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nmi_64.c

/*
 *  NMI watchdog support on APIC systems
 *
 *  Started by Ingo Molnar <mingo@redhat.com>
 *
 *  Fixes:
 *  Mikael Pettersson   : AMD K7 support for local APIC NMI watchdog.
 *  Mikael Pettersson   : Power Management for local APIC NMI watchdog.
 *  Pavel Machek and
 *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
 */

#include <linux/nmi.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sysdev.h>
#include <linux/sysctl.h>
#include <linux/kprobes.h>
#include <linux/cpumask.h>
#include <linux/kdebug.h>

#include <asm/smp.h>
#include <asm/nmi.h>
#include <asm/proto.h>
#include <asm/mce.h>

int unknown_nmi_panic;
int nmi_watchdog_enabled;
int panic_on_unrecovered_nmi;

static cpumask_t backtrace_mask = CPU_MASK_NONE;

/* nmi_active:
 * >0: the lapic NMI watchdog is active, but can be disabled
 * <0: the lapic NMI watchdog has not been set up, and cannot
 *     be enabled
 *  0: the lapic NMI watchdog is disabled, but can be enabled
 */
atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
int panic_on_timeout;

unsigned int nmi_watchdog = NMI_DEFAULT;
static unsigned int nmi_hz = HZ;

static DEFINE_PER_CPU(short, wd_enabled);

/* local prototypes */
static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);

/* Run after command line and cpu_init init, but before all other checks */
void nmi_watchdog_default(void)
{
      if (nmi_watchdog != NMI_DEFAULT)
            return;
      nmi_watchdog = NMI_NONE;
}

static int endflag __initdata = 0;

#ifdef CONFIG_SMP
/* The performance counters used by NMI_LOCAL_APIC don't trigger when
 * the CPU is idle. To make sure the NMI watchdog really ticks on all
 * CPUs during the test make them busy.
 */
static __init void nmi_cpu_busy(void *data)
{
      local_irq_enable_in_hardirq();
      /* Intentionally don't use cpu_relax here. This is
         to make sure that the performance counter really ticks,
         even if there is a simulator or similar that catches the
         pause instruction. On a real HT machine this is fine because
         all other CPUs are busy with "useless" delay loops and don't
         care if they get somewhat less cycles. */
      while (endflag == 0)
            mb();
}
#endif

int __init check_nmi_watchdog (void)
{
      int *counts;
      int cpu;

      if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DISABLED)) 
            return 0;

      if (!atomic_read(&nmi_active))
            return 0;

      counts = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
      if (!counts)
            return -1;

      printk(KERN_INFO "testing NMI watchdog ... ");

#ifdef CONFIG_SMP
      if (nmi_watchdog == NMI_LOCAL_APIC)
            smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
#endif

      for (cpu = 0; cpu < NR_CPUS; cpu++)
            counts[cpu] = cpu_pda(cpu)->__nmi_count;
      local_irq_enable();
      mdelay((20*1000)/nmi_hz); // wait 20 ticks

      for_each_online_cpu(cpu) {
            if (!per_cpu(wd_enabled, cpu))
                  continue;
            if (cpu_pda(cpu)->__nmi_count - counts[cpu] <= 5) {
                  printk(KERN_WARNING "WARNING: CPU#%d: NMI "
                         "appears to be stuck (%d->%d)!\n",
                         cpu,
                         counts[cpu],
                         cpu_pda(cpu)->__nmi_count);
                  per_cpu(wd_enabled, cpu) = 0;
                  atomic_dec(&nmi_active);
            }
      }
      if (!atomic_read(&nmi_active)) {
            kfree(counts);
            atomic_set(&nmi_active, -1);
            endflag = 1;
            return -1;
      }
      endflag = 1;
      printk("OK.\n");

      /* now that we know it works we can reduce NMI frequency to
         something more reasonable; makes a difference in some configs */
      if (nmi_watchdog == NMI_LOCAL_APIC)
            nmi_hz = lapic_adjust_nmi_hz(1);

      kfree(counts);
      return 0;
}

int __init setup_nmi_watchdog(char *str)
{
      int nmi;

      if (!strncmp(str,"panic",5)) {
            panic_on_timeout = 1;
            str = strchr(str, ',');
            if (!str)
                  return 1;
            ++str;
      }

      get_option(&str, &nmi);

      if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
            return 0;

      nmi_watchdog = nmi;
      return 1;
}

__setup("nmi_watchdog=", setup_nmi_watchdog);


static void __acpi_nmi_disable(void *__unused)
{
      apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
}

