how to kill a 'mount' command that has hung

[Saifi Khan <saifi.khan%fastpath.in@localhost>]

Hi:

How does one kill a 'mount' command that has hung ?

Environment:
NetBSD x53u 6.99.10 NetBSD 6.99.10 (GENERIC) #0: Tue Aug 28 05:55:38 UTC 2012  
builds%b6.netbsd.org@localhost:/home/builds/ab/HEAD/amd64/201208280330Z-obj/home/builds/ab/HEAD/src/sys/arch/amd64/compile/GENERIC
 amd64

Scenario:
 . Take a external USB disk formatted with ext3fs file system.
 . run a 'find *.*' or 'mplayer mp3.song'
 . after about 3-4 min. the mount will hang.
 . the LED on the disk will be blinking fast.

Observations:

1. Attempting to perform a 'kill -9 mountPID' simply returns a prompt, but the 
mount command continues to hang.

2. both WCPU and CPU show system CPU utilization range as 98.3 - 98.9%. after 
about 20 minutes or so, the CPU utilization comes down to 55%.

3. a user login in another terminal succeeds.

4. a user app eg. 'alpine' starting an alternate editor 'vi' hangs.

5. a kill -9 attempt to a user process from another root terminal has not 
affect, ie. the command simply returns but the process is there.

6. /sbin/shutdown -p now' command hangs at 'shutdown hooks' message. the only 
way to shutdown is to press the power switch.

if the 'kill' command is not the solution, what is the recommended approach ?


thanks
Saifi.