[ewg] MLX4 Strangeness

[Tom Tucker]

Hello,

I am seeing some very strange behavior on my MLX4 adapters running 2.7 
firmware and the latest OFED 1.5.1. Two systems are involved and each 
have dual ported MTHCA DDR adapter and MLX4 adapters.

The scenario starts with NFSRDMA stress testing between the two systems 
running bonnie++ and iozone concurrently. The test completes and there 
is no issue. Then 6 minutes pass and the server "times out" the 
connection and shuts down the RC connection to the client.

 From this point on, using the RDMA CM, a new RC QP can be brought up 
and moved to RTS, however, the first RDMA_SEND to the NFS SERVER system 
fails with IB_WC_RETRY_EXC_ERR. I have confirmed:

- that "arp" completed successfully and the neighbor entries are 
populated on both the client and server
- that the QP are in the RTS state on both the client and server
- that there are RECV WR posted to the RQ on the server and they did not 
error out
- that no RECV WR completed successfully or in error on the server
- that there are SEND WR posted to the QP on the client
- the client side SEND_WR fails with error 12 as mentioned above

I have also confirmed the following with a different application (i.e. 
rping):

server# rping -s
client# rping -c -a 192.168.80.129

fails with the exact same error, i.e.
client# rping -c -a 192.168.80.129
cq completion failed status 12
wait for RDMA_WRITE_ADV state 10
client DISCONNECT EVENT...

However, if I run rping the other way, it works fine, that is,

client# rping -s
server# rping -c -a 192.168.80.135

It runs without error until I stop it.

Does anyone have any ideas on how I might debug this?

Thanks,
Tom