arch/x86/kernel/nmi_32.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 <linux/delay.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/module.h>
  17 #include <linux/nmi.h>
  18 #include <linux/sysdev.h>
  19 #include <linux/sysctl.h>
  20 #include <linux/percpu.h>
  21 #include <linux/kprobes.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/kernel_stat.h>
  24 #include <linux/kdebug.h>
  25 #include <linux/slab.h>
  26
  27 #include <asm/smp.h>
  28 #include <asm/nmi.h>
  29
  30 #include "mach_traps.h"
  31
  32 int unknown_nmi_panic;
  33 int nmi_watchdog_enabled;
  34
  35 static cpumask_t backtrace_mask = CPU_MASK_NONE;
  36
  37 /* nmi_active:
  38  * >0: the lapic NMI watchdog is active, but can be disabled
  39  * <0: the lapic NMI watchdog has not been set up, and cannot
  40  *     be enabled
  41  *  0: the lapic NMI watchdog is disabled, but can be enabled
  42  */
  43 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  44
  45 unsigned int nmi_watchdog = NMI_DEFAULT;
  46 static unsigned int nmi_hz = HZ;
  47
  48 static DEFINE_PER_CPU(short, wd_enabled);
  49
  50 static int endflag __initdata = 0;
  51
  52 #ifdef CONFIG_SMP
  53 /* The performance counters used by NMI_LOCAL_APIC don't trigger when
  54  * the CPU is idle. To make sure the NMI watchdog really ticks on all
  55  * CPUs during the test make them busy.
  56  */
  57 static __init void nmi_cpu_busy(void *data)
  58 {
  59         local_irq_enable_in_hardirq();
  60         /* Intentionally don't use cpu_relax here. This is
  61            to make sure that the performance counter really ticks,
  62            even if there is a simulator or similar that catches the
  63            pause instruction. On a real HT machine this is fine because
  64            all other CPUs are busy with "useless" delay loops and don't
  65            care if they get somewhat less cycles. */
  66         while (endflag == 0)
  67                 mb();
  68 }
  69 #endif
  70
  71 int __init check_nmi_watchdog(void)
  72 {
  73         unsigned int *prev_nmi_count;
  74         int cpu;
  75
  76         if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DISABLED))
  77                 return 0;
  78
  79         if (!atomic_read(&nmi_active))
  80                 return 0;
  81
  82         prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
  83         if (!prev_nmi_count)
  84                 return -1;
  85
  86         printk(KERN_INFO "Testing NMI watchdog ... ");
  87
  88 #ifdef CONFIG_SMP
  89         if (nmi_watchdog == NMI_LOCAL_APIC)
  90                 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
  91 #endif
  92
  93         for_each_possible_cpu(cpu)
  94                 prev_nmi_count[cpu] = nmi_count(cpu);
  95         local_irq_enable();
  96         mdelay((20*1000)/nmi_hz); // wait 20 ticks
  97
  98         for_each_possible_cpu(cpu) {
  99 #ifdef CONFIG_SMP
 100                 /* Check cpu_callin_map here because that is set
 101                    after the timer is started. */
 102                 if (!cpu_isset(cpu, cpu_callin_map))
 103                         continue;
 104 #endif
 105                 if (!per_cpu(wd_enabled, cpu))
 106                         continue;
 107                 if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
 108                         printk(KERN_WARNING "WARNING: CPU#%d: NMI "
 109                                 "appears to be stuck (%d->%d)!\n",
 110                                 cpu,
 111                                 prev_nmi_count[cpu],
 112                                 nmi_count(cpu));
 113                         per_cpu(wd_enabled, cpu) = 0;
 114                         atomic_dec(&nmi_active);
 115                 }
 116         }
 117         endflag = 1;
 118         if (!atomic_read(&nmi_active)) {
 119                 kfree(prev_nmi_count);
 120                 atomic_set(&nmi_active, -1);
 121                 return -1;
 122         }
 123         printk("OK.\n");
 124
 125         /* now that we know it works we can reduce NMI frequency to
 126            something more reasonable; makes a difference in some configs */
 127         if (nmi_watchdog == NMI_LOCAL_APIC)
 128                 nmi_hz = lapic_adjust_nmi_hz(1);
 129
 130         kfree(prev_nmi_count);
 131         return 0;
 132 }
 133
 134 static int __init setup_nmi_watchdog(char *str)
 135 {
 136         int nmi;
 137
 138         get_option(&str, &nmi);
 139
 140         if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
 141                 return 0;
 142
 143         nmi_watchdog = nmi;
 144         return 1;
 145 }
 146
 147 __setup("nmi_watchdog=", setup_nmi_watchdog);
 148
 149
 150 /* Suspend/resume support */
 151
 152 #ifdef CONFIG_PM
 153
 154 static int nmi_pm_active; /* nmi_active before suspend */
 155
 156 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 157 {
 158         /* only CPU0 goes here, other CPUs should be offline */
 159         nmi_pm_active = atomic_read(&nmi_active);
 160         stop_apic_nmi_watchdog(NULL);
 161         BUG_ON(atomic_read(&nmi_active) != 0);
 162         return 0;
 163 }
 164
 165 static int lapic_nmi_resume(struct sys_device *dev)
 166 {
