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From: Robert Watson <rwatson@FreeBSD.org>
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To: Jung-uk Kim <jkim@FreeBSD.org>
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Cc: Alexey Dokuchaev <danfe@nsu.ru>, freebsd-current@FreeBSD.org
Subject: Re: Kernel panic with if_sf.ko
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On Wed, 1 Jul 2009, Jung-uk Kim wrote:

> I cannot reproduce it any more.  It must be fixed already.  FYI, when it 
> happened, I traced it down to:
>
> shutdown ->
> dhclient closing fd ->
> bpf_dtor() ->
> mac_bpfdesc_destroy() ->
> mac_bpfdesc_label_free() ->	d->bd_label corrupt!
> bpfmac_labelzone_free() ->
> uma_zfree() ->
> ... -> 				page fault!
>
> Any way, sorry for the noise and thanks for fixing this, whoever that is.

This is almost certainly an ifnet-related race condition that has been fixed 
in 8.x, and that MAC is panicking is just a symptom that it picked up on a 
double free (or the like) since it has internal validation.  It may still 
existing in 7.x as there's a lot of ifnet/ifaddr work I haven't MFC'd yet (and 
won't for a few weeks at least).

Thanks,

Robert N M Watson
Computer Laboratory
University of Cambridge