/*
 *  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 <asm/apic.h>

#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/percpu.h>
#include <linux/kprobes.h>
#include <linux/cpumask.h>
#include <linux/kernel_stat.h>
#include <linux/kdebug.h>
#include <linux/smp.h>

#include <asm/i8259.h>
#include <asm/io_apic.h>
#include <asm/smp.h>
#include <asm/nmi.h>
#include <asm/proto.h>
#include <asm/timer.h>

#include <asm/mce.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 */
EXPORT_SYMBOL(nmi_active);

unsigned int nmi_watchdog = NMI_NONE;
EXPORT_SYMBOL(nmi_watchdog);

static int panic_on_timeout;

static unsigned int nmi_hz = HZ;
static DEFINE_PER_CPU(short, wd_enabled);
static int endflag __initdata;

static inline unsigned int get_nmi_count(int cpu)
{
#ifdef CONFIG_X86_64
        return cpu_pda(cpu)->__nmi_count;
#else
        return nmi_count(cpu);
#endif
}

static inline int mce_in_progress(void)
{
#if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
        return atomic_read(&mce_entry) > 0;
#endif
        return 0;
}

/*
 * Take the local apic timer and PIT/HPET into account. We don't
 * know which one is active, when we have highres/dyntick on
 */
static inline unsigned int get_timer_irqs(int cpu)
{
#ifdef CONFIG_X86_64
        return read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
#else
        return per_cpu(irq_stat, cpu).apic_timer_irqs +
                per_cpu(irq_stat, cpu).irq0_irqs;
#endif
}

#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 void report_broken_nmi(int cpu, int *prev_nmi_count)
{
        printk(KERN_CONT "\n");

        printk(KERN_WARNING
                "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
                        cpu, prev_nmi_count[cpu], get_nmi_count(cpu));

        printk(KERN_WARNING
                "Please report this to bugzilla.kernel.org,\n");
        printk(KERN_WARNING
                "and attach the output of the 'dmesg' command.\n");

        per_cpu(wd_enabled, cpu) = 0;
        atomic_dec(&nmi_active);
}

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

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

        prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
        if (!prev_nmi_count)
                goto error;

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

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

        for_each_possible_cpu(cpu)
                prev_nmi_count[cpu] = get_nmi_count(cpu);
        local_irq_enable();
        mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */

        for_each_online_cpu(cpu) {
                if (!per_cpu(wd_enabled, cpu))
                        continue;
                if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
                        report_broken_nmi(cpu, prev_nmi_count);
        }
        endflag = 1;
        if (!atomic_read(&nmi_active)) {
                kfree(prev_nmi_count);
                atomic_set(&nmi_active, -1);
                goto error;
        }
        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;
error:
        if (nmi_watchdog == NMI_IO_APIC && !timer_through_8259)
                disable_8259A_irq(0);
#ifdef CONFIG_X86_32
        timer_ack = 0;
#endif
        return -1;
}

static int __init setup_nmi_watchdog(char *str)
{
        unsigned 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)
                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 = {
        .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(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, 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, 1);
}

/*
 * This function is called as soon the LAPIC NMI watchdog driver has everything
 * in place and it's ready to check if the NMIs belong to the NMI watchdog
 */
void cpu_nmi_set_wd_enabled(void)
{
        __get_cpu_var(wd_enabled) = 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:
                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_active())
                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 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_active()) {
                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;
                }
        }

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

notrace __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;
        }

        sum = get_timer_irqs(cpu);

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

        /* Could check oops_in_progress here too, but it's safer not to */
        if (mce_in_progress())
                touched = 1;

        /* if the none of the timers 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 will return ONLY if NOTIFY_STOP happens..
                         */
                        die_nmi("BUG: NMI Watchdog detected LOCKUP",
                                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;
}

#ifdef CONFIG_SYSCTL

static int __init setup_unknown_nmi_panic(char *str)
{
        unknown_nmi_panic = 1;
        return 1;
}
__setup("unknown_nmi_panic", setup_unknown_nmi_panic);

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_active()) {
                printk(KERN_WARNING
                        "NMI watchdog is permanently disabled\n");
                return -EIO;
        }

        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 /* CONFIG_SYSCTL */

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 __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);
        }
}