RTEMS 4.0.0 On-Line Library

Rate Monotonic Manager Assumptions

RTEMS C User's Guide

The schedulability analysis rules for RMS were developed based on the following assumptions:

The requests for all tasks for which hard deadlines exist are periodic, with a constant interval between requests.
Each task must complete before the next request for it occurs.
The tasks are independent in that a task does not depend on the initiation or completion of requests for other tasks.
The execution time for each task without preemption or interruption is constant and does not vary.
Any non-periodic tasks in the system are special. These tasks displace periodic tasks while executing and do not have hard, critical deadlines.

Once the basic schedulability analysis is understood, some of the above assumptions can be relaxed and the side-effects accounted for.

RTEMS C User's Guide