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/*

        FreeRTOS.org V4.2.0 - Copyright (C) 2003-2007 Richard Barry.

        This file is part of the FreeRTOS.org distribution.

        FreeRTOS.org is free software; you can redistribute it and/or modify

        it under the terms of the GNU General Public License as published by

        the Free Software Foundation; either version 2 of the License, or

        (at your option) any later version.

        FreeRTOS.org is distributed in the hope that it will be useful,

        but WITHOUT ANY WARRANTY; without even the implied warranty of

        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License

        along with FreeRTOS.org; if not, write to the Free Software

        Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

        A special exception to the GPL can be applied should you wish to distribute

        a combined work that includes FreeRTOS.org, without being obliged to provide

        the source code for any proprietary components.  See the licensing section

        of http://www.FreeRTOS.org for full details of how and when the exception

        can be applied.

        ***************************************************************************

        See http://www.FreeRTOS.org for documentation, latest information, license

        and contact details.  Please ensure to read the configuration and relevant

        port sections of the online documentation.

        ***************************************************************************

*/

/*

Changes from V1.01

        + More use of 8bit data types.

        + Function name prefixes changed where the data type returned has changed.

Changed from V2.0.0

        + Added the queue locking mechanism and make more use of the scheduler

          suspension feature to minimise the time interrupts have to be disabled

          when accessing a queue.

Changed from V2.2.0

        + Explicit use of 'signed' qualifier on portCHAR types added.

Changes from V3.0.0

        + API changes as described on the FreeRTOS.org WEB site.

Changes from V3.2.3

        + Added the queue functions that can be used from co-routines.

Changes from V4.0.5

        + Added a loop within xQueueSend() and xQueueReceive() to prevent the

          functions exiting when a block time remains and the function has

          not completed.

Changes from V4.1.2:

        + BUG FIX:  Removed the call to prvIsQueueEmpty from within xQueueCRReceive

          as it exited with interrupts enabled.  Thanks Paul Katz.

Changes from V4.1.3:

        + Modified xQueueSend() and xQueueReceive() to handle the (very unlikely)

        case whereby a task unblocking due to a temporal event can remove/send an

        item from/to a queue when a higher priority task is     still blocked on the

        queue.  This modification is a result of the SafeRTOS testing.

*/

#include <stdlib.h>

#include <string.h>

#include "FreeRTOS.h"

#include "task.h"

#include "croutine.h"

/*-----------------------------------------------------------

 * PUBLIC LIST API documented in list.h

 *----------------------------------------------------------*/

/* Constants used with the cRxLock and cTxLock structure members. */

#define queueUNLOCKED   ( ( signed portBASE_TYPE ) -1 )

#define queueERRONEOUS_UNBLOCK                                  ( -1 )

/*

 * Definition of the queue used by the scheduler.

 * Items are queued by copy, not reference.

 */

typedef struct QueueDefinition

{

        signed portCHAR *pcHead;                                /*< Points to the beginning of the queue storage area. */

        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. */

        signed portCHAR *pcWriteTo;                             /*< Points to the free next place in the storage area. */

        signed portCHAR *pcReadFrom;                    /*< Points to the last place that a queued item was read from. */

        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. */

        unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of items currently in the queue. */

        unsigned portBASE_TYPE uxLength;                /*< The length of the queue defined as the number of items it will hold, not the number of bytes. */

        unsigned portBASE_TYPE uxItemSize;              /*< The size of each items that the queue will hold. */

        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. */

        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. */

} xQUEUE;

/*-----------------------------------------------------------*/

/*

 * Inside this file xQueueHandle is a pointer to a xQUEUE structure.

 * To keep the definition private the API header file defines it as a

 * pointer to void.

 */

typedef xQUEUE * xQueueHandle;

/*

 * Prototypes for public functions are included here so we don't have to

 * include the API header file (as it defines xQueueHandle differently).  These

 * functions are documented in the API header file.

 */

xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize );

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

unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle pxQueue );

void vQueueDelete( xQueueHandle xQueue );

signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken );

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

signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );

#if configUSE_CO_ROUTINES == 1

        signed portBASE_TYPE xQueueCRSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xCoRoutinePreviouslyWoken );

        signed portBASE_TYPE xQueueCRReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken );

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

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

#endif

/*

 * Unlocks a queue locked by a call to prvLockQueue.  Locking a queue does not

 * prevent an ISR from adding or removing items to the queue, but does prevent

 * an ISR from removing tasks from the queue event lists.  If an ISR finds a

 * queue is locked it will instead increment the appropriate queue lock count

 * to indicate that a task may require unblocking.  When the queue in unlocked

 * these lock counts are inspected, and the appropriate action taken.

