Hang in fd_ebadf function
schmorp at schmorp.de
Tue Jun 3 05:37:53 CEST 2008
On Mon, Jun 02, 2008 at 11:31:22PM -0400, Marc-André Cournoyer <macournoyer at gmail.com> wrote:
> What I'm doing is: if the EV_ERROR bit is set, close the connection
> right away.
Which connection? EV_ERROR means the connection doesn't exist, so whatever
you close, likely is something else, another bug.
> I'm also closing the connection if there's any error send- ing or
> recv-ing on a socket.
Thats fine - you would not have to handle EV_ERROR if you did that (and
are single-threaded), as send/recv gives you the same error.
> By "it works" I meant that it stoped hanging when there was an error
> on the socket before the send or recv.
Yes, but your program is still buggy. What you did is trade a certain bug
against a bug that occurs more rarely.
Getting EV_ERROR is (in your case) a programming bug in your code, not something you
can work around by closing some unrelated fd - it means you register a
watcher on a fd that you cnanot register a watcher on, likely some that
doesn't have any conenction.
I mean, I could care less about your code, but not fixing the bug and relying
on libev detecting the condition for you and hoping all is well asks for
It is *much* better to fix your code instead.
> Let me know if you think I'm doing something wrong.
You are fighting the symptoms, you are not fixing the bug. EV_ERROR means
your code has a big bug somewhere. libev doesn't catch this bug with all
backends, not can it work efficiently in the presense of such a bug.
> But I know there is still something weird in there when using Ruby
> threads, I'm trying to figure it out.
If you are using threads, then all bets are off - libev cannot reliably
detect this bug when threads are in use, and closing an fd that is already
closed (the most likely cause for your EV_ERROR) means you *will* close an
unrelated fd if some other thread created a new fd.
This is an extremely big bug in your code. libev cannot reliably detect
it, and you cannot work around it afterwards, you have to avoid it in the
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