Uniprocessor Lock Implementation

The content discusses the implementation of a uniprocessor lock through different classes and methods. It covers various lock implementations for multi-core processors as well. The slides illustrate the locking mechanisms, thread handling, and atomic operations involved in maintaining mutual exclusion. Different versions of lock classes with thread queues, atomic variables, and spinlocks are explored.

• Lock Implementation
• Uniprocessor
• Multi-Core
• Thread Handling
• Atomic Operations

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1. Uniprocessor Lock Implementation class Lock { Lock() {} int locked = 0; ThreadQueue q; }; void Lock::unlock() { intrDisable(); if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } intrEnable(); } void Lock::lock() { intrDisable(); if (!locked) { locked = 1; } else { q.add(currentThread); blockThread(); } intrEnable(); } CS 111 Lecture Notes: Lock Implementation Slide 1

2. Uniprocessor Lock Implementation?? class Lock { Lock() {} int locked = 0; ThreadQueue q; }; void Lock::unlock() { intrDisable(); if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } intrEnable(); } void Lock::lock() { intrDisable(); if (!locked) { locked = 1; intrEnable(); } else { q.add(currentThread); intrEnable(); blockThread(); } } CS 111 Lecture Notes: Lock Implementation Slide 2

3. Locks for Multi-Core, v1 class Lock { Lock() {} std::atomic<int> locked(0); }; void Lock::unlock() { locked = 0; } void Lock::lock() { while (locked.exchange(1)) { /* Do nothing */ } } CS 111 Lecture Notes: Lock Implementation Slide 3

4. Locks for Multi-Core, v2 class Lock { Lock() {} std::atomic<int> locked(0); ThreadQueue q; }; void Lock::unlock() { if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } } void Lock::lock() { if (locked.exchange(1)) { q.add(currentThread); blockThread(); } } CS 111 Lecture Notes: Lock Implementation Slide 4

5. Locks for Multi-Core, v3 class Lock { Lock() {} int locked = 0; ThreadQueue q; std::atomic<int> spinlock; }; void Lock::unlock() { while (spinlock.exchange(1)) { /* Do nothing */ } if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } spinlock = 0; } void Lock::lock() { while (spinlock.exchange(1)) { /* Do nothing */ } if (!locked) { locked = 1; spinlock = 0; } else { q.add(currentThread); spinlock = 0; blockThread(); } } CS 111 Lecture Notes: Lock Implementation Slide 5

6. Locks for Multi-Core, v4 class Lock { Lock() {} int locked = 0; ThreadQueue q; std::atomic<int> spinlock; }; void Lock::unlock() { while (spinlock.exchange(1)) { /* Do nothing */ } if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } spinlock = 0; } void Lock::lock() { while (spinlock.exchange(1)) { /* Do nothing */ } if (!locked) { locked = 1; spinlock = 0; } else { q.add(currentThread); currentThread->state = BLOCKED; spinlock = 0; reschedule(); } } CS 111 Lecture Notes: Lock Implementation Slide 6

7. Locks for Multi-Core, v5 class Lock { Lock() {} int locked = 0; ThreadQueue q; std::atomic<int> spinlock; }; void Lock::unlock() { intrDisable(); while (spinlock.exchange(1)) { /* Do nothing */ } if (q.empty() { locked = 0; } else { unblockThread(q.remove()); } spinlock = 0; intrEnable(); } void Lock::lock() { intrDisable(); while (spinlock.exchange(1)) { /* Do nothing */ } if (!locked) { locked = 1; spinlock = 0; } else { q.add(currentThread); currentThread->state = BLOCKED; spinlock = 0; reschedule(); } intrEnable(); } CS 111 Lecture Notes: Lock Implementation Slide 7