On Wed, Mar 12, 2008 at 09:57:16AM +0100, Otto Moerbeek wrote:

quoted text
> zombie state happend if a child process exits, but its parent did not

> execute a wait(2) system call (or one if its alternatives) for the

> process (yet). So this seem a bug in the handling of CGIs.

I'd like to add a bit to the above and to Paul de Weerd's comments:
Zombie processes are there to maintain a little info in case the parent

process calls wait() later to retrieve it. Some program designs catch

SIGCHILD or have a thread block on wait*, and in those cases the zombie

lasts such a short time you'll probably never see it in top or ps. Other

designs use non-blocking forms and zombies may stick around long enough

to notice, but then disappear later when the parent makes a pass. If the

parent dies before calling wait, then the zombie is inherited by init

which will take care of it.
So, zombies happen, but the only time they stay around for a long time

is a negligent/misdesigned parent that is still alive but not calling

wait* on the children. The OS can't make a badly written program into a

well written program. So as admin you are stuck restarting the parent

periodically, switching to something else, or bugging the developers to

fix the problem.
--

Darrin Chandler            |  Phoenix BSD User Group  |  MetaBUG

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