 167         /* only CPU0 goes here, other CPUs should be offline */
 168         if (nmi_pm_active > 0) {
 169                 setup_apic_nmi_watchdog(NULL);
 170                 touch_nmi_watchdog();
 171         }
 172         return 0;
 173 }
 174
 175
 176 static struct sysdev_class nmi_sysclass = {
 177         .name           = "lapic_nmi",
 178         .resume         = lapic_nmi_resume,
 179         .suspend        = lapic_nmi_suspend,
 180 };
 181
 182 static struct sys_device device_lapic_nmi = {
 183         .id     = 0,
 184         .cls    = &nmi_sysclass,
 185 };
 186
 187 static int __init init_lapic_nmi_sysfs(void)
 188 {
 189         int error;
 190
 191         /* should really be a BUG_ON but b/c this is an
 192          * init call, it just doesn't work.  -dcz
 193          */
 194         if (nmi_watchdog != NMI_LOCAL_APIC)
 195                 return 0;
 196
 197         if (atomic_read(&nmi_active) < 0)
 198                 return 0;
 199
 200         error = sysdev_class_register(&nmi_sysclass);
 201         if (!error)
 202                 error = sysdev_register(&device_lapic_nmi);
 203         return error;
 204 }
 205 /* must come after the local APIC's device_initcall() */
 206 late_initcall(init_lapic_nmi_sysfs);
 207
 208 #endif  /* CONFIG_PM */
 209
 210 static void __acpi_nmi_enable(void *__unused)
 211 {
 212         apic_write_around(APIC_LVT0, APIC_DM_NMI);
 213 }
 214
 215 /*
 216  * Enable timer based NMIs on all CPUs:
 217  */
 218 void acpi_nmi_enable(void)
 219 {
 220         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 221                 on_each_cpu(__acpi_nmi_enable, NULL, 1);
 222 }
 223
 224 static void __acpi_nmi_disable(void *__unused)
 225 {
 226         apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
 227 }
 228
 229 /*
 230  * Disable timer based NMIs on all CPUs:
 231  */
 232 void acpi_nmi_disable(void)
 233 {
 234         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 235                 on_each_cpu(__acpi_nmi_disable, NULL, 1);
 236 }
 237
 238 void setup_apic_nmi_watchdog(void *unused)
 239 {
 240         if (__get_cpu_var(wd_enabled))
 241                 return;
 242
 243         /* cheap hack to support suspend/resume */
 244         /* if cpu0 is not active neither should the other cpus */
 245         if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
 246                 return;
 247
 248         switch (nmi_watchdog) {
 249         case NMI_LOCAL_APIC:
 250                 __get_cpu_var(wd_enabled) = 1; /* enable it before to avoid race with handler */
 251                 if (lapic_watchdog_init(nmi_hz) < 0) {
 252                         __get_cpu_var(wd_enabled) = 0;
 253                         return;
 254                 }
 255                 /* FALL THROUGH */
 256         case NMI_IO_APIC:
 257                 __get_cpu_var(wd_enabled) = 1;
 258                 atomic_inc(&nmi_active);
 259         }
 260 }
 261
 262 void stop_apic_nmi_watchdog(void *unused)
 263 {
 264         /* only support LOCAL and IO APICs for now */
 265         if ((nmi_watchdog != NMI_LOCAL_APIC) &&
 266             (nmi_watchdog != NMI_IO_APIC))
 267                 return;
 268         if (__get_cpu_var(wd_enabled) == 0)
 269                 return;
 270         if (nmi_watchdog == NMI_LOCAL_APIC)
 271                 lapic_watchdog_stop();
 272         __get_cpu_var(wd_enabled) = 0;
 273         atomic_dec(&nmi_active);
 274 }
 275
 276 /*
 277  * the best way to detect whether a CPU has a 'hard lockup' problem
 278  * is to check it's local APIC timer IRQ counts. If they are not
 279  * changing then that CPU has some problem.
 280  *
 281  * as these watchdog NMI IRQs are generated on every CPU, we only
 282  * have to check the current processor.
 283  *
 284  * since NMIs don't listen to _any_ locks, we have to be extremely
 285  * careful not to rely on unsafe variables. The printk might lock
 286  * up though, so we have to break up any console locks first ...
 287  * [when there will be more tty-related locks, break them up
 288  *  here too!]
 289  */
 290
 291 static unsigned int
 292         last_irq_sums [NR_CPUS],
 293         alert_counter [NR_CPUS];
 294
 295 void touch_nmi_watchdog(void)
 296 {
 297         if (nmi_watchdog > 0) {
 298                 unsigned cpu;
 299
 300                 /*
 301                  * Just reset the alert counters, (other CPUs might be
 302                  * spinning on locks we hold):
 303                  */
 304                 for_each_present_cpu(cpu) {
 305                         if (alert_counter[cpu])
 306                                 alert_counter[cpu] = 0;
 307                 }
 308         }
 309
 310         /*
 311          * Tickle the softlockup detector too:
 312          */
 313         touch_softlockup_watchdog();
 314 }
 315 EXPORT_SYMBOL(touch_nmi_watchdog);
 316
 317 extern void die_nmi(struct pt_regs *, const char *msg);
 318
 319 notrace __kprobes int
 320 nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 321 {
 322
 323         /*
 324          * Since current_thread_info()-> is always on the stack, and we
 325          * always switch the stack NMI-atomically, it's safe to use
 326          * smp_processor_id().
