rt_task_set_priority does not increase priority of other task

Harco Kuppens h.kuppens at cs.ru.nl
Thu Sep 17 14:01:20 CEST 2020

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.

> Jan

More information about the Xenomai mailing list