epoll - 当 epoll 文件描述符关闭时会发生什么？

Question

假设我通过调用创建 epoll 文件描述符 (epfd)

epfd = epoll_create( 10 );

接下来我通过调用 epoll_ctl(epfd,EPOLL_CTL_ADD,...) 将一些文件描述符添加到这个集合中，并通过在单独的线程中调用 epoll_wait 来等待事件循环中的事件。

如果我在 epoll 集不为空且 epoll_wait(epfd,...) 正在进行时关闭 epfd(通过在线程中调用 close(epfd)，而不是 epoll_wait 线程)会发生什么？ epoll_wait 终止了吗？有哪些结果？

Answer 1

可以预见的是，Linux 和 select(2) 做的事情是一样的。从手册页:

For a discussion of what may happen if a file descriptor in an epoll instance being monitored by epoll_wait() is closed in another thread, see select(2).

从 select(2) 页面:

If a file descriptor being monitored by select() is closed in another thread, the result is unspecified. [...] On Linux (and some other systems), closing the file descriptor in another thread has no effect on select()

tl;博士;是“不要这样做”:

In summary, any application that relies on a particular behavior in this scenario must be considered buggy.