A Prioritized Multiprocessor Spin Lock

In this paper, we present the PR-lock, a prioritized spin-lock mutual exclusion algorithm for real time systems. The PR-lock is a contention-free spin lock, in which blocked processes spin on locally stored or cached variables. In contrast to previous work on prioritized spin locks, our algorithm maintains a pointer to the lock holder. As a result, our spin lock can support priority inheritance protocols. In addition, all work to maintain a priority queue is done while a process acquires a lock, when it is blocked anyway. Releasing a lock is a constant time operation. We present simulation results that demonstrate the prioritized acquisition of locks, and compare the performance of the PR-lock against that of an alternative prioritized spin lock.