/* If critical section is being accessed, 
get current thread to leave it*/

if(lock_flag == 1)
  pthread_mutex_unlock( &cs_mutex);

if( (ret = pthread_mutex_destroy(&cs_mutex)) != 0)
{
    printf("\nError occurred in terminating mutex");
    exit(1);
}

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

#define INTERVAL 5

int flag = 0;
pthread_cond_t waitvar = PTHREAD_COND_INITIALIZER;

pthread_mutex_t *mutex_create(pthread_mutexattr_t * attr)
{
    pthread_mutex_t *new_mutex;

    if ((new_mutex = malloc(sizeof(pthread_mutex_t))) == NULL) {
	return NULL;
    }
    pthread_mutexattr_init(attr);
    pthread_mutex_init(new_mutex, attr);
    return new_mutex;
}



void *create_and_wait(void *mtx)
{
    time_t now, then;
    pthread_mutex_t *amtx = mtx;

    now = then = time(NULL);
    while ((now = time(NULL)) < then + INTERVAL) {
	sleep(1);
	printf("In thread %d doing countdown.\n", pthread_self());
    }
    pthread_mutex_lock(amtx);
    flag = pthread_self();
    pthread_cond_broadcast(&waitvar);
    pthread_mutex_unlock(amtx);
    pthread_exit(NULL);
}


int main(void)
{
    int y = 0, oldflag = flag;
    pthread_t _thread;
    pthread_mutexattr_t new;
    pthread_mutex_t *tmtx;


    while ((y++) < INTERVAL) {
	if ((tmtx = mutex_create(&new)) == NULL) {
	    break;
	}			/*might as well be NULL - but new could be set to whatever */
	pthread_mutex_lock(tmtx);	/*obtain lock before blocking on mutex */
	pthread_create(&_thread, NULL, create_and_wait, tmtx);

	/* 
	 * wait for thread to signal it's wait is over via setting the flag variable to it's thread id and calling pthread_cond_signal
	 * join on the exited thread and reset oldflag
	 * unlock the temp mutex - must be done before calling pthread_mutex_destroy or EBUSY
	 * clear the mutex attributes, etc.. (whatever pthread_mutex_destroy does for the implementation)
	 * cleanup and start over
	 */

	while (flag == oldflag) {
	    pthread_cond_wait(&waitvar, tmtx);
	    pthread_join(flag, NULL);
            oldflag = flag;
	    pthread_mutex_unlock(tmtx);
	    printf("Thread id %d exited.\npthread_mutex_destroy = %d.\n",
		   flag, pthread_mutex_destroy(tmtx));
	    printf("Mutex at %p.\n", tmtx);
	    free(tmtx);
	    tmtx = NULL;
	    break;
	}
    }
    return y;
}