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Date: Wed, 1 Jun 2005 11:58:49 +1200
From: Andrew Thompson <thompsa@freebsd.org>
To: Brian Fundakowski Feldman <green@freebsd.org>
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Sender: Andrew Thompson <thompsa@fud.org.nz>
Cc: pf@freebsd.org, hackers@freebsd.org, net@freebsd.org
Subject: Re: RFC: if_bridge
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On Tue, May 31, 2005 at 07:48:16PM -0400, Brian Fundakowski Feldman wrote:
> On Tue, May 31, 2005 at 11:25:54AM +1200, Andrew Thompson wrote:
> > Hi,
> > 
> > I am looking for testers and code review for if_bridge, the bridge
> > implementation from NetBSD (and OpenBSD).
> > 
> > The patch and instructions can be found at:
> > 
> > http://people.freebsd.org/~thompsa/
> > 
> 
> Some of these have since been fixed by you or I, but the most serious
> is the deadlock caused by not having consistency in data access
> between the input/output interfaces attached to the bridge and the
> bridge interface itself.  It was quite simple to reproduce using IPFW
> dynamic rules and two fxp(4).  The situation that occurs is the input
> path having locked the bridge, then the interface, and the output path
> locking the real interface and then trying to lock the bridge.  It
> can be fixed by deferring the if_start(9), but having not run it with
> WITNESS I'm not certain that is the only big problem.
> 
> Ideally, there should be a global bridge-list shared/exclusive lock
> and per-bridge shared/exclusive locks.  This will require a fair bit
> of code churn... but the current state is largely not productionable
> on FreeBSD thanks to a locking versus IPL model being used in the
> kernel versus the if_bridge(4) code having been structured for IPL.
> 

Have you looked at the patch above, I have been using bridge-list and
per-bridge locks for about a week now. There have been a couple of
changes from the original patch you have, are you able to re-test?

cheers,

Andrew