tasks.c

FreeRTOS source code as bundled with the book "Using FreeRTOS Real-Time Kernel - A Practical Approac

			if( !listLIST_IS_EMPTY( pxOverflowDelayedTaskList ) )
			{
				prvListTaskWithinSingleList( pcWriteBuffer, ( xList * ) pxOverflowDelayedTaskList, tskBLOCKED_CHAR );
			}

			if( !listLIST_IS_EMPTY( &xTasksWaitingTermination ) )
			{
				prvListTaskWithinSingleList( pcWriteBuffer, ( xList * ) &xTasksWaitingTermination, tskDELETED_CHAR );
			}

			if( !listLIST_IS_EMPTY( &xSuspendedTaskList ) )
			{
				prvListTaskWithinSingleList( pcWriteBuffer, ( xList * ) &xSuspendedTaskList, tskSUSPENDED_CHAR );
			}
		}
        xTaskResumeAll();
	}

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

#if ( configUSE_TRACE_FACILITY == 1 )

	void vTaskStartTrace( signed portCHAR * pcBuffer, unsigned portLONG ulBufferSize )
	{
		portENTER_CRITICAL();
		{
			pcTraceBuffer = ( signed portCHAR * )pcBuffer;
			pcTraceBufferStart = pcBuffer;
			pcTraceBufferEnd = pcBuffer + ( ulBufferSize - tskSIZE_OF_EACH_TRACE_LINE );
			xTracing = pdTRUE;
		}
		portEXIT_CRITICAL();
	}

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

#if ( configUSE_TRACE_FACILITY == 1 )

	unsigned portLONG ulTaskEndTrace( void )
	{
	unsigned portLONG ulBufferLength;

		portENTER_CRITICAL();
			xTracing = pdFALSE;
		portEXIT_CRITICAL();

		ulBufferLength = ( unsigned portLONG ) ( pcTraceBuffer - pcTraceBufferStart );

		return ulBufferLength;
	}

#endif



/*-----------------------------------------------------------
 * SCHEDULER INTERNALS AVAILABLE FOR PORTING PURPOSES
 * documented in task.h
 *----------------------------------------------------------*/


void vTaskIncrementTick( void )
{
	/* Called by the portable layer each time a tick interrupt occurs.
	Increments the tick then checks to see if the new tick value will cause any
	tasks to be unblocked. */
	if( uxSchedulerSuspended == ( unsigned portBASE_TYPE ) pdFALSE )
	{
		++xTickCount;
		if( xTickCount == ( portTickType ) 0 )
		{
			xList *pxTemp;

			/* Tick count has overflowed so we need to swap the delay lists.
			If there are any items in pxDelayedTaskList here then there is
			an error! */
			pxTemp = pxDelayedTaskList;
			pxDelayedTaskList = pxOverflowDelayedTaskList;
			pxOverflowDelayedTaskList = pxTemp;
            xNumOfOverflows++;
		}

		/* See if this tick has made a timeout expire. */
		prvCheckDelayedTasks();
	}
	else
	{
		++uxMissedTicks;

		/* The tick hook gets called at regular intervals, even if the
		scheduler is locked. */
		#if ( configUSE_TICK_HOOK == 1 )
		{
			extern void vApplicationTickHook( void );

			vApplicationTickHook();
		}
		#endif
	}

	#if ( configUSE_TICK_HOOK == 1 )
	{
		extern void vApplicationTickHook( void );

		/* Guard against the tick hook being called when the missed tick
		count is being unwound (when the scheduler is being unlocked. */
		if( uxMissedTicks == 0 )
		{
			vApplicationTickHook();
		}
	}
	#endif

	traceTASK_INCREMENT_TICK( xTickCount );
}
/*-----------------------------------------------------------*/

#if ( ( INCLUDE_vTaskCleanUpResources == 1 ) && ( INCLUDE_vTaskSuspend == 1 ) )

	void vTaskCleanUpResources( void )
	{
	unsigned portSHORT usQueue;
	volatile tskTCB *pxTCB;

		usQueue = ( unsigned portSHORT ) uxTopUsedPriority + ( unsigned portSHORT ) 1;

