ZOMBIE processes under sys5
Brandon Allbery
brandon at tdi2.UUCP
Sat Dec 13 03:29:20 AEST 1986
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
--
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