Method of executing perform locked operation instructions for su

Details Method of executing perform locked operation instructions for su Method of executing perform locked operation instructions for su

1997-09-05

1999-04-20

Lim, Krisna

Electrical computers and digital processing systems: memory

Storage accessing and control

Shared memory area

395392, G06F 1200

Patent

active

058954945

ABSTRACT:
Provides a processor method of executing instances of a Perform Locked Operation (PLO) instruction for enabling a recovery of the consistency of a resource unit being changed by a PLO instance when processor failure occurs anywhere during execution of the PLO instance. The method uses a PLO save area for each processor in a computer system capable of executing PLO instructions. Each PLO save area has a resource-inconsistency (RI) indicator having an RI state and a non-RI state, and stores the function code (FC) of the PLO instance. The RI state indicates that the resource is in a non-usable potentially inconsistent state, and the non-RI state indicates the resource is in the consistent state and may be used. A processor executing a PLO instance writes into its PLO save area all resource addresses where a change is to be made in the resource unit, and also writes in its PLO save area all operand values which will be used to change the resource at the associated addresses. After the processor has successfully written all of these addresses and associated operand data values into its PLO save area, the processor sets its RI indicator to the RI state, and then stores into the resource unit the data values stored in its PLO save area at the resource addresses also stored in its PLO save area, according to the FC also stored therein. After completing all changes in the resource, the processor sets its RI indicator to the non-RI (resource consistent) state. If the processor should ever fail while executing a PLO instance, it signals its failing condition to the system. Then, a RCR method is executed by any operational processor (acting as a RCR processor) to recover the consistency of the resource unit. The RCR method uses the state of the RI indicator with the failed processor's PLO save area, the FC stored therewith, and the content of the failed processor's PLO save area to restore the consistency of the resource unit.

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U.S. application No. 08/864,585, Greenspan et al., PO997053, filed May 28, 1997.
U.S. application No. 08/864,402, Greenspan et al., PO996083, filed May 28, 1997.

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