Re: Orocos and RTAI/LXRT

Herman Bruyninckx wrote:
> On Wed, 25 Jun 2003, Pierangelo Masarati wrote:
> 
> [...]
> 
>>Our multibody software is a mix of C++, F77 and C, linked to many
>>standard and specialized libraries, and the major effort in exploiting
>>LXRT was to ensure no system calls were performed during the normal
>>execution (e.g. after hard real-time is enforced), which required
>>patching a couple of libraries.
>>
> 
> Do you have more information on this topic you mention, i.e.,
> the programming policy to ensure no system calls are performed?

Basically,

any time a program in hard real-time executes a system call,
the process is kicked back to soft real-time.  All system calls
must be done thru LXRT calls.  This is basically
a trial-and-error process when adding real-time capabilities
to an existing program.  In our case, all logging and diagnostics
messaging has been wrapped by RTAI mailboxes, talking to a
low priority messaging dispatcher; the most annoying problem
was with Umfpack calling times() during linear algebra operations
for performance profiling even when no profiling was required.
We patched Umfpack to allow to programmatically disable profiling.

I'm not aware of specific documentation on this, there has been
a flourishing of howtos and informal documents on RTAI and LXRT.

I think you should ask Paolo (who's in CC and might answer in turn).

Pierangelo.

-- 
Dr. Pierangelo Masarati               | voice: +39 02 2399 8309
mailto:[email protected]  | fax:   +39 02 2399 8334
http://www.aero.polimi.it/~masarati
Dip. Ing. Aerospaziale Politecnico di Milano,
via La Masa 34, 20156 Milano, Italy