>I'm certain I'll end up doing some sort of userland thing like a
>semaphore rather than polling.  Polling is a smallish evil, but CPU
>cycles *really* matter in this case.  Also, using the "p" work around

Hi, have a read of http://www.quick.com.au/cgi-bin/rtfm?topic=batchin
these are the routines I use for reliable input into applications
such as yours.  All your data receiver needs to do is suck the input
into a uniquely named file, and when complete echo its pathname 
to the input queue file.  Batchin routines in the daemon do the rest.

You get reliable FIFO processing with no wasted cpu cycles.
I have equivalent routines in perl, though that's probably not relevant 
to you.

Oh, this is not (currently anyway) publicly available code.

--sjg