OS-1060 — Thread Synchronization in xv6-public

Implementation of thread synchronization mechanisms in a customized version of xv6-public, running inside QEMU, developed as part of the Operating Systems (CSL3030) course project.

---

Overview

This project extends the xv6-public operating system to include advanced process and thread management functionalities such as:

• Custom waitpid() system call
• User-space barrier synchronization
• Thread creation, joining, and termination
• Thread synchronization using locks and condition variables

All implementations were built and tested using QEMU, simulating an x86 machine.

---

Features

Custom waitpid() System Call

• Allows a parent process to wait for a specific child process to terminate.
• Enhances process control and management.

User-Space Barrier Synchronization

• Implements barrier synchronization to coordinate multiple threads.
• Ensures threads wait for each other at specific points in execution.

Thread Management

• Functions to create, join, and terminate threads.
• Enables concurrent execution within a single process.

Thread Synchronization

• Implements locks and condition variables for thread synchronization.
• Prevents race conditions and ensures data consistency.

---

Getting Started

Prerequisites

QEMU installed on your system.

Building and Running

Environment setup

1. Install dependencies

sudo apt-get update
sudo apt-get install -y build-essential git python3 ninja-build

2. Clone and build QEMU

git clone https://gitlab.com/qemu-project/qemu.git
cd qemu
./configure
make -j"$(nproc)"
sudo make install

If you see errors about Sphinx or missing documentation tools, install the recommended packages:

pip install "sphinx==6.2.1" "sphinx-rtd-theme==1.2.2"

Building xv6-public

Navigate to the xv6 directory for this project (replace with the required release):

cd OS-1060/xv6-public-<version>

Clean and build:

make clean
make

Running xv6 in QEMU

• With GUI:

make qemu

• Without GUI (terminal-only):

make qemu-nox

Running Test Programs

Run tests from the xv6 shell prompt ($):

Task	Executable(s)	Description
Task 1	t_waitpid	Tests the custom waitpid() syscall
Task 2	t_barrier	Tests user-space barrier synchronization
Task 3	t_threads	Tests multithreading (create, join, exit)
Task 4	t_lock, t_l_cv1, t_l_cv2	Tests lock and condition variable synchronization

---

Author

Sahil Narkhede
B.Tech, Computer Science & Engineering
Indian Institute of Technology, Jodhpur

---

References

• MIT xv6-public (GitHub)
• QEMU Official Documentation
• Operating Systems (CSL3030), IIT Jodhpur

---

This project demonstrates process management, synchronization primitives, and thread-level concurrency inside a pedagogical OS kernel (xv6).
It was built incrementally across four versions, each adding a core OS concept — from waitpid() to full thread synchronization.*