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CHAPTER 4. AVP ENGINE THREAD StateFilterParams VehicleState_TF VehicleVel_VF 64 VehicleState_TF Vehicle_Vel_VF VehicleState_TF VEhicleVel_VFRaw StateFilter Figure 4.9: Data Flow Diagram for CStateFilter thereby giving access to the external thread's data. However, if the external thread is modifying its data at every iteration, the data must be protected from reading by external threads at improper times, and from writing by more than one thread at once. Semaphores can be used to accomplish this. A client thread calls a server thread method that blocks until the external thread triggers a certain event (such as the end of an iteration). At this point, the client thread calls server thread methods that get or set certain variables. To enforce mutual exclusion, these access methods lock the variables against use by the server thread until the client has get/set the data. Using this model, CAVPEngineThread is the server thread, while all other threads in the application are client threads that pend on every iteration through the sample loop. In this fashion, other threads can get/set data at every iteration (synchronously), although it is not guaranteed that the other threads will nish their tasks in time to receive data from the very next iteration (i.e. reliable communication
