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Replace the #define that maps the uxRecursiveCallCount to the pcReadFrom pointer with a union - although this is against the coding standard it seemed the best way of ensuring complete adherence to the C standard and allow correct builds with LLVM when the optimiser is on.

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This commit is contained in:
Richard Barry 2013-06-24 12:20:00 +00:00
parent 00136d4b51
commit cdae14a8cb
1 changed files with 48 additions and 34 deletions
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82
FreeRTOS/Source/queue.c
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@ -96,13 +96,22 @@ task.h is included from an application file. */
#define queueERRONEOUS_UNBLOCK ( -1 ) #define queueERRONEOUS_UNBLOCK ( -1 )
/* Effectively make a union out of the xQUEUE structure. */ /* When the xQUEUE structure is used to represent a base queue its pcHead and
pcTail members are used as pointers into the queue storage area. When the
xQUEUE structure is used to represent a mutex pcHead and pcTail pointers are
not necessary, and the pcHead pointer is set to NULL to indicate that the
pcTail pointer actually points to the mutex holder (if any). Map alternative
names to the pcHead and pcTail structure members to ensure the readability of
the code is maintained despite this dual use of two structure members. An
alternative implementation would be to use a union, but use of a union is
against the coding standard (although an exception to the standard has been
permitted where the dual use also significantly changes the type of the
structure member). */
#define pxMutexHolder pcTail #define pxMutexHolder pcTail
#define uxQueueType pcHead #define uxQueueType pcHead
#define uxRecursiveCallCount pcReadFrom
#define queueQUEUE_IS_MUTEX NULL #define queueQUEUE_IS_MUTEX NULL
/* Semaphores do not actually store or copy data, so have an items size of /* Semaphores do not actually store or copy data, so have an item size of
zero. */ zero. */
#define queueSEMAPHORE_QUEUE_ITEM_LENGTH ( ( unsigned portBASE_TYPE ) 0 ) #define queueSEMAPHORE_QUEUE_ITEM_LENGTH ( ( unsigned portBASE_TYPE ) 0 )
#define queueDONT_BLOCK ( ( portTickType ) 0U ) #define queueDONT_BLOCK ( ( portTickType ) 0U )
@ -119,7 +128,12 @@ typedef struct QueueDefinition
signed char *pcTail; /*< Points to the byte at the end of the queue storage area. Once more byte is allocated than necessary to store the queue items, this is used as a marker. */ signed char *pcTail; /*< Points to the byte at the end of the queue storage area. Once more byte is allocated than necessary to store the queue items, this is used as a marker. */
signed char *pcWriteTo; /*< Points to the free next place in the storage area. */ signed char *pcWriteTo; /*< Points to the free next place in the storage area. */
signed char *pcReadFrom; /*< Points to the last place that a queued item was read from. */
union /* Use of a union is an exception to the coding standard to ensure two mutually exclusive structure members don't appear simultaneously (wasting RAM). */
{
signed char *pcReadFrom; /*< Points to the last place that a queued item was read from when the structure is used as a queue. */
unsigned portBASE_TYPE uxRecursiveCallCount;/*< Maintains a count of the numebr of times a recursive mutex has been recursively 'taken' when the structure is used as a mutex. */
} u;
xList xTasksWaitingToSend; /*< List of tasks that are blocked waiting to post onto this queue. Stored in priority order. */ xList xTasksWaitingToSend; /*< List of tasks that are blocked waiting to post onto this queue. Stored in priority order. */
xList xTasksWaitingToReceive; /*< List of tasks that are blocked waiting to read from this queue. Stored in priority order. */ xList xTasksWaitingToReceive; /*< List of tasks that are blocked waiting to read from this queue. Stored in priority order. */
@ -241,7 +255,7 @@ xQUEUE *pxQueue;
pxQueue->pcTail = pxQueue->pcHead + ( pxQueue->uxLength * pxQueue->uxItemSize ); pxQueue->pcTail = pxQueue->pcHead + ( pxQueue->uxLength * pxQueue->uxItemSize );
pxQueue->uxMessagesWaiting = ( unsigned portBASE_TYPE ) 0U; pxQueue->uxMessagesWaiting = ( unsigned portBASE_TYPE ) 0U;
pxQueue->pcWriteTo = pxQueue->pcHead; pxQueue->pcWriteTo = pxQueue->pcHead;
