Re: [Xenomai] Suggested approach to schedule N-RT work in kernel on a specific CPU core

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

On Sun, Mar 20, 2016 at 07:15:42AM +0000, Alex Plits wrote:
> Hi,
> 
> We have a requirement to schedule N-RT linux kernel specific work  (e.g. workQ) on a dedicated core from an RTDM driver running
> In Xenomai "context".
> The current RTDM API does in fact provide an API to schedule a N-RT workQ but this does not meet our needs as we need the N-RT job to run on
> A dedicated CPU. Current API implementation will run this special workQ on the CPU where the RT scheduling call occurred, so I have 2 queries we need help with -
> 
> 1.       Is there an API/example/configuration that will achieve our needs?
> 
> 2.       In case there isn't what would be the best approach to implement such a mechanism - I can think of solutions but it seems excessive:
> 
> a.       Run another Xenomai thread that has CPU affinity on the target cpu Core which will call a dedicated RTDM blocking call (e.g. IOCTL with semTake) and then the scheduling RTDM driver will release that semaphore - which will re-schedule the thread on the core we need and now it can call a N-RT IOCTL for example.
> 
> b.      Initialize a new WorkQ on I-Pipe init which will be binded on the target cpu Core only then add new RTDM api to schedule work on that WorkQ - although I'm not sure this will work as it will use the VIRQ  mechanism which will somehow need to change cores.

If the Linux kernel provides a function to do this, we could
implement a function mirroring that function in the RTDM API. Looks
simple. Am I missing something ?

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