tasks.c

一个开源的Modbus协议栈

	else
	{
		/* We cannot access the delayed or ready lists, so will hold this
		task pending until the scheduler is resumed. */
		vListInsertEnd( ( xList * ) &( xPendingReadyList ), &( pxUnblockedTCB->xEventListItem ) );
	}

	if( pxUnblockedTCB->uxPriority >= pxCurrentTCB->uxPriority )
	{
		/* Return true if the task removed from the event list has
		a higher priority than the calling task.  This allows
		the calling task to know if it should force a context
		switch now. */
		xReturn = pdTRUE;
	}
	else
	{
		xReturn = pdFALSE;
	}

	return xReturn;
}
/*-----------------------------------------------------------*/

void vTaskSetTimeOutState( xTimeOutType *pxTimeOut )
{
    pxTimeOut->xOverflowCount = xNumOfOverflows;
    pxTimeOut->xTimeOnEntering = xTickCount;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xTaskCheckForTimeOut( xTimeOutType *pxTimeOut, portTickType * const pxTicksToWait )
{
portBASE_TYPE xReturn;

	#if ( INCLUDE_vTaskSuspend == 1 )
		/* If INCLUDE_vTaskSuspend is set to 1 and the block time specified is
		the maximum block time then the task should block indefinitely, and
		therefore never time out. */
		if( *pxTicksToWait == portMAX_DELAY )
		{
			xReturn = pdFALSE;
		}
		else /* We are not blocking indefinitely, perform the checks below. */
	#endif

    if( ( xNumOfOverflows != pxTimeOut->xOverflowCount ) && ( xTickCount >= pxTimeOut->xTimeOnEntering ) )
    {
        /* The tick count is greater than the time at which vTaskSetTimeout()
		was called, but has also overflowed since vTaskSetTimeOut() was called.
        It must have wrapped all the way around and gone past us again. This
        passed since vTaskSetTimeout() was called. */
        xReturn = pdTRUE;
    }
    else if( ( xTickCount - pxTimeOut->xTimeOnEntering ) < *pxTicksToWait )
    {
        /* Not a genuine timeout. Adjust parameters for time remaining. */
        *pxTicksToWait -= ( xTickCount - pxTimeOut->xTimeOnEntering );
        vTaskSetTimeOutState( pxTimeOut );
        xReturn = pdFALSE;
    }
    else
    {
        xReturn = pdTRUE;
    }

    return xReturn;
}
/*-----------------------------------------------------------*/

void vTaskMissedYield( void )
{
	xMissedYield = pdTRUE;
}

/*
 * -----------------------------------------------------------
 * The Idle task.
 * ----------------------------------------------------------
 *
 * The portTASK_FUNCTION() macro is used to allow port/compiler specific
 * language extensions.  The equivalent prototype for this function is:
 *
 * void prvIdleTask( void *pvParameters );
 *
 */
static portTASK_FUNCTION( prvIdleTask, pvParameters )
{
	/* Stop warnings. */
	( void ) pvParameters;

	for( ;; )
	{
		/* See if any tasks have been deleted. */
		prvCheckTasksWaitingTermination();

		#if ( configUSE_PREEMPTION == 0 )
		{
			/* If we are not using preemption we keep forcing a task switch to
			see if any other task has become available.  If we are using
			preemption we don't need to do this as any task becoming available
			will automatically get the processor anyway. */
			taskYIELD();	
		}
		#endif

		#if ( ( configUSE_PREEMPTION == 1 ) && ( configIDLE_SHOULD_YIELD == 1 ) )
		{
			/* When using preemption tasks of equal priority will be
			timesliced.  If a task that is sharing the idle priority is ready
			to run then the idle task should yield before the end of the
			timeslice.
			
			A critical region is not required here as we are just reading from
			the list, and an occasional incorrect value will not matter.  If
			the ready list at the idle priority contains more than one task
			then a task other than the idle task is ready to execute. */
			if( listCURRENT_LIST_LENGTH( &( pxReadyTasksLists[ tskIDLE_PRIORITY ] ) ) > ( unsigned portBASE_TYPE ) 1 )
			{
				taskYIELD();
			}
		}
		#endif

		#if ( configUSE_IDLE_HOOK == 1 )
		{
			extern void vApplicationIdleHook( void );

