c - 僵尸进程在其父进程死亡后去了哪里？

Question

僵尸进程是一个已经完成执行的进程，但在进程表中仍然有一个条目(父进程还没有读取它的退出代码，或者换句话说，它还没有被“收割”)。

孤儿进程是指其父进程已完成但仍在运行的进程(其父进程已“去世”但仍“活着”)。在这种情况下，init 将采用它并等待它。

所以考虑一下:

int main(int argv, char *argc[]) {

    pid_t p=fork();

    if (p<0) {
        perror("fork");
    }

    // child
    if (p==0) {
        exit(2);
    }

    // parent sleeps for 2 seconds
    sleep(2);
    return 1;
}

这里创建的子进程将成为僵尸进程 2 秒，但是当父进程完成时它的状态是什么？孤儿僵尸？

进程表中的条目会发生什么情况？

“orphan-zombies”(如上面的)是否也被 init 采用并被它收割？

Answer 1

根据man 2 wait :

A child that terminates, but has not been waited for becomes a "zombie". The kernel maintains a minimal set of information about the zombie process (PID, termination status, resource usage information) in order to allow the parent to later perform a wait to obtain information about the child. As long as a zombie is not removed from the system via a wait, it will consume a slot in the kernel process table, and if this table fills, it will not be possible to create further processes. If a parent process terminates, then its "zombie" children (if any) are adopted by init(8), which automatically performs a wait to remove the zombies.

当父进程结束时，子进程(即使是僵尸进程)将被init收养。然后，正如您所说，init 将 wait() 获取其退出状态。

所以，我不认为“孤儿僵尸”有什么特殊情况。