Increases the specified semaphore object's count by a specified amount.

BOOLEAN ReleaseSemaphore(
    HANDLE hSemaphore,
    LONG lReleaseCount,
    LPLONG lpPreviousCount
);

BOOLEAN RtReleaseSemaphore(
    HANDLE hSemaphore,
    LONG lReleaseCount,
    LPLONG lpPreviousCount
);

Parameters

hSemaphore

Handle to the semaphore object. CreateSemaphore returns this handle.

lReleaseCount

The amount by which the semaphore object's current count increases. The value must be greater than zero. If the specified amount causes the semaphore count to exceed the maximum count specified when the semaphore was created, the count does not change and the function returns FALSE.

lpPreviousCount

Long pointer to a 32-bit variable to receive the semaphore's previous count. If the previous count is not required, this parameter can be NULL.

Remarks

The state of a semaphore object is signaled when its count exceeds zero and nonsignaled when its count equals zero. The process that calls CreateSemaphore specifies the semaphore's initial count. Each time a waiting thread is released because of the semaphore's signaled state, the semaphore's count decreases by one.

Typically, an application uses a semaphore to limit the number of threads using a resource. Before a thread uses the resource, it specifies the semaphore handle in a call to a wait function. When the wait function returns, it decreases the semaphore's count by one. When the thread finishes using the resource, it calls ReleaseSemaphore to increase the semaphore's count by one.

Another use of ReleaseSemaphore is during an application's initialization. The application can create a semaphore with an initial count of zero. This sets the semaphore's state to nonsignaled and blocks all threads from accessing the protected resource. When the application finishes its initialization, it uses ReleaseSemaphore to increase the count to its maximum value to permit normal access to the protected resource.

RtReleaseSemaphore can also be used from a Windows application to release a unit to an iwin32 semaphore.

Return Values

Non-zero

Success.

0 (zero)

Failure. For extended error information, see GetLastError

Requirements

Notes

• In the iwin32 API, ReleaseSemaphore and RtReleaseSemaphore are synonyms.
• This function operates in the real-time portion of your application.
• The iwin32x API also includes an RtReleaseSemaphore function that operates in the Windows portion of your application.

See Also

CreateSemaphore, iwin32 API, iwin32 Overview