nmi_timer_int.c

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#include <linux/init.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/oprofile.h>
#include <linux/perf_event.h>

#ifdef CONFIG_OPROFILE_NMI_TIMER

static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
static int ctr_running;

static struct perf_event_attr nmi_timer_attr = {
    .type           = PERF_TYPE_HARDWARE,
    .config         = PERF_COUNT_HW_CPU_CYCLES,
    .size           = sizeof(struct perf_event_attr),
    .pinned         = 1,
    .disabled       = 1,
};

static void nmi_timer_callback(struct perf_event *event,
                   struct perf_sample_data *data,
                   struct pt_regs *regs)
{
    event->hw.interrupts = 0;       /* don't throttle interrupts */
    oprofile_add_sample(regs, 0);
}

static int nmi_timer_start_cpu(int cpu)
{
    struct perf_event *event = per_cpu(nmi_timer_events, cpu);

    if (!event) {
        event = perf_event_create_kernel_counter(&nmi_timer_attr, cpu, NULL,
                             nmi_timer_callback, NULL);
        if (IS_ERR(event))
            return PTR_ERR(event);
        per_cpu(nmi_timer_events, cpu) = event;
    }

    if (event && ctr_running)
        perf_event_enable(event);

    return 0;
}

static void nmi_timer_stop_cpu(int cpu)
{
    struct perf_event *event = per_cpu(nmi_timer_events, cpu);

    if (event && ctr_running)
        perf_event_disable(event);
}

static int nmi_timer_cpu_notifier(struct notifier_block *b, unsigned long action,
                  void *data)
{
    int cpu = (unsigned long)data;
    switch (action) {
    case CPU_DOWN_FAILED:
    case CPU_ONLINE:
        nmi_timer_start_cpu(cpu);
        break;
    case CPU_DOWN_PREPARE:
        nmi_timer_stop_cpu(cpu);
        break;
    }
    return NOTIFY_DONE;
}

static struct notifier_block nmi_timer_cpu_nb = {
    .notifier_call = nmi_timer_cpu_notifier
};

static int nmi_timer_start(void)
{
    int cpu;

    get_online_cpus();
    ctr_running = 1;
    for_each_online_cpu(cpu)
        nmi_timer_start_cpu(cpu);
    put_online_cpus();

    return 0;
}

static void nmi_timer_stop(void)
{
    int cpu;

    get_online_cpus();
    for_each_online_cpu(cpu)
        nmi_timer_stop_cpu(cpu);
    ctr_running = 0;
    put_online_cpus();
}

static void nmi_timer_shutdown(void)
{
    struct perf_event *event;
    int cpu;

    get_online_cpus();
    unregister_cpu_notifier(&nmi_timer_cpu_nb);
    for_each_possible_cpu(cpu) {
        event = per_cpu(nmi_timer_events, cpu);
        if (!event)
            continue;
        perf_event_disable(event);
        per_cpu(nmi_timer_events, cpu) = NULL;
        perf_event_release_kernel(event);
    }

    put_online_cpus();
}

static int nmi_timer_setup(void)
{
    int cpu, err;
    u64 period;

    /* clock cycles per tick: */
    period = (u64)cpu_khz * 1000;
    do_div(period, HZ);
    nmi_timer_attr.sample_period = period;

    get_online_cpus();
    err = register_cpu_notifier(&nmi_timer_cpu_nb);
    if (err)
        goto out;
    /* can't attach events to offline cpus: */
    for_each_online_cpu(cpu) {
        err = nmi_timer_start_cpu(cpu);
        if (err)
            break;
    }
    if (err)
        nmi_timer_shutdown();
out:
    put_online_cpus();
    return err;
}

int __init op_nmi_timer_init(struct oprofile_operations *ops)
{
    int err = 0;

    err = nmi_timer_setup();
    if (err)
        return err;
    nmi_timer_shutdown();       /* only check, don't alloc */

    ops->create_files   = NULL;
    ops->setup      = nmi_timer_setup;
    ops->shutdown       = nmi_timer_shutdown;
    ops->start      = nmi_timer_start;
    ops->stop       = nmi_timer_stop;
    ops->cpu_type       = "timer";

    printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");

    return 0;
}

#endif