Research On Multitask Management Of Embedded Real-time Operating System Based On Forth Virtual Machine

Embedded systems have penetrated into every area of people's daily lives,faced with increasingly complex embedded application requirements,some special applications in the embedded field put forward higher requirements for embedded systems.In order to meet the needs of online maintenance and updating,repairing abnormal programs without downtime,safe and efficient embedded system,an embedded multitask operating system based on Forth virtual machine has emerged.The system adopts cooperative multitask scheduling algorithm based on Forth virtual machine with known scheduling timing and scheduling points,abstraction based on Forth virtual machine,the task context switching is simplified to save only one data stack pointer,but this scheduling algorithm can not meet the requirements of embedded applications for real-time.This thesis comes from the project of National Natural Science Foundation of China:Research on Key Technologies of Embedded Operating System Based on Forth Virtual Machine Architecture,in another sub-project of this project,the preemptive priority scheduling algorithm and time slice round-robin scheduling algorithm are implemented to improve the real-time performance of the system,the embedded multitask operating system based on Forth virtual machine is transformed into an embedded real-time operating system based on Forth virtual machine.Multitask management is the core and soul of real-time operating system,which determines the real-time performance of the operating system.In embedded real-time operating system based on Forth virtual machine,tasks are independent and asynchronous,but there are various constraints between tasks,and there may be cooperation or exclusion between them.In order to enable non-conflict,smooth and correct operation between tasks,better play the real-time nature of the system,and ensure the closedness and reproducibility of the task execution results,it is necessary to restrict the access to resources between tasks in order to prevent conflicts.Based on the embedded real-time operating system based on Forth virtual machine.this thesis studies its multitask management,analyzed the possible states and transitions between tasks under the system real-time scheduling algorithm.implemented task creation,deletion,hanging,recovery,blocking and wakeup algorithm based on Forth virtual machine.Consider the possible shared resource contention,mutual cooperation,and mutual constraints that may occur between tasks in an asynchronous environment.implemented inter-task synchronous and mutex mechanism based on Forth virtual machine,mutex is used to achieve mutually exclusive access to critical resources between tasks,and semaphores are used to achieve resource synchronization and activity synchronization between tasks.Finally,the experiment verifies the effectiveness and feasibility of the multitask management algorithm based on Forth virtual machine.