pthread_producer_consumer

pthread_producer_consumer.cpp

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

struct msg {
    struct msg *next;
    int num;
};

struct msg *head;
pthread_cond_t has_product = PTHREAD_COND_INITIALIZER;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

void *consumer(void *p)
{
    struct msg *mp;

    for (;;) {
        pthread_mutex_lock(&lock);//get the lock
        while(head == NULL)
            pthread_cond_wait(&has_product, &lock);//1. release lock. 2. waiting for the event. 3. get the lock, continue.
        mp = head;
        head = mp->next;
        pthread_mutex_unlock(&lock);//release the lock
        printf("Consume %d\n", mp->num);
        free(mp);
        sleep(rand() % 5);
    }
}


void *producer(void *p)
{
    struct msg *mp;
    for (;;) {
        mp = (struct msg *)malloc(sizeof(struct msg));
        mp->num = rand() % 1000 + 1;
        printf("Produce %d\n", mp->num);
        pthread_mutex_lock(&lock);//get the lock
        mp->next = head;
        head = mp;
        pthread_mutex_unlock(&lock);//release the lock
        pthread_cond_signal(&has_product);//send signal to notice event
        sleep(rand() % 5);
    }
}

int main(int argc, char *argv[])
{
    pthread_t pid, cid;

    srand(time(NULL));
    pthread_create(&pid, NULL, producer, NULL);
    pthread_create(&cid, NULL, consumer, NULL);

    pthread_join(pid, NULL);//waiting for pthread termination
    pthread_join(cid, NULL);
    return 0;
}