arch/x86/kernel/nmi.c

   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/smp.h>
  33 #include <asm/nmi.h>
  34 #include <asm/proto.h>
  35 #include <asm/timer.h>
  36
  37 #include <asm/mce.h>
  38
  39 #include <mach_traps.h>
  40
  41 int unknown_nmi_panic;
  42 int nmi_watchdog_enabled;
  43
  44 static cpumask_t backtrace_mask = CPU_MASK_NONE;
  45
  46 /* nmi_active:
  47  * >0: the lapic NMI watchdog is active, but can be disabled
  48  * <0: the lapic NMI watchdog has not been set up, and cannot
  49  *     be enabled
  50  *  0: the lapic NMI watchdog is disabled, but can be enabled
  51  */
  52 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  53 EXPORT_SYMBOL(nmi_active);
  54
  55 unsigned int nmi_watchdog = NMI_NONE;
  56 EXPORT_SYMBOL(nmi_watchdog);
  57
  58 static int panic_on_timeout;
  59
  60 static unsigned int nmi_hz = HZ;
  61 static DEFINE_PER_CPU(short, wd_enabled);
  62 static int endflag __initdata;
  63
  64 static inline unsigned int get_nmi_count(int cpu)
  65 {
  66 #ifdef CONFIG_X86_64
  67         return cpu_pda(cpu)->__nmi_count;
  68 #else
  69         return nmi_count(cpu);
  70 #endif
  71 }
  72
  73 static inline int mce_in_progress(void)
  74 {
  75 #if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
  76         return atomic_read(&mce_entry) > 0;
  77 #endif
  78         return 0;
  79 }
  80
  81 /*
  82  * Take the local apic timer and PIT/HPET into account. We don't
  83  * know which one is active, when we have highres/dyntick on
  84  */
  85 static inline unsigned int get_timer_irqs(int cpu)
  86 {
  87 #ifdef CONFIG_X86_64
  88         return read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
  89 #else
  90         return per_cpu(irq_stat, cpu).apic_timer_irqs +
  91                 per_cpu(irq_stat, cpu).irq0_irqs;
  92 #endif
  93 }
  94
  95 #ifdef CONFIG_SMP
  96 /*
  97  * The performance counters used by NMI_LOCAL_APIC don't trigger when
  98  * the CPU is idle. To make sure the NMI watchdog really ticks on all
  99  * CPUs during the test make them busy.
 100  */
 101 static __init void nmi_cpu_busy(void *data)
 102 {
 103         local_irq_enable_in_hardirq();
 104         /*
 105          * Intentionally don't use cpu_relax here. This is
 106          * to make sure that the performance counter really ticks,
 107          * even if there is a simulator or similar that catches the
 108          * pause instruction. On a real HT machine this is fine because
 109          * all other CPUs are busy with "useless" delay loops and don't
 110          * care if they get somewhat less cycles.
 111          */
 112         while (endflag == 0)
 113                 mb();
 114 }
 115 #endif
 116
 117 static void report_broken_nmi(int cpu, int *prev_nmi_count)
 118 {
 119         printk(KERN_CONT "\n");
 120
 121         printk(KERN_WARNING
 122                 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 123                         cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
 124
 125         printk(KERN_WARNING
 126                 "Please report this to bugzilla.kernel.org,\n");
 127         printk(KERN_WARNING
 128                 "and attach the output of the 'dmesg' command.\n");
 129
 130         per_cpu(wd_enabled, cpu) = 0;
 131         atomic_dec(&nmi_active);
 132 }
 133
 134 static void __acpi_nmi_disable(void *__unused)
 135 {
 136         apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
 137 }
 138
 139 int __init check_nmi_watchdog(void)
 140 {
 141         unsigned int *prev_nmi_count;
 142         int cpu;
 143
 144         if (!nmi_watchdog_active() || !atomic_read(&nmi_active))
 145                 return 0;
 146
 147         prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
 148         if (!prev_nmi_count)
 149                 goto error;
 150
 151         printk(KERN_INFO "Testing NMI watchdog ... ");
 152
 153 #ifdef CONFIG_SMP
 154         if (nmi_watchdog == NMI_LOCAL_APIC)
 155                 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
 156 #endif
 157
 158         for_each_possible_cpu(cpu)
 159                 prev_nmi_count[cpu] = get_nmi_count(cpu);
 160         local_irq_enable();
 161         mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 162
 163         for_each_online_cpu(cpu) {
 164                 if (!per_cpu(wd_enabled, cpu))
 165                         continue;
