On 9/04/2014 9:27 pm, Sebastian Huber wrote:
On 2014-04-09 13:17, Joel Sherrill wrote:
On Apr 9, 2014 1:06 AM, Sebastian Huber
<[email protected]> wrote:
>
> On 2014-04-08 17:09, Jennifer Averett wrote:
> > I thought the consensus was that non-smp systems would not
> > support affinity methods.
>
> I don't remember a discussion about this.
>
> I think it makes it easier for application developers if the don't
have to
> plaster their code with #ifdef RTEMS_SMP. You should also be able
to write
> libraries that work with SMP and non-SMP configurations. For this
we have to
> provide the same ABI. This should be the long term goal.
Ironically this is exactly what we have not done with disable
preemption and
task variables.
Originally it was a run-time error. Usage of RTEMS_PREEMPT is still a
run-time error. Maybe the removal of the task variables API for SMP was
a bit too fast.
Task variables are broken on many levels and there are suitable
alternatives. Removing them should have happened long ago. The
RTEMS_PREEMPT is a good example of something we will keep and support
for legacy reasons.
> I propose to add a new requirement:
>
> The non-SMP and SMP RTEMS Classic API should be ABI compatible.
>
> http://www.rtems.org/wiki/index.php?title=SMP#Requirements
So you propose to defer compile errors for task variables to run time?
I am not sure. The task variables are a broken concept even on non-SMP
configurations.
Yeap I agree.
> On Linux you can use the thread affinity functions also on non-SMP
systems.
For this I do not mind but we did discuss this at the beginning of the
implementation.
The short circuit logic for non-smp should be in the api level code
and the
score should have NO code for affinity.
Since the affinity support is used by the Classic and POSIX API it must
stay in the score.
Conditionally removed on uniprocessor builds ?
Otherwise you impact the minimum profile and this is 100% unacceptable.
There is no overhead in the non-SMP configurations if you don't use the
task set/get affinity functions. The scheduler get/set affinity
operations are only available in SMP configurations.
Could you please elaborate ? If I do not use the functions the score
includes no extra code related to this API, ie the scope is limited to
the API layer ?
Chris
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