Zombie process using CPU

[Andy Whitcroft]

On Tue, Apr 20, 2010 at 01:45:27PM +0900, John Tapsell wrote:
> Hi,
> 
>   After a program (vuze) crashed I ended up in the situation of having
> a process, java, using 100% CPU of a core while also being a zombie.
> 
>   Looking in /proc/<pid>/task  I saw two pids - the main task and a
> subtask.  The main task (cat /proc/<pid>/task/<pid>/status ) was
> indeed a zombie, but the subtask was still running and using CPU.
> 
>   I could not find any way to kill this process. kill -9  on the <pid>
>  and on the pid on the subtask did nothing.  In the end I had to
> reboot.
> 
>   is this situation supposed to be possible?  How do I kill a subtask?

A zombie should indeed be nothing more than a shell.  I am not sure
there is even anything to run once a process hits Z state.  It is more
likely that the accounting is wrong than it was actually consuming the
CPU claimed.  Cirtainly it is not something I have experienced here.

-apw