 327          */
 328         unsigned int sum;
 329         int touched = 0;
 330         int cpu = smp_processor_id();
 331         int rc = 0;
 332
 333         /* check for other users first */
 334         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
 335                         == NOTIFY_STOP) {
 336                 rc = 1;
 337                 touched = 1;
 338         }
 339
 340         if (cpu_isset(cpu, backtrace_mask)) {
 341                 static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
 342
 343                 spin_lock(&lock);
 344                 printk("NMI backtrace for cpu %d\n", cpu);
 345                 dump_stack();
 346                 spin_unlock(&lock);
 347                 cpu_clear(cpu, backtrace_mask);
 348         }
 349
 350         /*
 351          * Take the local apic timer and PIT/HPET into account. We don't
 352          * know which one is active, when we have highres/dyntick on
 353          */
 354         sum = per_cpu(irq_stat, cpu).apic_timer_irqs +
 355                 per_cpu(irq_stat, cpu).irq0_irqs;
 356
 357         /* if the none of the timers isn't firing, this cpu isn't doing much */
 358         if (!touched && last_irq_sums[cpu] == sum) {
 359                 /*
 360                  * Ayiee, looks like this CPU is stuck ...
 361                  * wait a few IRQs (5 seconds) before doing the oops ...
 362                  */
 363                 alert_counter[cpu]++;
 364                 if (alert_counter[cpu] == 5*nmi_hz)
 365                         /*
 366                          * die_nmi will return ONLY if NOTIFY_STOP happens..
 367                          */
 368                         die_nmi(regs, "BUG: NMI Watchdog detected LOCKUP");
 369         } else {
 370                 last_irq_sums[cpu] = sum;
 371                 alert_counter[cpu] = 0;
 372         }
 373         /* see if the nmi watchdog went off */
 374         if (!__get_cpu_var(wd_enabled))
 375                 return rc;
 376         switch (nmi_watchdog) {
 377         case NMI_LOCAL_APIC:
 378                 rc |= lapic_wd_event(nmi_hz);
 379                 break;
 380         case NMI_IO_APIC:
 381                 /* don't know how to accurately check for this.
 382                  * just assume it was a watchdog timer interrupt
 383                  * This matches the old behaviour.
 384                  */
 385                 rc = 1;
 386                 break;
 387         }
 388         return rc;
 389 }
 390
 391 #ifdef CONFIG_SYSCTL
 392
 393 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 394 {
 395         unsigned char reason = get_nmi_reason();
 396         char buf[64];
 397
 398         sprintf(buf, "NMI received for unknown reason %02x\n", reason);
 399         die_nmi(regs, buf);
 400         return 0;
 401 }
 402
 403 /*
 404  * proc handler for /proc/sys/kernel/nmi
 405  */
 406 int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
 407                         void __user *buffer, size_t *length, loff_t *ppos)
 408 {
 409         int old_state;
 410
 411         nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
 412         old_state = nmi_watchdog_enabled;
 413         proc_dointvec(table, write, file, buffer, length, ppos);
 414         if (!!old_state == !!nmi_watchdog_enabled)
 415                 return 0;
 416
 417         if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
 418                 printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
 419                 return -EIO;
 420         }
 421
 422         if (nmi_watchdog == NMI_DEFAULT) {
 423                 if (lapic_watchdog_ok())
 424                         nmi_watchdog = NMI_LOCAL_APIC;
 425                 else
 426                         nmi_watchdog = NMI_IO_APIC;
 427         }
 428
 429         if (nmi_watchdog == NMI_LOCAL_APIC) {
 430                 if (nmi_watchdog_enabled)
 431                         enable_lapic_nmi_watchdog();
 432                 else
 433                         disable_lapic_nmi_watchdog();
 434         } else {
 435                 printk( KERN_WARNING
 436                         "NMI watchdog doesn't know what hardware to touch\n");
 437                 return -EIO;
 438         }
 439         return 0;
 440 }
 441
 442 #endif
 443
 444 int do_nmi_callback(struct pt_regs *regs, int cpu)
 445 {
 446 #ifdef CONFIG_SYSCTL
 447         if (unknown_nmi_panic)
 448                 return unknown_nmi_panic_callback(regs, cpu);
 449 #endif
 450         return 0;
 451 }
 452
 453 void __trigger_all_cpu_backtrace(void)
 454 {
 455         int i;
 456
 457         backtrace_mask = cpu_online_map;
 458         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
 459         for (i = 0; i < 10 * 1000; i++) {
 460                 if (cpus_empty(backtrace_mask))
 461                         break;
 462                 mdelay(1);
 463         }
 464 }
 465
 466 EXPORT_SYMBOL(nmi_active);
 467 EXPORT_SYMBOL(nmi_watchdog);