Partial ordering of synchronization events for distributed debugging in tightly-coupled multiprocessor systems

Abstract

In this paper, a partial ordering of synchronization events for the debugging of distributed programs in tightly-coupled multiprocessor systems is defined. Techniques for the debugging of parallel programs require timestamping of events. The physical clocks of different processors are in general not suitable for time stamping events, because these clocks are not synchronized. Synchronization of the physical clocks of all processors in a multiprocessor system requires additional hardware mechanisms. In an alternative approach, a partial ordering of events can be derived using logical clocks for timestamping events with virtual time. The concept of virtual time has been used successfully to derive clock conditions in distributed systems, in which message-passing is the only form of interaction. In this paper, clock conditions are derived for tightly-coupled synchronization primitives in multiprocessor systems. Finally the concept is successfully used in the implementation of a distributed debugger in the EMPS multiprocessor system.