Pre-Run-Time Scheduling of Asynchronous and Periodic Processes With Offsets, Release Times, Deadlines, Precedence and Exclusion Relations

Utilizing non-zero offsets when scheduling real-time periodic processes significantly increases the chances of satisfying all the timing constraints in a real-time system. In this paper, a method that enables the utilization of non-zero offsets in the pre-run-time scheduling of asynchronous and periodic processes with release times, deadlines, precedence and exclusion relations on either a uniprocessor or on a multiprocessor in real-time embedded systems is presented. This paper also identifies for the first time, the set of general conditions that a periodic process newp_i with release time r_newpi, computation time c_newpi, deadline d_newpi, period prd_newpi, permitted range of offset o_newpi, must satisfy, in order to satisfy the timing constraints of any given asynchronous process a_i with computation time c_ai, deadline d_ai, minimum time between two consecutive requests min_ai, and earliest time that asynchronous process a_i can make a request for execution l_ai. A method based on these general conditions for converting asynchronous processes with earliest request times into new periodic processes with offset constraints is also introduced.