Questions about the implementation of RMS on rtems

yuanbin zhou hduffddybz at
Thu Mar 19 07:13:05 UTC 2015

I am now trying to study and implement an RM scheduler for an RTOS from
China. So what I to do first is to read the document and source code about
RMS on rtems, but I really get some troubles, can anyone give me some
explanations  on it.

1.I read the demos from the documentation(single periodic task with multi
sets of actions
(single periodic task with single set of action
so can provide the demo for multi periodic tasks with single or double
multi sets of actions?

It seems that each thread owns a rm period and the thread priority can
depend on the period time . Unfortunatelly I did not find the API to handle
the priority assignment.
2. How to use the processor utilization rule and first deadline rule to
guarantee as more as possible tasks to run since the execution time of each
tasks cannot accurately know before the task run?

3. Obey the rate monotonic scheduling algorithm, we can easily set the
priority of every periodic tasks. But in many applications, it consists
both periodic and aperiodic tasks(such as irregular interrupt which is also
essential task), so how to handle the priority setting for this situation
or just set the irregular task's priority by manual?
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