Advanced · Module 6 · Lesson 7 of 10

Process Synchronization with POSIX Semaphores

Coordinate concurrent process execution with named and unnamed POSIX semaphores, implement cross-process mutual exclusion, and build bounded-buffer producer-consumer queues.

ProAbout 16 minutes

By the end you can

Differentiate named semaphores (sem_open) from unnamed shared-memory semaphores (sem_init with pshared)
Execute atomic decrement (sem_wait) and increment (sem_post) operations
Trace how Linux implements user-space fast-path synchronization via futexes
Implement multi-process bounded buffers with binary mutexes and counting semaphores

Builds on POSIX Shared Memory: shm_open and Mapped Regions.

01 · A question first

What happens when two processes write to the same shared memory struct simultaneously? Data corruption, torn reads, and lost updates. And why can standard pthread mutexes fail across processes without special attributes, while POSIX semaphores synchronize them seamlessly?

Make a guess before you read on.

02 · The idea

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What's inside

Start with the problem
How the idea works
The Bounded-Buffer Producer-Consumer Pattern
Why it is correct
What it costs
Pitfalls and variations
Where it is used