通过FIFO通道传输数据时阻止独立进程

Question

我有2个独立的流程。我将2个值发送到第二个过程以计算其数量。这行得通，但是现在我需要将总和的值返回到第一个进程，并且由于锁定而不再起作用。第二个过程是等待某人进行读取，然后将其解锁。有什么想法可以将总和的值返回到第一个过程？ 代码如下：

test.c：

int main(int argc, char *argv[])
{
    int f1,f2;
    int a = 4;
    int b = 3;
    int summ = 0;

    unlink("mk.fifo");

    if (mkfifo("mk.fifo", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) == -1 && errno != EEXIST)
        error(0, errno, "mkfifo() error");

    f1 = open("mk.fifo", O_WRONLY);
    perror("Opening ");

    write(f1, &a, sizeof(int));
    write(f1, &b, sizeof(int));
    perror("Writing ");

    close(f1);

    f2 = open("mk.fifoSumm", O_RDONLY);
    perror("Opening ");

    read(f2, &summ, sizeof(int));
    perror("Reading ");

    close(f2);

    printf("Received string '%d'\n", summ);

    return 0;
}

test2.c：

int main(int argc, char *argv[])
{
    int f2,f1;
    int a = 0;
    int b = 0;
    int summ = 0;

    f2 = open("mk.fifo", O_RDONLY);
    perror("Opening ");

    read(f2, &a, sizeof(int));
    read(f2, &b, sizeof(int));
    perror("Reading ");

    close(f2);

    printf("Received string '%d'\n", a);
    printf("Received string '%d'\n", b);

    summ = a + b;

    unlink("mk.fifoSumm");

    if (mkfifo("mk.fifoSumm", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) == -1 && errno != EEXIST)
        error(0, errno, "mkfifo() error");

    f1 = open("mk.fifoSumm", O_WRONLY);
    perror("Opening ");

    write(f1, &summ, sizeof(int));
    perror("Writing ");
    close(f1);

    return 0;
}