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Mechanism for Queue Maintenance of Single Server Shared Queues in a Strict Priority Environment

IP.com Disclosure Number: IPCOM000076972D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Elliott, TM: AUTHOR [+2]

Abstract

This is a programming mechanism which maintains a single server queue, shared among several users whose relative dispatching priorities are constant. The mechanism uses the concept of queue preemption to achieve a short disablement time. It also uses the IBM System/370 Insert Characters Under Mask (ICM) instruction, dependent upon the response code of a zero mask equivalent to loading a zero constant, and the ability to modify and then execute the modified instruction.

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Mechanism for Queue Maintenance of Single Server Shared Queues in a Strict Priority Environment

This is a programming mechanism which maintains a single server queue, shared among several users whose relative dispatching priorities are constant. The mechanism uses the concept of queue preemption to achieve a short disablement time. It also uses the IBM System/370 Insert Characters Under Mask (ICM) instruction, dependent upon the response code of a zero mask equivalent to loading a zero constant, and the ability to modify and then execute the modified instruction.

There are six essential elements in the mechanism. 1) The Header Element contains a chain pointer for the queue composed of a new and an old address, an enqueue switch to detect conflicts among the users of enqueue, and a special DEQUE instruction. 2) The DEQUE Instruction is executed by the DEQUE element to detect an empty queue or a queue contention between the DEQUE element and some ENQ element. 3) The Queue Element contains a chain pointer and the enqueued data. The chain pointer must have the same format as the chain pointer of the Header Element. 4) The ENQ Mechanism is an algorithm which achieves the enqueue of an element (by means of the ENCHAIN mechanism) and resolves any queue contention that exists between the ENQ mechanism and the DEQ mechanism. 5) The DEQ Mechanism is an algorithm used by a queue server to remove elements from the queue. It executes the DEQUE instruction of the Header Elemen...