操作系统用kill()和signal()实现父子同步问题

Question

运行代码，输入CTRL +C的时候只输出了Parent process is killed! 子进程未显示被杀死，求指教

#include<stdio.h>
#include<unistd.h>
#include<signal.h>
#include<wait.h>

int flag;
void stop();

void main(){
        flag = 1;
        pid_t pid1;
        pid_t pid2;
        while((pid1 = fork()) == -1);
        if(pid1>0){
                while((pid2 = fork()) == -1);
                if(pid2 > 0){
                        signal(2,stop);
                        while(flag){
                                printf("parent process is waiting a ctrl+c signal\n");
                                sleep(1);
                        }
                        sleep(1);
                        kill(pid1,16);
                        sleep(1);
                        kill(pid2,17);
                        wait(0);
                        wait(0);
                        printf("Parent process is killed!\n");
                }else{
                        signal(17,stop);
                        flag = 1;
                        while(flag);
                        printf("Child process2 is killed by parent!\n");
                        exit(0);
                }
        }else{
                signal(16,stop);
                flag = 1;
                while(flag);
                printf("Child process1 is killed by parent!\n");
                exit(0);
        }
}

void stop(){
        flag = 0;
}