Chapter 7. Thread Synchronization

When threads require access to shared resources, it is coordinated using thread synchronization. The three thread synchronization mechanisms used on Linux are mutexes, barriers, and condvars.

7.1. Mutexes

The word mutex is derived from the term mutual exclusion. A mutex is a POSIX threads construct, and is created using the pthread_create_mutex library call. A mutex serializes access to each section of code, so that only one thread of an application is running the code at any one time.
Similar to a mutex is a futex, or Fast User muTEX, which is an internal mechanism used to implement mutexes. Futexes use shared conventions between the kernel and the C library. This allows an uncontended mutex to be locked or freed without a context switch to kernel space.