trace_sched_switch.c

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/*
 * trace context switch
 *
 * Copyright (C) 2007 Steven Rostedt <[email protected]>
 *
 */
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <trace/events/sched.h>

#include "trace.h"

static struct trace_array   *ctx_trace;
static int __read_mostly    tracer_enabled;
static int          sched_ref;
static DEFINE_MUTEX(sched_register_mutex);
static int          sched_stopped;


void
tracing_sched_switch_trace(struct trace_array *tr,
               struct task_struct *prev,
               struct task_struct *next,
               unsigned long flags, int pc)
{
    struct ftrace_event_call *call = &event_context_switch;
    struct ring_buffer *buffer = tr->buffer;
    struct ring_buffer_event *event;
    struct ctx_switch_entry *entry;

    event = trace_buffer_lock_reserve(buffer, TRACE_CTX,
                      sizeof(*entry), flags, pc);
    if (!event)
        return;
    entry   = ring_buffer_event_data(event);
    entry->prev_pid         = prev->pid;
    entry->prev_prio        = prev->prio;
    entry->prev_state       = prev->state;
    entry->next_pid         = next->pid;
    entry->next_prio        = next->prio;
    entry->next_state       = next->state;
    entry->next_cpu = task_cpu(next);

    if (!filter_check_discard(call, entry, buffer, event))
        trace_buffer_unlock_commit(buffer, event, flags, pc);
}

static void
probe_sched_switch(void *ignore, struct task_struct *prev, struct task_struct *next)
{
    struct trace_array_cpu *data;
    unsigned long flags;
    int cpu;
    int pc;

    if (unlikely(!sched_ref))
        return;

    tracing_record_cmdline(prev);
    tracing_record_cmdline(next);

    if (!tracer_enabled || sched_stopped)
        return;

    pc = preempt_count();
    local_irq_save(flags);
    cpu = raw_smp_processor_id();
    data = ctx_trace->data[cpu];

    if (likely(!atomic_read(&data->disabled)))
        tracing_sched_switch_trace(ctx_trace, prev, next, flags, pc);

    local_irq_restore(flags);
}

void
tracing_sched_wakeup_trace(struct trace_array *tr,
               struct task_struct *wakee,
               struct task_struct *curr,
               unsigned long flags, int pc)
{
    struct ftrace_event_call *call = &event_wakeup;
    struct ring_buffer_event *event;
    struct ctx_switch_entry *entry;
    struct ring_buffer *buffer = tr->buffer;

    event = trace_buffer_lock_reserve(buffer, TRACE_WAKE,
                      sizeof(*entry), flags, pc);
    if (!event)
        return;
    entry   = ring_buffer_event_data(event);
    entry->prev_pid         = curr->pid;
    entry->prev_prio        = curr->prio;
    entry->prev_state       = curr->state;
    entry->next_pid         = wakee->pid;
    entry->next_prio        = wakee->prio;
    entry->next_state       = wakee->state;
    entry->next_cpu         = task_cpu(wakee);

    if (!filter_check_discard(call, entry, buffer, event))
        ring_buffer_unlock_commit(buffer, event);
    ftrace_trace_stack(tr->buffer, flags, 6, pc);
    ftrace_trace_userstack(tr->buffer, flags, pc);
}

static void
probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success)
{
    struct trace_array_cpu *data;
    unsigned long flags;
    int cpu, pc;

    if (unlikely(!sched_ref))
        return;

    tracing_record_cmdline(current);

    if (!tracer_enabled || sched_stopped)
        return;

    pc = preempt_count();
    local_irq_save(flags);
    cpu = raw_smp_processor_id();
    data = ctx_trace->data[cpu];

    if (likely(!atomic_read(&data->disabled)))
        tracing_sched_wakeup_trace(ctx_trace, wakee, current,
                       flags, pc);

    local_irq_restore(flags);
}

static int tracing_sched_register(void)
{
    int ret;

    ret = register_trace_sched_wakeup(probe_sched_wakeup, NULL);
    if (ret) {
        pr_info("wakeup trace: Couldn't activate tracepoint"
            " probe to kernel_sched_wakeup\n");
        return ret;
    }

    ret = register_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
    if (ret) {
        pr_info("wakeup trace: Couldn't activate tracepoint"
            " probe to kernel_sched_wakeup_new\n");
        goto fail_deprobe;
    }

    ret = register_trace_sched_switch(probe_sched_switch, NULL);
    if (ret) {
        pr_info("sched trace: Couldn't activate tracepoint"
            " probe to kernel_sched_switch\n");
        goto fail_deprobe_wake_new;
    }

    return ret;
fail_deprobe_wake_new:
    unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
fail_deprobe:
    unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
    return ret;
}

static void tracing_sched_unregister(void)
{
    unregister_trace_sched_switch(probe_sched_switch, NULL);
    unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
    unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
}

static void tracing_start_sched_switch(void)
{
    mutex_lock(&sched_register_mutex);
    if (!(sched_ref++))
        tracing_sched_register();
    mutex_unlock(&sched_register_mutex);
}

static void tracing_stop_sched_switch(void)
{
    mutex_lock(&sched_register_mutex);
    if (!(--sched_ref))
        tracing_sched_unregister();
    mutex_unlock(&sched_register_mutex);
}

void tracing_start_cmdline_record(void)
{
    tracing_start_sched_switch();
}

void tracing_stop_cmdline_record(void)
{
    tracing_stop_sched_switch();
}

void tracing_start_sched_switch_record(void)
{
    if (unlikely(!ctx_trace)) {
        WARN_ON(1);
        return;
    }

    tracing_start_sched_switch();

    mutex_lock(&sched_register_mutex);
    tracer_enabled++;
    mutex_unlock(&sched_register_mutex);
}

void tracing_stop_sched_switch_record(void)
{
    mutex_lock(&sched_register_mutex);
    tracer_enabled--;
    WARN_ON(tracer_enabled < 0);
    mutex_unlock(&sched_register_mutex);

    tracing_stop_sched_switch();
}

void tracing_sched_switch_assign_trace(struct trace_array *tr)
{
    ctx_trace = tr;
}