enabled(void)
 306 {
 307         __get_cpu_var(wd_enabled) = 1;
 308 }
 309
 310 void setup_apic_nmi_watchdog(void *unused)
 311 {
 312         if (__get_cpu_var(wd_enabled))
 313                 return;
 314
 315         /* cheap hack to support suspend/resume */
 316         /* if cpu0 is not active neither should the other cpus */
 317         if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
 318                 return;
 319
 320         switch (nmi_watchdog) {
 321         case NMI_LOCAL_APIC:
 322                 if (lapic_watchdog_init(nmi_hz) < 0) {
 323                         __get_cpu_var(wd_enabled) = 0;
 324                         return;
 325                 }
 326                 /* FALL THROUGH */
 327         case NMI_IO_APIC:
 328                 __get_cpu_var(wd_enabled) = 1;
 329                 atomic_inc(&nmi_active);
 330         }
 331 }
 332
 333 void stop_apic_nmi_watchdog(void *unused)
 334 {
 335         /* only support LOCAL and IO APICs for now */
 336         if (!nmi_watchdog_active())
 337                 return;
 338         if (__get_cpu_var(wd_enabled) == 0)
 339                 return;
 340         if (nmi_watchdog == NMI_LOCAL_APIC)
 341                 lapic_watchdog_stop();
 342         else
 343                 __acpi_nmi_disable(NULL);
 344         __get_cpu_var(wd_enabled) = 0;
 345         atomic_dec(&nmi_active);
 346 }
 347
 348 /*
 349  * the best way to detect whether a CPU has a 'hard lockup' problem
 350  * is to check it's local APIC timer IRQ counts. If they are not
 351  * changing then that CPU has some problem.
 352  *
 353  * as these watchdog NMI IRQs are generated on every CPU, we only
 354  * have to check the current processor.
 355  *
 356  * since NMIs don't listen to _any_ locks, we have to be extremely
 357  * careful not to rely on unsafe variables. The printk might lock
 358  * up though, so we have to break up any console locks first ...
 359  * [when there will be more tty-related locks, break them up here too!]
 360  */
 361
 362 static DEFINE_PER_CPU(unsigned, last_irq_sum);
 363 static DEFINE_PER_CPU(local_t, alert_counter);
 364 static DEFINE_PER_CPU(int, nmi_touch);
 365
 366 void touch_nmi_watchdog(void)
 367 {
 368         if (nmi_watchdog_active()) {
 369                 unsigned cpu;
 370
 371                 /*
 372                  * Tell other CPUs to reset their alert counters. We cannot
 373                  * do it ourselves because the alert count increase is not
 374                  * atomic.
 375                  */
 376                 for_each_present_cpu(cpu) {
 377                         if (per_cpu(nmi_touch, cpu) != 1)
 378                                 per_cpu(nmi_touch, cpu) = 1;
 379                 }
 380         }
 381
 382         /*
 383          * Tickle the softlockup detector too:
 384          */
 385         touch_softlockup_watchdog();
 386 }
 387 EXPORT_SYMBOL(touch_nmi_watchdog);
 388
 389 notrace __kprobes int
 390 nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 391 {
 392         /*
 393          * Since current_thread_info()-> is always on the stack, and we
 394          * always switch the stack NMI-atomically, it's safe to use
 395          * smp_processor_id().
 396          */
 397         unsigned int sum;
 398         int touched = 0;
 399         int cpu = smp_processor_id();
 400         int rc = 0;
 401
 402         /* check for other users first */
 403         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
 404                         == NOTIFY_STOP) {
 405                 rc = 1;
 406                 touched = 1;
 407         }
 408
 409         sum = get_timer_irqs(cpu);
 410
 411         if (__get_cpu_var(nmi_touch)) {
 412                 __get_cpu_var(nmi_touch) = 0;
 413                 touched = 1;
 414         }
 415
 416         /* We can be called before check_nmi_watchdog, hence NULL check. */
 417         if (cpumask_test_cpu(cpu, &backtrace_mask)) {
 418                 static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
 419
 420                 spin_lock(&lock);
 421                 printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
 422                 show_regs(regs);
 423                 dump_stack();
 424                 spin_unlock(&lock);
 425                 cpumask_clear_cpu(cpu, &backtrace_mask);
 426
 427                 rc = 1;
 428         }
 429
 430         /* Could check oops_in_progress here too, but it's safer not to */
 431         if (mce_in_progress())
 432                 touched = 1;
 433
 434         /* if the none of the timers isn't firing, this cpu isn't doing much */
 435         if (!touched && __get_cpu_var(last_irq_sum) == sum) {
 436                 /*
 437                  * Ayiee, looks like this CPU is stuck ...
 438                  * wait a few IRQs (5 seconds) before doing the oops ...
