In this paper, we present the PR lock, a prioritized spin lock mutual exclusion algorithm. 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 operations on the lock holder (e.g., for abort ceiling protocols). Unlike previous algorithms, 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 the best alternative prioritized spin lock.