2 FreeRTOS.org V4.4.0 - Copyright (C) 2003-2007 Richard Barry.
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26 ***************************************************************************
27 See http://www.FreeRTOS.org for documentation, latest information, license
28 and contact details. Please ensure to read the configuration and relevant
29 port sections of the online documentation.
31 Also see http://www.SafeRTOS.com for an IEC 61508 compliant version along
32 with commercial development and support options.
33 ***************************************************************************
39 + More use of 8bit data types.
40 + Function name prefixes changed where the data type returned has changed.
44 + Added the queue locking mechanism and make more use of the scheduler
45 suspension feature to minimise the time interrupts have to be disabled
46 when accessing a queue.
50 + Explicit use of 'signed' qualifier on portCHAR types added.
54 + API changes as described on the FreeRTOS.org WEB site.
58 + Added the queue functions that can be used from co-routines.
62 + Added a loop within xQueueSend() and xQueueReceive() to prevent the
63 functions exiting when a block time remains and the function has
68 + BUG FIX: Removed the call to prvIsQueueEmpty from within xQueueCRReceive
69 as it exited with interrupts enabled. Thanks Paul Katz.
73 + Modified xQueueSend() and xQueueReceive() to handle the (very unlikely)
74 case whereby a task unblocking due to a temporal event can remove/send an
75 item from/to a queue when a higher priority task is still blocked on the
76 queue. This modification is a result of the SafeRTOS testing.
85 /*-----------------------------------------------------------
86 * PUBLIC LIST API documented in list.h
87 *----------------------------------------------------------*/
89 /* Constants used with the cRxLock and cTxLock structure members. */
90 #define queueUNLOCKED ( ( signed portBASE_TYPE ) -1 )
91 #define queueERRONEOUS_UNBLOCK ( -1 )
94 * Definition of the queue used by the scheduler.
95 * Items are queued by copy, not reference.
97 typedef struct QueueDefinition
99 signed portCHAR *pcHead; /*< Points to the beginning of the queue storage area. */
100 signed portCHAR *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. */
102 signed portCHAR *pcWriteTo; /*< Points to the free next place in the storage area. */
103 signed portCHAR *pcReadFrom; /*< Points to the last place that a queued item was read from. */
105 xList xTasksWaitingToSend; /*< List of tasks that are blocked waiting to post onto this queue. Stored in priority order. */
106 xList xTasksWaitingToReceive; /*< List of tasks that are blocked waiting to read from this queue. Stored in priority order. */
108 unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of items currently in the queue. */
109 unsigned portBASE_TYPE uxLength; /*< The length of the queue defined as the number of items it will hold, not the number of bytes. */
110 unsigned portBASE_TYPE uxItemSize; /*< The size of each items that the queue will hold. */
112 signed portBASE_TYPE xRxLock; /*< Stores the number of items received from the queue (removed from the queue) while the queue was locked. Set to queueUNLOCKED when the queue is not locked. */
113 signed portBASE_TYPE xTxLock; /*< Stores the number of items transmitted to the queue (added to the queue) while the queue was locked. Set to queueUNLOCKED when the queue is not locked. */
115 /*-----------------------------------------------------------*/
118 * Inside this file xQueueHandle is a pointer to a xQUEUE structure.
119 * To keep the definition private the API header file defines it as a
122 typedef xQUEUE * xQueueHandle;
125 * Prototypes for public functions are included here so we don't have to
126 * include the API header file (as it defines xQueueHandle differently). These
127 * functions are documented in the API header file.
129 xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );
130 signed portBASE_TYPE xQueueSend( xQueueHandle xQueue, const void * pvItemToQueue, portTickType xTicksToWait );
131 unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle pxQueue );
132 void vQueueDelete( xQueueHandle xQueue );
133 signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken );
134 signed portBASE_TYPE xQueueReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait );
135 signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );
137 #if configUSE_CO_ROUTINES == 1
138 signed portBASE_TYPE xQueueCRSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xCoRoutinePreviouslyWoken );
139 signed portBASE_TYPE xQueueCRReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );
140 signed portBASE_TYPE xQueueCRSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait );
141 signed portBASE_TYPE xQueueCRReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait );
145 * Unlocks a queue locked by a call to prvLockQueue. Locking a queue does not
146 * prevent an ISR from adding or removing items to the queue, but does prevent
147 * an ISR from removing tasks from the queue event lists. If an ISR finds a
148 * queue is locked it will instead increment the appropriate queue lock count
149 * to indicate that a task may require unblocking. When the queue in unlocked
150 * these lock counts are inspected, and the appropriate action taken.
