C2-4-Putchala

Synchron - ITS
An Interactive Tutoring System to Teach Process Synchronization
and Shared Memory Concepts in an Operating Systems Course
Manoj Kumar Putchala
Graduate Research Assistant
Wright State University
Dayton, Ohio - USA

What : OS Course Work
 Core Course in Computer Science Curricula across worldwide institutions
 Complicated coursework, and the internal processes and mechanisms are often difficult
for students to grasp, particularly those that still struggle with programming
High level abstractions of structures and algorithms are taught in class followed by
homework or project assignments
 What many students need is a way to connect the low-level details of an operating
system’s implementation with the high-level abstractions provided in the class, all while
being accessible to people who are still improving newly-acquired programming skills.

What : Synchronization Concepts
Process synchronization: when two or more processes share memory, they should access it in an
orderly fashion to avoid race conditions and deadlocks.
 Producer-Consumer Problem
 Process Synchronization using Mutex
 Critical Section Problem
 Monitor solution for Producer-Consumer Problem
 Dining Philosopher Problem

What : Tool Introduction
 Three step process :
1) Demonstrate the concepts and algorithms at high level
2) Self-Validate the understanding levels of concepts through an inquiry based system
3) Integrate the high-level models with low-level information collected from a running
operating system
 Engages Critical Thinking
 Multi-purpose – Simulator and Tutor
 Monitoring and Control
 Visual and Interactive Graphics

Why : Past Systems
 Operating systems run in supervisor mode which makes it more difficult to use the standard
debugging methods students are used to.
Instructional Operating Systems :
 Geek OS – “bare-hardware” approach but contains a substantial amount of source code (4,202
lines for Geek OS and 14,886 lines of MINIX)
 Nachos-OS, ICS-OS, Pintos and RCOS and Simple-OS – have poor visualization graphics
 Dex-OS – Written in FASM assembly code and C, covers only memory management concepts
Tutoring Systems:
 Proc_OS and Alg_OS – Provide only visualization of theoretical concepts but lack practical task
training

Why : Mission Need
 Must be easy to use, easy to understand, and accessible for students who have limited
knowledge of systems-level programming in C or assembly language,
 Must present theoretical concepts, data structures, and algorithms involved with synchronization
and shared memory, similar to the box-and-line diagrams found in Operating Systems textbooks,
 Must allow a student to interact with the tool to explore those concepts, data structures, and
algorithms work,
 Must present realistic source code examples that can help students connect theory to
implementation details, and
 Must collect, integrate, and visualize data from a running operating system so students can see
the implementation details in motion.

How: Approach
UC1. Select log in type (guest user or
registered user).
UC2. Create user account (if registered
user).
UC3. Select a concept from concept
list.
UC4. Choose a mode (Simulator,
Manual, or Self-check).
UC5. Estimate and validate self-check
results.
UC6. Logout.

How: Implementation UI-1
 Implemented using JAVA – JSwing.
 The home page lists the concepts to be
taught
 A user account is required to access the
system, so the first time a user access it, he
or she creates a new user account and logs
into the application with valid credentials.
 An administrator account is used for
teachers to evaluate students’ performance.

 Producer-Consumer Problem: Two CPU
threads, the one that produces data and the
other that consumes it
 Both share a data variable (in this case a
counter), which may cause inconsistency or
errors due to improper signaling or
synchronization.
 Synchron-ITS implements multithreading
techniques using POSIX threads in Java to
demonstrate this problem.

 Critical Section – program code that
contains crucial operations
 No two processes are allowed to be in
their critical sections at the same time
 Synchron- ITS shows five
different solutions for this problem,
each with its own disadvantage,
followed by an improved solution.

 Mutex – Binary Semaphores with
values 0 and 1
 Context Switch Mechanism
 Initial value of Mutex is 1
 Process gets blocked when the mutex
value is less than 0
 Process gets unblocked when values
turns to 1
 Busy Waiting Problem is an issue
here

 Monitor: An Abstract Data Type
where
multiple process defined in the
monitor are executed at one time
 Monitors resolve timing errors
caused by Semaphores
 Use of wait () and signal ()
operations on conditional variables ‘x’
and ‘y’

Dining Philosophers Problem:
 N-Philosophers with N-Chopsticks at a
circular table
 Each philosopher requires two chop sticks
to have rice from the bowl (processes
requiring resources)
 Possible States – Thinking, Eating
 Synchronization is achieved by using
shared semaphores along with primitive
operations wait () and signal ()

How: Modes of Operation - Autonomous
Three Modes of Operation :
a) Autonomous
b) Real-Time
c) Self-Validation
Autonomous:
 Algorithms execute with no interruption until it has completed
 Default Parameters are either taken from the database or hard-coded

How: Modes of Operation – Real Time
 The system will draw data from a running
Linux system so users inspect the behavior of
the operating system.
 Synchron-ITS is written in the Java
programming language, and modules for
accessing data from the operating system are
written as callable C programs in Linux.
 Synchron-ITS accesses them using inter-
process communication (IPC) through method
calls to the Java Native Interface (JNI).

How: Modes of Operation – Self Validation
 Program steps into a crucial step in the
algorithm and prompts the user to guess the
values that will result upon completion of
that step.
 If the student’s estimated output is
incorrect, the system presents a message
containing the actual correct values and an
explanation as to possible misunderstandings
that might have caused the error.
 Errors are captured and corrective actions
are recommended

How: Programming Assignments
The tool provides a set of small and focused programming assignments to implement concurrency in C
and Java. The list of concurrency assignments are:
 Implement a synchronization primitive to block multiple process that are depending on an event to get
triggered;
 Implement a mutex mechanism for multiple processes by a user-space daemon;
 Implement a monitor solution for the dining philosophers problem; and
 Select and implement an appropriate concurrency primitive which is efficient and correct for a various
synchronization problems.

How: Test Cases
 Black Box Testing
 UI Testing
 Start Pause Resume Terminate buttons
 Integration Testing
 Regression Testing
 Stress Testing

How: Technology Acceptance Model
 Selection of participants,
 Testing procedure
 Questionnaire
 Perceived usefulness
 Intention
 Attitude toward its use
 Subjective norm
 Perceived ease of use

Where : Present & Future
Present:
 Version 1 is developed
 User Experiments are yet to be done on Spring Students
 5 programming assignments
 Kernel Programming Approach
Future: Version 2
 3D visualizations – using Java 3D and Unity 3D
 Integration to Mobile Platform
 Experimenting with users (students and researchers)

Where : Summary
Anticipated Benefits
 Education Resource for Academic Community
 Reduce the difficulties for both the transmission of the concepts and for better understanding
 Reverse Engineering Tool
 OS Simulator
 Helps the students or researchers to develop a Operating System from scratch
 Programming Benefits

Questions & Collaborations?
Manoj Kumar Putchala, (937) 782-8653
putchala.3@wright.edu
Primary Research Work : Internet of Things (IoT) Security using Machine
Learning
- Thank you

C2-4-Putchala

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