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nmi_32.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.
 *  Mikael Pettersson   : Pentium 4 support for local APIC NMI watchdog.
 *  Pavel Machek and
 *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
 */

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

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

#include "mach_traps.h"

int unknown_nmi_panic;
int nmi_watchdog_enabled;

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 */

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);

static int endflag __initdata = 0;

/* 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)
{
#ifdef CONFIG_SMP
      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
}

static int __init check_nmi_watchdog(void)
{
      unsigned int *prev_nmi_count;
      int cpu;

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

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

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

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

      if (nmi_watchdog == NMI_LOCAL_APIC)
            smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);

      for_each_possible_cpu(cpu)
            prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
      local_irq_enable();
      mdelay((20*1000)/nmi_hz); // wait 20 ticks

      for_each_possible_cpu(cpu) {
#ifdef CONFIG_SMP
            /* Check cpu_callin_map here because that is set
               after the timer is started. */
            if (!cpu_isset(cpu, cpu_callin_map))
                  continue;
#endif
            if (!per_cpu(wd_enabled, cpu))
                  continue;
            if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
                  printk(KERN_WARNING "WARNING: CPU#%d: NMI "
                        "appears to be stuck (%d->%d)!\n",
                        cpu,
                        prev_nmi_count[cpu],
                        nmi_count(cpu));
                  per_cpu(wd_enabled, cpu) = 0;
                  atomic_dec(&nmi_active);
            }
      }
      endflag = 1;
      if (!atomic_read(&nmi_active)) {
            kfree(prev_nmi_count);
            atomic_set(&nmi_active, -1);
            return -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(prev_nmi_count);
      return 0;
}
/* This needs to happen later in boot so counters are working */
late_initcall(check_nmi_watchdog);

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

      get_option(&str, &nmi);

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

      nmi_watchdog = nmi;
      return 1;
}

__setup("nmi_watchdog=", setup_nmi_watchdog);


/* Suspend/resume support */

#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 */

static void __acpi_nmi_enable(void *__unused)
{
      apic_write_around(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);
}

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);
}

void setup_apic_nmi_watchdog (void *unused)
{
      if (__get_cpu_var(wd_enabled))
            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; /* enable it before to avoid race with handler */
            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.
 *
 * since NMIs don't listen to _any_ locks, we have to be extremely
 * careful not to rely on unsafe variables. The printk might lock
 * up though, so we have to break up any console locks first ...
 * [when there will be more tty-related locks, break them up
 *  here too!]
 */

static unsigned int
      last_irq_sums [NR_CPUS],
      alert_counter [NR_CPUS];

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

            /*
             * Just reset the alert counters, (other CPUs might be
             * spinning on locks we hold):
             */
            for_each_present_cpu(cpu) {
                  if (alert_counter[cpu])
                        alert_counter[cpu] = 0;
            }
      }

      /*
       * Tickle the softlockup detector too:
       */
      touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);

extern void die_nmi(struct pt_regs *, const char *msg);

__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
{

      /*
       * Since current_thread_info()-> is always on the stack, and we
       * always switch the stack NMI-atomically, it's safe to use
       * smp_processor_id().
       */
      unsigned 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;
      }

      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);
      }

      /*
       * Take the local apic timer and PIT/HPET into account. We don't
       * know which one is active, when we have highres/dyntick on
       */
      sum = per_cpu(irq_stat, cpu).apic_timer_irqs +
            per_cpu(irq_stat, cpu).irq0_irqs;

      /* if the none of the timers isn't firing, this cpu isn't doing much */
      if (!touched && last_irq_sums[cpu] == sum) {
            /*
             * Ayiee, looks like this CPU is stuck ...
             * wait a few IRQs (5 seconds) before doing the oops ...
             */
            alert_counter[cpu]++;
            if (alert_counter[cpu] == 5*nmi_hz)
                  /*
                   * die_nmi will return ONLY if NOTIFY_STOP happens..
                   */
                  die_nmi(regs, "BUG: NMI Watchdog detected LOCKUP");
      } else {
            last_irq_sums[cpu] = sum;
            alert_counter[cpu] = 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;
}

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;
}

#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(regs, buf);
      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 == NMI_DEFAULT) {
            if (lapic_watchdog_ok())
                  nmi_watchdog = NMI_LOCAL_APIC;
            else
                  nmi_watchdog = NMI_IO_APIC;
      }

      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);

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