New algorithms for asynchronous communication

Concurrent processes are said to communicate asynchronously when there is no mutual timing interference resulting from their communication operations. This property can be achieved by mechanisms which use multiple shared memory locations (slots) to transfer data, and where access to these slots is co-ordinated by small shared control variables. Algorithms are known which allow a writing process to communicate asynchronously with a reading process through a four-slot mechanism with no mutual timing constraints. The paper gives new algorithms for a four-slot mechanism, and shows how these may be applied in a design. The new algorithms have an access-control strategy which is complementary to that used by the previously known algorithms.