Date: Mon, 17 Apr 2006 18:06:27 -0700 (PDT) From: Cheng Jin <chengjin@cs.caltech.edu> To: freebsd-net@FreeBSD.org Subject: em in 6.0 missing rx interrupts? Message-ID: <Pine.LNX.4.60.0604171240190.31972@orchestra.cs.caltech.edu>
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Hi, I am running into a problem with em driver possibly missing rx interrupts. I have the following setup Linux NFS server -- FreeBSD 6.0 ethernet bridge -- Linux NFS client and I run a test on the NFS client that repeatedly mounts an NFS directory, retrieves a file, and unmounts the dir. The FreeBSD 6.0 runs on a machine with SuperMicro 5015M-MF motherboard with dual-port onboard Intel 82573v controller. The ethernet bridging was setup using bridge.ko with em0 connected to the NFS server, and em1 connected to the client. The problem is that after a while, the test freezes when the NFS client sends a SYN (NFS over TCP) and never receives the SYNACK for it, and neither are the subsequent retransmitted SYNACKs (some of them triggered by retransmitted SYNs from the client) ever received. I have verified that the NFS server indeed puts the SYNACKs on the wire, by putting an additional bridge with Broadcom ethernet ports (bge) in between the FreeBSD 6.0 bridge and the NFS server. This new bridge can see the SYNACK packets fine and forwards them on, but the bridge with em ports just can't see the SYNACKs. If I replace the bridge with em ports by the one with bge ports, the problem goes away. The test can eventually recover when the client uses a different port to contact the server. Also, this problem occurs for different src/dst port pairs, and once the first SYNACK goes missing, none of the subsequent SYNACKs will go through either. I have gotten the latest em driver code for RELENG_6 off the web cvs and instrumented the em_process_receive_interrupts function. I don't see this function called when this missing SYNACK situation occurs. I am not sure whether the interrupts themselves never occurred, or somehow the processing didn't reach this particular function due to something else. I could continue to add printfs to the em functions to see where things go wrong, but I would like to hear some suggestions from people on what might be going wrong here. Many thanks! Cheng P.S. I had an IPMI card in the machine that was generating gratuitous arps last week, and I suspected that it was swallowing the pkts, but I still have this problem after removing it.
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