			/* Call the user defined function from within the idle task.  This
			allows the application designer to add background functionality
			without the overhead of a separate task.
			NOTE: vApplicationIdleHook() MUST NOT, UNDER ANY CIRCUMSTANCES,
			CALL A FUNCTION THAT MIGHT BLOCK. */
			vApplicationIdleHook();
		}
		#endif
	}
} /*lint !e715 pvParameters is not accessed but all task functions require the same prototype. */







/*-----------------------------------------------------------
 * File private functions documented at the top of the file.
 *----------------------------------------------------------*/



static void prvInitialiseTCBVariables( tskTCB *pxTCB, unsigned portSHORT usStackDepth, const signed portCHAR * const pcName, unsigned portBASE_TYPE uxPriority )
{
	pxTCB->usStackDepth = usStackDepth;

	/* Store the function name in the TCB. */
	strncpy( ( char * ) pxTCB->pcTaskName, ( const char * ) pcName, ( unsigned portSHORT ) configMAX_TASK_NAME_LEN );
	pxTCB->pcTaskName[ ( unsigned portSHORT ) configMAX_TASK_NAME_LEN - ( unsigned portSHORT ) 1 ] = '\0';

	/* This is used as an array index so must ensure it's not too large. */
	if( uxPriority >= configMAX_PRIORITIES )
	{
		uxPriority = configMAX_PRIORITIES - 1;
	}

	pxTCB->uxPriority = uxPriority;

	vListInitialiseItem( &( pxTCB->xGenericListItem ) );
	vListInitialiseItem( &( pxTCB->xEventListItem ) );

	/* Set the pxTCB as a link back from the xListItem.  This is so we can get
	back to	the containing TCB from a generic item in a list. */
	listSET_LIST_ITEM_OWNER( &( pxTCB->xGenericListItem ), pxTCB );

	/* Event lists are always in priority order. */
	listSET_LIST_ITEM_VALUE( &( pxTCB->xEventListItem ), configMAX_PRIORITIES - ( portTickType ) uxPriority );
	listSET_LIST_ITEM_OWNER( &( pxTCB->xEventListItem ), pxTCB );
}
/*-----------------------------------------------------------*/

static void prvInitialiseTaskLists( void )
{
unsigned portBASE_TYPE uxPriority;

	for( uxPriority = 0; uxPriority < configMAX_PRIORITIES; uxPriority++ )
	{
		vListInitialise( ( xList * ) &( pxReadyTasksLists[ uxPriority ] ) );
	}

	vListInitialise( ( xList * ) &xDelayedTaskList1 );
	vListInitialise( ( xList * ) &xDelayedTaskList2 );
	vListInitialise( ( xList * ) &xPendingReadyList );

	#if ( INCLUDE_vTaskDelete == 1 )
	{
		vListInitialise( ( xList * ) &xTasksWaitingTermination );
	}
	#endif

	#if ( INCLUDE_vTaskSuspend == 1 )
	{
		vListInitialise( ( xList * ) &xSuspendedTaskList );
	}
	#endif

	/* Start with pxDelayedTaskList using list1 and the pxOverflowDelayedTaskList
	using list2. */
	pxDelayedTaskList = &xDelayedTaskList1;
	pxOverflowDelayedTaskList = &xDelayedTaskList2;
}
/*-----------------------------------------------------------*/

static void prvCheckTasksWaitingTermination( void )
{							
	#if ( INCLUDE_vTaskDelete == 1 )
	{				
		portBASE_TYPE xListIsEmpty;

		/* ucTasksDeleted is used to prevent vTaskSuspendAll() being called
		too often in the idle task. */
		if( uxTasksDeleted > ( unsigned portBASE_TYPE ) 0 )
		{
			vTaskSuspendAll();
				xListIsEmpty = listLIST_IS_EMPTY( &xTasksWaitingTermination );				
			xTaskResumeAll();

			if( !xListIsEmpty )
			{
				tskTCB *pxTCB;

				portENTER_CRITICAL();
				{			
					pxTCB = ( tskTCB * ) listGET_OWNER_OF_HEAD_ENTRY( ( ( xList * ) &xTasksWaitingTermination ) );
					vListRemove( &( pxTCB->xGenericListItem ) );
					--uxCurrentNumberOfTasks;
					--uxTasksDeleted;
				}
				portEXIT_CRITICAL();

				prvDeleteTCB( pxTCB );
			}
		}
	}
	#endif
}
/*-----------------------------------------------------------*/

static tskTCB *prvAllocateTCBAndStack( unsigned portSHORT usStackDepth )
{
tskTCB *pxNewTCB;

