Variable Safety Tips

– Do not forget to notify waiting threads!
– predicate change =>
signal/broadcast correct condition variable
– When in doblt broadcast
– but performance loss
– You do not need a mutex to signal/broadcast

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

#define BUF_SIZE 3 /* size of shared buffer */

int buffer[BUF_SIZE];
int add = 0;
int rem = 0;
int num = 0;

pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t c_cons = PTHREAD_COND_INITIALIZER;
pthread_cond_t c_prod = PTHREAD_COND_INITIALIZER;

void *producer(void *param);
void *consumer(void *param);

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

#define BUF_SIZE 3 /* size of shared buffer */

int buffer[BUF_SIZE];
int add = 0;
int rem = 0;
int num = 0;

pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t c_cons = PTHREAD_COND_INITIALIZER;
pthread_cond_t c_prod = PTHREAD_COND_INITIALIZER;

void *producer(void *param);
void *consumer(void *param);

int main(int argc, char *argv[]){
	pthread_t tid1, tid2;
	int i;

	if (pthread_create(&tid1, NULL, producer, NULL) != 0){
		fprintf(stderr, "Unable to create producer thread\n");
		exit(1);
	}

	if (pthread_create(&tid2, NULL, consumer, NULL) != 0){
		fprintf(stderr, "Unable to create consumer thread\n");
		exit(1);
	}

	pthread_join(tid1, NULL); /* wait for producer to exit */
	pthread_join(tid2, NULL); /* wait for consumer to exit */
	printf("Parent quiting\n");
}