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Date: Mon, 31 Mar 2014 13:06:43 -0700 (PDT)
Subject: Process handlers, and zombies, or preap(1)
From: "Chris H" <bsd-lists@bsdforge.com>
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Greetings,
 I'm evaluating/experimenting on releng_9. The install, and now
custom kernel have noting exotic, or anything out of the ordinary.
top(1), and ps(1) indicate a (1) zombie, or <defunct> process. On
my releng_8 systems, when I occasionally encounter one of these,
they soon disappear (are reaped) from the process table. While I
have not investigated this far enough on both versions to determine
whether the parent process reaped the child on the releng_8 systems,
and the parent on releng_9 is simply an irresponsible parent, eg;
a different parent. Before I do, I was wondering if there was any
specific difference between the 2 versions that might cause better
handling of such situations. While I recognize that resource
starvation is HIGHLY unlikely, except by perhaps a rouge parent
spawning multitudes of zombies. I thought it might be useful for
"housekeeping" to 1) provide a process table housekeeper (zombie
reaper), or 2) create a system utility/command like SunOS/OpenSolaris
has; preap(1).

http://www.freebsd.org/cgi/man.cgi?query=preap&manpath=SunOS+5.10

Thank you for your time, and consideration.

--Chris