Re: [Xenomai] Round robin scheduling seem not working in a specific case...

[Christophe Carton <christophe.carton@ixblue.com>]

Le 04/11/2014 11:41, Gilles Chanteperdrix a écrit :
> On Tue, Nov 04, 2014 at 11:34:47AM +0100, Christophe Carton wrote:
>> Hello,
>>
>> I am currently working with Xenomai 2.6.4 with native skin and with
>> a Linux kernel 3.14.17.
>> The linux and the xenomai have been taken from the following Git
>> repositories :
>> * http://git.xenomai.org/xenomai-2.6.git - tag v2.6.4
>> * http://git.xenomai.org/ipipe.git - tag ipipe-core-3.14.17-x86-4
>>
>> I am encountering a problem to enable the Round Robin scheduler in a
>> specific case :
>> * Two tasks ("rr task 1" and "rr task 2") of priority 10 are
>> launched by a task ("init task") of priority 90.
>> * All 3 of them are configured with a RR scheduler via
>> "rt_task_slice" API before they are started.
>> In this case the FIFO scheduling seems to be applied (could be seen
>> via rt_printf logs).
>>
>> I have found a thread on the mailing list that gives an example
>> demonstrating the good behavior of the RR scheduler.
>> http://www.xenomai.org/pipermail/xenomai/2011-November/024897.html
>> http://www.xenomai.org/pipermail/xenomai/2011-November/024899.html
>> This example implies that the tasks are locked via a semaphore at
>> startup and that this semaphore is unlocked by the main when all
>> threads have been started.
>> This is necessary in this case due to the fact that the main
>> function is no an RT task.
>>
>> This implementation (with the semaphore) applied to my test works.
>> Why is the semaphore needed in my case?
>> The 2 RT lower priority ("rr task 1" and "rr task 2") runs when my
>> high priority task ("init task") is waiting on the "rt_task_join".
>> They are are so launched at the "same time" with a RR scheduling.
>> But the FIFO scheduling seems to be taken into account when I look
>> at the logs...
>> Were am I wrong?
>>
>> You could find attached my source code.
> Are you running on an uniprocessor system or multiprocessor system?
>

I am running on a multiprocessor system and all my tasks are affine to 
CPU #1.

--

Christophe