在C、linux中同步进程

这个问题更难,但我想理解一个更容易的例子。 假设我有3个过程,我希望过程3在过程1之前开始,我该怎么做?或者,有可能做到吗?

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <semaphore.h>

int main() {
    sem_t semaphore;

    // Initialize semaphore with initial value 0
    if (sem_init(&semaphore, 0, 0) == -1) {
        perror("Semaphore initialization failed");
        exit(EXIT_FAILURE);
    }

    // Create child process 1
    if (fork() == 0) {
        // Child process 1 (Process 1) starts here
        printf("Process 1 started.\n");
        // Wait for signal from Process 3
        sem_wait(&semaphore); 
        printf("Process 1 completed its work.\n");
        exit(0);
    }

    // Create child process 2
    if (fork() == 0) {
        // Child process 2 (Process 2) starts here
        printf("Process 2 started.\n");
        printf("Process 2 completed its work.\n");
        exit(0);
    }

    // Create child process 3
    if (fork() == 0) {
        // Child process 3 (Process 3) starts here
        printf("Process 3 started.\n");
        // Signal Process 1 to start
        sem_post(&semaphore);
        exit(0);
    }

    wait(NULL);
    wait(NULL);
    wait(NULL);

    // Destroy semaphore
    sem_destroy(&semaphore);

    return 0;
}

这是我得到的输出:

Process 1 started.
Process 3 started.
Process 2 started.
Process 2 completed its work.

这就像运行到一个无限循环中,进程1和进程3不会终止。