Modification to the behaviour of xQueueSend() and xQueueReceive() in the case that a blocked task times out (bug fix).

git-svn-id: https://freertos.svn.sourceforge.net/svnroot/freertos/trunk@60 1d2547de-c912-0410-9cb9-b8ca96c0e9e2

1 files changed, 72 insertions, 38 deletions

diff --git a/Source/queue.c b/Source/queue.c
index d4da4a75..8eea22b6 100644
--- a/Source/queue.c
+++ b/Source/queue.c
@@ -240,7 +240,7 @@ size_t xQueueSizeInBytes;
 

 signed portBASE_TYPE xQueueSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait )

 {

-signed portBASE_TYPE xReturn;

+signed portBASE_TYPE xReturn = pdFAIL;

 xTimeOutType xTimeOut;

 

 	/* Make sure other tasks do not access the queue. */

@@ -337,6 +337,20 @@ xTimeOutType xTimeOut;
 					{

 						taskYIELD();

 					}

+

+					/* We want to check to see if the queue is still full

+					before leaving the critical section.  This is to prevent

+					this task placing an item into the queue due to an

+					interrupt making space on the queue between critical

+					sections (when there might be a higher priority task

+					blocked on the queue that cannot run yet because the

+					scheduler gets suspended). */

+					if( pxQueue->uxMessagesWaiting == pxQueue->uxLength )

+					{

+						/* We unblocked but there is no space in the queue,

+						we probably timed out. */

+						xReturn = errQUEUE_FULL;

+					}

 	

 					/* Before leaving the critical section we have to ensure

 					exclusive access again. */

@@ -347,29 +361,39 @@ xTimeOutType xTimeOut;
 			}

 		}

 			

-		/* When we are here it is possible that we unblocked as space became

-		available on the queue.  It is also possible that an ISR posted to the

-		queue since we left the critical section, so it may be that again there

-		is no space.  This would only happen if a task and ISR post onto the

-		same queue. */

-		taskENTER_CRITICAL();

+		/* If xReturn is errQUEUE_FULL then we unblocked when the queue

+		was still full.  Don't check it again now as it is possible that

+		an interrupt has removed an item from the queue since we left the

+		critical section and we don't want to write to the queue in case

+		there is a task of higher priority blocked waiting for space to

+		be available on the queue.  If this is the case the higher priority

+		task will execute when the scheduler is unsupended. */

+		if( xReturn != errQUEUE_FULL )

 		{

-			if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )

+			/* When we are here it is possible that we unblocked as space became

+			available on the queue.  It is also possible that an ISR posted to the

+			queue since we left the critical section, so it may be that again there

+			is no space.  This would only happen if a task and ISR post onto the

+			same queue. */

+			taskENTER_CRITICAL();

 			{

-				/* There is room in the queue, copy the data into the queue. */			

-				prvCopyQueueData( pxQueue, pvItemToQueue );		

-				xReturn = pdPASS;

-	

-				/* Update the TxLock count so prvUnlockQueue knows to check for

-				tasks waiting for data to become available in the queue. */

-				++( pxQueue->xTxLock );

-			}

-			else

-			{

-				xReturn = errQUEUE_FULL;

+				if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )

+				{

+					/* There is room in the queue, copy the data into the queue. */			

+					prvCopyQueueData( pxQueue, pvItemToQueue );		

+					xReturn = pdPASS;

+		

+					/* Update the TxLock count so prvUnlockQueue knows to check for

+					tasks waiting for data to become available in the queue. */

+					++( pxQueue->xTxLock );

+				}

+				else

+				{

+					xReturn = errQUEUE_FULL;

+				}

 			}

+			taskEXIT_CRITICAL();

 		}

-		taskEXIT_CRITICAL();

 

 		if( xReturn == errQUEUE_FULL )

 		{

@@ -435,7 +459,7 @@ signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItem
 

 signed portBASE_TYPE xQueueReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait )

 {

-signed portBASE_TYPE xReturn;

+signed portBASE_TYPE xReturn = pdFAIL;

 xTimeOutType xTimeOut;

 

 	/* This function is very similar to xQueueSend().  See comments within

@@ -467,6 +491,13 @@ xTimeOutType xTimeOut;
 					{

 						taskYIELD();

 					}

+

+					if( pxQueue->uxMessagesWaiting == ( unsigned portBASE_TYPE ) 0 )

+					{

+						/* We unblocked but the queue is empty.  We probably

+						timed out. */

+						xReturn = errQUEUE_EMPTY;

+					}

 	

 					vTaskSuspendAll();

 					prvLockQueue( pxQueue );

@@ -475,29 +506,32 @@ xTimeOutType xTimeOut;
 			}

 		}

 	

-		taskENTER_CRITICAL();

+		if( xReturn != errQUEUE_EMPTY )

 		{

-			if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )

+			taskENTER_CRITICAL();

 			{

-				pxQueue->pcReadFrom += pxQueue->uxItemSize;

-				if( pxQueue->pcReadFrom >= pxQueue->pcTail )

+				if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )

 				{

-					pxQueue->pcReadFrom = pxQueue->pcHead;

+					pxQueue->pcReadFrom += pxQueue->uxItemSize;

+					if( pxQueue->pcReadFrom >= pxQueue->pcTail )

+					{

+						pxQueue->pcReadFrom = pxQueue->pcHead;

+					}

+					--( pxQueue->uxMessagesWaiting );

+					memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );

+		

+					/* Increment the lock count so prvUnlockQueue knows to check for

+					tasks waiting for space to become available on the queue. */

+					++( pxQueue->xRxLock );

+					xReturn = pdPASS;

+				}

+				else

+				{

+					xReturn = errQUEUE_EMPTY;

 				}

-				--( pxQueue->uxMessagesWaiting );

-				memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );

-	

-				/* Increment the lock count so prvUnlockQueue knows to check for

-				tasks waiting for space to become available on the queue. */

-				++( pxQueue->xRxLock );

-				xReturn = pdPASS;

-			}

-			else

-			{

-				xReturn = errQUEUE_EMPTY;

 			}

+			taskEXIT_CRITICAL();

 		}

-		taskEXIT_CRITICAL();

 

 		if( xReturn == errQUEUE_EMPTY )

 		{