linux-kernel - Re: epoll with ONESHOT possibly fails to deliver events

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Message-ID: <20121222025414.GA6217@dcvr.yhbt.net>
Date:	Sat, 22 Dec 2012 02:54:14 +0000
From:	Eric Wong <normalperson@...t.net>
To:	"Junchang(Jason) Wang" <junchang.wang@...e.edu>
Cc:	Andreas Voellmy <andreas.voellmy@...e.edu>,
	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: epoll with ONESHOT possibly fails to deliver events

"Junchang(Jason) Wang" <junchang.wang@...e.edu> wrote:
> We still believe this is a bug in epoll system even though we can't
> prove that so far. Both Andi and I are very interested in this problem
> and helping you experts solve this it. Just let us know if we can
> help.

I'm just another epoll user, definitely not an expert.  Hopefully
somebody else can figure this out, because I'm unable to reproduce the
problem with your code and I haven't spotted any bugs from reading
through the kernel.

Curious, I also have a multi-threaded HTTP server which is a little
similar (multi-threaded, 2 epoll descriptors (only one epoll is heavily
used).  I run it on 2/4-core systems and haven't hit issues with epoll.

If you want to test, it should be easy to build from tarball:

  http://bogomips.org/cmogstored/files/cmogstored-1.0.0.tar.gz
  configure && make
  ./cmogstored --httplisten=8080 --docroot=/path/to/whatever

More info here: http://bogomips.org/cmogstored/README
git clone http://bogomips.org/cmogstored.git
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