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Task Dependency Analysis for Embedded ProgramsPresented by Bhaskar Roy14CS60R25

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 1Under the Guidance ofProf. Dr. Rajib Mall1Topics to be discussed: Introduction

Ordinary Programs

Task dependency in Embedded programs

Identification of task dependencies

Application 30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 2Introduction:Embedded System: A microcontroller-based control system which processes a fixed set of programmed instructions to control electromechanical equipment which may be part of an even larger system.

Embedded programs are programs that are embedded in a system to perform a dedicated function.

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 3Components of embedded system hardware:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 4

Types of Embedded system:Small Scale Embedded Systems: 8 bit or 16 bit processorCalculator can be the simplest example

Medium Scale Embedded Systems:16 bit or 32 bit processorWashing Machine , Microwave Oven

Sophisticated Embedded Systems:32 bit or 64 bit processorFlight Landing Gear Systems, Car Braking Systems, Military Applications, Robots.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 5

Applications:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 6

Characteristics of Embedded systems:Single Functioned

Tightly ConstraintManufacturing cost Performance, Size, Power

Real time and reactive Car breaking system Flights landing gear control

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Characteristics of Embedded systems:Complex algorithmDigital Camera

User interfaceATM

Multi RateDigital Camera

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Challenges in Embedded system design30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 9

Meeting DeadlinesOrdinary Programs30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 10Programs for general purpose ComputerPrograms consist of sequence of instructions, written to perform a specified task with a computer.

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 11Dependencies in Ordinary programs :Data dependency

Control dependency

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 12Dependency Analysis in Ordinary programs :Performed through Dependence GraphProgram Dependence Graph (PDG)Dependencies within one procedureIntraproceduralSystem Dependence Graph (SDG)Dependencies within entire systemInterprocedural

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 13Program Dependence Graph (PDG)

Control Flow Graph (CFG)PDG is union of:Control Dependence Graph

Flow Dependence Graph30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 1430-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 15Control Flow GraphEntersum = 0i = 1while(i < 11)printf(sum)printf(i)sum = sum + ii = i + iTFint main() {int sum = 0;int i = 1;while (i < 11) {sum = sum + i;i = i + 1;}printf(%d\n,sum);printf(%d\n,i);}30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 16q is reached from pif condition p istrue (T), not otherwise.Control Dependence GraphControl dependencepqTpqFSimilar for false (F).Entersum = 0i = 1while(i < 11)printf(sum)printf(i)sum = sum + ii = i + iTTTTTTTTint main() {int sum = 0;int i = 1;while (i < 11) {sum = sum + i;i = i + 1;}printf(%d\n,sum);printf(%d\n,i);}30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 17Flow Dependence Graphint main() {int sum = 0;int i = 1;while (i < 11) {sum = sum + i;i = i + 1;}printf(%d\n,sum);printf(%d\n,i);}Entersum = 0printf(sum)printf(i)sum = sum + ii = i + iFlow dependencepqValue of variableassigned at p may beused at q.i = 1while(i < 11)30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 18Program Dependence Graph (PDG)int main() {int sum = 0;int i = 1;while (i < 11) {sum = sum + i;i = i + 1;}printf(%d\n,sum);printf(%d\n,i);}Entersum = 0i = 1while(i < 11)printf(sum)printf(i)sum = sum + ii = i + iTTTTTControl dependenceFlow dependenceTTTSystem Dependence Graph (SDG)

combine PDGs to model inter-procedural dependences.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 1930-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 20System Dependence Graph (SDG)Enter mainCall pCall pEnter p30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 21A Program With Auxiliary Procedure int main() {int sum = 0;int i = 1;while (i < 11) { sum = add(sum,i); i = add(i,1);}printf(%d\n,sum);printf(%d\n,i);}int add(int x, int y) {return x + y;}30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 22SDG for the Sum ProgramEnter mainsum = 0i = 1while(i < 11)printf(sum)printf(i)Call addCall addxin = sumyin = isum = xoutxin = iyin= 1i = xoutEnter addx = xiny = yinx = x + yxout = xDependency in Embedded ProgramsIn addition the dependencies present in ordinary programs there is another type of dependency present called task dependency .