152 static void prvUnlockQueue( xQueueHandle pxQueue );
155 * Uses a critical section to determine if there is any data in a queue.
157 * @return pdTRUE if the queue contains no items, otherwise pdFALSE.
159 static signed portBASE_TYPE prvIsQueueEmpty( const xQueueHandle pxQueue );
162 * Uses a critical section to determine if there is any space in a queue.
164 * @return pdTRUE if there is no space, otherwise pdFALSE;
166 static signed portBASE_TYPE prvIsQueueFull( const xQueueHandle pxQueue );
169 * Macro that copies an item into the queue. This is done by copying the item
170 * byte for byte, not by reference. Updates the queue state to ensure it's
171 * integrity after the copy.
173 #define prvCopyQueueData( pxQueue, pvItemToQueue ) \
175 memcpy( ( void * ) pxQueue->pcWriteTo, pvItemToQueue, ( unsigned ) pxQueue->uxItemSize ); \
176 ++( pxQueue->uxMessagesWaiting ); \
177 pxQueue->pcWriteTo += pxQueue->uxItemSize; \
178 if( pxQueue->pcWriteTo >= pxQueue->pcTail ) \
180 pxQueue->pcWriteTo = pxQueue->pcHead; \
183 /*-----------------------------------------------------------*/
186 * Macro to mark a queue as locked. Locking a queue prevents an ISR from
187 * accessing the queue event lists.
189 #define prvLockQueue( pxQueue ) \
191 taskENTER_CRITICAL(); \
192 ++( pxQueue->xRxLock ); \
193 ++( pxQueue->xTxLock ); \
194 taskEXIT_CRITICAL(); \
196 /*-----------------------------------------------------------*/
199 /*-----------------------------------------------------------
200 * PUBLIC QUEUE MANAGEMENT API documented in queue.h
201 *----------------------------------------------------------*/
203 xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize )
206 size_t xQueueSizeInBytes;
208 /* Allocate the new queue structure. */
209 if( uxQueueLength > ( unsigned portBASE_TYPE ) 0 )
211 pxNewQueue = ( xQUEUE * ) pvPortMalloc( sizeof( xQUEUE ) );
212 if( pxNewQueue != NULL )
214 /* Create the list of pointers to queue items. The queue is one byte
215 longer than asked for to make wrap checking easier/faster. */
216 xQueueSizeInBytes = ( size_t ) ( uxQueueLength * uxItemSize ) + ( size_t ) 1;
218 pxNewQueue->pcHead = ( signed portCHAR * ) pvPortMalloc( xQueueSizeInBytes );
219 if( pxNewQueue->pcHead != NULL )
221 /* Initialise the queue members as described above where the
222 queue type is defined. */
223 pxNewQueue->pcTail = pxNewQueue->pcHead + ( uxQueueLength * uxItemSize );
224 pxNewQueue->uxMessagesWaiting = 0;
225 pxNewQueue->pcWriteTo = pxNewQueue->pcHead;
226 pxNewQueue->pcReadFrom = pxNewQueue->pcHead + ( ( uxQueueLength - 1 ) * uxItemSize );
227 pxNewQueue->uxLength = uxQueueLength;
228 pxNewQueue->uxItemSize = uxItemSize;
229 pxNewQueue->xRxLock = queueUNLOCKED;
230 pxNewQueue->xTxLock = queueUNLOCKED;
232 /* Likewise ensure the event queues start with the correct state. */
233 vListInitialise( &( pxNewQueue->xTasksWaitingToSend ) );
234 vListInitialise( &( pxNewQueue->xTasksWaitingToReceive ) );
240 vPortFree( pxNewQueue );
245 /* Will only reach here if we could not allocate enough memory or no memory
249 /*-----------------------------------------------------------*/
251 signed portBASE_TYPE xQueueSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait )
253 signed portBASE_TYPE xReturn = pdPASS;
254 xTimeOutType xTimeOut;
256 /* Make sure other tasks do not access the queue. */
259 /* Capture the current time status for future reference. */
260 vTaskSetTimeOutState( &xTimeOut );
262 /* It is important that this is the only thread/ISR that modifies the
263 ready or delayed lists until xTaskResumeAll() is called. Places where
264 the ready/delayed lists are modified include:
266 + vTaskDelay() - Nothing can call vTaskDelay as the scheduler is
267 suspended, vTaskDelay() cannot be called from an ISR.
