NFS clients hang, and on server the message "kernel: NFSD: setclientid: string in use by client" is seen

Issue

• NFS clients hang, and on the NFS server, the message kernel: NFSD: setclientid: string in use by client is seen.

• The NFS server logs messages similar to the following:

Mar 12 21:02:44 servername kernel: NFSD: setclientid: string in use by client(clientid 4f5e14e2/00000003)
Mar 12 21:03:47 servername kernel: NFSD: setclientid: string in use by client(clientid 4f5e14e2/00000004)

• The traces on the NFS client, for example this one, all result due to a problem with the NFS service:

Mar 12 19:04:36 hostname kernel: INFO: task java:11714 blocked for more than 120 seconds.
Mar 12 19:04:36 hostname kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 12 19:04:36 hostname kernel: java          D ffffffff801546d1     0 11714      1         11786 11713 (NOTLB)
Mar 12 19:04:36 hostname kernel:  ffff8101a68cb9d8 0000000000000086 0000000000000000 ffff81043fea8c00
Mar 12 19:04:36 hostname kernel:  ffff8101573685c8 000000000000000a ffff81023f907080 ffff81024730e040
Mar 12 19:04:36 hostname kernel:  000051c66e76af40 000000000014f7a5 ffff81023f907268 000000083d49ecb8
Mar 12 19:04:36 hostname kernel: Call Trace:
Mar 12 19:04:36 hostname kernel:  [<ffffffff885f8271>] :nfs:nfs4_xdr_enc_write+0x0/0x125
Mar 12 19:04:36 hostname kernel:  [<ffffffff8006ec8f>] do_gettimeofday+0x40/0x90
Mar 12 19:04:36 hostname kernel:  [<ffffffff885e22f5>] :nfs:nfs_wait_bit_uninterruptible+0x0/0xd
Mar 12 19:04:36 hostname kernel:  [<ffffffff800637ce>] io_schedule+0x3f/0x67
Mar 12 19:04:36 hostname kernel:  [<ffffffff885e22fe>] :nfs:nfs_wait_bit_uninterruptible+0x9/0xd
Mar 12 19:04:36 hostname kernel:  [<ffffffff800639fa>] __wait_on_bit+0x40/0x6e
Mar 12 19:04:36 hostname kernel:  [<ffffffff885e22f5>] :nfs:nfs_wait_bit_uninterruptible+0x0/0xd
Mar 12 19:04:36 hostname kernel:  [<ffffffff80063a94>] out_of_line_wait_on_bit+0x6c/0x78
Mar 12 19:04:36 hostname kernel:  [<ffffffff800a2e8b>] wake_bit_function+0x0/0x23
Mar 12 19:04:36 hostname kernel:  [<ffffffff885e6eb0>] :nfs:nfs_sync_inode_wait+0xe0/0x2d4
Mar 12 19:04:36 hostname kernel:  [<ffffffff885e7551>] :nfs:nfs_updatepage+0x17f/0x1ec
Mar 12 19:04:36 hostname kernel:  [<ffffffff885dcf4b>] :nfs:nfs_write_end+0x6b/0x92
Mar 12 19:04:36 hostname kernel:  [<ffffffff8000ff32>] generic_file_buffered_write+0x1cc/0x675
Mar 12 19:04:36 hostname kernel:  [<ffffffff8001678a>] __generic_file_aio_write_nolock+0x369/0x3b6
Mar 12 19:04:36 hostname kernel:  [<ffffffff800a5830>] futex_wake+0x50/0xd4
Mar 12 19:04:36 hostname kernel:  [<ffffffff800219bf>] generic_file_aio_write+0x67/0xc3
Mar 12 19:04:36 hostname kernel:  [<ffffffff885dd62d>] :nfs:nfs_file_write+0xd8/0x14f
Mar 12 19:04:36 hostname kernel:  [<ffffffff80018415>] do_sync_write+0xc7/0x104
Mar 12 19:04:36 hostname kernel:  [<ffffffff800a2e5d>] autoremove_wake_function+0x0/0x2e
Mar 12 19:04:36 hostname kernel:  [<ffffffff80016b92>] vfs_write+0xce/0x174
Mar 12 19:04:36 hostname kernel:  [<ffffffff8001745b>] sys_write+0x45/0x6e
Mar 12 19:04:36 hostname kernel:  [<ffffffff8006149d>] sysenter_do_call+0x1e/0x76

• After restarting the nfs service, the problem gets resolved.