Nonblocking k-compare-single-swap

The current literature o .ers two extremes of nonblocking software synchronization support for concurrent data structure design:intricate designs of specific structures based on single-location operations such as compare-and-swap (CAS), and general-purpose multilocation transactional memory implementations. While the former are sometimes efficient, they are invariably hard to extend and generalize. The latter are .exible and general, but costly. This paper aims at a middle ground:reasonably efficient multilocation operations that are general enough to reduce the design difficulties of algorithms based on CAS alone. We present an obstruction-free implementation of an atomic k-location-compare single-swap (KCSS)operation. KCSS allows for simple nonblocking manipulation of linked data structures by overcoming the key algorithmic difficulty in their design: making sure that while a pointer is being manipulated, neighboring parts of the data structure remain unchanged. Our algorithm is efficient in the common uncontended case: A successful k location KCSS operation requires only two CAS operations, two stores, and 2 k noncached loads when there is no contention. We therefore believe our results lend themselves to efficient and flexible nonblocking manipulation of list-based data structures in today's architectures.