ZOMBIE processes under sys5

[Brandon Allbery]

Quoted from <165 at hqda-ai.UUCP> ["Re: Zombies ???"], by merlin at hqda-ai.UUCP (David S. Hayes)...
(after comments about ZOMBIE procs not being reclaimed by init under 4.2)
+---------------
| The preceding was discovered on a VAX running 4.2BSD, as a result
| of some problem with emacs.  I think Sys V runs the same way, but
| I can't be sure, as I don't have a Sys V machine.
+---------------

>From what I have observed of its behavior, sys5 init spends most of its time
in wait().  When wait() returns, it checks the pid against its internal
table as loaded from /etc/inittab; if it's not found it ignores it, otherwise
it updates /etc/utmp and /etc/wtmp with the exit/termination status and does
whatever the "command" field says (respawn, once = don't respawn, etc.).  In
any case, sys5 has only the standard wait(), rather than multi-optioned and
unknown to me wait3(); as a result, when wait() returns, the zombie is gone.
(Maybe BSD init is using a wait3() option to keep the zombie around after
getting the exit status, then forgetting to issue another wait3() to clean
it up afterward?  --if wait3() can be made to work this way.  How would I
know?  The one BSD system I have access to lacks man pages [grrr].)

++Brandon
-- 
``for is he not of the Children of Luthien?  Never shall that line fail, though
the years may lengthen beyond count.''  --J. R. R. Tolkien

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