[PATCH v2 1/7] eal: add queue macro extensions from FreeBSD

[Morten Brørup]

> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Thursday, 13 March 2025 00.02
> 
> On Wed, 19 Feb 2025 15:55:17 +0100
> Thomas Monjalon <thomas at monjalon.net> wrote:
> 
> > 14/02/2025 18:20, Stephen Hemminger:
> > > The Linux version of sys/queue.h is frozen at an older version
> > > and is missing the _SAFE macro variants. Several drivers started
> > > introducing the own workarounds for this. Should be handled in EAL.
> > >
> > > Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> >
> > We may want to unify with lib/eal/windows/include/sys/queue.h
> >
> >
> 
> Not sure, we have several options here:
>   1. Keep using Linux sys/queue.h and add enhancements in rte_queue.h
>   2. Make rte_queue.h a copy of FreeBSD version of queue.h (that is
> what Windows did)
>   3. Use the bsd version of queue.h.
>      On Debian/Ubuntu this in libbsd-dev package and referred to as
> bsd/sys/queue.h
> 
> I chose #1 as simplest. But all of these could work. #3 means DPDK has
> least new
> code, but adds another dependency to the build.

+1 to #2:
If Linux sys/queue.h is frozen, and is a subset of FreeBSD queue.h, #2 would consolidate all the queue macros in one file.
That seems easier to navigate (for a developer/reviewer looking at the macro definitions/implementations) than including sys/queue.h, queue.h or lib/eal/windows/include/sys/queue.h depending on O/S, and then defining the missing macros in rte_queue.h.
A comment at the top of the rte_queue.h file could mention that it is a copy of the FreeBSD queue.h file.

-1 to #3; it adds an unnecessary dependency.

> 
> No matter what, should add to checkpatch to block any new files that
> include sys/queue.h
> directly.

+1 to this.