Brief Announcement: Dynamic-Sized Lock-Free Data Structures∗

Almost all previous dynamic-sized lock-free data structures are either unable to free memory to the memory allocator when it is no longer required, or require special system or hardware support. In the only exception we are aware of, a single thread failure can prevent further memory reclamation (see full paper for reference). We recently posed a problem — the Repeat Offenders Problem (ROP) — and presented one solution and its correctness proof [3]. Solutions to this problem can be used to design dynamic-sized lockfree implementations of shared data structures that overcome all of the problems mentioned above. In the full paper [2], we present two results. The first is a general methodology, based on any ROP solution, for transforming dynamic-sized lock-free data structure implementations that depend on garbage collection (GC) for memory management into equivalent ones that do not require GC. This methodology is based on reference counts, and therefore entails space and time overhead required to maintain reference counts. (This methodology improves on the one presented in [1] by removing the dependence on double compare-and-swap (DCAS).) ROP can also be applied directly to achieve more efficient (both in space and time) implementations of dynamic-sized lock-free data structures. In the full paper, we give an example to demonstrate this approach. Specifically, we show how to modify the widely-used lock-free FIFO queue implementation of Michael and Scott so that it can free memory to the memory allocator when it is no longer required. We also present the results of performance experiments