On Fri, May 29, 2009 at 12:31:37PM -0700, Alfred Perlstein wrote:
> * Dag-Erling Sm??rgrav <d...@des.no> [090529 02:49] wrote:
> > Alfred Perlstein <alf...@freebsd.org> writes:
> > > Dag-Erling Sm??rgrav <d...@des.no> writes:
> > > > 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?
> >
> > This is an example, Alfred. Like most examples, it is greatly
> > simplified. I invite you to peruse the source to find real-world
> > instances of non-trivial fork() / execve() usage.
>
> It wasn't meant to critisize, just ask a question for the specific
> instance because it made me curious. I know how bad it can be with
> vfork as I observed a few fixes involving mistaken use of vfork at
> another job.
It is still very interesting, because I currently have a similar problem
and wasn't aware of getdtablesize();
A threaded application which needs to call an external script of unknown
runtime.
I don't have all descriptors under my knowledge, because external libs
might open them.
I also believe there could be a race between retrieving the descriptor
and setting close-on-exec.
The only solution which I found so far is using rfork with RFCFDG.
If I undestand RFCFDG correctly the child process has no descriptors at
all.
This is Ok for me, since I don't need to inherit some.
--
B.Walter <be...@bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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