pxQueue->pcReadFrom = pxQueue->pcHead + ( ( pxQueue->uxLength - ( unsigned portBASE_TYPE ) 1U ) * pxQueue->uxItemSize ); pxQueue->u.pcReadFrom = pxQueue->pcHead + ( ( pxQueue->uxLength - ( unsigned portBASE_TYPE ) 1U ) * pxQueue->uxItemSize );
pxQueue->xRxLock = queueUNLOCKED; pxQueue->xRxLock = queueUNLOCKED;
pxQueue->xTxLock = queueUNLOCKED; pxQueue->xTxLock = queueUNLOCKED;
@ -354,7 +368,7 @@ xQueueHandle xReturn = NULL;
/* Queues used as a mutex no data is actually copied into or out /* Queues used as a mutex no data is actually copied into or out
of the queue. */ of the queue. */
pxNewQueue->pcWriteTo = NULL; pxNewQueue->pcWriteTo = NULL;
pxNewQueue->pcReadFrom = NULL; pxNewQueue->u.pcReadFrom = NULL;
/* Each mutex has a length of 1 (like a binary semaphore) and /* Each mutex has a length of 1 (like a binary semaphore) and
an item size of 0 as nothing is actually copied into or out an item size of 0 as nothing is actually copied into or out
@ -444,7 +458,7 @@ xQueueHandle xReturn = NULL;
this is the only condition we are interested in it does not matter if this is the only condition we are interested in it does not matter if
pxMutexHolder is accessed simultaneously by another task. Therefore no pxMutexHolder is accessed simultaneously by another task. Therefore no
mutual exclusion is required to test the pxMutexHolder variable. */ mutual exclusion is required to test the pxMutexHolder variable. */
if( pxMutex->pxMutexHolder == xTaskGetCurrentTaskHandle() ) if( pxMutex->pxMutexHolder == ( void * ) xTaskGetCurrentTaskHandle() )
{ {
traceGIVE_MUTEX_RECURSIVE( pxMutex ); traceGIVE_MUTEX_RECURSIVE( pxMutex );
@ -453,10 +467,10 @@ xQueueHandle xReturn = NULL;
uxRecursiveCallCount is only modified by the mutex holder, and as uxRecursiveCallCount is only modified by the mutex holder, and as
there can only be one, no mutual exclusion is required to modify the there can only be one, no mutual exclusion is required to modify the
uxRecursiveCallCount member. */ uxRecursiveCallCount member. */
( pxMutex->uxRecursiveCallCount )--; ( pxMutex->u.uxRecursiveCallCount )--;
/* Have we unwound the call count? */ /* Have we unwound the call count? */
if( pxMutex->uxRecursiveCallCount == 0 ) if( pxMutex->u.uxRecursiveCallCount == 0 )
{ {
/* Return the mutex. This will automatically unblock any other /* Return the mutex. This will automatically unblock any other
task that might be waiting to access the mutex. */ task that might be waiting to access the mutex. */
@ -494,9 +508,9 @@ xQueueHandle xReturn = NULL;
traceTAKE_MUTEX_RECURSIVE( pxMutex ); traceTAKE_MUTEX_RECURSIVE( pxMutex );
if( pxMutex->pxMutexHolder == xTaskGetCurrentTaskHandle() ) if( pxMutex->pxMutexHolder == ( void * ) xTaskGetCurrentTaskHandle() )
{ {
( pxMutex->uxRecursiveCallCount )++; ( pxMutex->u.uxRecursiveCallCount )++;
xReturn = pdPASS; xReturn = pdPASS;
} }
else else
@ -507,7 +521,7 @@ xQueueHandle xReturn = NULL;
we may have blocked to reach here. */ we may have blocked to reach here. */
if( xReturn == pdPASS ) if( xReturn == pdPASS )
{ {
( pxMutex->uxRecursiveCallCount )++; ( pxMutex->u.uxRecursiveCallCount )++;
} }
else else
{ {
@ -800,7 +814,7 @@ xQUEUE *pxQueue;
if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 ) if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
{ {
/* Remember our read position in case we are just peeking. */ /* Remember our read position in case we are just peeking. */
pcOriginalReadPosition = pxQueue->pcReadFrom; pcOriginalReadPosition = pxQueue->u.pcReadFrom;
prvCopyDataFromQueue( pxQueue, pvBuffer ); prvCopyDataFromQueue( pxQueue, pvBuffer );
@ -817,7 +831,7 @@ xQUEUE *pxQueue;
{ {
/* Record the information required to implement /* Record the information required to implement
priority inheritance should it become necessary. */ priority inheritance should it become necessary. */
pxQueue->pxMutexHolder = xTaskGetCurrentTaskHandle(); pxQueue->pxMutexHolder = ( void * ) xTaskGetCurrentTaskHandle();
} }
} }
#endif #endif
@ -836,7 +850,7 @@ xQUEUE *pxQueue;
/* We are not removing the data, so reset our read /* We are not removing the data, so reset our read
pointer. */ pointer. */
pxQueue->pcReadFrom = pcOriginalReadPosition; pxQueue->u.pcReadFrom = pcOriginalReadPosition;
/* The data is being left in the queue, so see if there are /* The data is being left in the queue, so see if there are
any other tasks waiting for the data. */ any other tasks waiting for the data. */
