pthreadTest.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <math.h>
#define NUM_THREADS 3
#define TCOUNT 10
#define COUNT_LIMIT 12

int count = 0;
int thread_ids[3] = {0, 1, 2};
pthread_mutex_t count_mutex;
pthread_cond_t count_threshold_cv;


void * inc_count(void *t) {
	int i;
	long my_id = (long) t;
	
	for (i = 0; i < TCOUNT; i++) {
		pthread_mutex_lock(&count_mutex);
		count++;
		
		if (count == COUNT_LIMIT) {
			pthread_cond_signal(&count_threshold_cv);
			printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count);
		}
		printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count);
		pthread_mutex_unlock(&count_mutex);
		
		sleep(1);
	}
	
	pthread_exit(NULL);
}


void * watch_count (void *t) {
	long my_id = (long) t;
	printf("Starting watch_count(): thread %ld\n", my_id);
	
	pthread_mutex_lock(&count_mutex);
	while (count < COUNT_LIMIT) {
		pthread_cond_wait(&count_threshold_cv, &count_mutex);
		printf("watch_count(): thread %ld Condition signal received.\n", my_id);
	}
	count = 0;
	printf("watch_count(): thread %ld count now = %d.\n", my_id, count);
	pthread_mutex_unlock(&count_mutex);
	pthread_exit(NULL);
}


void main () {
	int i, rc;
	long t1 = 1, t2 = 2, t3 = 3;
	pthread_t threads[3];
	pthread_attr_t attr;
	
	pthread_mutex_init(&count_mutex, NULL);
	pthread_cond_init(&count_threshold_cv, NULL);
	
	pthread_attr_init(&attr);
	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
	pthread_create(&threads[0], &attr, watch_count, (void *) t1);
	pthread_create(&threads[1], &attr, inc_count, (void *) t2);
	pthread_create(&threads[2], &attr, inc_count, (void *) t3);
	
	for (i = 0; i < NUM_THREADS; i++) {
		pthread_join(threads[i], NULL);
	}
	printf("Main(): Waited on %d threads. Done.\n", NUM_THREADS);
	
	pthread_attr_destroy(&attr);
	pthread_mutex_destroy(&count_mutex);
	pthread_cond_destroy(&count_threshold_cv);
	pthread_exit(NULL);
}