Subject: Re: bi-directional pipes?
To: NetBSD Kernel Technical Discussion List <tech-kern@NetBSD.ORG>
From: Jason R Thorpe <>
List: tech-kern
Date: 02/04/2003 11:29:48
On Tue, Feb 04, 2003 at 02:15:10PM -0500, Greg A. Woods wrote:

 > I would definitely say the complete opposite.

I figured you would :-)

 > Tearing out bi-directional pipe support makes the whole effort of
 > porting the FreeBSD pipe code seem useless -- it would have been much
 > easier to just start from scratch.

Possibly.  But the code did provide a decent starting point...

 > David Laight's concern about compatability with other very widely used
 > systems that support bi-directional pipes is also quite valid.

However, SUSv3 specifically leaves as "undefined" whether the pipe is
bi-directional.  Thus, any application that depends on bi-directional
pipes is non-portable (and, IMHO, broken) by definition.

I'd rather have the kernel pipe implementation be leaner, and push the
complexity down into the applications that need it, esp. if it makes it
easier to make the pipe code properly reentrant.

        -- Jason R. Thorpe <>