		/* Remove any TCB's from the ready queues. */
		do
		{
			usQueue--;

			while( !listLIST_IS_EMPTY( &( pxReadyTasksLists[ usQueue ] ) ) )
			{
				listGET_OWNER_OF_NEXT_ENTRY( pxTCB, &( pxReadyTasksLists[ usQueue ] ) );
				vListRemove( ( xListItem * ) &( pxTCB->xGenericListItem ) );

				prvDeleteTCB( ( tskTCB * ) pxTCB );
			}
		}while( usQueue > ( unsigned portSHORT ) tskIDLE_PRIORITY );

		/* Remove any TCB's from the delayed queue. */
		while( !listLIST_IS_EMPTY( &xDelayedTaskList1 ) )
		{
			listGET_OWNER_OF_NEXT_ENTRY( pxTCB, &xDelayedTaskList1 );
			vListRemove( ( xListItem * ) &( pxTCB->xGenericListItem ) );

			prvDeleteTCB( ( tskTCB * ) pxTCB );
		}

		/* Remove any TCB's from the overflow delayed queue. */
		while( !listLIST_IS_EMPTY( &xDelayedTaskList2 ) )
		{
			listGET_OWNER_OF_NEXT_ENTRY( pxTCB, &xDelayedTaskList2 );
			vListRemove( ( xListItem * ) &( pxTCB->xGenericListItem ) );

			prvDeleteTCB( ( tskTCB * ) pxTCB );
		}

		while( !listLIST_IS_EMPTY( &xSuspendedTaskList ) )
		{
			listGET_OWNER_OF_NEXT_ENTRY( pxTCB, &xSuspendedTaskList );
			vListRemove( ( xListItem * ) &( pxTCB->xGenericListItem ) );

			prvDeleteTCB( ( tskTCB * ) pxTCB );
		}		
	}

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

#if ( configUSE_APPLICATION_TASK_TAG == 1 )

	void vTaskSetApplicationTaskTag( xTaskHandle xTask, pdTASK_HOOK_CODE pxTagValue )
	{
	tskTCB *xTCB;

		/* If xTask is NULL then we are setting our own task hook. */
		if( xTask == NULL )
		{
			xTCB = ( tskTCB * ) pxCurrentTCB;
		}
		else
		{
			xTCB = ( tskTCB * ) xTask;
		}
		
		/* Save the hook function in the TCB. */
		portENTER_CRITICAL();
			xTCB->pxTaskTag = pxTagValue;
		portEXIT_CRITICAL();
	}
	
#endif
/*-----------------------------------------------------------*/

#if ( configUSE_APPLICATION_TASK_TAG == 1 )

	portBASE_TYPE xTaskCallApplicationTaskHook( xTaskHandle xTask, void *pvParameter )
	{
	tskTCB *xTCB;
	portBASE_TYPE xReturn;

		/* If xTask is NULL then we are calling our own task hook. */
		if( xTask == NULL )
		{
			xTCB = ( tskTCB * ) pxCurrentTCB;
		}
		else
		{
			xTCB = ( tskTCB * ) xTask;
		}

		if( xTCB->pxTaskTag != NULL )
		{
			xReturn = xTCB->pxTaskTag( pvParameter );
		}
		else
		{
			xReturn = pdFAIL;
		}

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

void vTaskSwitchContext( void )
{
	traceTASK_SWITCHED_OUT();

	if( uxSchedulerSuspended != ( unsigned portBASE_TYPE ) pdFALSE )
	{
		/* The scheduler is currently suspended - do not allow a context
		switch. */
		xMissedYield = pdTRUE;
		return;
	}

	taskCHECK_FOR_STACK_OVERFLOW();

	/* Find the highest priority queue that contains ready tasks. */
	while( listLIST_IS_EMPTY( &( pxReadyTasksLists[ uxTopReadyPriority ] ) ) )
	{
		--uxTopReadyPriority;
	}

