Pragmatic Primitives for Non-blocking Data Structures
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We define a new set of primitive operations that greatly simplify the implementation of non-blocking data structures in asynchronous shared-memory systems. The new operations operate on a set of Data-records, each of which contains multiple fields. The operations are generalizations of the well-known load-link (LL) and store-conditional (SC) operations called LLX and SCX. The LLX operation takes a snapshot of one Data-record. An SCX operation by a process p succeeds only if no Data-record in a specified set has been changed since p last performed an LLX on it. If successful, the SCX atomically updates one specific field of a Data-record in the set and prevents any future changes to some specified subset of those Data-records. We provide a provably correct implementation of these new primitives from single-word compare-and-swap. As a simple example, we show how to implement a non-blocking multiset data structure in a straightforward way using LLX and SCX.
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