We define a Concurrent Separation Logic with first-class locks and threads for the C language, and prove its soundness in Coq with respect to a compilable operataional semantics. We define the language Concurrent C minor, an extension of the C minor language of Leroy. C minor was designed as the highest-level intermediate language in the CompCert certified ANSI C compiler, and we add to it lock, unlock, and fork statements to make Concurrent C minor, giving it a standard Pthreads style of concurrency. We define a Concurrent Separation Logic for Concurrent C minor, which extends the original Concurrent Separation Logic of O’Hearn to handle firstclass locks and threads. We then prove the soundness of the logic with respect to the operational semantics of the language. First, we define an erased concurrent operational semantics for Concurrent C minor that is a reasonable abstraction for concurrent execution on a real machine. Second, we define

of a type-and-capability system