Inter- and intra-processor synchronizations in multiprocessor real-time kernel

In multiprocessor systems the worst case execution time of a task that exclusively accesses a shared resource is unavoidably prolonged as the number of contending processors is increased. In case of function distributed multiprocessors, because many of the tasks can be processed without synchronizing or communicating with other processors, it is advantageous that the worst case behavior of such tasks are determined independently of the activities of other processors and of the number of processors in the system. We propose two methods to realize multiprocessor real time kernels satisfying this property. The first method is an implementation technique in which the precedence in acquiring an interprocessor lock is given to the host processor of the lock. The second method is to classify tasks into local tasks and private tasks. Private tasks have improved scalability and responsiveness, though they cannot synchronize or communicate with other processors. The effectiveness of our proposals is demonstrated through performance evaluations