From: "Gilad Benjamini" <gilad@altornetworks.com>
To: <linux-kernel@vger.kernel.org>
Subject: epoll and closed file descriptors
Date: Wed, 16 Sep 2009 16:22:55 -0700
Message-ID: <023c01ca3724$9f90fcb0$deb2f610$@com>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Thread-Index: Aco3JJ3A4zG/sL37Rnq1Eo9A0f/YsQ==
Content-Language: en-us
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1141
Lines: 29

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/