kernel/trace/trace_sched_switch.c

/*
 * trace context switch
 *
 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <trace/events/sched.h>

#include "trace.h"

static int			sched_ref;
static DEFINE_MUTEX(sched_register_mutex);

static void
probe_sched_switch(void *ignore, bool preempt,
		   struct task_struct *prev, struct task_struct *next)
{
	if (unlikely(!sched_ref))
		return;

	tracing_record_cmdline(prev);
	tracing_record_cmdline(next);
}

static void
probe_sched_wakeup(void *ignore, struct task_struct *wakee)
{
	if (unlikely(!sched_ref))
		return;

	tracing_record_cmdline(current);
}

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();
}