 */

static void prvUnlockQueue( xQueueHandle pxQueue );

/*

 * Uses a critical section to determine if there is any data in a queue.

 *

 * @return pdTRUE if the queue contains no items, otherwise pdFALSE.

 */

static signed portBASE_TYPE prvIsQueueEmpty( const xQueueHandle pxQueue );

/*

 * Uses a critical section to determine if there is any space in a queue.

 *

 * @return pdTRUE if there is no space, otherwise pdFALSE;

 */

static signed portBASE_TYPE prvIsQueueFull( const xQueueHandle pxQueue );

/*

 * Macro that copies an item into the queue.  This is done by copying the item

 * byte for byte, not by reference.  Updates the queue state to ensure it's

 * integrity after the copy.

 */

#define prvCopyQueueData( pxQueue, pvItemToQueue )                                                                                              \

{                                                                                                                                                                                               \

        memcpy( ( void * ) pxQueue->pcWriteTo, pvItemToQueue, ( unsigned ) pxQueue->uxItemSize );       \

        ++( pxQueue->uxMessagesWaiting );                                                                                                                       \

        pxQueue->pcWriteTo += pxQueue->uxItemSize;                                                                                                      \

        if( pxQueue->pcWriteTo >= pxQueue->pcTail )                                                                                                     \

        {                                                                                                                                                                                       \

                pxQueue->pcWriteTo = pxQueue->pcHead;                                                                                                   \

        }                                                                                                                                                                                       \

}

/*-----------------------------------------------------------*/

/*

 * Macro to mark a queue as locked.  Locking a queue prevents an ISR from

 * accessing the queue event lists.

 */

#define prvLockQueue( pxQueue )                 \

{                                                                               \

        taskENTER_CRITICAL();                           \

                ++( pxQueue->xRxLock );                 \

                ++( pxQueue->xTxLock );                 \

        taskEXIT_CRITICAL();                            \

}

/*-----------------------------------------------------------*/

/*-----------------------------------------------------------

 * PUBLIC QUEUE MANAGEMENT API documented in queue.h

 *----------------------------------------------------------*/

xQueueHandle xQueueCreate( unsigned portBASE_TYPE uxQueueLength, unsigned portBASE_TYPE uxItemSize )

{

xQUEUE *pxNewQueue;

size_t xQueueSizeInBytes;

        /* Allocate the new queue structure. */

        if( uxQueueLength > ( unsigned portBASE_TYPE ) 0 )

        {

                pxNewQueue = ( xQUEUE * ) pvPortMalloc( sizeof( xQUEUE ) );

                if( pxNewQueue != NULL )

                {

                        /* Create the list of pointers to queue items.  The queue is one byte

                        longer than asked for to make wrap checking easier/faster. */

                        xQueueSizeInBytes = ( size_t ) ( uxQueueLength * uxItemSize ) + ( size_t ) 1;

                        pxNewQueue->pcHead = ( signed portCHAR * ) pvPortMalloc( xQueueSizeInBytes );

                        if( pxNewQueue->pcHead != NULL )

                        {

                                /* Initialise the queue members as described above where the

                                queue type is defined. */

                                pxNewQueue->pcTail = pxNewQueue->pcHead + ( uxQueueLength * uxItemSize );

                                pxNewQueue->uxMessagesWaiting = 0;

                                pxNewQueue->pcWriteTo = pxNewQueue->pcHead;

                                pxNewQueue->pcReadFrom = pxNewQueue->pcHead + ( ( uxQueueLength - 1 ) * uxItemSize );

                                pxNewQueue->uxLength = uxQueueLength;

                                pxNewQueue->uxItemSize = uxItemSize;

                                pxNewQueue->xRxLock = queueUNLOCKED;

                                pxNewQueue->xTxLock = queueUNLOCKED;

                                /* Likewise ensure the event queues start with the correct state. */

                                vListInitialise( &( pxNewQueue->xTasksWaitingToSend ) );

                                vListInitialise( &( pxNewQueue->xTasksWaitingToReceive ) );

                                return  pxNewQueue;

