[PATCH 3/3] score: Task get/set affinity
sebastian.huber at embedded-brains.de
Wed Apr 9 11:27:53 UTC 2014
On 2014-04-09 13:17, Joel Sherrill wrote:
> On Apr 9, 2014 1:06 AM, Sebastian Huber <sebastian.huber at embedded-brains.de> 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.
> > 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
> > 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
> 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
> 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.
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail : sebastian.huber at embedded-brains.de
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