Access Point Event Simulator (APES) for Legacy Software Systems (LESS) Stefan Resmerita Joint work with Patricia Derler and Edward Lee February 17, 2009

APES-LESS: February 17, Contents 1.Goals and motivation 2.Approach 3.Ptolemy II components 4.Further work 5.Demos Contents

APES-LESS: February 17, Main Goals Short-term: –Simulate (on a host computer) execution of embedded software written in C for OSEK-compliant OS and given platform model –Achieve fast Software-in-the-Loop testing Medium to long term: –Enable modeling of legacy applications –Apply MBD principles to legacy software Goals and Motivation

APES-LESS: February 17, Software in the Loop Testing Plant Model Actuator models Sensor Models Simulation of original application code Simulation of modified application code + – User Input Error Goals and Motivation

APES-LESS: February 17, Classical Problem DynamicsController.c void dC_step() { … write(angle); … } … … Memory MotorController.c void mC_step() { … read(angle); … } write(angle)read(angle) dC mC time Simulation dC mC time Execution on the ECU write(angle) read(angle) preemption S-function Goals and Motivation

APES-LESS: February 17, Simulation Engine Based on Ptolemy II Fast prototyping –Discrete event simulation –Java threads Component-based design Visual modeling Portability Enables execution of legacy code under different models of computation Approach

APES-LESS: February 17, Request Response Model Structure Functionality actors OSEK actors Actor execution Actor interaction Java-C bridge Ptolemy II components

APES-LESS: February 17, Event-Based Approach Access Point Event (APE) An access point is a line of source code with an I/O access or a system call In a run of the software, an access point event occurs whenever the code of an access point starts executing Access Point Event (APE) An access point is a line of source code with an I/O access or a system call In a run of the software, an access point event occurs whenever the code of an access point starts executing void dC_step() { … angle = t1*s1; … } void mC_step() { … tmp_a = angle; … } void dC_step() { … SendMessage(m_a, angle); … } void mC_step() { … ReceiveMessage(m_a,angle); … } void appDispatcher(){ while (appRunning){ WaitEvent(appDispatcherEvent); ClearEvent(appDispatcherEvent); if(simStep%5 == 0){ ActivateTask(dC_Task); } SetEvent(mC_Task, mC_Event); simStep++; } TerminateTask(); } Approach

APES-LESS: February 17, Execution Control at Access Points Insert a callback to the simulation engine at every access point –Determine the execution time since the previous APE –Send the timestamped APE to the task scheduler –Pause the execution of the task The task scheduler generates an Access Granted Event (AGE) The execution of the task is resumed upon receiving the AGE Approach activate(T 1 ) activate(T 2 ) AGE T 2 AGE T 1 APE T 1 (  1 ) APE T 2 (  2 ) terminate(T 2 ) APE T (  1 ’) T1T1 T2T2 t 1 t 2 t 2 +  2 t 1 +  1 +  2

APES-LESS: February 17, Example MotorController.c void mC_step() { … aPCallback(12); tmp_angle = angle; … aPCallback(42); WaitEvent(evMask); … } Thread cCodeThread; void fire() { notify(); } void aPCallback(time) { requestExecTime(time); sleep(); } CTask.java 2. start 6. resume 3. callback (stop) b. change task state, reschedule 1. Trigger 4. APE a. system call  CCodeLibrary 5. AGE Approach

APES-LESS: February 17, Functionality Actor: CTask Executes a C function mapped to an OSEK task in a dedicated thread Implements two callback methods: –accessPointCallback(executionTime, minimumDelay); before every access point where no monitoring is needed –accessPointCallback(executionTime, minimumDelay, varName, value); Inserted in the C code after the line where varName is updated Parameters: –The name of a C function mapped to an OSEK task –The priority of the task Ports: –Multicast output port, used to send APEs –Multicast input port, used to receive AGEs –Regular I/O ports for global variables Ptolemy II components