                        }

                        else

                        {

                                vPortFree( pxNewQueue );

                        }

                }

        }

        /* Will only reach here if we could not allocate enough memory or no memory

        was required. */

        return NULL;

}

/*-----------------------------------------------------------*/

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

{

signed portBASE_TYPE xReturn = pdPASS;

xTimeOutType xTimeOut;

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

        vTaskSuspendAll();

        /* Capture the current time status for future reference. */

        vTaskSetTimeOutState( &xTimeOut );

        /* It is important that this is the only thread/ISR that modifies the

        ready or delayed lists until xTaskResumeAll() is called.  Places where

        the ready/delayed lists are modified include:

                + vTaskDelay() -  Nothing can call vTaskDelay as the scheduler is

                  suspended, vTaskDelay() cannot be called from an ISR.

                + vTaskPrioritySet() - Has a critical section around the access.

                + vTaskSwitchContext() - This will not get executed while the scheduler

                  is suspended.

                + prvCheckDelayedTasks() - This will not get executed while the

                  scheduler is suspended.

                + xTaskCreate() - Has a critical section around the access.

                + vTaskResume() - Has a critical section around the access.

                + xTaskResumeAll() - Has a critical section around the access.

                + xTaskRemoveFromEventList - Checks to see if the scheduler is

                  suspended.  If so then the TCB being removed from the event is

                  removed from the event and added to the xPendingReadyList.

        */

        /* Make sure interrupts do not access the queue event list. */

        prvLockQueue( pxQueue );

        /* It is important that interrupts to not access the event list of the

        queue being modified here.  Places where the event list is modified

        include:

                + xQueueSendFromISR().  This checks the lock on the queue to see if

                  it has access.  If the queue is locked then the Tx lock count is

                  incremented to signify that a task waiting for data can be made ready

                  once the queue lock is removed.  If the queue is not locked then

                  a task can be moved from the event list, but will not be removed

                  from the delayed list or placed in the ready list until the scheduler

                  is unlocked.

                + xQueueReceiveFromISR().  As per xQueueSendFromISR().

        */

        /* If the queue is already full we may have to block. */

        do

        {

                if( prvIsQueueFull( pxQueue ) )

                {

                        /* The queue is full - do we want to block or just leave without

                        posting? */

                        if( xTicksToWait > ( portTickType ) 0 )

                        {

                                /* We are going to place ourselves on the xTasksWaitingToSend event

                                list, and will get woken should the delay expire, or space become

                                available on the queue.

                                As detailed above we do not require mutual exclusion on the event

                                list as nothing else can modify it or the ready lists while we

                                have the scheduler suspended and queue locked.

                                It is possible that an ISR has removed data from the queue since we

                                checked if any was available.  If this is the case then the data

                                will have been copied from the queue, and the queue variables

                                updated, but the event list will not yet have been checked to see if

                                anything is waiting as the queue is locked. */

                                vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToSend ), xTicksToWait );

                                /* Force a context switch now as we are blocked.  We can do

                                this from within a critical section as the task we are

                                switching to has its own context.  When we return here (i.e. we

                                unblock) we will leave the critical section as normal.

                                It is possible that an ISR has caused an event on an unrelated and

                                unlocked queue.  If this was the case then the event list for that

                                queue will have been updated but the ready lists left unchanged -

                                instead the readied task will have been added to the pending ready

                                list. */

                                taskENTER_CRITICAL();

                                {

                                        /* We can safely unlock the queue and scheduler here as

                                        interrupts are disabled.  We must not yield with anything

                                        locked, but we can yield from within a critical section.

                                        Tasks that have been placed on the pending ready list cannot

                                        be tasks that are waiting for events on this queue.  See

                                        in comment xTaskRemoveFromEventList(). */

                                        prvUnlockQueue( pxQueue );

                                        /* Resuming the scheduler may cause a yield.  If so then there

                                        is no point yielding again here. */

                                        if( !xTaskResumeAll() )

                                        {

                                                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. */

                                        vTaskSuspendAll();

                                        prvLockQueue( pxQueue );

                                }

                                taskEXIT_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 )

                {

                        /* 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( 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();

                }

                if( xReturn == errQUEUE_FULL )

                {

                        if( xTicksToWait > 0 )

                        {

                                if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )

                                {

                                        xReturn = queueERRONEOUS_UNBLOCK;

