Mutex

CORE DEFINITION

A mutex (short for mutual exclusion) is a mechanism used in multithreaded programming to prevent two threads from simultaneously reading and writing to the same shared resource (such as a global variable). This is achieved by dividing the code into critical sections. A critical section is a block of code that accesses a shared resource; it is not a mechanism or algorithm. A program, process, or thread can have multiple critical sections, but they may not necessarily use a mutex. Examples of resources that require this mechanism include flags, queues, counters, interrupt handlers, and other resources used to pass data or synchronize state among multiple concurrently running code paths. Maintaining synchronization, consistency, and integrity of these resources is difficult because a thread can be paused (suspended) or resumed (awakened) at any moment. For example, code (A) is modifying a piece of data step by step. At that moment, another thread (B) is awakened for some reason.