Search

Many lock-free data structures in the literature exploit techniques that are possible only because state-of-the-art 64-bit processors are still running 32-bit operating systems and applications. As software catches up to hardware, "64-bit-clean" lock-free data structures, which cannot use such techniques, are needed.We present several 64-bit-clean lock-free implementations: load-linked/store-conditional variables of arbitrary size, a FIFO queue, and a freelist. In addition to being portable to 64-bit software, our implementations also improve on previous ones in that they are space-adaptive and do not require knowledge of the number of threads that will access them.

Non-blocking data structure implementations can be useful for performance and fault-tolerance reasons. And they are far easier to use correctly in a signal- or interrupt-handler context.We describe a weaker class of "almost non-blocking" data structures, which block only if more than some number N of threads attempt to simultaneously access the same data structure. We argue that this gives much of the benefit of fully non-blocking data structures, particularly for signal or interrupt handlers.We present an almost non-blocking linked stack implementation which is efficiently implementable even on hardware providing a single word compare-and-swap operation, while potentially providing the same interface as a well-known fully non-blocking solution, which relies on a double-width compare-and-swap instruction. By making a platform-dependent choice between these, we can implement a signal-handler-safe stack or free-list abstraction that is both portable and exhibits uniformly high performance with any flavor of compare-and-swap instruction.