panic: ifc_free_unit: bit is already cleared

[Brooks Davis]

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.  It's going to be hard to trigger, but it probably
should be fixed.  Since cloning isn't performance critical, I think
adding a dead flag to the clone structure and failing all attempts once
the flag is set.

-- Brooks

-- 
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