The software transactional memory system described herein may implement a revocable mechanism for managing read ownership in a shared memory. In this system, write ownership may be revoked by readers or writers at any time other than when a writer transaction is in a commit state, wherein its write ownership is irrevocable. An ownership record associated with one or more locations in the shared memory may include an indication of whether the memory locations are owned for writing, and an identifier of the latest writer. A read ownership array may record data indicating which, if any, threads currently own the memory locations for reading. The system may provide an efficient read-validation operation, in which a full read-set validation is avoided unless a change in a global read-write conflict counter value indicates a potential conflict. The system may support a wide range of contention management policies, and may provide implicit privatization.