The mutex, short for mutual exclusion, is not an Oracle invention. Just like the readv and select system calls, mutexes are available to programmers. A simple Linux manual page request for mutex (man 9 mutex) will return a number of mutex-related calls.

Developed for fine-grained and high-concurrency thread control, mutexes are implemented at a very low system call level, whereas latches rely more on Oracle kernel code. Each mutex call starts with the mutex abbreviation mtx, and the call names should come as no surprise. Here is a partial list of mutex calls: initialization (mtx_init), destruction (mtx_destroy), spinning (mtx_lock_spin, mtx_unlock_spin), and sleeping (mtx_sleep).

Because mutexes are based on standard system calls, they form a base functionality on which Oracle can build to meet its specific objectives. For example, suppose Oracle wants greater control then the standard mutex spin call provides. Instead of using only the mutex spin request call, Oracle can add code to meet its objectives. This gives Oracle a tremendous amount of flexibility, and also allows Oracle to more easily integrate new facilities, like mutexes, into its existing code base.