Advanced · Module 7 · Lesson 4 of 8

Read-Write Locks and Barrier Synchronization

Scale concurrent read workloads with pthread read-write locks, resolve reader/writer starvation policies, and synchronize parallel phases using pthread barriers.

ProAbout 16 minutes

By the end you can

Permit concurrent shared reads while enforcing exclusive writes using pthread_rwlock_t
Diagnose and prevent writer starvation using writer-preference lock attributes
Synchronize multi-threaded computation phases across threads using pthread_barrier_t
Identify the serial coordinating thread using the PTHREAD_BARRIER_SERIAL_THREAD return code

Builds on Condition Variables: pthread_cond_wait, Predicate Loops, and Spurious Wakeups.

01 · A question first

Why does replacing a standard mutex with a read-write lock sometimes make an application run slower instead of faster, while on read-heavy workloads it yields near-linear multi-core scaling? And how do parallel compute pipelines synchronize discrete step phases without spinning or joining threads?

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
Barrier Synchronization (pthread_barrier_t)
Why it is correct
What it costs
Pitfalls and variations
Where it is used