linux-kernel - epoll and closed file descriptors

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Message-ID: <023c01ca3724$9f90fcb0$deb2f610$@com>
Date:	Wed, 16 Sep 2009 16:22:55 -0700
From:	"Gilad Benjamini" <gilad@...ornetworks.com>
To:	<linux-kernel@...r.kernel.org>
Subject: epoll and closed file descriptors

I am running repeatedly into a scenario  where epoll notifies userland of
events on a closed file descriptor.
I am running a single thread application, on a single CPU machine so
multiple threads isn't the issue. 

A sample set of events that I have seen
- File descriptor (13) for a socket is closed
- epoll_wait returns with no events.
- Several epoll related calls happen
- More than 20 seconds after the "close", epoll_wait finds an event on fd 13
with EPOLLIN|EPOLLERR|EPOLLHUP.
- epoll_wait continues to report this event

Running kernel 2.6.24. Some technical problems are preventing me from trying
a newer kernel at the moment.

One more thing worth mentioning: the application uses libcurl, leading to a
situation where the file is closed before the descriptor was removed from
the epoll descriptor. The code should be able to handle that AFAIK.

Any ideas would be appreciated.
Gilad

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