Specifying and Verifying RDMA Synchronisation (Extended Version)

2026-01-21

AI Summary

Existing formal semantics for RDMA lack support for remote synchronization mechanisms, making it difficult to verify the correctness of synchronization primitives such as locks. This work proposes RDMA^{TSO}_{RMW}, the first RDMA semantic model supporting remote read-modify-write (RMW) operations, reveals its weak atomicity properties, and constructs a composable synchronization library, RDMA^{WAIT}_{RMW}. Building on this foundation, the paper designs, implements, and formally verifies three classes of remote locks tailored to different usage scenarios. Furthermore, it introduces RDMA^{SC}_{RMW}, a stronger consistency model that is compatible with the high-performance LOCO library while preserving both composability and verifiability, thereby addressing a critical theoretical gap in the formal verification of RDMA-based synchronization primitives.

Technology Category

• Multiagent Systems: Agreement, Argumentation & Negotiation
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Virtualization and resource management in Web systems and infrastructures
• Security and Privacy: Applications of cryptography
• Semantics and Knowledge: Provenance, trust, security and privacy, and ethical issues in managing semantic data

Abstract

Remote direct memory access (RDMA) allows a machine to directly read from and write to the memory of remote machine, enabling high-throughput, low-latency data transfer. Ensuring correctness of RDMA programs has only recently become possible with the formalisation of $\text{RDMA}^\text{TSO}$ semantics (describing the behaviour of RDMA networking over a TSO CPU). However, this semantics currently lacks a formalisation of remote synchronisation, meaning that the implementations of common abstractions such as locks cannot be verified. In this paper, we close this gap by presenting $\text{RDMA}^{\text{TSO}}_{\text{RMW}}$, the first semantics for remote `read-modify-write'(RMW) instructions over TSO. It turns out that remote RMW operations are weak and only ensure atomicity against other remote RMWs. We therefore build a set of composable synchronisation abstractions starting with the $\text{RDMA}^{\text{WAIT}}_{\text{RMW}}$ library. Underpinned by $\text{RDMA}^{\text{WAIT}}_{\text{RMW}}$, we then specify, implement and verify three classes of remote locks that are suitable for different scenarios. Additionally, we develop the notion of a strong RDMA model, $\text{RDMA}^{\text{SC}}_{\text{RMW}}$, which is akin to sequential consistency in shared memory architectures. Our libraries are built to be compatible with an existing set of high-performance libraries called LOCO, which ensures compositionality and verifiability.

Problem

• RDMA
• synchronization
• formal semantics
• remote locks
• read-modify-write

Innovation

• RDMA
• read-modify-write
• synchronization
• formal semantics
• remote locks