/*
 **************************************
 *
 *	Updating a global counter, with mutex.
 *	Silvia Figueira -- Winter 09
 *
 **************************************
 */

#include <stdio.h>
#include <pthread.h>


/*
 *	functions
 */
void *loop (void *arg);


/*
 *	global variables
 */
pthread_mutex_t	mutex;
int		count = 0;


/*
 *	main
 */
int
main ( )
{
	int		i;
	pthread_t	thr[3];


	pthread_mutex_init (&mutex, NULL);

	for (i = 0; i < 3; i++)
		pthread_create(&thr[i], NULL, loop,(void *) i);

	for (i = 0; i < 3; i++)
		pthread_join (thr[i], NULL); 

	printf ("Final: %d\n", count);
}


/*
 *	loop
 */
void *
loop (void *arg)
{
	int	i, j;
	int	threadNo = (int) arg;


	for (i = 0; i < 100000; i++)
	{
		pthread_mutex_lock (&mutex);
		count++;
		pthread_mutex_unlock (&mutex);

		for (j = 0; j < 10000; j++);
	}

	printf ("%d: %d\n", threadNo, count);

}