	/* Allocate space for the TCB.  Where the memory comes from depends on
	the implementation of the port malloc function. */
	pxNewTCB = ( tskTCB * ) pvPortMalloc( sizeof( tskTCB ) );

	if( pxNewTCB != NULL )
	{
		/* Allocate space for the stack used by the task being created.
		The base of the stack memory stored in the TCB so the task can
		be deleted later if required. */
		pxNewTCB->pxStack = ( portSTACK_TYPE * ) pvPortMalloc( ( ( size_t )usStackDepth ) * sizeof( portSTACK_TYPE ) );

		if( pxNewTCB->pxStack == NULL )
		{
			/* Could not allocate the stack.  Delete the allocated TCB. */
			vPortFree( pxNewTCB );			
			pxNewTCB = NULL;			
		}		
		else
		{
			/* Just to help debugging. */
			memset( pxNewTCB->pxStack, tskSTACK_FILL_BYTE, usStackDepth * sizeof( portSTACK_TYPE ) );
		}
	}

	return pxNewTCB;
}
/*-----------------------------------------------------------*/

#if ( configUSE_TRACE_FACILITY == 1 )

	static void prvListTaskWithinSingleList( signed portCHAR *pcWriteBuffer, xList *pxList, signed portCHAR cStatus )
	{
	volatile tskTCB *pxNextTCB, *pxFirstTCB;
	static portCHAR pcStatusString[ 50 ];
	unsigned portSHORT usStackRemaining;

		/* Write the details of all the TCB's in pxList into the buffer. */
		listGET_OWNER_OF_NEXT_ENTRY( pxFirstTCB, pxList );
		do
		{
			listGET_OWNER_OF_NEXT_ENTRY( pxNextTCB, pxList );
			usStackRemaining = usTaskCheckFreeStackSpace( ( unsigned portCHAR * ) pxNextTCB->pxStack );
			sprintf( pcStatusString, ( portCHAR * ) "%s\t\t%c\t%u\t%u\t%u\r\n", pxNextTCB->pcTaskName, cStatus, ( unsigned int ) pxNextTCB->uxPriority, usStackRemaining, ( unsigned int ) pxNextTCB->uxTCBNumber );
			strcat( ( portCHAR * ) pcWriteBuffer, ( portCHAR * ) pcStatusString );

		} while( pxNextTCB != pxFirstTCB );
	}

#endif
/*-----------------------------------------------------------*/

#if ( configUSE_TRACE_FACILITY == 1 )
	unsigned portSHORT usTaskCheckFreeStackSpace( const unsigned portCHAR *pucStackByte )
	{
	register unsigned portSHORT usCount = 0;

		while( *pucStackByte == tskSTACK_FILL_BYTE )
		{
			pucStackByte -= portSTACK_GROWTH;
			usCount++;
		}

		usCount /= sizeof( portSTACK_TYPE );

		return usCount;
	}
#endif
/*-----------------------------------------------------------*/



#if ( ( INCLUDE_vTaskDelete == 1 ) || ( INCLUDE_vTaskCleanUpResources == 1 ) )

	static void prvDeleteTCB( tskTCB *pxTCB )
	{
		/* Free up the memory allocated by the scheduler for the task.  It is up to
		the task to free any memory allocated at the application level. */
		vPortFree( pxTCB->pxStack );
		vPortFree( pxTCB );
	}

#endif


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

#if ( INCLUDE_xTaskGetCurrentTaskHandle == 1 )

	xTaskHandle xTaskGetCurrentTaskHandle( void )
	{
	xTaskHandle xReturn;

		portENTER_CRITICAL();
		{
			xReturn = ( xTaskHandle ) pxCurrentTCB;
		}
		portEXIT_CRITICAL();

		return xReturn;
	}

#endif

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

#if ( INCLUDE_xTaskGetSchedulerState == 1 )

	portBASE_TYPE xTaskGetSchedulerState( void )
	{
	portBASE_TYPE xReturn;
	
		if( xSchedulerRunning == pdFALSE )
		{
			xReturn = taskSCHEDULER_NOT_STARTED;
		}
		else
		{
			if( uxSchedulerSuspended == ( unsigned portBASE_TYPE ) pdFALSE )
			{
				xReturn = taskSCHEDULER_RUNNING;
			}
			else
			{
				xReturn = taskSCHEDULER_SUSPENDED;
			}
		}
		
		return xReturn;
	}

#endif