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1.3.5 Causality Identifiers

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Each ORPC call carries with it, within the ORPCTHIS structure, a GUID known as the causality identifier (CID). The CID connects a chain of ORPC calls that are causally related. Object exporters can use the CID to provide synchronization around ORPC calls. They can also use the CID to prevent deadlocks within ORPC calls.

If a new ORPC call is made from a client that is already executing an ORPC call, the new call is required to be assigned the same CID as the existing call. If a new ORPC call is made from a client that is not already executing an ORPC call, then a new CID is required to be allocated for it. For more information, see section 3.2.4.2.

An object exporter needs to use the CID of an incoming ORPC call to detect whether it belongs to the same causality chain as that of a currently executing outgoing ORPC. If the incoming and outgoing CIDs are not the same, the object exporter might not process the incoming ORPC until the outgoing ORPC completes. However, if they are the same, the object exporter needs to process the incoming ORPC; otherwise, a deadlock occurs. For details, see section 3.1.1.5.4.