# PR_NotifyCondVar

Notifies a condition variable of a change in its associated monitored
data.

## Syntax

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

PRStatus PR_NotifyCondVar(PRCondVar *cvar);
```

### Parameter

{ref}`PR_NotifyCondVar` has one parameter:

`cvar`

: The condition variable to notify.

### Returns

The function returns one of the following values:

- If successful, `PR_SUCCESS`.
- If unsuccessful (for example, if the caller has not locked the lock
  associated with the condition variable), `PR_FAILURE`.

## Description

The calling thread must hold the lock that protects the condition, as
well as the invariants that are tightly bound to the condition.

Notification of a condition variable signals a change of state in some
monitored data. When the notification occurs, the runtime promotes a
thread that is waiting on the condition variable to a ready state. If
more than one thread is waiting, the selection of which thread gets
promoted cannot be predicted. This implies that all threads waiting on a
single condition variable must have the same semantics. If no thread is
waiting on the condition variable, the notify operation is a no-op.