Crossbeam is a Rust library workspace providing a comprehensive set of concurrent programming primitives. It includes multi-producer multi-consumer (MPMC) channels with a select! macro for multiplexing, work-stealing deques (Chase-Lev), lock-free queues (bounded ArrayQueue and unbounded SegQueue), epoch-based memory reclamation for safe lock-free memory management, lock-free skip lists (SkipMap/SkipSet), and utilities like cache-padded values, exponential backoff, thread parking, sharded locks, and scoped threads. The library is designed for building high-performance concurrent systems and supports no_std environments. The architecture is modular: each major component lives in its own crate (crossbeam-channel, crossbeam-deque, crossbeam-epoch, crossbeam-queue, crossbeam-skiplist, crossbeam-utils) with a root umbrella crate that re-exports them. The implementations are based on academic literature (Chase-Lev, Michael-Scott, Vyukov queues) and include extensive testing with Miri, Loom model checking, and sanitizers. The codebase demonstrates advanced Rust patterns: unsafe but carefully encapsulated atomic operations, macro_rules-based DSLs, and trait-based abstraction for selectable channels. While primarily a library, the repository also contains benchmarks and examples that serve as both documentation and performance validation. The project is actively maintained with a clear MSRV policy and regular releases. Some components, like the epoch GC and work-stealing deque, are self-contained patterns that could be extracted for use in other concurrent Rust projects.
lockfree is a header-only C++11 library providing lock-free data structures for concurrent programming. It offers both single-producer single-consumer (SPSC) and multi-producer multi-consumer (MPMC) variants of queues, ring buffers, bipartite buffers, and priority queues. The library is designed for use across a wide spectrum of systems from deeply embedded to HPC, featuring no dynamic allocation and optimized for high performance. Architecture-wise, it's organized into spsc/ and mpmc/ namespaces with each data structure having separate header and implementation files, aggregated through lockfree.hpp. The implementation uses atomic operations and clever algorithms to achieve lock-free behavior without mutexes.