268 + vTaskPrioritySet() - Has a critical section around the access.
269 + vTaskSwitchContext() - This will not get executed while the scheduler
271 + prvCheckDelayedTasks() - This will not get executed while the
272 scheduler is suspended.
273 + xTaskCreate() - Has a critical section around the access.
274 + vTaskResume() - Has a critical section around the access.
275 + xTaskResumeAll() - Has a critical section around the access.
276 + xTaskRemoveFromEventList - Checks to see if the scheduler is
277 suspended. If so then the TCB being removed from the event is
278 removed from the event and added to the xPendingReadyList.
281 /* Make sure interrupts do not access the queue event list. */
282 prvLockQueue( pxQueue );
284 /* It is important that interrupts to not access the event list of the
285 queue being modified here. Places where the event list is modified
288 + xQueueSendFromISR(). This checks the lock on the queue to see if
289 it has access. If the queue is locked then the Tx lock count is
290 incremented to signify that a task waiting for data can be made ready
291 once the queue lock is removed. If the queue is not locked then
292 a task can be moved from the event list, but will not be removed
293 from the delayed list or placed in the ready list until the scheduler
296 + xQueueReceiveFromISR(). As per xQueueSendFromISR().
299 /* If the queue is already full we may have to block. */
302 if( prvIsQueueFull( pxQueue ) )
304 /* The queue is full - do we want to block or just leave without
306 if( xTicksToWait > ( portTickType ) 0 )
308 /* We are going to place ourselves on the xTasksWaitingToSend event
309 list, and will get woken should the delay expire, or space become
310 available on the queue.
312 As detailed above we do not require mutual exclusion on the event
313 list as nothing else can modify it or the ready lists while we
314 have the scheduler suspended and queue locked.
316 It is possible that an ISR has removed data from the queue since we
317 checked if any was available. If this is the case then the data
318 will have been copied from the queue, and the queue variables
319 updated, but the event list will not yet have been checked to see if
320 anything is waiting as the queue is locked. */
321 vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToSend ), xTicksToWait );
323 /* Force a context switch now as we are blocked. We can do
324 this from within a critical section as the task we are
325 switching to has its own context. When we return here (i.e. we
326 unblock) we will leave the critical section as normal.
328 It is possible that an ISR has caused an event on an unrelated and
329 unlocked queue. If this was the case then the event list for that
330 queue will have been updated but the ready lists left unchanged -
331 instead the readied task will have been added to the pending ready
333 taskENTER_CRITICAL();
335 /* We can safely unlock the queue and scheduler here as
336 interrupts are disabled. We must not yield with anything
337 locked, but we can yield from within a critical section.
339 Tasks that have been placed on the pending ready list cannot
340 be tasks that are waiting for events on this queue. See
341 in comment xTaskRemoveFromEventList(). */
342 prvUnlockQueue( pxQueue );
344 /* Resuming the scheduler may cause a yield. If so then there
345 is no point yielding again here. */
346 if( !xTaskResumeAll() )
351 /* We want to check to see if the queue is still full
352 before leaving the critical section. This is to prevent
353 this task placing an item into the queue due to an
354 interrupt making space on the queue between critical
355 sections (when there might be a higher priority task
356 blocked on the queue that cannot run yet because the
357 scheduler gets suspended). */
358 if( pxQueue->uxMessagesWaiting == pxQueue->uxLength )
360 /* We unblocked but there is no space in the queue,
361 we probably timed out. */
362 xReturn = errQUEUE_FULL;
365 /* Before leaving the critical section we have to ensure
366 exclusive access again. */
368 prvLockQueue( pxQueue );
374 /* If xReturn is errQUEUE_FULL then we unblocked when the queue
375 was still full. Don't check it again now as it is possible that
376 an interrupt has removed an item from the queue since we left the
377 critical section and we don't want to write to the queue in case
378 there is a task of higher priority blocked waiting for space to
379 be available on the queue. If this is the case the higher priority
380 task will execute when the scheduler is unsupended. */
381 if( xReturn != errQUEUE_FULL )
383 /* When we are here it is possible that we unblocked as space became
