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<div class="title">xSemaphoreGive</div> </div>
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<p>semphr. h </p><pre><a class="el" href="semphr_8h.html#aae55761cabfa9bf85c8f4430f78c0953">xSemaphoreGive( SemaphoreHandle_t xSemaphore )</a></pre><p><em>Macro</em> to release a semaphore. The semaphore must have previously been created with a call to xSemaphoreCreateBinary(), xSemaphoreCreateMutex() or xSemaphoreCreateCounting(). and obtained using sSemaphoreTake().</p>
<p>This macro must not be used from an ISR. See xSemaphoreGiveFromISR () for an alternative which can be used from an ISR.</p>
<p>This macro must also not be used on semaphores created using xSemaphoreCreateRecursiveMutex().</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">xSemaphore</td><td>A handle to the semaphore being released. This is the handle returned when the semaphore was created.</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>pdTRUE if the semaphore was released. pdFALSE if an error occurred. Semaphores are implemented using queues. An error can occur if there is no space on the queue to post a message - indicating that the semaphore was not first obtained correctly.</dd></dl>
<p>Example usage: </p><pre>
SemaphoreHandle_t xSemaphore = NULL;</pre><pre>void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = vSemaphoreCreateBinary();</pre><pre> if( xSemaphore != NULL )
{
if( <a class="el" href="semphr_8h.html#aae55761cabfa9bf85c8f4430f78c0953">xSemaphoreGive( xSemaphore )</a> != pdTRUE )
{
// We would expect this call to fail because we cannot give
// a semaphore without first "taking" it!
}</pre><pre> // Obtain the semaphore - don't block if the semaphore is not
// immediately available.
if( <a class="el" href="semphr_8h.html#af116e436d2a5ae5bd72dbade2b5ea930">xSemaphoreTake( xSemaphore, ( TickType_t ) 0 )</a> )
{
// We now have the semaphore and can access the shared resource.</pre><pre> // ...</pre><pre> // We have finished accessing the shared resource so can free the
// semaphore.
if( <a class="el" href="semphr_8h.html#aae55761cabfa9bf85c8f4430f78c0953">xSemaphoreGive( xSemaphore )</a> != pdTRUE )
{
// We would not expect this call to fail because we must have
// obtained the semaphore to get here.
}
}
}
}
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