nmi.c

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/* Pseudo NMI support on sparc64 systems.
 *
 * Copyright (C) 2009 David S. Miller <[email protected]>
 *
 * The NMI watchdog support and infrastructure is based almost
 * entirely upon the x86 NMI support code.
 */
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/nmi.h>
#include <linux/export.h>
#include <linux/kprobes.h>
#include <linux/kernel_stat.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/kdebug.h>
#include <linux/delay.h>
#include <linux/smp.h>

#include <asm/perf_event.h>
#include <asm/ptrace.h>
#include <asm/pcr.h>

#include "kstack.h"

/* We don't have a real NMI on sparc64, but we can fake one
 * up using profiling counter overflow interrupts and interrupt
 * levels.
 *
 * The profile overflow interrupts at level 15, so we use
 * level 14 as our IRQ off level.
 */

static int panic_on_timeout;

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

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

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

void touch_nmi_watchdog(void)
{
    if (atomic_read(&nmi_active)) {
        int cpu;

        for_each_present_cpu(cpu) {
            if (per_cpu(nmi_touch, cpu) != 1)
                per_cpu(nmi_touch, cpu) = 1;
        }
    }

    touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);

static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
{
    if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
               pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
        return;

    console_verbose();
    bust_spinlocks(1);

    printk(KERN_EMERG "%s", str);
    printk(" on CPU%d, ip %08lx, registers:\n",
           smp_processor_id(), regs->tpc);
    show_regs(regs);
    dump_stack();

    bust_spinlocks(0);

    if (do_panic || panic_on_oops)
        panic("Non maskable interrupt");

    nmi_exit();
    local_irq_enable();
    do_exit(SIGBUS);
}

notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
{
    unsigned int sum, touched = 0;
    void *orig_sp;

    clear_softint(1 << irq);

    local_cpu_data().__nmi_count++;

    nmi_enter();

    orig_sp = set_hardirq_stack();

    if (notify_die(DIE_NMI, "nmi", regs, 0,
               pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
        touched = 1;
    else
        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);

    sum = local_cpu_data().irq0_irqs;
    if (__get_cpu_var(nmi_touch)) {
        __get_cpu_var(nmi_touch) = 0;
        touched = 1;
    }
    if (!touched && __get_cpu_var(last_irq_sum) == sum) {
        __this_cpu_inc(alert_counter);
        if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
            die_nmi("BUG: NMI Watchdog detected LOCKUP",
                regs, panic_on_timeout);
    } else {
        __get_cpu_var(last_irq_sum) = sum;
        __this_cpu_write(alert_counter, 0);
    }
    if (__get_cpu_var(wd_enabled)) {
        pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
    }

    restore_hardirq_stack(orig_sp);

    nmi_exit();
}

static inline unsigned int get_nmi_count(int cpu)
{
    return cpu_data(cpu).__nmi_count;
}

static __init void nmi_cpu_busy(void *data)
{
    local_irq_enable_in_hardirq();
    while (endflag == 0)
        mb();
}

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);
}

void stop_nmi_watchdog(void *unused)
{
    pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
    __get_cpu_var(wd_enabled) = 0;
    atomic_dec(&nmi_active);
}

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

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

    prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(unsigned int), GFP_KERNEL);
    if (!prev_nmi_count) {
        err = -ENOMEM;
        goto error;
    }

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

    smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);

    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);
        err = -ENODEV;
        goto error;
    }
    printk("OK.\n");

    nmi_hz = 1;

    kfree(prev_nmi_count);
    return 0;
error:
    on_each_cpu(stop_nmi_watchdog, NULL, 1);
    return err;
}

void start_nmi_watchdog(void *unused)
{
    __get_cpu_var(wd_enabled) = 1;
    atomic_inc(&nmi_active);

    pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
    pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));

    pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
}

static void nmi_adjust_hz_one(void *unused)
{
    if (!__get_cpu_var(wd_enabled))
        return;

    pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
    pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));

    pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
}

void nmi_adjust_hz(unsigned int new_hz)
{
    nmi_hz = new_hz;
    on_each_cpu(nmi_adjust_hz_one, NULL, 1);
}
EXPORT_SYMBOL_GPL(nmi_adjust_hz);

static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
{
    on_each_cpu(stop_nmi_watchdog, NULL, 1);
    return 0;
}

static struct notifier_block nmi_reboot_notifier = {
    .notifier_call = nmi_shutdown,
};

int __init nmi_init(void)
{
    int err;

    on_each_cpu(start_nmi_watchdog, NULL, 1);

    err = check_nmi_watchdog();
    if (!err) {
        err = register_reboot_notifier(&nmi_reboot_notifier);
        if (err) {
            on_each_cpu(stop_nmi_watchdog, NULL, 1);
            atomic_set(&nmi_active, -1);
        }
    }

    return err;
}

static int __init setup_nmi_watchdog(char *str)
{
    if (!strncmp(str, "panic", 5))
        panic_on_timeout = 1;

    return 0;
}
__setup("nmi_watchdog=", setup_nmi_watchdog);