Star On Embedded Real-time The Acos Task Management Study

The correctness of the real-time system depends not only on the results of computations, but also on the time at which the results are produced. The most important characteristic of real-time application systems is that they must receive and respond to a set of external stimuli within rigid and critical time constraints referred to as deadlines, otherwise, a overload fault will probably result in a catastrophic event. ACOS is no other than a real-time operating system which provides a high performance environment for embedded military applications.This thesis expatiates the implement principle of ACOS task management. The purpose of task management is to create and allocate and schedule tasks on processor to ensure that deadlines are met. Each ACOS task is the smallest thread of execution which can compete on its own for system resources ,it may exist in one of the folio whig five states: executing, ready, blocked,dormant,non-existent .One or more tasks may be active hi the system simultaneously. Multiple tasks communicate, synchronize, and compete for system resources with each other via system calls.The scheduling of a task is based on its current state and priority. Each is dispatched to the CPU for periods of time determined by scheduling algorithm. RMS(Rate-Monntonic Scheduling Algorithm ) in ACOS is an optimal static priority algorithm for scheduling independent, preemptible, periodic tasks.These mechanisms that manage acos task define a set of directives and functions. These contents reseached in the thesis, include the creation, start, run, switch of tasks and the communications with one another. The specific operation directives of task management have been explained detailedly in the thesis, these directives are TASK_CREATC, TASK_START, TASK_SUSPEND, TASK RESUME , TASK_ DELETE and so on.To testify the correctness of the system's design ,three routines are designed in this thesis:1.CLOCK TICK TEST; 2.TASK MANAGEMENT DIRECTIVES TEST;3.CPU USAGE TEST. The first routine tests that ACOS how to support task running associated with tune using tick. The second routine tests a set of directives and system functions concerned with task management. The third routine tests that task how to occupy CPU via time slice composed of tick, indicates that CPU usage be represented by ticks spent on tasks.These routines test the implement principles and operation directives for ACOS task management, testify the correctness for ACOS task management, supplies the theory and test references for ACOS developer.