Tasks, RM Tasks, Queues and priorities.

[John Bebbington]

Hello RTEMS users,
I am experiencing a problem with the interaction of tasks and queues and
wanted to know if I was doing anything wrong.

Here is the scenario:
=====================






Problem:

The problem is that the Task B seems to suspend and not wake although there
is a message pending in Queue B.

If a second message is sent later then the Task B resumes and processes both
messages.



My question is :

Am I causing problems by assigning a higher priority to sporadic Tasks A & B
than the periodic Rate Monotonic task?

Is it possible that because there is a RM task present that the sporadic
task B does not get resumed until a 2nd message enters the queue?

Can the "readying" of a RM task have priority over the sporadic task B if
the task B's priority is greater than that of the RM task?

I have read in the users manual for RTEMS that critical RM tasks should have
higher priority than the non-critical tasks. When "relaxing the rules a bit"
the sporadic tasks are okay as long as these sporadic tasks don't take much
time and can be treated the same as ISRs for calculating the processor
utilisation.

Any comments would be helpful

regards

John Bebbington.










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