About the rate_monotonic_manager

Gedare Bloom gedare at rtems.org
Mon Jul 13 15:12:32 UTC 2015


You must assign the priorities of tasks similarly to their periods
where smaller periods require higher priority. See
testsuites/sptests/sp20/task1.c for an example.


On Wed, Jul 1, 2015 at 4:21 PM, Kuan Hsun Chen
<kuan-hsun.chen at tu-dortmund.de> wrote:
> Hello everyone,
> Does Rate Monotonic Manager update the priorities of tasks and suspend the
> lower priority task accordingly?
> In C_user manual, I cannot find any description about the priority
> management in Chapter 10.
> Therefore, I assume RM has the scheduler to handle the priority according to
> the registered tasks periods as the common design in the most of real-time
> literature.
> After using Rate Monotonic Manager APIs, indeed, I can have the periodic
> task executions.
> Moreover, I also have tried on the semaphore to reappear the priority
> inversion case.
> However, I cannot observe the preemption scenario by using Rate Monotonic
> Manager, if all the initial priorities in rtems_task_create() are set to 1.
> Even if I set up the priorities of tasks manually, it seems to me that Rate
> Monotonic Manager doesn't really suspend the task properly.
> I have checked that the task attribute and task mode allow the preemption.
> Instead of the example_v2/triple period case (one task with RM), I cannot
> find any example including multitasking with RM scheduling.
> Do you have the same issue or any useful reference?
> Probably I misunderstand the meaning of APIs usage...
> Many thanks,
> Kuan-Hsun
> --
> M.Sc. Kuan-Hsun Chen
> TU Dortmund
> Department of Computer Science 12
> Design Automation of Embedded Systems
> Otto-Hahn-Strasse 16, Room 102
> 44227 Dortmund
> Germany
> Phone:  +49 231 755 6124
> Mail:   kuan-hsun.chen at tu-dortmund.de
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