Concurrency & Multithreading

Master C++ concurrency — threads, mutexes, condition variables, atomics, futures/promises, and lock-free programming.

55 min•By Priygop Team•Last updated: Feb 2026

C++ Threading Model

std::thread: Launch threads — std::thread t(function, args). Join (t.join()) or detach (t.detach()). std::jthread (C++20) auto-joins and supports cancellation
std::mutex: Mutual exclusion — only one thread can hold the lock. Always use std::lock_guard or std::unique_lock (RAII) instead of manual lock/unlock
std::condition_variable: Wait for conditions — consumer waits until producer signals data is ready. Always use with a predicate to handle spurious wakeups
std::atomic<T>: Lock-free operations on primitive types — atomic<int> counter; counter.fetch_add(1). No mutex needed for simple operations
std::future & std::promise: Pass results between threads — future.get() blocks until promise.set_value(). async(func) launches a task and returns a future
Thread Pool: Pre-create worker threads, dispatch tasks from a queue — avoid thread creation overhead per task. Use std::async or custom implementation

Minimize Shared State: Design systems where threads own their data — message passing instead of shared memory eliminates races
Lock Ordering: Always acquire multiple locks in the same order — prevents deadlocks. Use std::scoped_lock(mutex1, mutex2) for automatic deadlock avoidance
Reader-Writer Locks: std::shared_mutex — multiple readers (shared_lock) OR one writer (unique_lock). Ideal when reads >> writes
Lock-Free Data Structures: Use atomics and CAS (compare-and-swap) — concurrent queues, stacks without locks. Hard to implement correctly but highest performance
Data Races are UB: Two threads accessing the same memory without synchronization where at least one writes = undefined behavior. Use ThreadSanitizer (-fsanitize=thread) to detect