Applied Operating System: Semaphores, Mutex, and Condition Variables

Welcome and Introduction

• Welcome in the new video
• Video focus: Applied Operating System
• Thanks for your love
• Likes and comments motivate
• Upcoming playlist: Build Your Own Redis in C++

Topics Covered

• Semaphores, Mutex, Condition Variables
• Important for interviews
• Important from the perspective of CS fundamentals

Recap of the Previous Video

• Different principles of concurrency
• How to achieve mutual exclusion?
• Busy-wait techniques and CPU cycles waste

Wait and Signal Approach

• Solution to the Producer-Consumer problem
• Saving CPU cycles without while loop
• Demo by coding

Producer-Consumer Problem

• Shared data structure: Buffer
• Multiple producers and consumers
• Identification of critical section
• Possibilities of race condition and deadlock

Semaphores: Introduction

• Integer variable
• Two operations: down (wait) and up (signal)
• Down: counter decreases, thread sleeps if negative
• Up: counter increases, thread wakes if negative

Functioning of Semaphores

• Operation must be atomic
• Disabling CPU interrupts
• Use of hardware instructions

Mutex and Condition Variables

• Mutex: Binary state (lock/unlock)
• Condition variables: Threads wait on a condition
• Necessary with mutex

Implementation of Producer-Consumer Problem

• Use of semaphores
• Coding details
• Thread spawning and management
• Real-world application of semaphores, mutex, and condition variables

Code Explanation

• Implementation of class Semaphore
• Lock guard and unique lock
• Operation being atomic
• Initialization of feed slots and empty slots

Thread Management

• 20 producer and 20 consumer threads
• Behavior of the buffer
• Consistent productivity and consumption

Conclusion

• Solution to the Producer-Consumer problem
• Importance of coding
• Information on the next video

Stay Alert

• Using ChatGPT to understand code
• Code availability on GitHub
• Upcoming video: Discussing taking it to production on AWS