What the futex? A linux concurrency fundamental

Short summary

Futexes are Linux kernel primitives enabling efficient thread synchronization by sleeping when waiting for state changes and waking when conditions are met. Implemented as protected integers with FUTEX_WAIT and FUTEX_WAKE syscalls, they underpin efficient locks and conditional variables with minimal kernel context switching. This tutorial explains the mechanics and provides working C++ code for building synchronization patterns.

• •Futexes are fast userspace mutexes implemented as protected integers at the kernel level
• •FUTEX_WAIT and FUTEX_WAKE syscalls enable threads to sleep/wake without busy-waiting or constant kernel overhead
• •Tutorial walks through lock and conditional variable implementations with working C++ code examples

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