Re: is killing zombies possible w/o a reboot?

[DervishD <lkml@dervishd.net>]

    Hi Bill :)

 * Bill Davidsen <davidsen@tmr.com> dixit:
> >    Probably it won't do. If the zombies are there due to a signal
> >delivery problem, sending a SIGCHLD to the parent will (probably)
> >solve the problem. But the common case is that the parent is screwed
> >up or simply so badly programmed that the only way of getting rid of
> >the zombies is to kill the parent...
> Wait a minute, in another message you just suggested that a SIGCHLD to 
> init would cause the status to be reaped.

    I don't consider init the parent of such processes. It just
'adopts' them when the real parent doesn't care for them. I was
talking, in the paragraph above, about the *real* parent. I don't see
any contradiction, although sending SIGCHLD to a program that has not
waited for a children is risky: if the programmer was so clueless
that children were not waited for in the first place, chances are
that SIGCHLD handling is damaged, too.

> >    Anyway I suppose that sending the SIGCHLD won't do any harm so it
> >may be worth trying.
> It won't hurt init, but some processes do use the SIGCHLD to trigger a 
> wait(), which might hang the parent.

    If a parent does 'wait()' instead of 'waitpid', that's lazy
programming. The signal won't hurt anyway: if the parent blocks (bug
in the program), then a 'kill -9' is the correct medication (it's
what I use for buggy programs), the children are reparented to init
and correctly handled (because a good init should, IMHO, use waitpid
instead of wait). Let's say that sending SIGCHLD is 'mostly harmless'
;))

    Raúl Núñez de Arenas Coronado

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