/*
 *  linux/arch/i386/nmi.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;

#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

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

        if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
                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("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);
                }
        }
        if (!atomic_read(&nmi_active)) {
                kfree(prev_nmi_count);
                atomic_set(&nmi_active, -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(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)
                        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 + kstat_irqs(0);

        /* 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) {
                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);