Re: [Xenomai] Xenomai and normal linux application - Wait time with select() not reliable

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

On 11/19/2012 02:29 PM, Jens Köhler wrote:
> Hello,
> 
> Now is Xenomai 2.6 installed. But I have sometimes still delays in
> user space applications.
> 
> Delay: 0.003064
> Delay: 0.003066
> Delay: 0.003504
> Delay: 0.003066
> Delay: 0.003066
> Delay: 0.003066
> Delay: 0.003090
> Delay: 0.003064
> Delay: 0.003066
> Delay: 0.003067
> Delay: 0.053807 <- 53 ms instead 3ms
> Delay: 0.003067
> Delay: 0.003067
> 
> I found out that problem depends from a real time queue between two
> Xenomai tasks.
> 
> retval = rt_queue_create(&RtMeasureData, "RtMeasureData", 1000 * 256,
> Q_UNLIMITED, Q_FIFO | Q_SHARED);
> 
> A real time task writes measurement data every 2 ms to a rt_queue.
> retval = rt_queue_write(&RtMeasureData, &FifoMeasureData, 256, Q_NORMAL);
> 
> Another Xenomai task reads all measured data from queue and makes them
> available for user land applications. (Task is not real time, context
> switches)
> 
> retval = rt_queue_read(&RtMeasureData, &FifoMeasureData, 256, TM_NONBLOCK);
> 
> When nothing is written to queue is there also never an unexpected delay.
> 
> Any ideas or recommendations to find reason for problem?

Without seeing any code, there is strictly nothing we can do.
If you are able to reduce the code to a simple, self-contained test case
we can run anywhere, then we can have a look at it.
If not, then use the I-pipe tracer.

-- 
					    Gilles.