A Progressive Approach to Handling Message-Dependent Deadlock in Parallel Computer Systems

Handling deadlocks is essential for providing reliable communication paths between processing nodes in parallel computer systems. The existence of multiple message types and associated intermessage dependencies may cause message-dependent deadlocks in networks that are designed to be free of routing deadlock. Most methods currently used for dealing with messagedependent deadlocks require more system resources than are necessary and/or do not use system resources efficiently. This may have an adverse effect on system performance if resources are scarce. In this paper, we characterize the frequency of messagedependent deadlocks in multiprocessor/multicomputer systems. We also propose a handling technique for message-dependent deadlocks based on progressive deadlock recovery and evaluate its performance with other approaches. Results show that messagedependent deadlocks occur very infrequently under typical circumstances thus, rendering approaches based on avoiding them overly restrictive in the common case. The proposed technique relaxes restrictions considerably, allowing the routing of packets and the handling of message-dependent deadlocks to be much more efficient—particularly when network resources are scarce.