posix job control and setting process group of controlling tty

[Mark Davies]

When forking off children to run in the foreground both tcsh (and csh I
presume)  and bash do basically the following (in the child process):


		pgrp = getpid();
			:
		ioctl(cntl_tty, TIOCSPGRP, &pgrp);
			:
		setpgrp(0, pgrp);

If I remember correctly from the discussion here a few months ago (and the
comments in the bash code) the ioctl is done first to avoid a race
condition.  All well and good, but now POSIX (in the form of HP-UX 7.0)
makes an appearance and doing things in the above order causes the ioctl to
fail with EPERM which, reading the manual, means:

	"The process ID referenced by arg is a supported value but does not
	match the process group ID of a process in the same session as the
	calling process."

This is reasonable as the process group with that ID is not actually
created until the setpgrp.  Reversing the order of the setpgrp and ioctl
allows things to work, but what about the race condition?  What is the
correct way to do this with POSIX style job control?

cheers
mark