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Date: Thu, 28 May 2009 14:30:17 -0700
From: Alfred Perlstein <alfred@freebsd.org>
To: Dag-Erling Sm??rgrav <des@des.no>
Message-ID: <20090528213017.GX67847@elvis.mu.org>
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	<4A1594DA.2010707@rawbw.com> <86ljoig08o.fsf@ds4.des.no>
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Cc: Nate Eldredge <neldredge@math.ucsd.edu>, yuri@rawbw.com,
	freebsd-hackers@freebsd.org
Subject: Re: Why kernel kills processes that run out of memory instead of
	just failing memory allocation system calls?
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* Dag-Erling Sm??rgrav <des@des.no> [090527 06:10] wrote:
> Yuri <yuri@rawbw.com> writes:
> > I don't have strong opinion for or against "memory overcommit". But I
> > can imagine one could argue that fork with intent of exec is a faulty
> > scenario that is a relict from the past. It can be replaced by some
> > atomic method that would spawn the child without ovecommitting.
> 
> You will very rarely see something like this:
> 
> if ((pid = fork()) == 0) {
>         execve(path, argv, envp);
>         _exit(1);
> }
> 
> Usually, what you see is closer to this:
> 
> if ((pid = fork()) == 0) {
>         for (int fd = 3; fd < getdtablesize(); ++fd)
>                 (void)close(fd);
>         execve(path, argv, envp);
>         _exit(1);
> }

I'm probably missing something, but couldn't you iterate 
in the parent setting the close-on-exec flag then vfork?

I guess that wouldn't work for threads AND you'd have to
undo it after the fork if you didn't want to retain that
behavior?

thanks,
-Alfred