kern/153497: [netgraph] netgraph panic with ipv6 enabled

[Bjoern A. Zeeb]

The following reply was made to PR kern/153497; it has been noted by GNATS.

From: "Bjoern A. Zeeb" <bz at FreeBSD.org>
To: Mike Tancsa <mike at sentex.net>
Cc: bug-followup at FreeBSD.org
Subject: Re: kern/153497: [netgraph] netgraph panic with ipv6 enabled
Date: Thu, 6 Jan 2011 14:21:39 +0000 (UTC)

 On Thu, 6 Jan 2011, Mike Tancsa wrote:
 
 I would just like to add two things:
 
 a) this isn't really IPv6 related; it's just a matetr of timing and
     depending on options and modules used it's more or less likely.
     It's basically races in the netgraph code.
 
 b) the XXXBZ printfs come from where he was previously seeing a NULL
     pointer de-ref, which in the last case looks like random memory
     corruption or indeed just another race.
     The debugging patch was:
     http://people.freebsd.org/~bz/20101228-01-ng-base-race-pr153497.diff
     with the printf in the hook == NULL case removed again, as that
     happened a lot, which I think isn't right either but ...
 
 -- 
 Bjoern A. Zeeb                                 You have to have visions!
          <ks> Going to jail sucks -- <bz> All my daemons like it!
    http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/jails.html