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Date: Thu, 6 Oct 2005 10:09:50 +1300
From: Andrew Thompson <thompsa@freebsd.org>
To: Brooks Davis <brooks@one-eyed-alien.net>
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	Brooks Davis <brooks@one-eyed-alien.net>,
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	Brooks Davis <brooks@FreeBSD.org>
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Cc: Brooks Davis <brooks@FreeBSD.org>, Pawel Jakub Dawidek <pjd@FreeBSD.org>,
	FreeBSD Current <current@FreeBSD.org>
Subject: Re: panic: ifc_free_unit: bit is already cleared
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On Wed, Oct 05, 2005 at 01:55:15PM -0700, Brooks Davis wrote:
> On Wed, Oct 05, 2005 at 10:36:39PM +0200, Pawel Jakub Dawidek wrote:
> > On Wed, Oct 05, 2005 at 03:49:03PM +1300, Andrew Thompson wrote:
> > +> Hi,
> > +> 
> > +> I have found a repeatable panic with network device cloning, unfortunatly I am
> > +> unable to dump on this box. This is sparc64 with a 2 day old current.
> > 
> > The order is wrong in vlan_modevent().
> > 
> > if_clone_detach() is freeing ifc_units field, so ifc_free_unit() should not
> > be called after that.
> > 
> > This patch should fix the problem:
> > 
> > 	http://people.freebsd.org/~pjd/patches/if_vlan.c.patch
> 
> Yes.  This does introduce a race in that a new interface could
> be created between the vlan_clone_destroy loop and the call to
> if_clone_detach.

I dont think this is the problem. IF_CLONE_REMREF(ifc) is freeing
ifc->ifc_units in if_clone_detach(). It look like the ref counting isnt
working quite right.

Andrew