 166                 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 167                         report_broken_nmi(cpu, prev_nmi_count);
 168         }
 169         endflag = 1;
 170         if (!atomic_read(&nmi_active)) {
 171                 kfree(prev_nmi_count);
 172                 atomic_set(&nmi_active, -1);
 173                 goto error;
 174         }
 175         printk("OK.\n");
 176
 177         /*
 178          * now that we know it works we can reduce NMI frequency to
 179          * something more reasonable; makes a difference in some configs
 180          */
 181         if (nmi_watchdog == NMI_LOCAL_APIC)
 182                 nmi_hz = lapic_adjust_nmi_hz(1);
 183
 184         kfree(prev_nmi_count);
 185         return 0;
 186 error:
 187         if (nmi_watchdog == NMI_IO_APIC) {
 188                 if (!timer_through_8259)
 189                         disable_8259A_irq(0);
 190                 on_each_cpu(__acpi_nmi_disable, NULL, 1);
 191         }
 192
 193 #ifdef CONFIG_X86_32
 194         timer_ack = 0;
 195 #endif
 196         return -1;
 197 }
 198
 199 static int __init setup_nmi_watchdog(char *str)
 200 {
 201         unsigned int nmi;
 202
 203         if (!strncmp(str, "panic", 5)) {
 204                 panic_on_timeout = 1;
 205                 str = strchr(str, ',');
 206                 if (!str)
 207                         return 1;
 208                 ++str;
 209         }
 210
 211         get_option(&str, &nmi);
 212
 213         if (nmi >= NMI_INVALID)
 214                 return 0;
 215
 216         nmi_watchdog = nmi;
 217         return 1;
 218 }
 219 __setup("nmi_watchdog=", setup_nmi_watchdog);
 220
 221 /*
 222  * Suspend/resume support
 223  */
 224 #ifdef CONFIG_PM
 225
 226 static int nmi_pm_active; /* nmi_active before suspend */
 227
 228 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 229 {
 230         /* only CPU0 goes here, other CPUs should be offline */
 231         nmi_pm_active = atomic_read(&nmi_active);
 232         stop_apic_nmi_watchdog(NULL);
 233         BUG_ON(atomic_read(&nmi_active) != 0);
 234         return 0;
 235 }
 236
 237 static int lapic_nmi_resume(struct sys_device *dev)
 238 {
 239         /* only CPU0 goes here, other CPUs should be offline */
 240         if (nmi_pm_active > 0) {
 241                 setup_apic_nmi_watchdog(NULL);
 242                 touch_nmi_watchdog();
 243         }
 244         return 0;
 245 }
 246
 247 static struct sysdev_class nmi_sysclass = {
 248         .name           = "lapic_nmi",
 249         .resume         = lapic_nmi_resume,
 250         .suspend        = lapic_nmi_suspend,
 251 };
 252
 253 static struct sys_device device_lapic_nmi = {
 254         .id     = 0,
 255         .cls    = &nmi_sysclass,
 256 };
 257
 258 static int __init init_lapic_nmi_sysfs(void)
 259 {
 260         int error;
 261
 262         /*
 263          * should really be a BUG_ON but b/c this is an
 264          * init call, it just doesn't work.  -dcz
 265          */
 266         if (nmi_watchdog != NMI_LOCAL_APIC)
 267                 return 0;
 268
 269         if (atomic_read(&nmi_active) < 0)
 270                 return 0;
 271
 272         error = sysdev_class_register(&nmi_sysclass);
 273         if (!error)
 274                 error = sysdev_register(&device_lapic_nmi);
 275         return error;
 276 }
 277
 278 /* must come after the local APIC's device_initcall() */
 279 late_initcall(init_lapic_nmi_sysfs);
 280
 281 #endif  /* CONFIG_PM */
 282
 283 static void __acpi_nmi_enable(void *__unused)
 284 {
 285         apic_write(APIC_LVT0, APIC_DM_NMI);
 286 }
 287
 288 /*
 289  * Enable timer based NMIs on all CPUs:
 290  */
 291 void acpi_nmi_enable(void)
 292 {
 293         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 294                 on_each_cpu(__acpi_nmi_enable, NULL, 1);
 295 }
 296
 297 /*
 298  * Disable timer based NMIs on all CPUs:
 299  */
 300 void acpi_nmi_disable(void)
 301 {
 302         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 303                 on_each_cpu(__acpi_nmi_disable, NULL, 1);
 304 }
 305
 306 /*
 307  * This function is called as soon the LAPIC NMI watchdog driver has everything
 308  * in place and it's ready to check if the NMIs belong to the NMI watchdog
 309  */
 310 void cpu_nmi_set_wd_enabled(void)
 311 {
 312         __get_cpu_var(wd_enabled) = 1;
 313 }
 314
 315 void setup_apic_nmi_watchdog(void *unused)
 316 {
 317         if (__get_cpu_var(wd_enabled))
