Patent ID: 9146872
Filing Date: 2015-09-29
Classification: G06F

Abstract:
1. A method of data processing, comprising: a coherent attached processor, proxy (CAPP) of a primary coherent system, receiving a memory access request from an attached processor (AP) external to the primary coherent system, wherein the CAPP includes a CAPP directory of contents of a cache memory in the AP that holds copies of memory blocks belonging to a coherent address space of the primary coherent system, and wherein the receiving the CAPP receiving, from the AP, an expected coherence state of a target address of the memory access request with respect to the cache memory of the AP; in response to receiving the memory access request at the CAPP, the CAPP determining whether the CAPP is servicing a conflicting request snooped on a system fabric of the primary coherent system that conflicts with the memory access request; in response to determining that the CAPP is servicing a conflicting snooped request, allocating a master machine of the CAPP in a Parked state to service the memory access request; based on the master being in the Parked state, the CAPP preventing servicing by the CAPP of a further conflicting request snooped on a system fabric of the primary coherent system that conflicts with the target address; and in response to completion of service of the conflicting request, the master machine transitioning out of the Parked state and issuing on the system fabric a memory access request corresponding to that received from the AP.