# PR_CWait

Wait for a notification that a monitor's state has changed.

## Syntax

```{code}
#include <prcmon.h>

PRStatus PR_CWait(
   void *address,
   PRIntervalTime timeout);
```

### Parameters

The function has the following parameters:

`address`

: The address of the protected object--the same address previously
  passed to {ref}`PR_CEnterMonitor`.

`timeout`

: The amount of time (in {ref}`PRIntervalTime` units) that the thread is
  willing to wait for an explicit notification before being
  rescheduled. If you specify `PR_INTERVAL_NO_TIMEOUT`, the function
  returns if and only if the object is notified.

### Returns

The function returns one of the following values:

> - `PR_SUCCESS` indicates either that the monitored object has been
>   notified or that the interval specified in the timeout parameter has
>   been exceeded.
> - `PR_FAILURE` indicates either that the monitor could not be located
>   in the cache or that the monitor was located and the calling thread
>   was not the thread that held the monitor's mutex.

## Description

Using the value specified in the `address` parameter to find a monitor
in the monitor cache, {ref}`PR_CWait` waits for a notification that the
monitor's state has changed. While the thread is waiting, it exits the
monitor (just as if it had called {ref}`PR_CExitMonitor` as many times as
it had called {ref}`PR_CEnterMonitor`). When the wait has finished, the
thread regains control of the monitor's lock with the same entry count
as before the wait began.

The thread waiting on the monitor resumes execution when the monitor is
notified (assuming the thread is the next in line to receive the notify)
or when the interval specified in the `timeout` parameter has been
exceeded. When the thread resumes execution, it is the caller's
responsibility to test the state of the monitored data to determine the
appropriate action.