Browse Prior Art Database

Shared Storage Locking Facility

IP.com Disclosure Number: IPCOM000075622D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Bidwell, AW: AUTHOR [+2]

Abstract

Associative Lock Store array LS exerts hardware control over access to shared storage SS. LS is accessed by: a) Lock and Unlock processor instruction ("Program Entry Point" Locking); b) Microcoded points of execution of processor instructions affecting shared storage integrity; e.g. instructions to read from SS, modify and rewrite to SS ("Single Copy" Locking); or c) Master over-ride control ("Lock-Unlock Special").

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Shared Storage Locking Facility

Associative Lock Store array LS exerts hardware control over access to shared storage SS. LS is accessed by:
a) Lock and Unlock processor instruction ("Program Entry Point"

Locking);
b) Microcoded points of execution of processor instructions

affecting shared storage integrity; e.g. instructions to

read from SS, modify and rewrite to SS ("Single Copy"

Locking); or
c) Master over-ride control ("Lock-Unlock Special").

Processor storage access requests are channeled simultaneously to SS and the Lock Compare Register-LCR of LS. If lock action is in effect for the requesting user, an associative match comparison between address representations in LCR and LS (representing address ranges of SS) causes disallowance of access to SS and the request of the waiting user is placed in a queue. If Lock Action is not in effect for the requesting user and the latter's Lock Bit L = 1, an "empty" location in LS is selected, if available, by examining status bits associated with the storage spaces of LS. The address and user identity (ID) information in LCR is transferred to an available location in LS, and the access to SS is allowed to continue without hindrance. When the locking user no longer requires exclusive control, it enters an unlock type of request (Lock Bit L = 0) resetting vacant status in the chosen LS location; usually while completing a final access to SS.

As previously suggested, the foregoing entries to LCR are developed either from...