arch/arm/mach-msm/perf_trace_counters.c

/* Copyright (c) 2013, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
#include <asm/thread_notify.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#define CREATE_TRACE_POINTS
#include "perf_trace_counters.h"

static unsigned int tp_pid_state;

static int tracectr_notifier(struct notifier_block *self, unsigned long cmd,
		void *v)
{
	static int old_pid = -1;
	struct thread_info *thread = v;
	int current_pid;

	if (cmd != THREAD_NOTIFY_SWITCH)
		return old_pid;

	current_pid = thread->task->pid;
	if (old_pid != -1)
		trace_sched_switch_with_ctrs(old_pid, current_pid);
	old_pid = current_pid;
	return old_pid;
}

static struct notifier_block tracectr_notifier_block = {
	.notifier_call  = tracectr_notifier,
};

static void enable_tp_pid(void)
{
	if (tp_pid_state == 0) {
		tp_pid_state = 1;
		thread_register_notifier(&tracectr_notifier_block);
	}
}

static void disable_tp_pid(void)
{
	if (tp_pid_state == 1) {
		tp_pid_state = 0;
		thread_unregister_notifier(&tracectr_notifier_block);
	}
}

static ssize_t read_enabled_perftp_file_bool(struct file *file,
		char __user *user_buf, size_t count, loff_t *ppos)
{
	char buf[2];
	buf[1] = '\n';
	if (tp_pid_state == 0)
		buf[0] = '0';
	else
		buf[0] = '1';
	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
}

static ssize_t write_enabled_perftp_file_bool(struct file *file,
		const char __user *user_buf, size_t count, loff_t *ppos)
{
	char buf[32];
	size_t buf_size;

	buf_size = min(count, (sizeof(buf)-1));
	if (copy_from_user(buf, user_buf, buf_size))
		return -EFAULT;
	switch (buf[0]) {
	case 'y':
	case 'Y':
	case '1':
		enable_tp_pid();
		break;
	case 'n':
	case 'N':
	case '0':
		disable_tp_pid();
		break;
	}

	return count;
}

static const struct file_operations fops_perftp = {
	.read =		read_enabled_perftp_file_bool,
	.write =	write_enabled_perftp_file_bool,
	.llseek =	default_llseek,
};

int __init init_tracecounters(void)
{
	struct dentry *dir;
	struct dentry *file;
	unsigned int value = 1;

	dir = debugfs_create_dir("perf_debug_tp", NULL);
	if (!dir)
		return -ENOMEM;
	file = debugfs_create_file("enabled", 0660, dir,
		&value, &fops_perftp);
	if (!file) {
		debugfs_remove(dir);
		return -ENOMEM;
	}
	return 0;
}
late_initcall(init_tracecounters);