[英]Is epoll thread-safe?
There are two functions in epoll: epoll中有两个功能:
Are they thread-safe when I use the same epoll_fd?当我使用相同的 epoll_fd 时它们是线程安全的吗?
What will happen if one thread calls epoll_wait and others call epoll_ctl at the same time?如果一个线程调用 epoll_wait 而其他线程同时调用 epoll_ctl 会发生什么?
It is thread-safe, but there isn't much documentation that explicitly states that.它是线程安全的,但没有太多文档明确说明这一点。 See here看这里
BTW, you can also have multiple threads waiting on a single epoll_fd
, but in that case it can get a bit tricky.顺便说一句,您也可以让多个线程在单个epoll_fd
上等待,但在这种情况下,它会变得有点棘手。 (Ie you might want to use edge-triggered EPOLLET
or oneshot mode EPOLLONESHOT
. See here .) (即,您可能想使用边缘触发的EPOLLET
或 oneshot 模式EPOLLONESHOT
。请参见此处。)
Note: The existing accepted answer is correct, but it mentions " there isn't much documentation that explicitly states that ", while epoll documentation does state it.注意:现有接受的答案是正确的,但它提到“没有多少文档明确指出”,而 epoll 文档确实 state 。
The manual page for epoll_wait
explicitly allows adding a file descriptor to an epoll set while it is being waited for in another thread: epoll_wait
的 手册页明确允许在另一个线程中等待时将文件描述符添加到 epoll 集中:
Section "Notes": “注释”部分:
While one thread is blocked in a call to epoll_wait() , it is possible for another thread to add a file descriptor to the waited-upon epoll instance.当一个线程在对epoll_wait()的调用中被阻塞时,另一个线程可以将文件描述符添加到等待的epoll实例中。 If the new file descriptor becomes ready, it will cause the epoll_wait() call to unblock.如果新的文件描述符准备就绪,它将导致epoll_wait()调用解除阻塞。
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