A Scalable Lock-Free Universal Construction with Best Effort Transactional Hardware

The imminent arrival of best-effort transactional hardware has spurred new interest in the construction of nonblocking data structures, such as those that require atomic updates to k words of memory (for some small value of k). Since transactional memory itself (TM) was originally proposed as a universal construction for crafting scalable lock-free data structures, we explore the possibility of using this emerging transactional hardware to implement a scalable, unbounded transactional memory that is simultaneously nonblocking and compatible with strong language-level semantics. Our results show that it is possible to use this new hardware to build nonblocking TM systems that perform as well as their blocking counterparts. We also find that while the construction of a lock-free TM is possible, correctness arguments are complicated by the many caveats and corner cases that are built into current transactional hardware proposals.