Generalized signals: an interrupt-based communication system for hypercubes

This paper describes a communication system designed to support highly asynchronous application or system software on a distributed-memory multicomputer such as a hypercube. The system is called generalized signals because it is based on the signal facility in System V UNIX, with enhancements to allow signals to carry data. Any processor can send a signal to any other processor at any time. When a signal arrives, the receiving processor traps to a user-specified subroutine; when this subroutine is finished the interrupted code is resumed. Signal interrupts happen in a controlled manner, thereby simplifying the programmer's task. There is a facility for protection of critical sections in user programs. The generalized signals system has been implemented on the NCUBE hypercube. This implementation is based on a modified version of NCUBE's VERTEX message-passing system. Generalized signals can coexist with VERTEX messages and the enhancements to VERTEX are transparent to ordinary programs.