Study On Thread Technology Used In Embedded System

Thread technology is one of the most important functions of modern operating system, and it is also a useful method for programmer to develop high-performance parallel program. However, almost all the thread mechanisms used in embedded system have problems in compatibility and efficiency. These problems cause a lot of inconvenience when the embedded systems which using multithread applications apply in different platforms, and also make the multithread technology used in corresponding embedded system stay at a low level.Native POSIX Thread Library, which bases on POSIX standard, cooperated with Glibc and Linux2.6 kernel in optimizing signal mechanism, synchronization mechanism, memory management and etal. It has better performance than LinuxThreads in overall perspective. Therefor, after analysing the principles of NPTL, migrated NPTL to a specific embedded system, which using DSP BF533 as core processor and uClinux2.6 as operating system.uClinux2.6 inherits most new characteristics of Linux2.6, for example, the way kernel implement thread, improved synchronization and signal mechanism and etal. These new characteristics provide kernel level support for NPTL. By adding corresponding systemcalls in uClinux2.6, these new characteristics can be used by user level thread library.The migration of NPTL should be combined with the traits of embedded system. The thread stack structure and it's cache queue should be modified according to the real storage management mechanism of uClinux. At the same time, the function which used to get the pointer of thread structure should be rewite too. Based on the special requirement of BF533's instructions, atomic functions were implemented in NPTL by adding a device driver. Combined the atomic functions with the synchronization mechanism provided by kernel, rewrote the synchronization functions in NPTL.Tests were carried out in the embedded system. The results show that, compared to LinuxThreads, NPTL improves POSIX compatibility and efficiency of threads. So it can be seen that, along with the widely use of Linux, NPTL will play a more and more important role in embedded system.