netdev - Re: IPv6 FIB related crash with MACVLANs in 3.9.11+ kernel.

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Message-ID: <20140208172310.GF16198@order.stressinduktion.org>
Date:	Sat, 8 Feb 2014 18:23:10 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Ben Greear <greearb@...delatech.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: IPv6 FIB related crash with MACVLANs in 3.9.11+ kernel.

On Sat, Feb 08, 2014 at 08:43:32AM -0800, Ben Greear wrote:
> On 02/03/2014 02:06 PM, Ben Greear wrote:
> > On 02/03/2014 02:03 PM, Hannes Frederic Sowa wrote:
> >> Hi Ben,
> >>
> >> On Mon, Feb 03, 2014 at 12:37:52PM -0800, Ben Greear wrote:
> >>> The kernel has some additional patches, but not much to IPv6.
> >>>
> >>> The bug is that when we have lots of mac-vlans on some ixgbe ports
> >>> (500 per interface in this case), and boot up the system with the ports unplugged,
> >>> we get this crash almost every time.  Boot-up is going to do normal bootup
> >>> stuff plus create and configure the 1000 mac-vlans, dump their routing
> >>> tables, etc.
> >>>
> >>> We are using one routing table per network device, and some
> >>> ip rules.
> >>>
> >>> If we plug in the ixgbe ports, we do not ever see a crash.
> >>>
> >>> We have not yet tried reproducing it on other drivers, but I suspect
> >>> the issue is not related to ixgbe.
> >>>
> >>> Any ideas on this one?
> >>
> >> Could you bring the machine to a panic again with enabling RT6_DEBUG at the
> >> top of ip6_fib.c and send a dump of the trace?
> > 
> > Yes, but it will be a bit until we can create a duplicate machine.
> > We ended up delivering the machine with a note to make sure the
> > interfaces were plugged in (we found the bug hours before shipping
> > the system, of course).
> 
> According to my system test guy, it took a lot longer to reproduce
> the problem with the debug enabled kernel, but I do not see any extra
> debug messages on the serial console logging or in /var/log/messages

Sounds like a race, then, like I thought.

I forgot, those are pr_debugs, I usually enable them with

$ echo file net/ipv6/ip6_fib.c +p > /sys/kernel/debug/dynamic_debug/control

RT6_TRACE is pretty noisy so you should see output immediatley if you do ipv6
traffic. Other way is to specify dyndbg="file net/ipv6/ip6_fib.c +p" on the
kernel command line.

Try before doing to play with that until you can confirm the output showes up
on the console.

Thanks again,

  Hannes

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