@ -1033,7 +1047,7 @@ xQUEUE *pxQueue;
if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 ) if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
{ {
/* Remember our read position in case we are just peeking. */ /* Remember our read position in case we are just peeking. */
pcOriginalReadPosition = pxQueue->pcReadFrom; pcOriginalReadPosition = pxQueue->u.pcReadFrom;
prvCopyDataFromQueue( pxQueue, pvBuffer ); prvCopyDataFromQueue( pxQueue, pvBuffer );
@ -1050,7 +1064,7 @@ xQUEUE *pxQueue;
{ {
/* Record the information required to implement /* Record the information required to implement
priority inheritance should it become necessary. */ priority inheritance should it become necessary. */
pxQueue->pxMutexHolder = xTaskGetCurrentTaskHandle(); pxQueue->pxMutexHolder = ( void * ) xTaskGetCurrentTaskHandle();
} }
} }
#endif #endif
@ -1069,7 +1083,7 @@ xQUEUE *pxQueue;
/* The data is not being removed, so reset the read /* The data is not being removed, so reset the read
pointer. */ pointer. */
pxQueue->pcReadFrom = pcOriginalReadPosition; pxQueue->u.pcReadFrom = pcOriginalReadPosition;
/* The data is being left in the queue, so see if there are /* The data is being left in the queue, so see if there are
any other tasks waiting for the data. */ any other tasks waiting for the data. */
@ -1319,11 +1333,11 @@ static void prvCopyDataToQueue( xQUEUE *pxQueue, const void *pvItemToQueue, port
} }
else else
{ {
memcpy( ( void * ) pxQueue->pcReadFrom, pvItemToQueue, ( size_t ) pxQueue->uxItemSize ); memcpy( ( void * ) pxQueue->u.pcReadFrom, pvItemToQueue, ( size_t ) pxQueue->uxItemSize );
pxQueue->pcReadFrom -= pxQueue->uxItemSize; pxQueue->u.pcReadFrom -= pxQueue->uxItemSize;
if( pxQueue->pcReadFrom < pxQueue->pcHead ) if( pxQueue->u.pcReadFrom < pxQueue->pcHead )
{ {
pxQueue->pcReadFrom = ( pxQueue->pcTail - pxQueue->uxItemSize ); pxQueue->u.pcReadFrom = ( pxQueue->pcTail - pxQueue->uxItemSize );
} }
} }
@ -1335,12 +1349,12 @@ static void prvCopyDataFromQueue( xQUEUE * const pxQueue, const void *pvBuffer )
{ {
if( pxQueue->uxQueueType != queueQUEUE_IS_MUTEX ) if( pxQueue->uxQueueType != queueQUEUE_IS_MUTEX )
{ {
pxQueue->pcReadFrom += pxQueue->uxItemSize; pxQueue->u.pcReadFrom += pxQueue->uxItemSize;
if( pxQueue->pcReadFrom >= pxQueue->pcTail ) if( pxQueue->u.pcReadFrom >= pxQueue->pcTail )
{ {
pxQueue->pcReadFrom = pxQueue->pcHead; pxQueue->u.pcReadFrom = pxQueue->pcHead;
} }
memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( size_t ) pxQueue->uxItemSize ); memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->u.pcReadFrom, ( size_t ) pxQueue->uxItemSize );
} }
} }
/*-----------------------------------------------------------*/ /*-----------------------------------------------------------*/
@ -1633,13 +1647,13 @@ signed portBASE_TYPE xReturn;
if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 ) if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
{ {
/* Data is available from the queue. */ /* Data is available from the queue. */
pxQueue->pcReadFrom += pxQueue->uxItemSize; pxQueue->u.pcReadFrom += pxQueue->uxItemSize;
if( pxQueue->pcReadFrom >= pxQueue->pcTail ) if( pxQueue->u.pcReadFrom >= pxQueue->pcTail )
{ {
pxQueue->pcReadFrom = pxQueue->pcHead; pxQueue->u.pcReadFrom = pxQueue->pcHead;
} }
--( pxQueue->uxMessagesWaiting ); --( pxQueue->uxMessagesWaiting );
memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize ); memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->u.pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
xReturn = pdPASS; xReturn = pdPASS;
@ -1717,13 +1731,13 @@ signed portBASE_TYPE xReturn;
if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 ) if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
{ {
/* Copy the data from the queue. */ /* Copy the data from the queue. */
pxQueue->pcReadFrom += pxQueue->uxItemSize; pxQueue->u.pcReadFrom += pxQueue->uxItemSize;
if( pxQueue->pcReadFrom >= pxQueue->pcTail ) if( pxQueue->u.pcReadFrom >= pxQueue->pcTail )
{ {
pxQueue->pcReadFrom = pxQueue->pcHead; pxQueue->u.pcReadFrom = pxQueue->pcHead;
} }
--( pxQueue->uxMessagesWaiting ); --( pxQueue->uxMessagesWaiting );
memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize ); memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->u.pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
if( ( *pxCoRoutineWoken ) == pdFALSE ) if( ( *pxCoRoutineWoken ) == pdFALSE )
{ {