This chapter describes the NSPR API for creation and manipulation of a
mutex of type {ref}`PRLock`.

- [Lock Type](#Lock_Type)
- [Lock Functions](#Lock_Functions)

In NSPR, a mutex of type {ref}`PRLock` controls locking, and associated
condition variables communicate changes in state among threads. When a
programmer associates a mutex with an arbitrary collection of data, the
mutex provides a protective monitor around the data.

In general, a monitor is a conceptual entity composed of a mutex, one or
more condition variables, and the monitored data. Monitors in this
generic sense should not be confused with monitors used in Java
programming. In addition to {ref}`PRLock`, NSPR provides another mutex
type, {ref}`PRMonitor`, which is reentrant and can have only one associated
condition variable. {ref}`PRMonitor` is intended for use with Java and
reflects the Java approach to thread synchronization.

For an introduction to NSPR thread synchronization, including locks and
condition variables, see [Introduction to
NSPR](Introduction_to_NSPR).

For reference information on NSPR condition variables, see [Condition
Variables](Condition_Variables).

(lock-type)=

# Lock Type

> - {ref}`PRLock`

(lock-functions)=

# Lock Functions

> - {ref}`PR_NewLock` creates a new lock object.
> - {ref}`PR_DestroyLock` destroys a specified lock object.
> - {ref}`PR_Lock` locks a specified lock object.
> - {ref}`PR_Unlock` unlocks a specified lock object.