Efficiently distributing information used for lock management among distributed resource objects using sequence numbers

Abstract

A system for managing locks that give permission to access resources in a computer system is disclosed. The lock management system is distributed and provides deadlock protection. The lock management system is distributed in that information about which locks have been granted for a resource is stored at both a master node and at the nodes on which are located processes that desire to access to the resource. A master resource object located on the master node grants locks to shadow resource objects located on the nodes on which are located the processes that desire to access the resource. Each shadow resource object grants locks on the resource to the processes that are located on the same node as the shadow resource object. According to an aspect of the invention, the master resource object stores data indicating what is knows about a shadow resource object. The master node increments a sequence number when the master resource object changes what is knows about the shadow resource object. The master resource object transmits the sequence number in messages it sends to the shadow resource object. A shadow resource object maintains master knowledge data indicating what the master resource object knows about the shadow resource object. The sequence number is used to determine whether what the master resource object knows about the shadow resource object is current.