System for negotiating access to a shared resource by arbitration logic in a shared resource negotiator

Abstract

A resource negotiation technique and apparatus which streamlines arbitration for access to a shared resource by centralizing arbitration for groups of shared resources such as control registers into an access register. An accessing agent first writes a request to an appropriate bit of a resource negotiation register (RNR), and then reads back a grant status. If the request for access to the shared resource is not successful in the first attempt, the requesting processor may continuously read the grant status until it is successful. Alternatively, the resource negotiation register may cause an interrupt in the requesting processor upon grant of access to the shared resource. A logic level indicating that access is denied generally indicates that another processor in the multi-processor system is currently granted access to the corresponding shared resource. Once the processor requesting permission for writing to the shared resource has been granted permission, that winning processor is expected to complete its access to the shared resource, and then indicate back to the shared resource negotiator that access is no longer required, e.g., by clearing the corresponding request bit.