unregister_netdevice deadlock with linux 2.6.28

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Hi,

I got the famous "unregister_netdevice: waiting for br0 to become
free. Usage count = 1" deadlock with a linux-2.6.28 kernel when trying
to destroy a bridge.
I read in previous posts that it should have been fixed already.
Some posts mentionned that IPv6 and/or ip_queue could cause this to happen.

IPv6 is not compiled in my kernel, but I am using IP_QUEUE to mangle
some packets

Here is my environment:
- Debian etch, with a non-patched original kernel 2.6.28 downloaded
from www.kernel.org
- netfilter/iptables, used to queue packets
- a home-made program using ipqueue, which always sets a verdict to
ip_queue, and reinjecting packets as fast as it can.

The bad point is that I tried for a week to reproduce the bug without
success; it just happens "sometimes" in heavy load.

And here are my tests:
- Tried to lose packets (no verdict set), until the queue is full
(test failure: doesn't crash the kernel)
- Tried to overload the system (network overload), sending SIGKILL
from times to times to the home-made program (test "sometimes" crashed
the kernel)
- Any other nicer tests failed to crash the kernel too.
- The home-made program may use up to 99% CPU time, as told by the
`top` command; the hardware is a bi-processor, so I don't know the
meaning of CPU time in this case
- Since I try to find a way to reproduce the bug, I reboot after each test

I also had kernel messages like:
"nf_queue: full at 1024 entries, dropping packets(s). Dropped: 5" and
"__ratelimit: 16 callbacks suppressed"
at crash and non-crash times, which should not be alarming since it
just tells that ip_queue can't handle the load


I don't have any clues on how to track down this bug and the fact it
seems random to me doesn't help.

Thanks for the help
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