PintOS - Project 1 (Alarm Clock)

👀 Overview

This project extends the functionality of the thread system in PintOS, with a focus on synchronization and implementing a non-busy wait version of timer_sleep()

📝 Implementation Details

The goal of this project is to reimplement the timer_sleep() function in devices/timer.c to avoid busy waiting. This function suspends the calling thread until a specified number of timer ticks have elapsed.

Function to Implement

• void timer_sleep (int64_t ticks);
  • Suspends the calling thread until at least ticks timer ticks have elapsed.
  • Threads do not need to wake up exactly after ticks ticks unless the system is idle.

📂 Modified Files:

• timer.c
  • Implemented timer_sleep()
  • Added wake_up_thread(ticks); in timer_interrupt()
• thread.h
  • Added int64_t wake_up; to the struct thread
  • Declared typedef struct thread Thread;
  • Added void thread_sleep(int64_t ticks);
  • Added void wake_up_thread(int64_t ticks);
• thread.c
  • Initialized static struct list blocked_list;
  • Initialized list_init(&blocked_list); in void thread_init(void)
  • Implemented void thread_sleep(int64_t ticks);
  • Implemented void wake_up_thread(int64_t ticks);

🛠️ Code Modifications:

• /*Start*/: Indicates the start of modifications
• /*End*/: Indicates the end of modifications
• Original code is commented using //

🛠️ Build Instructions

1. Navigate to the directory:

cd pintos/src/threads

2. Execute the command:

make   

⚙️ Running PintOS

Ensure PintOS is compiled before ruuning:

1. Navigate to the directory:

cd build

2. Execute the command:

pintos

3. Execute the command:

pintos -v -k -T 60 --qemu -- -q run alarm-single

🧪 Test Cases

Using the command make check checks all the tests of PintOS, but your program should only pass these tests:

• alarm-single
• alarm-multiple
• alarm-simultaneous
• alarm-zero
• alarm-negative