                                }

                        }

                }

        }

        while( xReturn == queueERRONEOUS_UNBLOCK );

        prvUnlockQueue( pxQueue );

        xTaskResumeAll();

        return xReturn;

}

/*-----------------------------------------------------------*/

signed portBASE_TYPE xQueueSendFromISR( xQueueHandle pxQueue, const void *pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken )

{

        /* Similar to xQueueSend, except we don't block if there is no room in the

        queue.  Also we don't directly wake a task that was blocked on a queue

        read, instead we return a flag to say whether a context switch is required

        or not (i.e. has a task with a higher priority than us been woken by this

        post). */

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

        {

                prvCopyQueueData( pxQueue, pvItemToQueue );

                /* If the queue is locked we do not alter the event list.  This will

                be done when the queue is unlocked later. */

                if( pxQueue->xTxLock == queueUNLOCKED )

                {

                        /* We only want to wake one task per ISR, so check that a task has

                        not already been woken. */

                        if( !xTaskPreviouslyWoken )

                        {

                                if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )

                                {

                                        if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )

                                        {

                                                /* The task waiting has a higher priority so record that a

                                                context switch is required. */

                                                return pdTRUE;

                                        }

                                }

                        }

                }

                else

                {

                        /* Increment the lock count so the task that unlocks the queue

                        knows that data was posted while it was locked. */

                        ++( pxQueue->xTxLock );

                }

        }

        return xTaskPreviouslyWoken;

}

/*-----------------------------------------------------------*/

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

{

signed portBASE_TYPE xReturn = pdTRUE;

xTimeOutType xTimeOut;

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

        xQueueSend() for a more detailed explanation.

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

        vTaskSuspendAll();

        /* Capture the current time status for future reference. */

        vTaskSetTimeOutState( &xTimeOut );

        /* Make sure interrupts do not access the queue. */

        prvLockQueue( pxQueue );

        do

        {

                /* If there are no messages in the queue we may have to block. */

                if( prvIsQueueEmpty( pxQueue ) )

                {

                        /* There are no messages in the queue, do we want to block or just

                        leave with nothing? */

                        if( xTicksToWait > ( portTickType ) 0 )

                        {

                                vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToReceive ), xTicksToWait );

                                taskENTER_CRITICAL();

                                {

                                        prvUnlockQueue( pxQueue );

                                        if( !xTaskResumeAll() )

                                        {

                                                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 );

                                }

                                taskEXIT_CRITICAL();

                        }

                }

                if( xReturn != errQUEUE_EMPTY )

                {

                        taskENTER_CRITICAL();

                        {

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

                                {

                                        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;

                                }

                        }

                        taskEXIT_CRITICAL();

                }

                if( xReturn == errQUEUE_EMPTY )

                {

                        if( xTicksToWait > 0 )

                        {

                                if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )

                                {

                                        xReturn = queueERRONEOUS_UNBLOCK;

                                }

                        }

                }

        } while( xReturn == queueERRONEOUS_UNBLOCK );

        /* We no longer require exclusive access to the queue. */

        prvUnlockQueue( pxQueue );

        xTaskResumeAll();

        return xReturn;

}

/*-----------------------------------------------------------*/

signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, void *pvBuffer, signed portBASE_TYPE *pxTaskWoken )

{

signed portBASE_TYPE xReturn;

        /* We cannot block from an ISR, so check there is data available. */

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

        {

                /* Copy the data from the queue. */

                pxQueue->pcReadFrom += pxQueue->uxItemSize;

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

                {

                        pxQueue->pcReadFrom = pxQueue->pcHead;

                }

                --( pxQueue->uxMessagesWaiting );

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

                /* If the queue is locked we will not modify the event list.  Instead

                we update the lock count so the task that unlocks the queue will know

                that an ISR has removed data while the queue was locked. */

                if( pxQueue->xRxLock == queueUNLOCKED )

                {

                        /* We only want to wake one task per ISR, so check that a task has

                        not already been woken. */

                        if( !( *pxTaskWoken ) )

                        {

                                if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )

                                {

                                        if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )

                                        {

                                                /* The task waiting has a higher priority than us so

                                                force a context switch. */

                                                *pxTaskWoken = pdTRUE;

                                        }

                                }

                        }

                }

                else

                {

                        /* Increment the lock count so the task that unlocks the queue

                        knows that data was removed while it was locked. */

                        ++( pxQueue->xRxLock );

                }

                xReturn = pdPASS;

