子进程不能同时运行

Question

因此，我正在编写一个酒店预订系统，其中我的酒店房间存储在共享内存中，并将有x个客户预订，取消，付款等房间。每个客户都是一个子进程，他们都应同时运行，并尝试对房间进行规定的交易。

这是我对子进程进行分叉的代码：

int pid[10];
for(int i = 0; i < numOfCustomers; i++) {
    pid[i] = fork();
    if(pid[i] < 0) {
        perror("Bad fork");
    }
    else if(pid[i] == 0) { //is child i (Each customer is a child process)
        cout << "CUSTOMER: " << i << endl;
        while(!customers[i].transactions.empty()) { //runs until customer finishes all transactions
            string op = customers[i].transactions.front();
            if(op == "reserve") {
                if(sem_wait(semid, 0))
                    exit(1);
                Reserve tempq = customers[i].reservequeue.front();
                for(int i = 0; i < tempq.roomcounter; i++) {
                    int roomnum = tempq.roomqueue.front();
                    if(shared_memory[roomnum-1].isavailable == true) {
                        shared_memory[roomnum-1].isavailable = false;
                        shared_memory[roomnum-1].day = tempq.day;
                        shared_memory[roomnum-1].month = tempq.month;
                        shared_memory[roomnum-1].year = tempq.year;
                        shared_memory[roomnum-1].customer = cust;
                    }
                    else {
                        cout << "Room " << roomnum << " already taken." << endl;
                    }
                    tempq.roomqueue.pop();
                }
                customers[i].reservequeue.pop();
                if(sem_signal(semid, 0))
                    exit(1);
            }
            else if(op == "cancel") { //not done yet
                cout << "cancel" << endl; 
            }
            else if(op == "check") { //not done yet
                cout << "check" << endl;
            }
            else if(op == "pay") { //not done yet
                cout << "pay" << endl;
            }
            customers[i].transactions.pop();
        }
        exit(0);
    }
    else { //is parent

    }
}

//waits for each process to finish
for (int i = 0; i < numOfCustomers; i++) {
    wait(NULL);
}

问题在于，它首先在子级中完成所有操作，然后再在子级2中完成所有操作。进程不是同时运行的，这破坏了拥有共享内存和使用信号量的全部目的。

非常感谢您的帮助。