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Locked Line Indication Disclosure Number: IPCOM000040150D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-01

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Emma, PG Knight, JW Pomerene, JH Rechtschaffen, RN Sparacio, FJ [+details]


This invention reduces the number of cache-to-cache transfers required for a class of data that is likely to be shared and changed in many-way multiprocessor (MP) systems. In many-way MP configurations, careful programming is required to assure consistent results. In particular, systems usually provide some synchronizing instructions that allow the appropriate coordination of work among the processors in a complex. In the IBM System 370/XA, the instructions "compare and swap" (CS), and "compare double and swap" (CDS) provide atomic update (read followed by write) of storage locations and serialization. In addition, specific assists for MVS such as "obtain cms lock" (E506) and "release cms lock" (E507) also perform these atomic update and serialization functions.