 318                 return;
 319
 320         /* cheap hack to support suspend/resume */
 321         /* if cpu0 is not active neither should the other cpus */
 322         if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
 323                 return;
 324
 325         switch (nmi_watchdog) {
 326         case NMI_LOCAL_APIC:
 327                 if (lapic_watchdog_init(nmi_hz) < 0) {
 328                         __get_cpu_var(wd_enabled) = 0;
 329                         return;
 330                 }
 331                 /* FALL THROUGH */
 332         case NMI_IO_APIC:
 333                 __get_cpu_var(wd_enabled) = 1;
 334                 atomic_inc(&nmi_active);
 335         }
 336 }
 337
 338 void stop_apic_nmi_watchdog(void *unused)
 339 {
 340         /* only support LOCAL and IO APICs for now */
 341         if (!nmi_watchdog_active())
 342                 return;
 343         if (__get_cpu_var(wd_enabled) == 0)
 344                 return;
 345         if (nmi_watchdog == NMI_LOCAL_APIC)
 346                 lapic_watchdog_stop();
 347         else
 348                 __acpi_nmi_disable(NULL);
 349         __get_cpu_var(wd_enabled) = 0;
 350         atomic_dec(&nmi_active);
 351 }
 352
 353 /*
 354  * the best way to detect whether a CPU has a 'hard lockup' problem
 355  * is to check it's local APIC timer IRQ counts. If they are not
 356  * changing then that CPU has some problem.
 357  *
 358  * as these watchdog NMI IRQs are generated on every CPU, we only
 359  * have to check the current processor.
 360  *
 361  * since NMIs don't listen to _any_ locks, we have to be extremely
 362  * careful not to rely on unsafe variables. The printk might lock
 363  * up though, so we have to break up any console locks first ...
 364  * [when there will be more tty-related locks, break them up here too!]
 365  */
 366
 367 static DEFINE_PER_CPU(unsigned, last_irq_sum);
 368 static DEFINE_PER_CPU(local_t, alert_counter);
 369 static DEFINE_PER_CPU(int, nmi_touch);
 370
 371 void touch_nmi_watchdog(void)
 372 {
 373         if (nmi_watchdog_active()) {
 374                 unsigned cpu;
 375
 376                 /*
 377                  * Tell other CPUs to reset their alert counters. We cannot
 378                  * do it ourselves because the alert count increase is not
 379                  * atomic.
 380                  */
 381                 for_each_present_cpu(cpu) {
 382                         if (per_cpu(nmi_touch, cpu) != 1)
 383                                 per_cpu(nmi_touch, cpu) = 1;
 384                 }
 385         }
 386
 387         /*
 388          * Tickle the softlockup detector too:
 389          */
 390         touch_softlockup_watchdog();
 391 }
 392 EXPORT_SYMBOL(touch_nmi_watchdog);
 393
 394 notrace __kprobes int
 395 nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 396 {
 397         /*
 398          * Since current_thread_info()-> is always on the stack, and we
 399          * always switch the stack NMI-atomically, it's safe to use
 400          * smp_processor_id().
 401          */
 402         unsigned int sum;
 403         int touched = 0;
 404         int cpu = smp_processor_id();
 405         int rc = 0;
 406
 407         /* check for other users first */
 408         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
 409                         == NOTIFY_STOP) {
 410                 rc = 1;
 411                 touched = 1;
 412         }
 413
 414         sum = get_timer_irqs(cpu);
 415
 416         if (__get_cpu_var(nmi_touch)) {
 417                 __get_cpu_var(nmi_touch) = 0;
 418                 touched = 1;
 419         }
 420
 421         if (cpu_isset(cpu, backtrace_mask)) {
 422                 static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
 423
 424                 spin_lock(&lock);
 425                 printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
 426                 dump_stack();
 427                 spin_unlock(&lock);
 428                 cpu_clear(cpu, backtrace_mask);
 429         }
 430
 431         /* Could check oops_in_progress here too, but it's safer not to */
 432         if (mce_in_progress())
 433                 touched = 1;
 434
 435         /* if the none of the timers isn't firing, this cpu isn't doing much */
 436         if (!touched && __get_cpu_var(last_irq_sum) == sum) {
 437                 /*
 438                  * Ayiee, looks like this CPU is stuck ...
