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From: Kyle Evans <kevans@freebsd.org>
Date: Tue, 14 May 2019 10:34:30 -0500
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Subject: Re: panic in tunstart_l2()
To: Mark Johnston <markj@freebsd.org>
Cc: FreeBSD Current <freebsd-current@freebsd.org>
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On Tue, May 14, 2019 at 10:10 AM Mark Johnston <markj@freebsd.org> wrote:
>
> Hi,
>
> I hit the following panic last night on a non-INVARIANTS kernel at
> r347549.  The workload involves running a number of bhyve VMs with
> frequent restarts, during which a tap interface is destroyed and
> recreated.  I'm a bit short on time to debug this today, so while I
> retry with INVARIANTS on I thought I'd also report the issue in case
> anyone else is seeing it.
>
> The panic occurred because the ifnet's softc field is NULL.

Ah, foo. I'll have to re-examine the ioctl/destroy race... tun_destroy
grabs the ioctl sx and kills off the if_softc, but it can not and
should not do this before if_detach or else things go wrong because
it's still a part of the bridge.