Memory management in lock-free data structures remains a major challenge in concurrent programming. Design techniques including read-copy-update (RCU) and hazard pointers provide workable solutions, and are widely used to great effect. These techniques rely on the concept of a grace period: nodes that should be freed are not deallocated immediately, and all threads obey a protocol to ensure that the deallocating thread can detect when all possible readers have completed their use of the object. This provides an approach to safe deallocation, but only when these subtle protocols are implemented correctly. We present a static type system to ensure correct use of RCU memory management: that nodes removed from a data structure are always scheduled for subsequent deallocation, and that nodes are scheduled for deallocation at most once. As part of our soundness proof, we give an abstract semantics for RCU memory management primitives which captures the fundamental properties of RCU. Our type system allows us to give the first proofs of memory safety for RCU linked list and binary search tree implementations without requiring full verification.

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Abstract. We present the PaRV tool for runtime detection of and recovery from data races in multi-threaded C and C++ programs. PaRV uses transactional memory technology for parallelizing runtime verification and for buffering write accesses during race checking. Application threads are slowed down only due to instrumentation, but not due to the computation performed by runtime verification algorithms since the latter are run concurrently on different threads. Buffering writes allows us to recover from races and to safeguard against later ones.

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