Re: [Monotone-devel] auto updates

[Nuno Lucas]

On 10/30/06, Nathaniel Smith <address@hidden> wrote:
> On Sun, Oct 29, 2006 at 09:13:15AM +0000, Nuno Lucas wrote:
> > Just do this for POSIX systems (I don't believe there is a problem
> > with zombie processes on other systems):
> >
> > static void signal_handler( int sig, siginfo_t* si, void * context )
> > {
> >   int status;
> >   wait (&status);
> > }
>
> FYI, this is a bit buggy -- it can leave zombies if signals get
> coalesced, or freeze if other processes might call wait() before the
> signal handler runs.

That is new to me. I got that code on some book on advanced unix
programming and that's what I use in my programs (if I want to wait
for a program, I just use system() and WEXITSTATUS). Have to find that
book again...

Always hated unix signals because of their racy conditions and stupid
behaviours. This just adds to my global feeling...

> But this technique is what I meant by "unconditionally get rid of
> zombies" -- I'm not sure what happens when you have a signal handler
> like this, _and_ you sometimes want to call waitpid() in your program
> explicitly.

Well, you can disable the signal when you do it. But my dislike for
signals and now knowing I got it wrong the first time doesn't let me
add more.


Best regards,
~Nuno Lucas