Access Point Event Simulator (APES) for Legacy Software Systems (LESS)

Stefan Resmerita

Joint work with Patricia Derler and Edward LeeFebruary 17, 2009

February 17, 2009 2APES-LESS:

Contents

1. Goals and motivation

2. Approach

3. Ptolemy II components

4. Further work

5. Demos

Contents

February 17, 2009 3APES-LESS:

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

February 17, 2009 4APES-LESS:

Software in the Loop Testing

Plant Model

Actuator modelsSensor Models

Simulation of original application code

Simulation of modified application code

+

–

User Input

Error

Goals and Motivation

February 17, 2009 5APES-LESS:

Classical Problem

DynamicsController.cvoid dC_step() {

…write(angle);…

}

…

0023456 12

0023457 0

0023459 6

0023460 23

0023461 0

0023463 0

…

MemoryMotorController.cvoid mC_step() {

…read(angle);…

}

write(angle) read(angle)

dCmC

time

Simulation

dCmC

time

Execution on the ECU

write(angle)read(angle)

preemption

S-function

Goals and Motivation

February 17, 2009 6APES-LESS:

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

February 17, 2009 7APES-LESS:

Request

Response

Model Structure

• Functionality actors• OSEK actors• Actor execution• Actor interaction• Java-C bridge

Ptolemy II components

February 17, 2009 8APES-LESS:

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

February 17, 2009 9APES-LESS:

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(T1) activate(T2) AGET2

AGET1

APET1(1) APET

2(2) terminate(T2)

APET(1’)

T1

T2

t1 t2 t2 + 2 t1 + 1 + 2

February 17, 2009 10APES-LESS:

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. T

rigg

er

4. A

PE

a. s

yste

m c

all

CCodeLibrary

5. A

GE

Approach

February 17, 2009 11APES-LESS:

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

February 17, 2009 12APES-LESS:

Multithreaded DE Simulation: Problem

Ptolemy II components

t1t2 t3 model time

real timeProcess ev1

Trigger task 1Wake up threadof C task 1 (CT1)

Process ev2Process ev3

CT1 callback(t1)Generate APE1 withtimestamp t1 + 1

ev1 ev2

t1 + 1

APE1 ev3

CT2

CT1 1

February 17, 2009 13APES-LESS:

Multithreaded DE Simulation: Solution

Ptolemy II components

t1t2 t3 model time

real timeProcess ev1

Trigger task 1Wake up threadof C task 1 (CT1)Ask to be re-fired at t1 + 1

Process ev2ProcessAPE1

CT1 callback(1, 2)Resume DE threadSuspend C thread

ev1 ev2

t1 + 1

APE1 ev3

CT2

CT1 1, 1

t1 + 1

ev´1

Process ev´1

Suspend executionof DE thread

Generate APE1

Finish ev´1

processing

February 17, 2009 14APES-LESS:

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

AG

E

pre

em

ptio

n

even

t/re

sour

cere

ceiv

ed

wait for event

resource blocked

term

iate

tas

k

Ptolemy II components

February 17, 2009 15APES-LESS:

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

February 17, 2009 16APES-LESS:

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

February 17, 2009 17APES-LESS:

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

February 17, 2009 18APES-LESS:

Monitoring

• Task execution: Visualization of task states in time

• Global variables

Ptolemy II components

February 17, 2009 19APES-LESS:

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

February 17, 2009 20APES-LESS:

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

February 17, 2009 21APES-LESS:

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

February 17, 2009 22APES-LESS:

Modeling of Legacy Applications

• Task Model

• Functional Model

• Timing Model

• Modal Model

Further work

February 17, 2009 23APES-LESS:

Demos: Active Rear Steering Control

• Simulink model:

Demos

February 17, 2009 24APES-LESS:

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

February 17, 2009 25APES-LESS:

The ARS Model for Demo 1

February 17, 2009 26APES-LESS:

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

February 17, 2009 27APES-LESS:

The ARS Model for Demo 2

Demos

Thank you for your attention!