From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: nfs stalls over loopback interface (no sk_data_ready events?) Date: Mon, 27 Oct 2014 15:26:10 -0400 Message-ID: <20141027152610.3568616f@tlielax.poochiereds.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Christoph Hellwig , Linux NFS Mailing List , Bruce Fields , Trond Myklebust To: netdev-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Return-path: Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org 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 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html