Patent Number: 6,763,434

Title: Data processing system and method for resolving a conflict between requests to modify a shared cache line

Abstract: Disclosed herein are a data processing system and method of operating a data processing system that arbitrate between conflicting requests to modify data cached in a shared state and that protect ownership of the cache line granted during such arbitration until modification of the data is complete. The data processing system includes a plurality of agents coupled to an interconnect that supports pipelined transactions. While data associated with a target address are cached at a first agent among the plurality of agents in a shared state, the first agent issues a transaction on the interconnect. In response to snooping the transaction, a second agent provides a snoop response indicating that the second agent has a pending conflicting request and a coherency decision point provides a snoop response granting the first agent ownership of the data. In response to the snoop responses, the first agent is provided with a combined response representing a collective response to the transaction of all of the agents that grants the first agent ownership of the data. In response to the combined response, the first agent is permitted to modify the data.

Inventors: Arimilli; Ravi Kumar (Austin, TX), Dodson; John Steven (Pflugerville, TX), Guthrie; Guy Lynn (Austin, TX), Williams; Derek Edward (Austin, TX)

Assignee: International Business Machines Corporation

International Classification: G06F 12/08 (20060101); G06F 012/00 ()

Expiration Date: 07/13/2021