384 available on the queue. It is also possible that an ISR posted to the
385 queue since we left the critical section, so it may be that again there
386 is no space. This would only happen if a task and ISR post onto the
388 taskENTER_CRITICAL();
390 if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )
392 /* There is room in the queue, copy the data into the queue. */
393 prvCopyQueueData( pxQueue, pvItemToQueue );
396 /* Update the TxLock count so prvUnlockQueue knows to check for
397 tasks waiting for data to become available in the queue. */
398 ++( pxQueue->xTxLock );
402 xReturn = errQUEUE_FULL;
408 if( xReturn == errQUEUE_FULL )
410 if( xTicksToWait > 0 )
412 if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )
414 xReturn = queueERRONEOUS_UNBLOCK;
419 while( xReturn == queueERRONEOUS_UNBLOCK );
421 prvUnlockQueue( pxQueue );
426 /*-----------------------------------------------------------*/
428 signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken )
430 /* Similar to xQueueSend, except we don't block if there is no room in the
431 queue. Also we don't directly wake a task that was blocked on a queue
432 read, instead we return a flag to say whether a context switch is required
433 or not (i.e. has a task with a higher priority than us been woken by this
435 if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )
437 prvCopyQueueData( pxQueue, pvItemToQueue );
439 /* If the queue is locked we do not alter the event list. This will
440 be done when the queue is unlocked later. */
441 if( pxQueue->xTxLock == queueUNLOCKED )
443 /* We only want to wake one task per ISR, so check that a task has
444 not already been woken. */
445 if( !xTaskPreviouslyWoken )
447 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )
449 if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
451 /* The task waiting has a higher priority so record that a
452 context switch is required. */
460 /* Increment the lock count so the task that unlocks the queue
461 knows that data was posted while it was locked. */
462 ++( pxQueue->xTxLock );
466 return xTaskPreviouslyWoken;
468 /*-----------------------------------------------------------*/
470 signed portBASE_TYPE xQueueReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait )
472 signed portBASE_TYPE xReturn = pdTRUE;
473 xTimeOutType xTimeOut;
475 /* This function is very similar to xQueueSend(). See comments within
476 xQueueSend() for a more detailed explanation.
478 Make sure other tasks do not access the queue. */
481 /* Capture the current time status for future reference. */
482 vTaskSetTimeOutState( &xTimeOut );
484 /* Make sure interrupts do not access the queue. */
485 prvLockQueue( pxQueue );
489 /* If there are no messages in the queue we may have to block. */
490 if( prvIsQueueEmpty( pxQueue ) )
492 /* There are no messages in the queue, do we want to block or just
493 leave with nothing? */
494 if( xTicksToWait > ( portTickType ) 0 )
496 vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToReceive ), xTicksToWait );
497 taskENTER_CRITICAL();
499 prvUnlockQueue( pxQueue );
500 if( !xTaskResumeAll() )
505 if( pxQueue->uxMessagesWaiting == ( unsigned portBASE_TYPE ) 0 )
507 /* We unblocked but the queue is empty. We probably
509 xReturn = errQUEUE_EMPTY;
513 prvLockQueue( pxQueue );
519 if( xReturn != errQUEUE_EMPTY )
521 taskENTER_CRITICAL();
523 if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
525 pxQueue->pcReadFrom += pxQueue->uxItemSize;
526 if( pxQueue->pcReadFrom >= pxQueue->pcTail )
528 pxQueue->pcReadFrom = pxQueue->pcHead;
530 --( pxQueue->uxMessagesWaiting );
531 memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
533 /* Increment the lock count so prvUnlockQueue knows to check for
534 tasks waiting for space to become available on the queue. */
535 ++( pxQueue->xRxLock );
540 xReturn = errQUEUE_EMPTY;
546 if( xReturn == errQUEUE_EMPTY )
548 if( xTicksToWait > 0 )
550 if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )
552 xReturn = queueERRONEOUS_UNBLOCK;
556 } while( xReturn == queueERRONEOUS_UNBLOCK );
558 /* We no longer require exclusive access to the queue. */
559 prvUnlockQueue( pxQueue );
564 /*-----------------------------------------------------------*/
566 signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken )
568 signed portBASE_TYPE xReturn;
570 /* We cannot block from an ISR, so check there is data available. */
571 if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
573 /* Copy the data from the queue. */
574 pxQueue->pcReadFrom += pxQueue->uxItemSize;
575 if( pxQueue->pcReadFrom >= pxQueue->pcTail )
577 pxQueue->pcReadFrom = pxQueue->pcHead;
