Linux Real-time Embedded Operating System

Linux is widely used in constructing real-time operating system because of the advantages of open-source code,powerful function,modular design,support multi-hardware platforms,function interface with international industry standards. However, because Linux is an all-purpose operation system,lack of real-time ability,which serious limits its development in the embedded field. Linux 2.4 kernel occupies a large part of embedded Linux market because of its smart,stable and reliable characteristics. Therefore,improving the preempt-ability of Linux 2.4 kernel to enhance real time ability is important.Based on Linux 2.4.36 kernel source codes,this thesis analyses the principle structure and the factors that impact Linux real-time performance, then proposed a solution for improving real-time ability, the main idea of the solution is through modifying standard Linux kernel to make it to have kernel-preempt capability, then system can scheduling process even in the kernel state, consequently response to higher priority process as soon as possible. In order to avoid synchronization problems that bring by kernel-preempt, this solution designed kernel-preempt forbid section to protect system to be preempted safety in kernel state, the main approach is to modify spin lock,interrupt processing module,Scheduling module and other kernel mechanism.This thesis also designs and realizes a solution for testing the real-time ability of Linux system, and used it to test the latency of the standard kernel and preempt kernel. Test results show that the real-time ability is improved after modifies.Finally,this thesis summarizes the solution for improving real-time kernel and point out the further tasks of our study,such as detailing the critical section and testing in CPU system.