freebsd stable - Apr 2010 - em regression, UDP LOR followed by ssh stall

Hello,

with RELENG_8 from 6 weeks ago I never ran into the problem that my ssh 
connection stalled.
With today's RELENG_8 it reproducably hangs at first login. After some 
time I can open another ssh session which seems to stay without 
problems, but the first sessions is always dying a few seconds after login.
here's a LOR:

lock order reversal:
  1st 0xffffff0001801018 em0:rx(1) (em0:rx(1)) @ 
/usr/src/sys/dev/e1000/if_em.c:4057
  2nd 0xffffffff80938908 udp (udp) @ /usr/src/sys/netinet/udp_usrreq.c:474
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x49
witness_checkorder() at witness_checkorder+0x7ea
_rw_rlock() at _rw_rlock+0x58
udp_input() at udp_input+0x1cd
ip_input() at ip_input+0xb3
netisr_dispatch_src() at netisr_dispatch_src+0x9e
ether_demux() at ether_demux+0x176
ether_input() at ether_input+0x176
em_rxeof() at em_rxeof+0x175
em_msix_rx() at em_msix_rx+0x22
intr_event_execute_handlers() at intr_event_execute_handlers+0x67
ithread_loop() at ithread_loop+0xae
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff8075507d30, rbp = 0 ---

FreeBSD 8.0-STABLE #0: Fri Apr 16 10:34:36 CEST 2010 
admin@korso.rzhp.omnilan.net:/usr/obj/usr/src/sys/ILZ-S32  amd64

em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=399b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_UCAST,WOL_MCAST,WOL_MAGIC>
	ether 00:1b:21:3e:90:52
	inet 10.21.0.2 netmask 0xffffff00 broadcast 10.21.0.255
	media: Ethernet autoselect (1000baseT <full-duplex>)
	status: active

em0: <Intel(R) PRO/1000 Network Connection 7.0.0> port 0x2000-0x201f mem 
0xe1a80000-0xe1a9ffff,0xe1a00000-0xe1a7ffff,0xe1aa0000-0xe1aa3fff irq 16 
at device 0.0 on pci1
em0: Using MSIX interrupts with 5 vectors
em0: [ITHREAD]
em0: [ITHREAD]
em0: [ITHREAD]
em0: [ITHREAD]
em0: [ITHREAD]
em0: Ethernet address: 00:1b:21:3e:90:52


Thanks for any help

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On Fri, Apr 16, 2010 at 11:18:56AM +0200, Harald Schmalzbauer
wrote:
> with RELENG_8 from 6 weeks ago I never ran into the problem that my
> ssh connection stalled.
> With today's RELENG_8 it reproducably hangs at first login. After
> some time I can open another ssh session which seems to stay without
> problems, but the first sessions is always dying a few seconds after
> login.
> here's a LOR:
> {snip}
The e1000/em driver was recently modified (heavily).  I saw the large
number of commits come across in a csup a few weeks ago, and there's
even more coming across in recent days (~38 hours ago):

http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/e1000/

This is the 2nd problem report to come in about the recent e1000/em
changes.  Because of this, I've avoided building kernel on all of my
systems, and would recommend others avoid doing the same until these
problems can get worked out.

Jack, can you shed some light on what's going on here?

-- 
| Jeremy Chadwick                                   jdc@parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |