Relaxed separation logic: a program logic for C11 concurrency

Abstract

We introduce relaxed separation logic (RSL), the first program logic for reasoning about concurrent programs running under the C11 relaxed memory model. From a user's perspective, RSL is an extension of concurrent separation logic (CSL) with proof rules for the various kinds of C11 atomic accesses. As in CSL, individual threads are allowed to access non-atomically only the memory that they own, thus preventing data races. Ownership can, however, be transferred via certain atomic accesses. For SC-atomic accesses, we permit arbitrary ownership transfer; for acquire/release atomic accesses, we allow ownership transfer only in one direction; whereas for relaxed atomic accesses, we rule out ownership transfer completely. We illustrate RSL with a few simple examples and prove its soundness directly over the axiomatic C11 weak memory model.