APES-LESS: February 17, Multithreaded DE Simulation: Problem Ptolemy II components t1t1 t2t2 t3t3 model time real time Process ev 1 Trigger task 1 Wake up thread of C task 1 (CT1) Process ev 2 Process ev 3 CT1 callback(  t 1 ) Generate APE 1 with timestamp t 1 +  1 ev 1 ev 2 t 1 +  1 APE 1 ev 3 CT2 CT1 11

APES-LESS: February 17, Multithreaded DE Simulation: Solution Ptolemy II components t1t1 t2t2 t3t3 model time real time Process ev 1 Trigger task 1 Wake up thread of C task 1 (CT1) Ask to be re-fired at t 1 +  1 Process ev 2 Process APE 1 CT1 callback(  1,  2 ) Resume DE thread Suspend C thread ev 1 ev 2 t 1 +  1 APE 1 ev 3 CT2 CT1  1,  1 t 1 +  1 ev´ 1 Process ev´ 1 Suspend execution of DE thread Generate APE 1 Finish ev´ 1 processing

APES-LESS: February 17, OSEK Actor: TaskScheduler Maintains task status information Implements task system services –ActivateTask, TerminateTask Receives task status notifications from other OSEK actors Sends AGEs to functionality actors Fixed priority preemptive scheduling Receives APEs from CTask actors ready running waiting suspended trigger AGE preemption event/resource received wait for event resource blocked termiate task Ptolemy II components

APES-LESS: February 17, OSEK Actor: EventManager Implements event OSEK services –SendEvent –GetEvent –ClearEvent Notifies the TaskScheduler to change task status –If a task needs to wait for an event –If a waiting task receives an event Ptolemy II components

APES-LESS: February 17, Source (sensor) Actor: FormattedLineReader Reads data from an input file –At each iteration, data from one line is send to the output ports Assumes input text in tabular format –A column is a sampled signal –A line contains the values of all signals at a sample time Maps port names and types to named columns Buffered reading –All the file is processed at initialization, when all tokens are created and stored in memory Ptolemy II components

APES-LESS: February 17, Infrastructure Element: MultiCastIOPort Provides line-free connectivity between actors Output port: –Destination actors are specified at runtime in each send action –Static filter for eligible destinations given as a parameter Input: –Static filter for source actors specified as a parameter Can help in modeling service oriented applications Ptolemy II components

APES-LESS: February 17, Monitoring Task execution: Visualization of task states in time Global variables Ptolemy II components

APES-LESS: February 17, Java-C bridge Java classes –OSEKEntryPoint: Receives all system calls from C tasks and routes them to the appropriate OSEK actors –AccessPointCallbackDispatcher: Routes the callbacks from C to the appropriate functionality actors C wrapping code –APES layer –OS layer –Application layer Ptolemy II components

APES-LESS: February 17, Next Steps: The Simulator Methods –Refine source line granularity –Adapt and use existing methods for estimation of execution time Automatization tools –Code instrumentation –Generation of the APES model Visualization tools Performance evaluation Further work

APES-LESS: February 17, Application Performance Evaluation Simulation of closed-loop control applications –Bridging different simulation environments –Tool support Testing with code coverage Stability analysis/validation with regard to execution times Further work

APES-LESS: February 17, Modeling of Legacy Applications Task Model Functional Model Timing Model Modal Model Further work

APES-LESS: February 17, Demos: Active Rear Steering Control Simulink model: Demos

APES-LESS: February 17, Demo 1: Building a Basic APES model C code is generated from the Simulink model for each of the three subsystems Both controllers and the plant model are compiled in the same native library Input is read in the C part from a file CTask actors are used only for execution control No connections necessary at the Ptolemy level Demos

APES-LESS: February 17, The ARS Model for Demo 1

APES-LESS: February 17, Demo 2: APES model with plant actor in C The two controllers are compiled in the same native library Speed input is provided by a Ptolemy DE actor, and front angle input from a file at the Ptolemy level The plant is wrapped in an EmbeddedCActor Connections are needed between controllers and their environment Demos

APES-LESS: February 17, The ARS Model for Demo 2 Demos

Thank you for your attention!