Dataflow Resource Managers and Their Synthesis from Open Path Expressions

The control of concurrent access to shared resources is an important feature of both centralized and distributed operating systems. In conventional systems, exclusive access is the rule while concurrent access is the exception. Dataflow computer systems, along with an applicative style of programming, provide an execution environment in which this philosophy is reversed. In these latter systems, it is necessary to reexamine the manner in which synchronization of access to shared resources is specified and implemented. A basic design for a dataflow resource manager is reviewed, illustrating the clear separation between access mechanism and scheduling policy. The semantics of the access mechanism is based solely on the principle of data dependency. Specifications are presented for a general scheduler to further constrain or order accesses to the resource. Using ``open path expressions'' as a very high-level specification language for synchronization, it is shown how to automatically synthesize a scheduler as a distributed network of communicating modules.