📄 queue.c
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/*
FreeRTOS.org V4.7.1 - Copyright (C) 2003-2008 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.
***************************************************************************
Please ensure to read the configuration and relevant port sections of the
online documentation.
+++ http://www.FreeRTOS.org +++
Documentation, latest information, license and contact details.
+++ http://www.SafeRTOS.com +++
A version that is certified for use in safety critical systems.
+++ http://www.OpenRTOS.com +++
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***************************************************************************
*/
#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 )
/* For internal use only. */
#define queueSEND_TO_BACK ( 0 )
#define queueSEND_TO_FRONT ( 1 )
/* Effectively make a union out of the xQUEUE structure. */
#define pxMutexHolder pcTail
#define uxQueueType pcHead
#define uxRecursiveCallCount pcReadFrom
#define queueQUEUE_IS_MUTEX NULL
/* Semaphores do not actually store or copy data, so have an items size of
zero. */
#define queueSEMAPHORE_QUEUE_ITEM_LENGTH ( 0 )
#define queueDONT_BLOCK ( ( portTickType ) 0 )
#define queueMUTEX_GIVE_BLOCK_TIME ( ( portTickType ) 0 )
/*
* 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. */
volatile 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 xQueueGenericSend( xQueueHandle xQueue, const void * const pvItemToQueue, portTickType xTicksToWait, portBASE_TYPE xCopyPosition );
unsigned portBASE_TYPE uxQueueMessagesWaiting( const xQueueHandle pxQueue );
void vQueueDelete( xQueueHandle xQueue );
signed portBASE_TYPE xQueueGenericSendFromISR( xQueueHandle pxQueue, const void * const pvItemToQueue, signed portBASE_TYPE xTaskPreviouslyWoken, portBASE_TYPE xCopyPosition );
signed portBASE_TYPE xQueueGenericReceive( xQueueHandle pxQueue, const void * const pvBuffer, portTickType xTicksToWait, portBASE_TYPE xJustPeeking );
signed portBASE_TYPE xQueueReceiveFromISR( xQueueHandle pxQueue, const void * const pvBuffer, signed portBASE_TYPE *pxTaskWoken );
xQueueHandle xQueueCreateMutex( void );
xQueueHandle xQueueCreateCountingSemaphore( unsigned portBASE_TYPE uxCountValue, unsigned portBASE_TYPE uxInitialCount );
portBASE_TYPE xQueueTakeMutexRecursive( xQueueHandle xMutex, portTickType xBlockTime );
portBASE_TYPE xQueueGiveMutexRecursive( xQueueHandle xMutex );
signed portBASE_TYPE xQueueAltGenericSend( xQueueHandle pxQueue, const void * const pvItemToQueue, portTickType xTicksToWait, portBASE_TYPE xCopyPosition );
signed portBASE_TYPE xQueueAltGenericReceive( xQueueHandle pxQueue, const void * const pvBuffer, portTickType xTicksToWait, portBASE_TYPE xJustPeeking );
#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 );
/*
* Copies an item into the queue, either at the front of the queue or the
* back of the queue.
*/
static void prvCopyDataToQueue( xQUEUE *pxQueue, const void *pvItemToQueue, portBASE_TYPE xPosition );
/*
* Copies an item out of a queue.