/*
 * Disable timer based NMIs on all CPUs:
 */
void acpi_nmi_disable(void)
{
      if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
            on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
}

static void __acpi_nmi_enable(void *__unused)
{
      apic_write(APIC_LVT0, APIC_DM_NMI);
}

/*
 * Enable timer based NMIs on all CPUs:
 */
void acpi_nmi_enable(void)
{
      if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
            on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
}
#ifdef CONFIG_PM

static int nmi_pm_active; /* nmi_active before suspend */

static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
{
      /* only CPU0 goes here, other CPUs should be offline */
      nmi_pm_active = atomic_read(&nmi_active);
      stop_apic_nmi_watchdog(NULL);
      BUG_ON(atomic_read(&nmi_active) != 0);
      return 0;
}

static int lapic_nmi_resume(struct sys_device *dev)
{
      /* only CPU0 goes here, other CPUs should be offline */
      if (nmi_pm_active > 0) {
            setup_apic_nmi_watchdog(NULL);
            touch_nmi_watchdog();
      }
      return 0;
}

static struct sysdev_class nmi_sysclass = {
      set_kset_name("lapic_nmi"),
      .resume           = lapic_nmi_resume,
      .suspend    = lapic_nmi_suspend,
};

static struct sys_device device_lapic_nmi = {
      .id         = 0,
      .cls  = &nmi_sysclass,
};

static int __init init_lapic_nmi_sysfs(void)
{
      int error;

      /* should really be a BUG_ON but b/c this is an
       * init call, it just doesn't work.  -dcz
       */
      if (nmi_watchdog != NMI_LOCAL_APIC)
            return 0;

      if ( atomic_read(&nmi_active) < 0 )
            return 0;

      error = sysdev_class_register(&nmi_sysclass);
      if (!error)
            error = sysdev_register(&device_lapic_nmi);
      return error;
}
/* must come after the local APIC's device_initcall() */
late_initcall(init_lapic_nmi_sysfs);

#endif      /* CONFIG_PM */

void setup_apic_nmi_watchdog(void *unused)
{
      if (__get_cpu_var(wd_enabled) == 1)
            return;

      /* cheap hack to support suspend/resume */
      /* if cpu0 is not active neither should the other cpus */
      if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
            return;

      switch (nmi_watchdog) {
      case NMI_LOCAL_APIC:
            __get_cpu_var(wd_enabled) = 1;
            if (lapic_watchdog_init(nmi_hz) < 0) {
                  __get_cpu_var(wd_enabled) = 0;
                  return;
            }
            /* FALL THROUGH */
      case NMI_IO_APIC:
            __get_cpu_var(wd_enabled) = 1;
            atomic_inc(&nmi_active);
      }
}

void stop_apic_nmi_watchdog(void *unused)
{
      /* only support LOCAL and IO APICs for now */
      if ((nmi_watchdog != NMI_LOCAL_APIC) &&
          (nmi_watchdog != NMI_IO_APIC))
            return;
      if (__get_cpu_var(wd_enabled) == 0)
            return;
      if (nmi_watchdog == NMI_LOCAL_APIC)
            lapic_watchdog_stop();
      __get_cpu_var(wd_enabled) = 0;
      atomic_dec(&nmi_active);
}

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check it's local APIC timer IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * as these watchdog NMI IRQs are generated on every CPU, we only
 * have to check the current processor.
 */

static DEFINE_PER_CPU(unsigned, last_irq_sum);
static DEFINE_PER_CPU(local_t, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);

void touch_nmi_watchdog(void)
{
      if (nmi_watchdog > 0) {
            unsigned cpu;

            /*
             * Tell other CPUs to reset their alert counters. We cannot
             * do it ourselves because the alert count increase is not
             * atomic.
             */
            for_each_present_cpu(cpu) {
                  if (per_cpu(nmi_touch, cpu) != 1)
                        per_cpu(nmi_touch, cpu) = 1;
            }
      }

      touch_softlockup_watchdog();
}

int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
{
      int sum;
      int touched = 0;
      int cpu = smp_processor_id();
      int rc = 0;