 439                  */
 440                 local_inc(&__get_cpu_var(alert_counter));
 441                 if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
 442                         /*
 443                          * die_nmi will return ONLY if NOTIFY_STOP happens..
 444                          */
 445                         die_nmi("BUG: NMI Watchdog detected LOCKUP",
 446                                 regs, panic_on_timeout);
 447         } else {
 448                 __get_cpu_var(last_irq_sum) = sum;
 449                 local_set(&__get_cpu_var(alert_counter), 0);
 450         }
 451
 452         /* see if the nmi watchdog went off */
 453         if (!__get_cpu_var(wd_enabled))
 454                 return rc;
 455         switch (nmi_watchdog) {
 456         case NMI_LOCAL_APIC:
 457                 rc |= lapic_wd_event(nmi_hz);
 458                 break;
 459         case NMI_IO_APIC:
 460                 /*
 461                  * don't know how to accurately check for this.
 462                  * just assume it was a watchdog timer interrupt
 463                  * This matches the old behaviour.
 464                  */
 465                 rc = 1;
 466                 break;
 467         }
 468         return rc;
 469 }
 470
 471 #ifdef CONFIG_SYSCTL
 472
 473 static void enable_ioapic_nmi_watchdog_single(void *unused)
 474 {
 475         __get_cpu_var(wd_enabled) = 1;
 476         atomic_inc(&nmi_active);
 477         __acpi_nmi_enable(NULL);
 478 }
 479
 480 static void enable_ioapic_nmi_watchdog(void)
 481 {
 482         on_each_cpu(enable_ioapic_nmi_watchdog_single, NULL, 1);
 483         touch_nmi_watchdog();
 484 }
 485
 486 static void disable_ioapic_nmi_watchdog(void)
 487 {
 488         on_each_cpu(stop_apic_nmi_watchdog, NULL, 1);
 489 }
 490
 491 static int __init setup_unknown_nmi_panic(char *str)
 492 {
 493         unknown_nmi_panic = 1;
 494         return 1;
 495 }
 496 __setup("unknown_nmi_panic", setup_unknown_nmi_panic);
 497
 498 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 499 {
 500         unsigned char reason = get_nmi_reason();
 501         char buf[64];
 502
 503         sprintf(buf, "NMI received for unknown reason %02x\n", reason);
 504         die_nmi(buf, regs, 1); /* Always panic here */
 505         return 0;
 506 }
 507
 508 /*
 509  * proc handler for /proc/sys/kernel/nmi
 510  */
 511 int proc_nmi_enabled(struct ctl_table *table, int write,
 512                         void __user *buffer, size_t *length, loff_t *ppos)
 513 {
 514         int old_state;
 515
 516         nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
 517         old_state = nmi_watchdog_enabled;
 518         proc_dointvec(table, write, buffer, length, ppos);
 519         if (!!old_state == !!nmi_watchdog_enabled)
 520                 return 0;
 521
 522         if (atomic_read(&nmi_active) < 0 || !nmi_watchdog_active()) {
 523                 printk(KERN_WARNING
 524                         "NMI watchdog is permanently disabled\n");
 525                 return -EIO;
 526         }
 527
 528         if (nmi_watchdog == NMI_LOCAL_APIC) {
 529                 if (nmi_watchdog_enabled)
 530                         enable_lapic_nmi_watchdog();
 531                 else
 532                         disable_lapic_nmi_watchdog();
 533         } else if (nmi_watchdog == NMI_IO_APIC) {
 534                 if (nmi_watchdog_enabled)
 535                         enable_ioapic_nmi_watchdog();
 536                 else
 537                         disable_ioapic_nmi_watchdog();
 538         } else {
 539                 printk(KERN_WARNING
 540                         "NMI watchdog doesn't know what hardware to touch\n");
 541                 return -EIO;
 542         }
 543         return 0;
 544 }
 545
 546 #endif /* CONFIG_SYSCTL */
 547
 548 int do_nmi_callback(struct pt_regs *regs, int cpu)
 549 {
 550 #ifdef CONFIG_SYSCTL
 551         if (unknown_nmi_panic)
 552                 return unknown_nmi_panic_callback(regs, cpu);
 553 #endif
 554         return 0;
 555 }
 556
 557 void arch_trigger_all_cpu_backtrace(void)
 558 {
 559         int i;
 560
 561         cpumask_copy(&backtrace_mask, cpu_online_mask);
 562
 563         printk(KERN_INFO "sending NMI to all CPUs:\n");
 564         apic->send_IPI_all(NMI_VECTOR);
 565
 566         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
 567         for (i = 0; i < 10 * 1000; i++) {
 568                 if (cpumask_empty(&backtrace_mask))
 569                         break;
 570                 mdelay(1);
 571         }
 572 }