netdev - Re: + ppp_generic-fix-lockdep-warning.patch added to -mm tree

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Date:	Tue, 17 Apr 2007 09:37:44 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	"Yuriy N\. Shkandybin" <jura@...ams.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Mackerras <paulus@...ba.org>, netdev@...r.kernel.org,
	Michal Ostrowski <mostrows@...akeasy.net>
Subject: Re: + ppp_generic-fix-lockdep-warning.patch added to -mm tree

On Wed, Apr 11, 2007 at 12:52:28PM +0400, Yuriy N. Shkandybin wrote:
...
> >On Wed, 11 Apr 2007 09:57:33 +0400 "Yuriy N. Shkandybin" <jura@...ams.com> 
> >wrote:
> >
> >>I've tested  2.6.21-rc6-mm1
> >>Linux vpn1 2.6.21-rc6-mm1 #4 SMP Wed Apr 11 03:34:26 MSD 2007 x86_64
> >>Intel(R) Pentium(R) D CPU 2.80GHz GenuineIntel GNU/Linux
> >>
> >>warn appeares upon first pppoe connection to rp-pppoe server in kernel 
> >>mode
> >>
> >
> >Thanks.  So you're saying that
> >ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc6/2.6.21-rc6-mm1/broken-out/ppp_generic-fix-lockdep-warning.patch
> >did not fix anything?
> As i understand this patch already in -mm tree, so I've booted into last mm 
> kernel and received this locked warning.
> Or i've mistaked and should apply this patch manually?

Hi!

Yuriy - thanks for testing my patch ...(pause) Not!

It seems this patch is not visible in this version - probably
is overpatched by something else. But your new log shows there
is another connection between these locks (ppp_xmit_process
and ppp_push instead of ppp_channel_push in "-> #0"), so the
patch is not sufficient (and could be dumped).

I don't know your vlans configuration, but it seems the real
lockup isn't very probable here - it's rather lockdep question.
I think vlan's too broad lockdep class is the main "guilty"
here, but probably pppoe also could be enhanced: it's making
the things unnecessarily complicated by calling dev_queue_xmit
under ppp_generic's xmit locks. I wonder if there is any reason
against using a tasklet here.

I'll try to find more time to untie this yet - or maybe some
maintainer will find this interesting, too...

Regards,
Jarek P.

PS: sorry for late responding (vacations).
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