panic in deadlkres() on r267110

[Ryan Stone]

On Fri, Jun 6, 2014 at 10:12 AM, Glen Barber <gjb at freebsd.org> wrote:
> Two machines in the cluster panic last night with the same backtrace.
> It is unclear yet exactly what was happening on the systems, but both
> are port building machines using ports-mgmt/tinderbox.
>
> Any ideas or information on how to further debug this would be
> appreciated.

The first thing that I would do is try to figure out who holds the
allproc_lock.  If the lock is held exclusively then
the pointer to the thread struct will be in allproc_lock.sx_lock.

If the lock is held shared then it gets trickier.  I'm not sure if
there is a better possible way than doing a thread apply all bt in
kgdb and finding which stack(s) could hold allproc_lock.