A methodology for implementing highly concurrent data objects

Abstract

A concurrent object is a data structure shared by concurrent processes. Conventional techniques for implementing concurrent objects typically rely on critical sections ; ensuring that only one process at a time can operate on the object. Nevertheless, critical sections are poorly suited for asynchronous systems: if one process is halted or delayed in a critical section, other, nonfaulty processes will be unable to progress. By contrast, a concurrent object implementation is lock free if it always guarantees that some process will complete an operation in a finite number of steps, and it is wait free if it guarantees that each process will complete an operation in a finite number of steps. This paper proposes a new methodology for constructing lock-free and wait-free implementations of concurrent objects. The object's representation and operations are written as stylized sequential programs, with no explicit synchronization. Each sequential operation is atutomatically transformed into a lock-free or wait-free operation using novel synchronization and memory management algorithms. These algorithms are presented for a multiple instruction/multiple data (MIMD) architecture in which n processes communicate by applying atomic read, write, load_linked, and store_conditional operations to a shared memory.