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# 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.