Method and apparatus for a compare and swap instruction
US4584640A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 27, 1984 |
| Grant date | Apr 22, 1986 |
| Priority date | — |
| Expiry date | Jun 27, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F9/30021
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
In a data processing system having linked lists it is useful to be able to add and delete items from such lists while maintaining the integrity of the linked nature of such lists. A new compare and swap instruction provides for effectively simultaneously swapping 2 values which is useful for safely adding and deleting items from linked lists. Prior to the instruction the status of the two value are read at the locations to be swapped. During the instruction these locations are checked again to ensure that no change has occurred at these locations before the instruction performs the swap of the two new values. The instruction then performs the proposed 2 value swap but only if no change has occurred at these two locations where the swap is to be performed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.