Why is my system stuck due to soft lockup, while nfs is used?

Issue

• Soft lockups while running commands like 'mv' or 'find' using nfsv3 mounted filesystems:

  kernel: CPU 12:
  kernel: Modules linked in: iptable_filter ip_tables x_tables nfs fscache nfs_acl lockd autofs4 mptctl mptbase ipmi_si(U) ipmi_devintf(U) ipmi_msghandler(U) hidp rfcomm l2cap bluetooth sunrpc dm_multipath scsi_dh video backlight sbs power_meter hwmon i2c_ec i2c_core dell_wmi wmi button battery asus_acpi acpi_memhotplug ac parport_pc lp parport sr_mod cdrom sg hpilo e1000e bnx2 shpchp serio_raw pcspkr dm_raid45 dm_message dm_region_hash dm_mem_cache dm_snapshot dm_zero dm_mirror dm_log dm_mod ata_piix libata cciss sd_mod scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd
  kernel: Pid: 11830, comm: java Tainted: G      2.6.18-194.el5 #1
  kernel: RIP: 0010:[<ffffffff80048a97>]  [<ffffffff80048a97>] lock_rename+0x3f/0xbd
  kernel: RSP: 0018:ffff810115ff1df8  EFLAGS: 00000206
  kernel: RAX: ffff810297e483d8 RBX: ffff810279c6ba98 RCX: 0000000000000402
  kernel: RDX: ffffffff8001283d RSI: ffff810279c6ba98 RDI: ffff810299ceb248
  kernel: RBP: ffff81013b6b9320 R08: 0000000000000002 R09: ffff81042e2b8b80
  kernel: R10: 0000000000000002 R11: ffffffff8002c728 R12: ffff810336a68810
  kernel: R13: ffff81042e1813c0 R14: ffff81018840905a R15: 00000009f6922168
  kernel: FS:  000000004388b940(0063) GS:ffff81010ebce6c0(0000) knlGS:0000000000000000
  kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  kernel: CR2: 00002aabaf2725d0 CR3: 00000002bb69d000 CR4: 00000000000006e0
  kernel:
  kernel: Call Trace:
  kernel:  [<ffffffff80048a85>] lock_rename+0x2d/0xbd
  kernel:  [<ffffffff80036e60>] sys_renameat+0xd7/0x1eb
  kernel:  [<ffffffff800b878c>] audit_syscall_entry+0x180/0x1b3
  kernel:  [<ffffffff8005e28d>] tracesys+0xd5/0xe0
  

• top output, system log:

  top - 10:56:21 up 27 days,  8:29,  8 users,  load average: 47.24, 45.92, 39.87
  Tasks: 673 total,   6 running, 667 sleeping,   0 stopped,   0 zombie
  Cpu(s):  2.1%us,  0.3%sy,  0.0%ni, 97.3%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:  16304952k total, 16168080k used,   136872k free,    54524k buffers
  Swap:  8191992k total,      292k used,  8191700k free,  5380468k cached
  
    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                      
  3218 cbradm    16   0 69656  732  624 R 99.0  0.0  40:21.83 mv                                                                                            
  14527 root      15   0 13160 1456  732 R  3.8  0.0   0:00.03 top                                                                                           
  10031 useradm    16   0 5311m 3.4g  10m S  1.9 21.6 979:24.56 java                                                                                          
  18992 useradm    24   0 5295m 4.1g  10m S  1.9 26.4 348:15.59 java                                                                                          
      1 root      15   0 10372  700  592 S  0.0  0.0   0:03.19 init
  
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  kernel: BUG: soft lockup - CPU#4 stuck for 60s! [mv:3218]
  

• Why do entries like the following appear in my systemlog?

  kernel: VFS: Lookup of 'exampledirectory' in nfs 0:18 would have caused loop