*/
static void prvCopyDataFromQueue( xQUEUE * const pxQueue, const void *pvBuffer );
/*-----------------------------------------------------------*/
/*
* 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;
}
/*-----------------------------------------------------------*/
#if ( configUSE_MUTEXES == 1 )
xQueueHandle xQueueCreateMutex( void )
{
xQUEUE *pxNewQueue;
/* Allocate the new queue structure. */
pxNewQueue = ( xQUEUE * ) pvPortMalloc( sizeof( xQUEUE ) );
if( pxNewQueue != NULL )
{
/* Information required for priority inheritance. */
pxNewQueue->pxMutexHolder = NULL;
pxNewQueue->uxQueueType = queueQUEUE_IS_MUTEX;
/* Queues used as a mutex no data is actually copied into or out
of the queue. */
pxNewQueue->pcWriteTo = NULL;
pxNewQueue->pcReadFrom = NULL;
/* 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
of the mutex. */
pxNewQueue->uxMessagesWaiting = 0;
pxNewQueue->uxLength = 1;
pxNewQueue->uxItemSize = 0;
pxNewQueue->xRxLock = queueUNLOCKED;
pxNewQueue->xTxLock = queueUNLOCKED;
/* Ensure the event queues start with the correct state. */
vListInitialise( &( pxNewQueue->xTasksWaitingToSend ) );
vListInitialise( &( pxNewQueue->xTasksWaitingToReceive ) );
/* Start with the semaphore in the expected state. */
xQueueGenericSend( pxNewQueue, NULL, 0, queueSEND_TO_BACK );
}
return pxNewQueue;
}
#endif /* configUSE_MUTEXES */
/*-----------------------------------------------------------*/
#if configUSE_RECURSIVE_MUTEXES == 1
portBASE_TYPE xQueueGiveMutexRecursive( xQueueHandle pxMutex )
{
portBASE_TYPE xReturn;
/* If this is the task that holds the mutex then pxMutexHolder will not
change outside of this task. If this task does not hold the mutex then
pxMutexHolder can never coincidentally equal the tasks handle, and as
this is the only condition we are interested in it does not matter if
pxMutexHolder is accessed simultaneously by another task. Therefore no
mutual exclusion is required to test the pxMutexHolder variable. */
if( pxMutex->pxMutexHolder == xTaskGetCurrentTaskHandle() )
{
/* uxRecursiveCallCount cannot be zero if pxMutexHolder is equal to
the task handle, therefore no underflow check is required. Also,
uxRecursiveCallCount is only modified by the mutex holder, and as
there can only be one, no mutual exclusion is required to modify the
uxRecursiveCallCount member. */
( pxMutex->uxRecursiveCallCount )--;
/* Have we unwound the call count? */
if( pxMutex->uxRecursiveCallCount == 0 )
{
/* Return the mutex. This will automatically unblock any other
task that might be waiting to access the mutex. */
xQueueGenericSend( pxMutex, NULL, queueMUTEX_GIVE_BLOCK_TIME, queueSEND_TO_BACK );
}
xReturn = pdPASS;
}
else
{
/* We cannot give the mutex because we are not the holder. */
xReturn = pdFAIL;
}
return xReturn;
}
#endif /* configUSE_RECURSIVE_MUTEXES */
/*-----------------------------------------------------------*/
#if configUSE_RECURSIVE_MUTEXES == 1
portBASE_TYPE xQueueTakeMutexRecursive( xQueueHandle pxMutex, portTickType xBlockTime )
{
portBASE_TYPE xReturn;
/* Comments regarding mutual exclusion as per those within
xQueueGiveMutexRecursive(). */
if( pxMutex->pxMutexHolder == xTaskGetCurrentTaskHandle() )
{
( pxMutex->uxRecursiveCallCount )++;
xReturn = pdPASS;
}
else
{
xReturn = xQueueGenericReceive( pxMutex, NULL, xBlockTime, pdFALSE );
/* pdPASS will only be returned if we successfully obtained the mutex,
we may have blocked to reach here. */
if( xReturn == pdPASS )
{
( pxMutex->uxRecursiveCallCount )++;
}
}
return xReturn;
}
#endif /* configUSE_RECURSIVE_MUTEXES */
/*-----------------------------------------------------------*/
#if configUSE_COUNTING_SEMAPHORES == 1
xQueueHandle xQueueCreateCountingSemaphore( unsigned portBASE_TYPE uxCountValue, unsigned portBASE_TYPE uxInitialCount )
{
xQueueHandle pxHandle;
pxHandle = xQueueCreate( ( unsigned portBASE_TYPE ) uxCountValue, queueSEMAPHORE_QUEUE_ITEM_LENGTH );
if( pxHandle != NULL )
{
pxHandle->uxMessagesWaiting = uxInitialCount;
}
return pxHandle;
}
#endif /* configUSE_COUNTING_SEMAPHORES */
/*-----------------------------------------------------------*/
signed portBASE_TYPE xQueueGenericSend( xQueueHandle pxQueue, const void * const pvItemToQueue, portTickType xTicksToWait, portBASE_TYPE xCopyPosition )
{
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:
+ xQueueGenericSendFromISR(). 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 xQueueGenericSendFromISR().
*/
/* 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
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