Overview

This section focuses on Hardware Support for Synchronization, particularly for kernel developers and high-level synchronization tools. The lecture covers mechanisms like Memory Barriers, Atomic Hardware Instructions, and the implementation of Mutex Locks using atomic instructions. It also discusses alternative approaches such as Transactional Memory and OpenMP.

Topics Covered:

1. Memory Barriers or Fences
2. Atomic Hardware Instructions (Test-and-Set, Compare-and-Swap)
3. Mutex Implementation with Atomic Instructions
4. Atomic Variables
5. Alternative Synchronization Approaches (Transactional Memory, OpenMP)

Hardware Support for Synchronization

Modern computer architectures provide hardware-based synchronization tools to help manage concurrent access to shared resources. These are often essential in kernel development and the implementation of higher-level synchronization mechanisms.

1. Memory Barriers (or Memory Fences)

Memory Barriers prevent the CPU from reordering instructions, which is a common optimization strategy but can cause data inconsistency in multi-threaded environments.

Key Concept:

• Memory Barrier Instruction: Ensures that all memory operations (loads and stores) are completed before the next memory operation is executed.

Example:

x = 100;
memory_barrier();
flag = true;

Here, the memory_barrier() ensures that the assignment x = 100 is completed before setting flag = true.

Atomic Hardware Instructions