多进程失败拉起的demo

 #include <iostream>
 #include <vector>
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>
 #include <sys/wait.h>
 #include <errno.h>

 void RunChild(int idx) {
     for (int i = ; i < ; i++) {
         printf("worker %d %d\n", getpid(), idx);
         sleep();
     }
 }

 int main() {
     int worker_cnt = ;
     std::vector<int> worker_pids(worker_cnt);
     for (int i = ; i < worker_cnt; i++) {
         int pid = fork();
         if(pid != ) {
             //no process < 0 ?
             worker_pids[i] = pid;
             continue;
         }

         RunChild(i);
         exit();
     }

     //avoid some unkown action for SIGCHLD
     signal(SIGCHLD, SIG_DFL);
     while (true) {
         //1.get exit child
         //2.get worker by pid
         //3.fork it
         //4.child run

         //1.get exit child
         int pid = -;
         while((pid = wait(NULL)) == -) {
             if (errno == EINTR) {
                 printf("wait pid err %d %s\n", errno, strerror(errno));
                 continue;
             }
             else {
                 break;
             }
         }
         if(pid == -) {
             printf("wait pid err %d %s\n", errno, strerror(errno));
             //sleep( 1 );
             continue;
         }
         printf("wait pid %d\n", pid);

         //2.get worker by pid
         int worker_id = -;
         for (int i = ; i < worker_cnt; i++) {
             if (worker_pids[i] == pid) {
                 worker_id = i;
                 break;
             }
         }
         printf("worker pid %d id %d exit\n", pid, worker_id);
         if( worker_id == - ) {
             printf("master wait pid %d not worker\n", pid);
             continue;
         }

         //3.fork it
         usleep();
         pid = fork();
         if (pid != ) {
             // no process pid < 0 ?
             printf("%s new worker id %d\n", __func__, pid);
             worker_pids[worker_id] = pid;
             continue;
         }

         //4.child run
         RunChild(worker_id);
         exit();
     }
     return ;
 }

这里有个问题，父进程退出了，子进程还没退出。解决方案是在RunChild中调用：

 void RunChild(int idx) {
     prctl(PR_SET_PDEATHSIG, SIGHUP);
     for (;true;) {
         printf("worker %d %d\n", getpid(), idx);
         sleep();
     }
 }

可以查看下man 2 prctl。

https://stackoverflow.com/questions/284325/how-to-make-child-process-die-after-parent-exits/284443