Sending this to netdev since I think I've now determined that this is
not a NFS specific problem. Recently Christoph mentioned that he was
seeing stalls when running xfstests generic/075 test on NFS over the
loopback interface with v3.18-rc1-ish kernel.
The configuration in this case is the nfs server and client on same box
communicating over the lo interface.
Here's are tracepoints from a typical request as it's supposed to work:
mount.nfs-906 [002] ...1 22711.996969: xprt_transmit: xprt=0xffff8800ce961000 xid=0xa8a34513 status=0
nfsd-678 [000] ...1 22711.997082: svc_recv: rq_xid=0xa8a34513 status=164
nfsd-678 [000] ..s8 22711.997185: xprt_lookup_rqst: xprt=0xffff8800ce961000 xid=0xa8a34513 status=0
nfsd-678 [000] ..s8 22711.997186: xprt_complete_rqst: xprt=0xffff8800ce961000 xid=0xa8a34513 status=140
nfsd-678 [000] ...1 22711.997236: svc_send: rq_xid=0xa8a34513 dropme=0 status=144
nfsd-678 [000] ...1 22711.997236: svc_process: rq_xid=0xa8a34513 dropme=0 status=144
...basically, we send a request to the server. Server picks it up and
sends the reply, and then the client IDs that reply and processes it.
This runs along just fine for ~ a minute or so. At some point, the
client stops seeing replies come in:
kworker/2:2-107 [002] ...1 22741.696070: xprt_transmit: xprt=0xffff8800ce961000 xid=0xc3a84513 status=0
nfsd-678 [002] .N.1 22741.696917: svc_recv: rq_xid=0xc3a84513 status=208
nfsd-678 [002] ...1 22741.699890: svc_send: rq_xid=0xc3a84513 dropme=0 status=262252
nfsd-678 [002] ...1 22741.699891: svc_process: rq_xid=0xc3a84513 dropme=0 status=262252
...a bit more tracepoint work seems to show that we just stop getting
sk_data_ready callbacks on the socket at all. I'm not terribly familiar
with the lower-level socket code, so I figured I'd email here and ask...
Anyone have insight into why this might be happening?
Thanks,
--
Jeff Layton <[email protected]>