Transcript OSEK OS
Mar.11. 2009 OSEK/VDK Woo Dong Kyun Contents 1.OSEK OS Introduce 2.OSEK OS Processing Level 3.OSEK OS Task Concept 4.OSEK OS Task Scheduler 5.Task API 6.Priority Ceiling OSEK OS 1. Event Driven Control System 2. portability and re-usability of application software 3. Special support for automotive requirements 4. ProOSEK(3Soft), OSEKTurbo(Metrowerks) 5. OSEK/VDK Specification - OSEK OS - OSEK COM - OSEK Time OS - OSEK FTCOM - OIL OSEK OS(cont..) Task management • Activation and termination of tasks • Management of task states, task switching Synchronisation • Event control • Resource management Interrupt management • Services for interrupt processing Alarms • Relative and absolute alarms Intra processor message handling • Services for exchange of data Error treatment • Mechanisms supporting the user in case of various errors OSEK Processing Level Processing levels of the OSEK operating system OSEK defines three processing levels: • Interrupt level • Logical level for scheduler • Task level OSEK Processing Level(cont.) The following priority rules have been established: • Interrupts have precedence over tasks • The interrupt processing level consists of one or more interrupt priority levels • Assignment of interrupt service routines to interrupt priority levels is dependent on Implementation and hardware architecture • For task priorities and resource ceiling-priorities bigger numbers refer to higher priorities. • The task’s priority is statically assigned by the user OSEK Task Concept Task concept • basic tasks - Basic tasks switches to a higher-priority task OSEK Task Concept •Extended Task 1. The OSEK operating system provides a task switching mechanism 2. The OSEK operating system is responsible for saving and restoring task context in conjunction with task state transitions whenever necessary. 3. Extended Task state model OSEK Task Concept 1. Running - The CPU is assigned to the task - Task instructions execute 2. Ready - Task waits for allocation of the processor - The scheduler decides which ready task is executed next. 3. Waiting - A task cannot continue execution because it shall wait for at least one event 4. Suspended - Task is passive and can be activated OSEK Task Scheduler 1. 0~15 Priority of a Task 2. Use 16 FIFO Queue Scheduler Ready Queue OSEK Task API Task API - DeclareTask(TaskIdentifier) Parameter : TaskIdentifier DeclareTask serves as an external declaration of a task. - ActivateTask(TaskID) Parameter : TaskID The task<TaskID) is transferred from the suspended state into the ready state - TerminateTask(void) The task is transferred from the running state into the suspend state - ChainTask(TaskID) This service causes the termination of the calling task. Next The Task(TaskID) is activated. Priority Ceiling To avoid the problems of priority inversion and deadlocks OSEK use Priority Ceiling Protocol High Low OSEK Priority Ceiling Protocol Priority Ceiling Resource assignment with priority ceiling between preemptable tasks and interrupt services routines. The task T1 is running and requests a resource shared with the interrupt service routine INT1 Priority Ceiling Resource assignment with priority ceiling between interrupt services routines Reference - SNU RTOSLab http://redwood.snu.ac.kr/ -OSEK/VDX Portal http://www.osek-vdx.org/ Q&A 감사합니다