579 --( pxQueue->uxMessagesWaiting );
580 memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
582 /* If the queue is locked we will not modify the event list. Instead
583 we update the lock count so the task that unlocks the queue will know
584 that an ISR has removed data while the queue was locked. */
585 if( pxQueue->xRxLock == queueUNLOCKED )
587 /* We only want to wake one task per ISR, so check that a task has
588 not already been woken. */
589 if( !( *pxTaskWoken ) )
591 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )
593 if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
595 /* The task waiting has a higher priority than us so
596 force a context switch. */
597 *pxTaskWoken = pdTRUE;
604 /* Increment the lock count so the task that unlocks the queue
605 knows that data was removed while it was locked. */
606 ++( pxQueue->xRxLock );
618 /*-----------------------------------------------------------*/
620 unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle pxQueue )
622 unsigned portBASE_TYPE uxReturn;
624 taskENTER_CRITICAL();
625 uxReturn = pxQueue->uxMessagesWaiting;
630 /*-----------------------------------------------------------*/
632 void vQueueDelete( xQueueHandle pxQueue )
634 vPortFree( pxQueue->pcHead );
635 vPortFree( pxQueue );
637 /*-----------------------------------------------------------*/
639 static void prvUnlockQueue( xQueueHandle pxQueue )
641 /* THIS FUNCTION MUST BE CALLED WITH THE SCHEDULER SUSPENDED. */
643 /* The lock counts contains the number of extra data items placed or
644 removed from the queue while the queue was locked. When a queue is
645 locked items can be added or removed, but the event lists cannot be
647 taskENTER_CRITICAL();
649 --( pxQueue->xTxLock );
651 /* See if data was added to the queue while it was locked. */
652 if( pxQueue->xTxLock > queueUNLOCKED )
654 pxQueue->xTxLock = queueUNLOCKED;
656 /* Data was posted while the queue was locked. Are any tasks
657 blocked waiting for data to become available? */
658 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )
660 /* Tasks that are removed from the event list will get added to
661 the pending ready list as the scheduler is still suspended. */
662 if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
664 /* The task waiting has a higher priority so record that a
665 context switch is required. */
673 /* Do the same for the Rx lock. */
674 taskENTER_CRITICAL();
676 --( pxQueue->xRxLock );
678 if( pxQueue->xRxLock > queueUNLOCKED )
680 pxQueue->xRxLock = queueUNLOCKED;
682 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )
684 if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
693 /*-----------------------------------------------------------*/
695 static signed portBASE_TYPE prvIsQueueEmpty( const xQueueHandle pxQueue )
697 signed portBASE_TYPE xReturn;
699 taskENTER_CRITICAL();
700 xReturn = ( pxQueue->uxMessagesWaiting == ( unsigned portBASE_TYPE ) 0 );
705 /*-----------------------------------------------------------*/
707 static signed portBASE_TYPE prvIsQueueFull( const xQueueHandle pxQueue )
709 signed portBASE_TYPE xReturn;
711 taskENTER_CRITICAL();
712 xReturn = ( pxQueue->uxMessagesWaiting == pxQueue->uxLength );
717 /*-----------------------------------------------------------*/
719 #if configUSE_CO_ROUTINES == 1
720 signed portBASE_TYPE xQueueCRSend( xQueueHandle pxQueue, const void *pvItemToQueue, portTickType xTicksToWait )
722 signed portBASE_TYPE xReturn;
724 /* If the queue is already full we may have to block. A critical section
725 is required to prevent an interrupt removing something from the queue
726 between the check to see if the queue is full and blocking on the queue. */
727 portDISABLE_INTERRUPTS();
729 if( prvIsQueueFull( pxQueue ) )
731 /* The queue is full - do we want to block or just leave without
733 if( xTicksToWait > ( portTickType ) 0 )
735 /* As this is called from a coroutine we cannot block directly, but
736 return indicating that we need to block. */
737 vCoRoutineAddToDelayedList( xTicksToWait, &( pxQueue->xTasksWaitingToSend ) );
738 portENABLE_INTERRUPTS();
739 return errQUEUE_BLOCKED;
743 portENABLE_INTERRUPTS();
744 return errQUEUE_FULL;
748 portENABLE_INTERRUPTS();
752 portDISABLE_INTERRUPTS();
754 if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )
756 /* There is room in the queue, copy the data into the queue. */
757 prvCopyQueueData( pxQueue, pvItemToQueue );
760 /* Were any co-routines waiting for data to become available? */
761 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )
763 /* In this instance the co-routine could be placed directly
764 into the ready list as we are within a critical section.