        }

        else

        {

                xReturn = pdFAIL;

        }

        return xReturn;

}

/*-----------------------------------------------------------*/

unsigned portBASE_TYPE uxQueueMessagesWaiting( xQueueHandle pxQueue )

{

unsigned portBASE_TYPE uxReturn;

        taskENTER_CRITICAL();

                uxReturn = pxQueue->uxMessagesWaiting;

        taskEXIT_CRITICAL();

        return uxReturn;

}

/*-----------------------------------------------------------*/

void vQueueDelete( xQueueHandle pxQueue )

{

        vPortFree( pxQueue->pcHead );

        vPortFree( pxQueue );

}

/*-----------------------------------------------------------*/

static void prvUnlockQueue( xQueueHandle pxQueue )

{

        /* THIS FUNCTION MUST BE CALLED WITH THE SCHEDULER SUSPENDED. */

        /* The lock counts contains the number of extra data items placed or

        removed from the queue while the queue was locked.  When a queue is

        locked items can be added or removed, but the event lists cannot be

        updated. */

        taskENTER_CRITICAL();

        {

                --( pxQueue->xTxLock );

                /* See if data was added to the queue while it was locked. */

                if( pxQueue->xTxLock > queueUNLOCKED )

                {

                        pxQueue->xTxLock = queueUNLOCKED;

                        /* Data was posted while the queue was locked.  Are any tasks

                        blocked waiting for data to become available? */

                        if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )

                        {

                                /* Tasks that are removed from the event list will get added to

                                the pending ready list as the scheduler is still suspended. */

                                if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToReceive ) ) != pdFALSE )

                                {

                                        /* The task waiting has a higher priority so record that a

                                        context switch is required. */

                                        vTaskMissedYield();

                                }

                        }

                }

        }

        taskEXIT_CRITICAL();

        /* Do the same for the Rx lock. */

        taskENTER_CRITICAL();

        {

                --( pxQueue->xRxLock );

                if( pxQueue->xRxLock > queueUNLOCKED )

                {

                        pxQueue->xRxLock = queueUNLOCKED;

                        if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) )

                        {

                                if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )

                                {

                                        vTaskMissedYield();

                                }

                        }

                }

        }

        taskEXIT_CRITICAL();

}

/*-----------------------------------------------------------*/

static signed portBASE_TYPE prvIsQueueEmpty( const xQueueHandle pxQueue )

{

signed portBASE_TYPE xReturn;

        taskENTER_CRITICAL();

                xReturn = ( pxQueue->uxMessagesWaiting == ( unsigned portBASE_TYPE ) 0 );

        taskEXIT_CRITICAL();

        return xReturn;

}

/*-----------------------------------------------------------*/

static signed portBASE_TYPE prvIsQueueFull( const xQueueHandle pxQueue )

{

signed portBASE_TYPE xReturn;

        taskENTER_CRITICAL();

                xReturn = ( pxQueue->uxMessagesWaiting == pxQueue->uxLength );

        taskEXIT_CRITICAL();

        return xReturn;

}

/*-----------------------------------------------------------*/

#if configUSE_CO_ROUTINES == 1

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

{

signed portBASE_TYPE xReturn;

        /* If the queue is already full we may have to block.  A critical section

        is required to prevent an interrupt removing something from the queue

        between the check to see if the queue is full and blocking on the queue. */

        portDISABLE_INTERRUPTS();

        {

                if( prvIsQueueFull( pxQueue ) )

                {

                        /* The queue is full - do we want to block or just leave without

                        posting? */

                        if( xTicksToWait > ( portTickType ) 0 )

                        {

                                /* As this is called from a coroutine we cannot block directly, but

                                return indicating that we need to block. */

                                vCoRoutineAddToDelayedList( xTicksToWait, &( pxQueue->xTasksWaitingToSend ) );

                                portENABLE_INTERRUPTS();

                                return errQUEUE_BLOCKED;

                        }

                        else

                        {

                                portENABLE_INTERRUPTS();

                                return errQUEUE_FULL;

                        }

                }

        }

        portENABLE_INTERRUPTS();

        portNOP();

        portDISABLE_INTERRUPTS();

        {

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

                {

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

                        prvCopyQueueData( pxQueue, pvItemToQueue );

                        xReturn = pdPASS;

                        /* Were any co-routines waiting for data to become available? */

                        if( !listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToReceive ) ) )