Simple, Fast and Widely Applicable Concurrent Memory Reclamation via Neutralization

Reclaiming memory in non-blocking dynamic data structures in unmanaged languages like C/C++ presents a unique challenge due to the risk of use-after-free errors caused by concurrent accesses. Existing safe memory reclamation (SMR) algorithms fall short of satisfying five key properties: high performance, bounded garbage, usability, consistency, and applicability. In particular, bounded garbage and high performance are quite difficult to achieve simultaneously. In this paper, we address this limitation by proposing a new, provably correct technique called neutralization based reclamation (NBR) that neutralizes threads using POSIX signals to provide the synchronization required for safe memory reclamation. NBR uses atomic reads and writes and achieves bounded garbage and high performance without imposing significant overhead on concurrent readers and writers. An extensive experimental evaluation serves to demonstrate the efficiency of our technique across various data structures, reclamation algorithms, and workloads. A detailed survey of popular concurrent data structures suggests NBR is applicable to a wide range of data structures, many of which could not be used with prior SMR algorithms that guarantee bounded garbage.