netdev - Re: [PATCH net] ipv6: don't stop backtracking in fib6_lookup

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Date:	Fri, 9 Aug 2013 16:57:43 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Teco Boot <teco@...-net.nl>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: don't stop backtracking in fib6_lookup_1 if subtree does not match

On Fri, Aug 09, 2013 at 04:40:03PM +0200, Teco Boot wrote:
> 
> Op 9 aug. 2013, om 16:19 heeft Hannes Frederic Sowa <hannes@...essinduktion.org> het volgende geschreven:
> 
> > On Fri, Aug 09, 2013 at 04:12:20PM +0200, Teco Boot wrote:
> >> Double checked, it works. Tested with Common Open Research Emulator (CORE, from NRL).
> >> 
> >> === But ===
> >> 
> >> I had some problems with CORE. Could be me, new kernel version, the patch, CORE using network namespaces, or combination of that. sudo hangs, reboot hangs, ip address show hangs.
> >> With ps -ef, I see some suspected items:
> >> root      4858  4161  0 15:57 ?        00:00:00 /sbin/ip -6 addr flush dev eth0
> >> root      4859     2  0 15:57 ?        00:00:00 [kworker/0:3]
> >> In the emulation I use, there was no IPv6.
> >> 
> >> I'll try to figure out if it is CORE & netns in combination with patch. Or just the patch. Or just the new kernel.
> >> Just to speed up, any idea where to look for?
> > 
> > echo t > /proc/sysrq-trigger and check dmesg while the system hangs. Maybe you
> > have to use a serial console and send the sysrq over keyboard/break.
> 
> System was still running.
> Cleared dmesg, silence.
> Then performed echo t > /proc/sysrq-trigger.
> Quite large dump.
> Afterwards, silence again.

I think you are experience high fib6_gc_lock contention (and while the lock is
held you also hold rtnl_lock, which let's all the other processes hang).
Please test if these patches make things more smooth for you:

https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=2ac3ac8f86f2fe065d746d9a9abaca867adec577
https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=49a18d86f66d33a20144ecb5a34bba0d1856b260

Thanks,

  Hannes

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