xSemaphoreGive
[信号量]

xSemaphoreGive( SemaphoreHandle_t xSemaphore );

用于释放信号量的宏。该信号量此前必须 通过调用 xSemaphoreCreateBinary()、xSemaphoreCreateMutex() 或 xSemaphoreCreateCounting() 创建。

不得在 ISR 中使用此宏。请参阅 xSemaphoreGiveFromISR ()，了解可以从 ISR 中使用的替代方案。

此宏不得用于由 xSemaphoreCreateRecursiveMutex() 创建的信号量。

参数：

xSemaphore

要释放的信号量的句柄。这是创建信号量时返回的句柄。

返回：

如果信号量释放成功，则返回 pdTRUE；如果发生错误，则返回 pdFALSE。信号量的实现基于队列。发布消息时，如果队列上没有空间，那么可能会发生错误，这表明最初未能正确获取信号量。

 SemaphoreHandle_t xSemaphore = NULL;
 void vATask( void * pvParameters )
 {
    // Create the semaphore to guard a shared resource.  As we are using
    // the semaphore for mutual exclusion we create a mutex semaphore
    // rather than a binary semaphore.
    xSemaphore = xSemaphoreCreateMutex();

    if( xSemaphore != NULL )
    {
        if( xSemaphoreGive( xSemaphore ) != pdTRUE )
        {
            // We would expect this call to fail because we cannot give
            // a semaphore without first "taking" it!
        }
        // Obtain the semaphore - don't block if the semaphore is not
        // immediately available.
        if( xSemaphoreTake( xSemaphore, ( TickType_t ) 0 ) )
        {
            // We now have the semaphore and can access the shared resource.
            // ...
            // We have finished accessing the shared resource so can free the
            // semaphore.
            if( xSemaphoreGive( xSemaphore ) != pdTRUE )
            {
                // We would not expect this call to fail because we must have
                // obtained the semaphore to get here.
            }
        }
    }
 }