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From: Matthew Macy <mmacy@freebsd.org>
Date: Sun, 19 Aug 2018 16:52:34 -0700
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Subject: Re: panic excl->shared for an AF_LOCAL socket
To: Rick Macklem <rmacklem@uoguelph.ca>
Cc: freebsd-current <freebsd-current@freebsd.org>
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On Sun, Aug 19, 2018 at 4:32 PM Rick Macklem <rmacklem@uoguelph.ca> wrote:

> Hi,
>
> PR#230752 shows a witness panic() for "excl->shared" on a vnode lock.
> In this case, the kernel RPC code is trying to do a soconnect() on an
> AF_LOCAL
> socket. The code is unp_connectat() looks like is does a straightforward
> namei()/lookup(), so I am surprised to see this.
>
> Does anyone know if AF_LOCAL (unix domain) sockets are somehow handled
> differently for namei()/lookup() which might cause this?
>
> I've requested more info from the reporter w.r.t. when this happens.
> (I'd guess when the nfsuserd is terminating or has terminated or ???)
>
> Thanks for any help with this, rick
>

I don't know what's special in this case, but I did revamp the locking
there several months back so I'll take a look next weekend.
-M