Re: [Xenomai] Unexpected CPU assignment on iMX6Q

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

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.

> 
> 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.

> 
> 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.

-- 
					    Gilles.
https://click-hack.org