 439                  * wait a few IRQs (5 seconds) before doing the oops ...
 440                  */
 441                 local_inc(&__get_cpu_var(alert_counter));
 442                 if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
 443                         /*
 444                          * die_nmi will return ONLY if NOTIFY_STOP happens..
 445                          */
 446                         die_nmi("BUG: NMI Watchdog detected LOCKUP",
 447                                 regs, panic_on_timeout);
 448         } else {
 449                 __get_cpu_var(last_irq_sum) = sum;
 450                 local_set(&__get_cpu_var(alert_counter), 0);
 451         }
 452
 453         /* see if the nmi watchdog went off */
 454         if (!__get_cpu_var(wd_enabled))
 455                 return rc;
 456         switch (nmi_watchdog) {
 457         case NMI_LOCAL_APIC:
 458                 rc |= lapic_wd_event(nmi_hz);
 459                 break;
 460         case NMI_IO_APIC:
 461                 /*
 462                  * don't know how to accurately check for this.
 463                  * just assume it was a watchdog timer interrupt
 464                  * This matches the old behaviour.
 465                  */
 466                 rc = 1;
 467                 break;
 468         }
 469         return rc;
 470 }
 471
 472 #ifdef CONFIG_SYSCTL
 473
 474 static void enable_ioapic_nmi_watchdog_single(void *unused)
 475 {
 476         __get_cpu_var(wd_enabled) = 1;
 477         atomic_inc(&nmi_active);
 478         __acpi_nmi_enable(NULL);
 479 }
 480
 481 static void enable_ioapic_nmi_watchdog(void)
 482 {
 483         on_each_cpu(enable_ioapic_nmi_watchdog_single, NULL, 1);
 484         touch_nmi_watchdog();
 485 }
 486
 487 static void disable_ioapic_nmi_watchdog(void)
 488 {
 489         on_each_cpu(stop_apic_nmi_watchdog, NULL, 1);
 490 }
 491
 492 static int __init setup_unknown_nmi_panic(char *str)
 493 {
 494         unknown_nmi_panic = 1;
 495         return 1;
 496 }
 497 __setup("unknown_nmi_panic", setup_unknown_nmi_panic);
 498
 499 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 500 {
 501         unsigned char reason = get_nmi_reason();
 502         char buf[64];
 503
 504         sprintf(buf, "NMI received for unknown reason %02x\n", reason);
 505         die_nmi(buf, regs, 1); /* Always panic here */
 506         return 0;
 507 }
 508
 509 /*
 510  * proc handler for /proc/sys/kernel/nmi
 511  */
 512 int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
 513                         void __user *buffer, size_t *length, loff_t *ppos)
 514 {
 515         int old_state;
 516
 517         nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
 518         old_state = nmi_watchdog_enabled;
 519         proc_dointvec(table, write, file, buffer, length, ppos);
 520         if (!!old_state == !!nmi_watchdog_enabled)
 521                 return 0;
 522
 523         if (atomic_read(&nmi_active) < 0 || !nmi_watchdog_active()) {
 524                 printk(KERN_WARNING
 525                         "NMI watchdog is permanently disabled\n");
 526                 return -EIO;
 527         }
 528
 529         if (nmi_watchdog == NMI_LOCAL_APIC) {
 530                 if (nmi_watchdog_enabled)
 531                         enable_lapic_nmi_watchdog();
 532                 else
 533                         disable_lapic_nmi_watchdog();
 534         } else if (nmi_watchdog == NMI_IO_APIC) {
 535                 if (nmi_watchdog_enabled)
 536                         enable_ioapic_nmi_watchdog();
 537                 else
 538                         disable_ioapic_nmi_watchdog();
 539         } else {
 540                 printk(KERN_WARNING
 541                         "NMI watchdog doesn't know what hardware to touch\n");
 542                 return -EIO;
 543         }
 544         return 0;
 545 }
 546
 547 #endif /* CONFIG_SYSCTL */
 548
 549 int do_nmi_callback(struct pt_regs *regs, int cpu)
 550 {
 551 #ifdef CONFIG_SYSCTL
 552         if (unknown_nmi_panic)
 553                 return unknown_nmi_panic_callback(regs, cpu);
 554 #endif
 555         return 0;
 556 }
 557
 558 void __trigger_all_cpu_backtrace(void)
 559 {
 560         int i;
 561
 562         backtrace_mask = cpu_online_map;
 563         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
 564         for (i = 0; i < 10 * 1000; i++) {
 565                 if (cpus_empty(backtrace_mask))
 566                         break;
 567                 mdelay(1);
 568         }
 569 }