My system is locks up when an application attempts to copy a large file to an nfs mount. The system becomes unresponsive to the point that I cannot even reboot via the command line over SSH.

For example, when soundKonverter copies an ogg file from /tmp to /home/music (nfs share).

I am unable to kill the copy command:

nate      2791     1  0 10:32 ?        00:00:00 cp /tmp/kde-nate/soundkonverterkMTAC0.ogg /home/music/Foo Fighters/[Foo Fighters] One By One - 07. Halo.ogg

And I see lots of messages like this in /var/log/syslog:

May 22 10:44:31 nereidum kernel: [ 1680.390484] INFO: task cp:2791 blocked for more than 120 seconds.
May 22 10:44:31 nereidum kernel: [ 1680.390488] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 22 10:44:31 nereidum kernel: [ 1680.390492] cp            D 00000000ffffffff     0  2791   2503 0x00000000
May 22 10:44:31 nereidum kernel: [ 1680.390501]  ffff88012a457c48 0000000000000082 0000000000015bc0 0000000000015bc0
May 22 10:44:31 nereidum kernel: [ 1680.390508]  ffff8801291331a0 ffff88012a457fd8 0000000000015bc0 ffff880129132de0
May 22 10:44:31 nereidum kernel: [ 1680.390516]  0000000000015bc0 ffff88012a457fd8 0000000000015bc0 ffff8801291331a0
May 22 10:44:31 nereidum kernel: [ 1680.390523] Call Trace:
May 22 10:44:31 nereidum kernel: [ 1680.390545]  [<ffffffffa0cff2b0>] ? nfs_wait_bit_uninterruptible+0x0/0x20 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390552]  [<ffffffff8153eb87>] io_schedule+0x47/0x70
May 22 10:44:31 nereidum kernel: [ 1680.390573]  [<ffffffffa0cff2be>] nfs_wait_bit_uninterruptible+0xe/0x20 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390579]  [<ffffffff8153f3df>] __wait_on_bit+0x5f/0x90
May 22 10:44:31 nereidum kernel: [ 1680.390587]  [<ffffffff812b6234>] ? __lookup_tag+0x64/0x120
May 22 10:44:31 nereidum kernel: [ 1680.390608]  [<ffffffffa0cff2b0>] ? nfs_wait_bit_uninterruptible+0x0/0x20 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390615]  [<ffffffff8153f488>] out_of_line_wait_on_bit+0x78/0x90
May 22 10:44:31 nereidum kernel: [ 1680.390622]  [<ffffffff81085360>] ? wake_bit_function+0x0/0x40
May 22 10:44:31 nereidum kernel: [ 1680.390643]  [<ffffffffa0cff29f>] nfs_wait_on_request+0x2f/0x40 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390665]  [<ffffffffa0d036af>] nfs_wait_on_requests_locked+0x7f/0xd0 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390688]  [<ffffffffa0d04aee>] nfs_sync_mapping_wait+0x9e/0x1a0 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390711]  [<ffffffffa0d04ed9>] nfs_write_mapping+0x79/0xb0 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390733]  [<ffffffffa0d04f47>] nfs_wb_all+0x17/0x20 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390751]  [<ffffffffa0cf3eba>] nfs_do_fsync+0x2a/0x60 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390770]  [<ffffffffa0cf4105>] nfs_file_flush+0x75/0xa0 [nfs]
May 22 10:44:31 nereidum kernel: [ 1680.390777]  [<ffffffff8114051c>] filp_close+0x3c/0x90
May 22 10:44:31 nereidum kernel: [ 1680.390783]  [<ffffffff81140627>] sys_close+0xb7/0x120
May 22 10:44:31 nereidum kernel: [ 1680.390790]  [<ffffffff810131b2>] system_call_fastpath+0x16/0x1b

$ uname -a
Linux nereidum 2.6.32-22-generic #33-Ubuntu SMP Wed Apr 28 13:28:05 UTC 2010 x86_64 GNU/Linux

$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=10.04
DISTRIB_CODENAME=lucid
DISTRIB_DESCRIPTION="Ubuntu 10.04 LTS"