Search⌘ K
Home
Courses
Operating Systems: Virtualization, Concurrency & Persistence

Locks: The Basic Idea

Explore the fundamentals of locks and their role in concurrency control. Understand how locks function to protect critical sections, enable thread synchronization, and prevent conflicts during shared resource access. This lesson provides a clear example and explains how lock and unlock operations manage thread execution for safer programming.

We'll cover the following...

As an example, assume some critical section looks like this, the canonical update of a shared variable:

C
balance = balance + 1;

Of course, other critical sections are possible, such as adding an element to a linked list or other more complex updates to shared structures but let’s just keep to this simple example for now. To use a lock, you add some code around the critical section like this:

C
lock_t mutex; // some globally-allocated lock ’mutex’
...
lock(&mutex);
balance = balance + 1;
unlock(&mutex);

A lock is just a variable, and thus to use one, you must declare a lock variable of some kind (such as mutex above). This lock variable (or just ...