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 23Some Assumptions:Tasks are statically created and are assigned static priority values

The tasks are periodic in nature and are scheduled using a priority-driven preemptive task scheduler

Tasks communicate using either shared memory or message passing primitives30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 24Reason behind task dependencies in Embedded programs:Task Priority

Task precedence

Inter task communicationShared MemoryMessage Passing30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 25Task execution dependencies due to priorities:A delay to the completion of higher priority task may delay a lower priority task30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 26Task execution dependencies due to priorities:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 2712pri(3)>pri(2)>pri(1)3TasksTasksExecution Order: 1, 2, 31TimeTime23Execution Order: 1, 2, 3Task execution dependencies due to precedencies:A precedence relation between two tasks arises when one task is dependent on some actions or results produced by the other task.Precedence relation defines a partial order(PO) among tasks.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 2813245Task execution dependencies due to precedencies:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 29123TimeTask Arrival368123TimeTask Arrival368DelayedDeadline MissDeadlineTask execution dependencies due to Inter task communication:Message Passing.

Shared Memory.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 30Task execution dependencies due to Message Passing:When two tasks communicate using a message passing strategy a delay to one of the task can delay to the other task.

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 31Task execution dependencies due to Message Passing:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 32Some ComputationSend MsgWaitingijTask execution dependencies due to Message Passing:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 33Some ComputationSend MsgWaitingijModificationsDeadline MissTask execution dependencies due to Shared Memory:Accessing of shared memory is synchronized through semaphore or locks.

If a task lock a synchronization variable for an unusually long time , then it will affect the execution of other tasks. 30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 34Task execution dependencies due to Shared Memory:30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 35lock semwrite varunlock semlock semread varcompute varwrite varunlock semvarijTiming dependency among tasks.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 36123Time123DeadlineDelayIDENTIFICATION OF TASK EXECUTION DEPENDENCIES30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 37Algorithm: Pseudo code for identifying execution-dependent tasks.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 38IDENTIFICATION OF TASK EXECUTION DEPENDENCIES30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 39Application30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 40APPLICATION OF TASK EXECUTION DEPENDENCE ANALYSIS :Regression Test Selection For Embedded Programs.

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 41Regression Test Selection For Embedded Programs :Regression testingis a type of softwaretestingthat seeks to uncover new software bugs, orregressions, in existing functional and non-functional areas of a system after changes have been made to them.

RTS concerns selection of a subset of valid test cases from an initial test suite that tests the affected but unmodified parts of a program.

30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 42Use of RTS:Use of an effective RTS technique can help to substantially reduce the testing costs in environments in which a program undergoes frequent modifications.

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Testing Real Time Embedded Systems30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 44Difficulty In Testing Real Time Embedded SystemsThe timing constraints and concurrency features in multitasking causes embedded systems to produce non-deterministic outputs.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 45Defining Coverage Metric For Real-Time Embedded System 30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 46Coverage Metrics In Real-Time Embedded SystemsIn addition to the metrics used in normal programs some new types of metrics are needed to cover embedded real-time dependencies present in real-time embedded systems30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 47References: [1] Swarnendu Biswas, Graduate Student Member, IEEE, Rajib Mall, Senior Member, IEEE, and Manoranjan Satpathy; Task Dependency Analysis for Regression Test Selection of Embedded Programs.

[2] SWARNENDU BISWAS and RAJIB MALL, Indian Institute of Technology Kharagpur MANORANJAN SATPATHY, GM India Science Lab; A Regression Test Selection Technique for Embedded Software.

[3] Susan Horwitz, Thomas Reps, and David Binkley;Interprocedural Slicing Using Dependence Graphs.

[4] Todd M. Austin and Gurindar S. Sohi; Dynamic Dependency Analysis of Ordinary Programs.30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 48Questions ?30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 49Thank You30-Jun-15Bhaskar Roy , 14CS60R215 , Task Dependency Analysis for Embedded Programs. 50