Re: AIX and Interix also do early PID recycling.

[Steven W. Orr]

On 7/25/2012 8:14 AM, Greg Wooledge wrote:
> On Wed, Jul 25, 2012 at 09:59:28AM +0200, Michael Haubenwallner wrote:
> > OTOH, AFAICT, as long as a PID isn't waitpid()ed for, it isn't reused by fork().
> > However, I'm unable to find that in the POSIX spec.
>
> A process that hasn't been waited for should become a zombie, which
> should be sufficient to prevent its PID being reused.  Are you saying
> that AIX and Interix don't have zombies?

One small nit:

A process that hasn't been waited for should become a zombie *if* the parent 
dies *or* the parent has set SIGCHLD to SIG_IGN. If the parent persists and 
the children are not harvested then the children are in a defunct state.

I don't know what Internix is, but I once discovered an AIX system that had 
over 10,000 defunct processes. The people would detect a slowdown every few 
days and just reboot it. Turns out that a programmer had written a server that 
did not manage its slaves, so they all just sat there waiting to be waited for.

I went in and added a few lines of code to do the wait calls. It never needed 
a reboot since.

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