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From: John Baldwin <jhb@freebsd.org>
To: Sergey Kandaurov <pluknet@freebsd.org>
Date: Tue, 20 Mar 2012 14:53:52 -0400
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Cc: svn-src-stable@freebsd.org, svn-src-all@freebsd.org,
	src-committers@freebsd.org, svn-src-stable-8@freebsd.org
Subject: Re: svn commit: r233199 - in stable/8/sys: i386/conf netinet6
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On Tuesday, March 20, 2012 5:02:48 am Sergey Kandaurov wrote:
> On 20 March 2012 00:15, John Baldwin <jhb@freebsd.org> wrote:
> > Author: jhb
> > Date: Mon Mar 19 20:15:18 2012
> > New Revision: 233199
> > URL: http://svn.freebsd.org/changeset/base/233199
> >
> > Log:
> >  MFC 225096:
> >  Fix if_addr_mtx recursion in mld6.
> 
> Ehh.. Thank you for doing this.
> As I mentioned earlier I could not reproduce this problem myself
> in RELENG_8, that's why it was not MFCed so far...

To be honest, my main movitation was to remove a merge conflict in my
subsequent MFC of the IF_ADDR locking changes.  I could have patched
the locking in the old mld6.c, but when I reviewed your diff, I figured
it would be better to merge it first instead.

> >
> >  mld_set_version() is called only from mld_v1_input_query() and
> >  mld_v2_input_query() both holding the if_addr_mtx lock, and then calling
> >  into mld_v2_cancel_link_timers() acquires it the second time, which results
> >  in mtx recursion. To avoid that, delay if_addr_mtx acquisition until after
> >  mld_set_version() is called; while here, further reduce locking scope
> >  to protect only the needed pieces: if_multiaddrs, in6m_lookup_locked().
> 
> [...]
> 
> -- 
> wbr,
> pluknet
> 

-- 
John Baldwin