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我正在用 C 编写一个生产者-消费者线程程序。我的程序中的所有内容都运行良好,但有一个主要例外。当我有多个消费者线程时(几乎总是如此),实际上只有第一个消费者线程会终止。我已经尝试了我能想到的一切,但问题仍然存在。这是我的代码,去掉了它的内脏,这样你就可以看到相关的部分。

我可以从我的输出中看到两个终止条件变量都变为零,这当然是第一个消费者线程终止的原因。但是为什么其他消费者线程也不终止呢?

谢谢!

sem_t full, empty, mutex;
int threads;
int to_consume;
FILE* inputfp[5];
FILE* outputfp = NULL;
char in[BUF];

void* p(void* inpFile) {

    while (fscanf(inpFile, FMTSTRING, in) > 0) {
        sem_wait(&empty);
        sem_wait(&mutex);
        // production code here
        to_consume++;
        sem_post(&mutex);
        sem_post(&full);
     }

    fclose (inpFile);

    sem_wait(&mutex);
    threads--;
    sem_post(&mutex);

    return NULL;
}

void* c() {

    int continuing = 1;

    while (continuing) {

        sem_wait(&full);
        sem_wait(&mutex);
        //consumption code here
        to_consume--;
        fprintf("%d %d\n", threads, to_consume); //these both go to zero by the end

        if ( (threads <= 0) && (to_consume <= 0) ) {
            continuing = 0;
        }

        sem_post(&mutex);
        sem_post(&empty);
    }

    return NULL;
}

int main (int argc, char* argv[]) {

    int i;
    int con_threads;
    con_threads = 3;
    to_consume = 0;

    pthread_t *pr_thread[argc-2];
    pthread_t *con_thread[2];

    sem_init(&full, 0, 0);
    sem_init(&empty, 0, 50);
    sem_init(&mutex, 0, 1);

    for (i = 0; i < (argc-2); i++) {
        pr_thread[i] = (pthread_t *) malloc(sizeof(pthread_t)); 
        inputfp[i] = fopen(argv[i+1], "r");
        int rc = pthread_create (pr_thread[i], NULL, p, inputfp[i]);
        sem_wait(&mutex);
        threads++;
        sem_post(&mutex);
    }

    outputfp = fopen(argv[(argc-1)], "wb");

    for (i = 0; i con_threads 3; i++) {
        con_thread[i] = (pthread_t *) malloc(sizeof(pthread_t));
        int rc = pthread_create (con_thread[i], NULL, c, NULL);
    }

    for (i = 0; i < (argc - 2); i++) {
        pthread_join(*pr_thread[i], 0);
        free(pr_thread[i]);
    }

    for (i = 0; i con_threads 3; i++) {
        fprintf(stderr, "About to close consumer thread %d.\n", i);
        pthread_join(*res_thread[i], 0);
        fprintf(stderr, "Consumer thread %d closed successfully.\n", i);
        free(res_thread[i]);
    }

    printf ("About to close the output file.\n");
    /* Close the output file */
    fclose (outputfp);

    return EXIT_SUCCESS;
}
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1 回答 1

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full我认为您的问题是当第一个消费者检测到没有线程剩余时您不会再次发布,因此第二个消费者正在等待full但信号永远不会到达。您可能需要对消费者进行计数,但对于第一次通过(概念证明),您可以留下full从未阅读过的帖子。

于 2013-02-26T01:58:43.983 回答