Re: [Xenomai] Unexpected CPU assignment on iMX6Q

["Javier Martínez Cantos" <jmartinez@ixion.es>]

On 15/02/16 13:15, Gilles Chanteperdrix wrote:
> On Mon, Feb 15, 2016 at 12:39:29PM +0100, Javier Martínez Cantos wrote:
>> Hi everybody,
>>
>> I'm currently working on Toradex Apalis iMX6Q (4 cores) with Xenomai
>> 2.6.4. The system runs fine.
>>
>> However, I'm playing around with rt_task_create and T_CPU obtaining the
>> following results:
>>
>> - T_CPU(0-3) leads to task creation on expected core, i.e. 1 to 4,
>>
>> - while T_CPU(>3) leads to task creation always on first core.
>>
>> Affinity is configured as follows:
>>
>> cat /proc/xenomai/affinity
>> 0000000f
>>
>> I expect rt_task_create to return an EINVAL error or something like that
>> when T_CPU is higher than RTHAL_NR_CPUS - 1.
> The affinity is used when starting the task with rt_task_start, not
> when creating it. And indeed, rt_task_start should return -EINVAL if
> no cpu is found for running the task.
Ok, I misunderstood. Anyway it is unexpected.

Once rt_task_create is called with -say- T_CPU(20), rt_task_start 
returns 0 (success) and the target task is launched on first core (index 0).

What's wrong?
>> Could RTHAL_NR_CPUS has a value higher than 4? How can I check this? I
>> have already checked that CONFIG_NR_CPUS is 4.
> NR_CPUS does not matter, xnpod_start_thread does a "bitwise and" with
> cpu_online_mask.
I'll explore this path.
>> On runtime, how can I query the "task to core assignment" through
>> Xenomai API?
> I am not sure there is a way. You can check /proc/xenomai/sched or
> /proc/xenomai/stat though.
>
Thank you Gilles.

-- 


Javier Martínez Cantos

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