选择EBADF：哪些FD是坏？ [英] Select EBADF : which FD is bad?

问题描述

我们已经在我们的生产code长期存在的BUG。这本质上是基于套接字守护进程。它侦听一堆使用选择filedescriptors的。

We have a long standing bug in our production code. This is essentially a socket based daemon. It listens to a bunch of filedescriptors using select.

偶尔（每天一次左右），选择将与EBADF回来。

Occasionally (once a day or so), select will return with EBADF.

我已经写了code搜索坏文件描述符，即遍历每个FD并呼吁将其选中。这些调用不返回EBADF。我也试过FSTAT。他们也不会返回EBADF。

I have written code to search for the bad filedescriptor, that loops over each fd and calls select on it. These calls never return EBADF. I also tried fstat. They also never return EBADF.

我还改写了后台程序使用轮询。这并没有帮助。

I also rewrote the daemon to use poll. This did not help.

有没有人有一些其他的想法？ （除了我犯了一个愚蠢的错误，这是所有容易选择做）。

Does anyone have some other ideas ? (apart from i made a dumb mistake, which is all to easy to do with select).

推荐答案

我同意詹姆斯。随着民调（），你必须每它可以轻松地进行检查FD revents中。

I agree with James. With poll(), you have revents per fd which can easily be checked.

即

struct pollfd fds[NUM_FDS];
int ret, i;

...

ret = poll(fds, NUM_FDS, POLL_TIMEOUT);
for (i = 0; i < NUM_FDS; i++)
  if (fds[i].revents & POLLHUP || fds[i].revents & POLLNVAL)
     ... do something ...

当然，你也不会实现它在现实世界的方式，它只是一个例子。我停止使用select（）很久以前，民意调查（）是一个更好的界面。你是正确的，它只是太容易搬起石头砸自己的脚用select（）。

Of course you would not implement it that way in the real world, its just an example. I stopped using select() a long time ago, poll() is a much better interface. You're correct, its just too easy to shoot yourself in the foot with select().

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