1.133 How do I kill a process that ignores kill -QUIT -KILL -STOP

If there is i/o pending in a device driver, and the driver does not
catch the signal, you can't kill it - a reboot is the only way to
clear it.

Furthermore, if the process stays hung for more than a few minutes,
you can find out what device is wedged by doing this --

% echo trace -k $(expr <pid> / 256) | crash | tee stack

If you can't figure out what is wrong, print that trace out and call
1-800-237-5511 and tell them that something is broken.  Tell them you
want to fax in the nice stack trace that you have as your testcase.