[Xenomai-help] /proc/xenomai/affinity and T_CPU(n) in rt_task_create

["M. Koehrer" <mathias_koehrer@domain.hid>]

Hi everybody,

I am currently evaluating the latest Xenomai release 2.4.0 on a Dual Core Pentium 4 using
the 2.6.23 kernel and also the latest rtnet 0.9.10-rc1.
I have one question concerning the relation of the /proc/xenomai/affinity entry and the parameter
T_CPU(n) I pass with rt_task_create (native API).
If I set /proc/xenomai/affinity to 1 (which means to run all real time tasks on CPU 0). I am not allowed
to pass T_CPU(1) with rt_task_create. rt_task_start returns with a -EINVAL.

Background for my question is:
rtnet uses a internal system task For this task I cannot pass the CPU I want to run this CPU on.
My idea is now to set /proc/xenomai/affinity to 1 which means (in my mind) that all tasks that do
not have specified explicitly a task number (T_CPU(n)) will run on the CPU(s) specified by /proc/xenomai/affinity.
All those tasks that specify T_CPU explicitly will run on the specified CPU, no matter what value 
/proc/xenomai/affinity is.
However, this seems not to work.

I want to run rtnet on CPU 0 and my own code on CPU 1. For this I write 1 to /proc/xenomai/affinity and 
pass T_CPU(1) with all my calls to rt_task_create. However, these tasks return with -EINVAL.
I debugged into Xenomai and found out that is caused in xnpod_start_thread() at the condition
if (xnarch_cpus_empty(thread->affinity)) ...

When I write 3 to /proc/xenomai/affinity my tasks start fine, however I have now no control of the
CPU placement of the rtnet system task.


Any hints on that are highly welcome.

 
Regards

Mathias


-- 
Mathias Koehrer
mathias_koehrer@domain.hid


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