Posix message queues in linux?

Posix message queues in linux?

[Alan Cudmore]

Hi,
I sent this message to the mailing list before, but I figured that everyone
was at Linuxworld in New York :)

I was reading the EL/IX draft spec under 3.13 Message Passing:

Does linux support POSIX message passing?
If linux does not support it, is it going to be part of an EL/IX API that
runs on Linux?

Is there a better way to do message passing in Linux & EL/IX. I am looking
to have a capability similar to the RTOSs I am used to such as vxWorks and
Nucleus.

Thanks,
Alan


Alan Cudmore
Flight Software Branch
Code 582
NASA Goddard Space Flight Center
Greenbelt, MD 20771 USA

Re: Posix message queues in linux?

[Stuart Hughes]

Alan Cudmore wrote:
> 
> Hi,
> I sent this message to the mailing list before, but I figured that everyone
> was at Linuxworld in New York :)
> 
> I was reading the EL/IX draft spec under 3.13 Message Passing:
> 
> Does linux support POSIX message passing?
> If linux does not support it, is it going to be part of an EL/IX API that
> runs on Linux?
> 
> Is there a better way to do message passing in Linux & EL/IX. I am looking
> to have a capability similar to the RTOSs I am used to such as vxWorks and
> Nucleus.
> 

Hi Alan,

This may be slightly off topic, but we have provided an LGPL module for
RTAI (linux real time extensions) that implement POSIX queues (for
RTAI).  We are hoping that we will be able to provide some level of
EL/IX compliance for realtime under Linux by adding to this set of
modules.  It may be possible to make use of this code from Linux ?? I
think the latest RTAI release comes with this modules (look at
http://www.rtai.org/ )

Regards, Stuart

Re: Posix message queues in linux?

[Nick Garnett]

"Alan Cudmore" <Alan.P.Cudmore.1@gsfc.nasa.gov> writes:

> Hi,
> I sent this message to the mailing list before, but I figured that everyone
> was at Linuxworld in New York :)
> 
> I was reading the EL/IX draft spec under 3.13 Message Passing:
> 
> Does linux support POSIX message passing?
> If linux does not support it, is it going to be part of an EL/IX API that
> runs on Linux?

At present Linux does not support message passing. This is a minor
problem with some parts of the EL/IX specification: Linux is not yet
fully POSIX compliant. We expect this to change - there are already
patches available for some areas, and others are amenable to a
user-level implementation in glibc.

> 
> Is there a better way to do message passing in Linux & EL/IX. I am looking
> to have a capability similar to the RTOSs I am used to such as vxWorks and
> Nucleus.
> 

I do not believe that Linux provides any alternative message passing
mechanism - unless you count pipes! Since one of the goals of EL/IX is
to work with existing standards as much as possible, it would not be
appropriate for us to define a whole new message passing mechanism. I
do agree, however, that the message passing facilities in POSIX fall
somewhat short of what other RTOSs provide. 


-- 
Nick Garnett
Cygnus Solutions, a Red Hat Company
Cambridge, UK