765 Instead the same pending ready list mechansim is used as if
766 the event were caused from within an interrupt. */
767 if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
769 /* The co-routine waiting has a higher priority so record
770 that a yield might be appropriate. */
771 xReturn = errQUEUE_YIELD;
777 xReturn = errQUEUE_FULL;
780 portENABLE_INTERRUPTS();
785 /*-----------------------------------------------------------*/
787 #if configUSE_CO_ROUTINES == 1
788 signed portBASE_TYPE xQueueCRReceive( xQueueHandle pxQueue, void *pvBuffer, portTickType xTicksToWait )
790 signed portBASE_TYPE xReturn;
792 /* If the queue is already empty we may have to block. A critical section
793 is required to prevent an interrupt adding something to the queue
794 between the check to see if the queue is empty and blocking on the queue. */
795 portDISABLE_INTERRUPTS();
797 if( pxQueue->uxMessagesWaiting == ( unsigned portBASE_TYPE ) 0 )
799 /* There are no messages in the queue, do we want to block or just
800 leave with nothing? */
801 if( xTicksToWait > ( portTickType ) 0 )
803 /* As this is a co-routine we cannot block directly, but return
804 indicating that we need to block. */
805 vCoRoutineAddToDelayedList( xTicksToWait, &( pxQueue->xTasksWaitingToReceive ) );
806 portENABLE_INTERRUPTS();
807 return errQUEUE_BLOCKED;
811 portENABLE_INTERRUPTS();
812 return errQUEUE_FULL;
816 portENABLE_INTERRUPTS();
820 portDISABLE_INTERRUPTS();
822 if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
824 /* Data is available from the queue. */
825 pxQueue->pcReadFrom += pxQueue->uxItemSize;
826 if( pxQueue->pcReadFrom >= pxQueue->pcTail )
828 pxQueue->pcReadFrom = pxQueue->pcHead;
830 --( pxQueue->uxMessagesWaiting );
831 memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
835 /* Were any co-routines waiting for space to become available? */
836 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )
838 /* In this instance the co-routine could be placed directly
839 into the ready list as we are within a critical section.
840 Instead the same pending ready list mechansim is used as if
841 the event were caused from within an interrupt. */
842 if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
844 xReturn = errQUEUE_YIELD;
853 portENABLE_INTERRUPTS();
858 /*-----------------------------------------------------------*/
862 #if configUSE_CO_ROUTINES == 1
863 signed portBASE_TYPE xQueueCRSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xCoRoutinePreviouslyWoken )
865 /* Cannot block within an ISR so if there is no space on the queue then
866 exit without doing anything. */
867 if( pxQueue->uxMessagesWaiting < pxQueue->uxLength )
869 prvCopyQueueData( pxQueue, pvItemToQueue );
871 /* We only want to wake one co-routine per ISR, so check that a
872 co-routine has not already been woken. */
873 if( !xCoRoutinePreviouslyWoken )
875 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )
877 if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )
885 return xCoRoutinePreviouslyWoken;
888 /*-----------------------------------------------------------*/
890 #if configUSE_CO_ROUTINES == 1
891 signed portBASE_TYPE xQueueCRReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxCoRoutineWoken )
893 signed portBASE_TYPE xReturn;
895 /* We cannot block from an ISR, so check there is data available. If
896 not then just leave without doing anything. */
897 if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TYPE ) 0 )
899 /* Copy the data from the queue. */
900 pxQueue->pcReadFrom += pxQueue->uxItemSize;
901 if( pxQueue->pcReadFrom >= pxQueue->pcTail )
903 pxQueue->pcReadFrom = pxQueue->pcHead;
905 --( pxQueue->uxMessagesWaiting );
906 memcpy( ( void * ) pvBuffer, ( void * ) pxQueue->pcReadFrom, ( unsigned ) pxQueue->uxItemSize );
908 if( !( *pxCoRoutineWoken ) )
910 if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )
912 if( xCoRoutineRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
914 *pxCoRoutineWoken = pdTRUE;
929 /*-----------------------------------------------------------*/