diff --git a/FreeRTOS/Source/include/queue.h b/FreeRTOS/Source/include/queue.h index 50110f9c3..0f12794b7 100644 --- a/FreeRTOS/Source/include/queue.h +++ b/FreeRTOS/Source/include/queue.h @@ -420,19 +420,20 @@ typedef void * xQueueSetMemberHandle; *
portBASE_TYPE xQueueOverwrite( xQueueHandle xQueue, - const void * pvItemToQueue, + const void * pvItemToQueue ); ** - * Only for use with queues that can hold a single item - so the queue is either + * Only for use with queues that have a length of one - so the queue is either * empty or full. * * Post an item on a queue. If the queue is already full then overwrite the * value held in the queue. The item is queued by copy, not by reference. + * * This function must not be called from an interrupt service routine. * See xQueueOverwriteFromISR () for an alternative which may be used in an ISR. * - * @param xQueue The handle to the queue on which the item is to be posted. + * @param xQueue The handle of the queue to which the data is being sent. * * @param pvItemToQueue A pointer to the item that is to be placed on the * queue. The size of the items the queue will hold was defined when the @@ -440,9 +441,9 @@ typedef void * xQueueSetMemberHandle; * into the queue storage area. * * @return xQueueOverwrite() is a macro that calls xQueueGenericSend(), and - * therefore has the same return values as xQueueSendToFront(). However, as - * xQueueOverwrite() will write to the queue even when the queue is full pdPASS - * will be returned in all cases (errQUEUE_FULL will never be returned). + * therefore has the same return values as xQueueSendToFront(). However, pdPASS + * is the only value that can be returned because xQueueOverwrite() will write + * to the queue even when the queue is already full. * * Example usage:
@@ -470,7 +471,7 @@ typedef void * xQueueSetMemberHandle;
if( ulValReceived != 10 )
{
- // Error!
+ // Error unless the item was removed by a different task.
}
// The queue is still full. Use xQueueOverwrite() to overwrite the
@@ -1086,7 +1087,7 @@ void vQueueDelete( xQueueHandle xQueue ) PRIVILEGED_FUNCTION;
);
*
*
- * A version of xQueueOverwrite() that can be used from an interrupt service
+ * A version of xQueueOverwrite() that can be used in an interrupt service
* routine (ISR).
*
* Only for use with queues that can hold a single item - so the queue is either
@@ -1105,14 +1106,14 @@ void vQueueDelete( xQueueHandle xQueue ) PRIVILEGED_FUNCTION;
* @param pxHigherPriorityTaskWoken xQueueOverwriteFromISR() will set
* *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task
* to unblock, and the unblocked task has a priority higher than the currently
- * running task. If xQueueSendFromISR() sets this value to pdTRUE then
+ * running task. If xQueueOverwriteFromISR() sets this value to pdTRUE then
* a context switch should be requested before the interrupt is exited.
*
- * @return xQueueOverwriteFromISR() is a macro that calls
- * xQueueGenericSendFromISR(), and therefore has the same return values as
- * xQueueSendToFrontFromISR(). However, as xQueueOverwriteFromISR() will write
- * to the queue even when the queue is full pdPASS will be returned in all cases
- * (errQUEUE_FULL will never be returned).
+ * @return xQueueOverwriteFromISR() is a macro that calls
+ * xQueueGenericSendFromISR(), and therefore has the same return values as
+ * xQueueSendToFrontFromISR(). However, pdPASS is the only value that can be
+ * returned because xQueueOverwriteFromISR() will write to the queue even when
+ * the queue is already full.
*
* Example usage:
@@ -1122,7 +1123,7 @@ void vQueueDelete( xQueueHandle xQueue ) PRIVILEGED_FUNCTION;
void vFunction( void *pvParameters )
{
// Create a queue to hold one unsigned long value. It is strongly
- // recommended *not* to use xQueueOverwrite() on queues that can
+ // recommended *not* to use xQueueOverwriteFromISR() on queues that can
// contain more than one value, and doing so will trigger an assertion
// if configASSERT() is defined.
xQueue = xQueueCreate( 1, sizeof( unsigned long ) );
@@ -1142,11 +1143,20 @@ unsigned long ulVarToSend, ulValReceived;
// pass because the value held in the queue will be overwritten with the
// new value.
ulVarToSend = 100;
- xQueueOverwrite( xQueue, &ulVarToSend, &xHigherPriorityTaskWoken );
+ xQueueOverwriteFromISR( xQueue, &ulVarToSend, &xHigherPriorityTaskWoken );
// Reading from the queue will now return 100.
// ...
+
+ if( xHigherPrioritytaskWoken == pdTRUE )
+ {
+ // Writing to the queue caused a task to unblock and the unblocked task
+ // has a priority higher than or equal to the priority of the currently
+ // executing task (the task this interrupt interrupted). Perform a context
+ // switch so this interrupt returns directly to the unblocked task.
+ portYIELD_FROM_ISR(); // or portEND_SWITCHING_ISR() depending on the port.
+ }
}
* \defgroup xQueueOverwriteFromISR xQueueOverwriteFromISR