	/* listGET_OWNER_OF_NEXT_ENTRY walks through the list, so the tasks of the
	same priority get an equal share of the processor time. */
	listGET_OWNER_OF_NEXT_ENTRY( pxCurrentTCB, &( pxReadyTasksLists[ uxTopReadyPriority ] ) );

	traceTASK_SWITCHED_IN();
	vWriteTraceToBuffer();
}
/*-----------------------------------------------------------*/

void vTaskPlaceOnEventList( const xList * const pxEventList, portTickType xTicksToWait )
{
portTickType xTimeToWake;

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

	/* Place the event list item of the TCB in the appropriate event list.
	This is placed in the list in priority order so the highest priority task
	is the first to be woken by the event. */
	vListInsert( ( xList * ) pxEventList, ( xListItem * ) &( pxCurrentTCB->xEventListItem ) );

	/* We must remove ourselves from the ready list before adding ourselves
	to the blocked list as the same list item is used for both lists.  We have
	exclusive access to the ready lists as the scheduler is locked. */
	vListRemove( ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );


	#if ( INCLUDE_vTaskSuspend == 1 )
	{			
		if( xTicksToWait == portMAX_DELAY )
		{
			/* Add ourselves to the suspended task list instead of a delayed task
			list to ensure we are not woken by a timing event.  We will block
			indefinitely. */
			vListInsertEnd( ( xList * ) &xSuspendedTaskList, ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );
		}
		else
		{
			/* Calculate the time at which the task should be woken if the event does
			not occur.  This may overflow but this doesn't matter. */
			xTimeToWake = xTickCount + xTicksToWait;
		
			listSET_LIST_ITEM_VALUE( &( pxCurrentTCB->xGenericListItem ), xTimeToWake );
		
			if( xTimeToWake < xTickCount )
			{
				/* Wake time has overflowed.  Place this item in the overflow list. */
				vListInsert( ( xList * ) pxOverflowDelayedTaskList, ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );
			}
			else
			{
				/* The wake time has not overflowed, so we can use the current block list. */
				vListInsert( ( xList * ) pxDelayedTaskList, ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );
			}
		}
	}
	#else
	{
			/* Calculate the time at which the task should be woken if the event does
			not occur.  This may overflow but this doesn't matter. */
			xTimeToWake = xTickCount + xTicksToWait;
		
			listSET_LIST_ITEM_VALUE( &( pxCurrentTCB->xGenericListItem ), xTimeToWake );
		
			if( xTimeToWake < xTickCount )
			{
				/* Wake time has overflowed.  Place this item in the overflow list. */
				vListInsert( ( xList * ) pxOverflowDelayedTaskList, ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );
			}
			else
			{
				/* The wake time has not overflowed, so we can use the current block list. */
				vListInsert( ( xList * ) pxDelayedTaskList, ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );
			}
	}
	#endif
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xTaskRemoveFromEventList( const xList * const pxEventList )
{
tskTCB *pxUnblockedTCB;
portBASE_TYPE xReturn;

	/* THIS FUNCTION MUST BE CALLED WITH INTERRUPTS DISABLED OR THE
	SCHEDULER SUSPENDED.  It can also be called from within an ISR. */

	/* The event list is sorted in priority order, so we can remove the
	first in the list, remove the TCB from the delayed list, and add
	it to the ready list.
	
	If an event is for a queue that is locked then this function will never
	get called - the lock count on the queue will get modified instead.  This
	means we can always expect exclusive access to the event list here. */
	pxUnblockedTCB = ( tskTCB * ) listGET_OWNER_OF_HEAD_ENTRY( pxEventList );
	vListRemove( &( pxUnblockedTCB->xEventListItem ) );

	if( uxSchedulerSuspended == ( unsigned portBASE_TYPE ) pdFALSE )
	{
		vListRemove( &( pxUnblockedTCB->xGenericListItem ) );
		prvAddTaskToReadyQueue( pxUnblockedTCB );
	}
	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 * const pxTimeOut )
{
    pxTimeOut->xOverflowCount = xNumOfOverflows;
    pxTimeOut->xTimeOnEntering = xTickCount;
}
/*-----------------------------------------------------------*/

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

	portENTER_CRITICAL();
	{
		#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;
		}