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Re: libgomp support for RTEMS


On 30/01/15 12:50, Jakub Jelinek wrote:
On Fri, Jan 30, 2015 at 12:14:26PM +0100, Sebastian Huber wrote:
>Hello,
>
>I would like to add support for libgomp for the RTEMS operating system. I
>likely cannot use the standard Pthread API for this in some places since I
>have to account for RTEMS specifics related to partitioned/clustered
>scheduling and the priority based scheduler. If I implement for example
>functions like this
>
>void gomp_init_thread_affinity (pthread_attr_t *attr, unsigned int place)
>
>outside of the GCC provided libgomp (e.g. in the RTEMS sources) can I choose
>an arbitrary license for this or do I have to use the GPLv3 with the GCC
>Runtime Library Exception for it?
>
>Is it possible to add a gomp_free() to complement the gomp_malloc() etc.?
>This would enable the usage of a dedicated heap for OpenMP in RTEMS.
Why would you want to implement it outside of libgomp?
libgomp has a config/ tree, so just add config/rtems/ in there and implement
it in there.

RTEMS uses the same method for the thread model. It is easier to maintain since I don't have to build and install a new compiler just to change the libgomp support. The RTEMS API header file <rtems.h> is not available during GCC build. I would like to make some parts application configurable via function pointers (e.g. the heap functions). On RTEMS we have a single address space for the operating system, support libraries and the application. In the application we have parts of different criticality and dynamic behaviour, so the management of dynamic memory is highly application dependent. Some systems must run months without a re-boot.

I would like to add a config/rtems and implement most of the stuff inside the RTEMS source tree or let even the application provide the implementation.

--
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber@embedded-brains.de
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