[Xenomai] real-time guarantee issues on xenomai

Gilles Chanteperdrix gilles.chanteperdrix at xenomai.org
Thu Aug 7 19:22:43 CEST 2014

On 08/07/2014 06:57 PM, Alexander Herzog wrote:
> Hi Gilles,

Hi Alexander,

we do not use top-posting on xenomai mailing list.

> I haven't replied to your email for a few months. I am sorry for
> that, we didn't have time to dig further into this problem. However,
> now we went back to the issue and installed Xenomai 2.6.3 with Linux
> kernel 3.8.13 . Now, if we do not run 'watch -n .1 cat
> /proc/xeno/stat', the latency test is running just fine without

You mean /proc/xenomai/stat, right?

> significant latencies. However, the moment we run the watch command
> in parallel, things break down and the latency goes up. Is this an
> issue that other people see as well and is there a fix for it? Thanks
> for your help.

The problem is not watch, the problem is probably /proc/xenomai/stat,
which creates large latencies by holding the nucleus lock for too long.
The issue probably does not get the attention it deserves, because
/proc/xenomai/stat is something people usually use during debugging
phases, not really on a final system. And it also probably happens in
some conditions only (with a large number of Xenomai threads for
instance), because I never observed it on the systems where I run Xenomai.



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