/*
 * Copyright (c) 2017, GlobalLogic Ukraine LLC
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the GlobalLogic.
 * 4. Neither the name of the GlobalLogic nor the
 *    names of its contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY GLOBALLOGIC UKRAINE LLC ``AS IS`` AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL GLOBALLOGIC UKRAINE LLC BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/slab.h>

#define DEBUG

MODULE_AUTHOR("Serhii Popovych <serhii.popovych@globallogic.com>");
MODULE_DESCRIPTION("Hello, world in Linux Kernel Training");
MODULE_LICENSE("Dual BSD/GPL");

struct TimingList {
	struct TimingList *next;
	ktime_t time_before, time_after;
};

static struct TimingList *list_head;
static unsigned int bug_generator;

static struct TimingList *write_first_node(void)
{
	list_head = kmalloc(sizeof(struct TimingList), GFP_KERNEL);
	list_head->next = NULL;

	return list_head;
}

static struct TimingList *insert_next_node(struct TimingList *tail)
{
	struct TimingList *new_node = kmalloc(sizeof(struct TimingList),
						GFP_KERNEL);

	if (bug_generator == 5) {
		new_node = NULL;
	} else {
		tail->next = new_node;
		new_node->next = NULL;
	}

	return new_node;
}

static struct TimingList *add_new_node(struct TimingList *tail)
{
	if (tail == NULL)
		return write_first_node();
	else
		return insert_next_node(tail);
}

static void print_time_diff(struct TimingList *node)
{
	pr_debug("%lld\n", node->time_after - node->time_before);
}

void destroy_list(void)
{
	struct TimingList *current_node = list_head;
	struct TimingList *next_node = NULL;

	list_head = NULL;

	while (current_node != NULL) {
		print_time_diff(current_node);

		next_node = current_node->next;
		kfree(current_node);
		current_node = next_node;
	}
}
EXPORT_SYMBOL(destroy_list);

static int __init hello_init(void)
{
	return 0;
}

void print_hello(int message_count)
{
	int i;
	struct TimingList *current_tail = list_head;

	for (i = 0; i < message_count; i++) {
		bug_generator = i;

		current_tail = add_new_node(current_tail);

		current_tail->time_before = ktime_get();
		pr_info("Hello, world!\n");
		current_tail->time_after = ktime_get();
	}
}
EXPORT_SYMBOL(print_hello);

static void __exit hello_exit(void)
{
	destroy_list();
}


module_init(hello_init);
module_exit(hello_exit);