      /* check for other users first */
      if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
                  == NOTIFY_STOP) {
            rc = 1;
            touched = 1;
      }

      sum = read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
      if (__get_cpu_var(nmi_touch)) {
            __get_cpu_var(nmi_touch) = 0;
            touched = 1;
      }

      if (cpu_isset(cpu, backtrace_mask)) {
            static DEFINE_SPINLOCK(lock); /* Serialise the printks */

            spin_lock(&lock);
            printk("NMI backtrace for cpu %d\n", cpu);
            dump_stack();
            spin_unlock(&lock);
            cpu_clear(cpu, backtrace_mask);
      }

#ifdef CONFIG_X86_MCE
      /* Could check oops_in_progress here too, but it's safer
         not too */
      if (atomic_read(&mce_entry) > 0)
            touched = 1;
#endif
      /* if the apic timer isn't firing, this cpu isn't doing much */
      if (!touched && __get_cpu_var(last_irq_sum) == sum) {
            /*
             * Ayiee, looks like this CPU is stuck ...
             * wait a few IRQs (5 seconds) before doing the oops ...
             */
            local_inc(&__get_cpu_var(alert_counter));
            if (local_read(&__get_cpu_var(alert_counter)) == 5*nmi_hz)
                  die_nmi("NMI Watchdog detected LOCKUP on CPU %d\n", regs,
                        panic_on_timeout);
      } else {
            __get_cpu_var(last_irq_sum) = sum;
            local_set(&__get_cpu_var(alert_counter), 0);
      }

      /* see if the nmi watchdog went off */
      if (!__get_cpu_var(wd_enabled))
            return rc;
      switch (nmi_watchdog) {
      case NMI_LOCAL_APIC:
            rc |= lapic_wd_event(nmi_hz);
            break;
      case NMI_IO_APIC:
            /* don't know how to accurately check for this.
             * just assume it was a watchdog timer interrupt
             * This matches the old behaviour.
             */
            rc = 1;
            break;
      }
      return rc;
}

static unsigned ignore_nmis;

asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
{
      nmi_enter();
      add_pda(__nmi_count,1);
      if (!ignore_nmis)
            default_do_nmi(regs);
      nmi_exit();
}

int do_nmi_callback(struct pt_regs * regs, int cpu)
{
#ifdef CONFIG_SYSCTL
      if (unknown_nmi_panic)
            return unknown_nmi_panic_callback(regs, cpu);
#endif
      return 0;
}

void stop_nmi(void)
{
      acpi_nmi_disable();
      ignore_nmis++;
}

void restart_nmi(void)
{
      ignore_nmis--;
      acpi_nmi_enable();
}

#ifdef CONFIG_SYSCTL

static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
{
      unsigned char reason = get_nmi_reason();
      char buf[64];

      sprintf(buf, "NMI received for unknown reason %02x\n", reason);
      die_nmi(buf, regs, 1);  /* Always panic here */
      return 0;
}

/*
 * proc handler for /proc/sys/kernel/nmi
 */
int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
                  void __user *buffer, size_t *length, loff_t *ppos)
{
      int old_state;

      nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
      old_state = nmi_watchdog_enabled;
      proc_dointvec(table, write, file, buffer, length, ppos);
      if (!!old_state == !!nmi_watchdog_enabled)
            return 0;

      if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
            printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
            return -EIO;
      }

      /* if nmi_watchdog is not set yet, then set it */
      nmi_watchdog_default();

      if (nmi_watchdog == NMI_LOCAL_APIC) {
            if (nmi_watchdog_enabled)
                  enable_lapic_nmi_watchdog();
            else
                  disable_lapic_nmi_watchdog();
      } else {
            printk( KERN_WARNING
                  "NMI watchdog doesn't know what hardware to touch\n");
            return -EIO;
      }
      return 0;
}

#endif

void __trigger_all_cpu_backtrace(void)
{
      int i;

      backtrace_mask = cpu_online_map;
      /* Wait for up to 10 seconds for all CPUs to do the backtrace */
      for (i = 0; i < 10 * 1000; i++) {
            if (cpus_empty(backtrace_mask))
                  break;
            mdelay(1);
      }
}

EXPORT_SYMBOL(nmi_active);
EXPORT_SYMBOL(nmi_watchdog);
EXPORT_SYMBOL(touch_nmi_watchdog);

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