rt_task_set_priority does not increase priority of other task

Philippe Gerum rpm at xenomai.org
Thu Sep 17 15:26:08 CEST 2020

Harco Kuppens via Xenomai <xenomai at xenomai.org> writes:

> On 17/09/2020 13:51, Jan Kiszka wrote:
>> On 16.09.20 20:12, Harco Kuppens via Xenomai wrote:
>>> Hi,
>>> I found a problem with rt_task_set_priority function which does not
>>> increase priority of another task.
>>> However it works fine if you increase the priority of another task.
>>> Below is an en example program and its output, and we run this program
>>> on xenomai 3.08.
>>> The problem appears if we run the program on our xenomai image for the
>>> raspberry pi 3,
>>> and is also appears in our virtual box image.
>>> Both images can be found at :
>>>    * http://www.cs.ru.nl/lab/xenomai/raspberrypi.html
>>>    * http://www.cs.ru.nl/lab/xenomai/virtualbox.html
>>> The easiest way is to run the virtualbox image.
>>> The final question I have: is there an wrong usage of xenomai API in the
>>> example program,
>>> or is this a bug in xenomai?
>> Something is inconsistent here. Did you also check via
>> /proc/xenomai/sched/threads if that view is consistent with the result
>> of inquire?
> yes, and they also said the priority was not increased.
> You can repeat the experiment in the virtualbox image.
> Note: we use virtualbox so that students can do some exercise at
> home. The exerecises on hardware they must do on raspberry pi 3 in the
> lab.
> Normally a rt os on virtualbox would make no sense.
>> I vaguely recall issues of the latter but I also do not
>> recall any fix to 3.1, not to speak of anything that was not backported.
>> BTW, tried 3.1 as well?
> no, because I don't have it  installed. Could someone who has it
> running try this example on it, and check whether this   problem also
> occurs there?
> Anyway it was pretty difficult to get xenomai 3.08 with gpio support
> to work on the raspberry pi 3.
> Took me a long time, and I rather stick with 3.0.8.
> We use raspberry pi's in a course on the radboud university where
> students get exercises in learning to use xenomai.
> Switching to new version would mean lot of work for me.

Ok, I'll have a look asap in the coming days and follow up on this.


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