如何在完成线程后继续运行一个进程？

Question

我在尝试打印所有线程的摘要（即一组线程的总计）时卡住了。

下面的C代码运行10个线程，模拟售票代理。运行 & 完成线程后（即售出所有门票后），我想打印代理商名单和该代理商售出的相应门票数量。然而，主进程在到达行 pthread_exit(NULL) 时立即终止（用前面的注释标记）并且代码不会 return 到 main，它应该打印 grand总计（此块也标有注释）。

谁能告诉我代码有什么问题？

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

struct ThreadArgs {
    int thNum;
    int *numTickets;
    int *soldTickets;
    sem_t *lock;
};

void *SellTickets(void *th) {
    struct ThreadArgs *thArgs;
    int sleepTime;

    thArgs = th;

    while (1) {
        sleepTime = rand();

        if (sleepTime % 2) {
            usleep(sleepTime % 1000000);
        }

        sem_wait(thArgs->lock);

        if (*thArgs->numTickets == 0) {
            break;
        }

        printf("There are %3d ticket(s). Agent %d sold a ticket.\n", *thArgs->numTickets, thArgs->thNum);
        (*thArgs->numTickets)--;
        sem_post(thArgs->lock);
        (*thArgs->soldTickets)++;
    }

    sem_post(thArgs->lock);
    pthread_exit(NULL);
}

void runThreads(int numAgents, int numTickets, int soldTickets[]) {
    struct ThreadArgs thArgs[numAgents];
    int agent;
    pthread_t th[numAgents];
    sem_t lock;

    sem_init(&lock, 1, 1);

    for (agent = 0; agent < numAgents; agent++) {
        thArgs[agent].thNum = agent;
        thArgs[agent].soldTickets = &soldTickets[agent];
        thArgs[agent].numTickets = &numTickets;
        thArgs[agent].lock = &lock;
        pthread_create(&th[agent], NULL, SellTickets, &thArgs[agent]);
    }
    // when debugging, the process terminates here
    pthread_exit(NULL);
}

int main() {
    int agent, numAgents, numTickets, soldTickets[10];

    numAgents = 10;
    numTickets = 150;

    for (agent = 0; agent < numAgents; agent++) {
        soldTickets[agent] = 0;
    }

    runThreads(numAgents, numTickets, soldTickets);

    // the process never executes the following block    
    for (agent = 0; agent < numAgents; agent++) {
        printf("Agent %d sold %d ticket(s).\n", agent, soldTickets[agent]);
    }

    return 0;
}

Answer 1

pthread_exit() 退出一个线程，即使是 "main"-线程。

如果 main() 结束，所有其他线程也会关闭。

由于 "main"-thread 需要做一些最后的日志记录，它应该等到所有产生的线程都结束。

要在 runThreads() 中完成此操作，请替换对

的调用

      pthread_exit(NULL);

通过循环为 pthread_create() 返回的所有 PThread-ID 调用 pthread_join()。

您还想为所有 pthread*() 调用添加错误检查，就像您应该对返回任何相关信息的每个函数调用所做的那样，例如指示 failure 调用.

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