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Use of Processor Masking As a Locking Technique for Multilevel Multiprocessor

IP.com Disclosure Number: IPCOM000047394D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Abraham, RL: AUTHOR [+3]

Abstract

A multilevel processor is a processor in which independent processing of tasks is possible at each of a plurality of priority levels, current processing taking place at the most significant level at which at least one pending task exists, providing that such level is not inhibited by masking. The masking out of higher levels by appropriate setting of the mask by a running task enables the current task to run uninterrupted, no lower task being able to interrupt. At the time of setting of the mask, no task can be pending at an unmasked upper level or the current task would be at that level. Such setting of the mask is permitted in at least a semi-supervisor state to enable known short sequences of code to run uninterrupted.

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Use of Processor Masking As a Locking Technique for Multilevel Multiprocessor

A multilevel processor is a processor in which independent processing of tasks is possible at each of a plurality of priority levels, current processing taking place at the most significant level at which at least one pending task exists, providing that such level is not inhibited by masking. The masking out of higher levels by appropriate setting of the mask by a running task enables the current task to run uninterrupted, no lower task being able to interrupt. At the time of setting of the mask, no task can be pending at an unmasked upper level or the current task would be at that level. Such setting of the mask is permitted in at least a semi- supervisor state to enable known short sequences of code to run uninterrupted. With two or more such processors combined into a multiprocessor system, there is only one mask which controls each processor. The mask becomes the property of one processor and a serially reusable resource. If another processor, running at the same or a lower level than the owner of the mask, if such exists, requests ownership of the mask, its processing is suspended until the current ownership of the mask is released. If no such request for ownership is made, each processor is free to process. The mask, when not owned, permits processing at all levels. The same mechanism is effective if the opposite masking protocol is observed in which the mask permits rather than i...