Re: [Xenomai] cpu usage

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-07-27 15:04, Frederik Bayart wrote:
> I'm running Xenomai 2.6.0 on Linux 2.6.38
> 
> I have a dual core processor.
> When I run a busywait loop on cpu 0 (see source in attachment), I
> can't do anything anymore on the computer although cpu 1 is almost
> entirely idle. I can't interrupt the busywait loop, login, type
> something in a shell, ...
> This is even the case if I run linux entirely on cpu 1 (by using
> isolcpus=0 as kernel parameter)
> 
> How can this be explained ?
> 
> Is it possible to use cpu 0 at 100% for a xenomai tasks and cpu 1 for
> normal linux tasks so that you can still work on the computer ?

It's a FAQ: This is not possible with current Linux. It will lock up
quite quickly if kernel helper threads for RCU or work queues cannot run
once in a while. Also, time keeping will be affected. Due to the latter,
you should release the core to Linux once every scheduling tick.

Jan

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