tasks.c

一个开源的Modbus协议栈

				they should be processed now.  This ensures the tick count does not
				slip, and that any delayed tasks are resumed at the correct time. */
				if( uxMissedTicks > ( unsigned portBASE_TYPE ) 0 )
				{
					while( uxMissedTicks > ( unsigned portBASE_TYPE ) 0 )
					{
						vTaskIncrementTick();
						--uxMissedTicks;
					}

					/* As we have processed some ticks it is appropriate to yield
					to ensure the highest priority task that is ready to run is
					the task actually running. */
					xYieldRequired = pdTRUE;
				}
				
				if( ( xYieldRequired == pdTRUE ) || ( xMissedYield == pdTRUE ) )
				{
					xAlreadyYielded = pdTRUE;
					xMissedYield = pdFALSE;
					taskYIELD();
				}
			}
		}
	}
	portEXIT_CRITICAL();

	return xAlreadyYielded;
}






/*-----------------------------------------------------------
 * PUBLIC TASK UTILITIES documented in task.h
 *----------------------------------------------------------*/



portTickType xTaskGetTickCount( void )
{
portTickType xTicks;

	/* Critical section required if running on a 16 bit processor. */
	taskENTER_CRITICAL();
	{
		xTicks = xTickCount;
	}
	taskEXIT_CRITICAL();

	return xTicks;
}
/*-----------------------------------------------------------*/

unsigned portBASE_TYPE uxTaskGetNumberOfTasks( void )
{
unsigned portBASE_TYPE uxNumberOfTasks;

	taskENTER_CRITICAL();
		uxNumberOfTasks = uxCurrentNumberOfTasks;
	taskEXIT_CRITICAL();

	return uxNumberOfTasks;
}
/*-----------------------------------------------------------*/

#if ( ( configUSE_TRACE_FACILITY == 1 ) && ( INCLUDE_vTaskDelete == 1 ) && ( INCLUDE_vTaskSuspend == 1 ) )

	void vTaskList( signed portCHAR *pcWriteBuffer )
	{
	unsigned portBASE_TYPE uxQueue;

		/* This is a VERY costly function that should be used for debug only.
		It leaves interrupts disabled for a LONG time. */

        vTaskSuspendAll();
		{
			/* Run through all the lists that could potentially contain a TCB and
			report the task name, state and stack high water mark. */

			pcWriteBuffer[ 0 ] = ( signed portCHAR ) 0x00;
			strcat( ( portCHAR * ) pcWriteBuffer, ( const portCHAR * ) "\r\n" );

			uxQueue = uxTopUsedPriority + 1;

			do
			{
				uxQueue--;

				if( !listLIST_IS_EMPTY( &( pxReadyTasksLists[ uxQueue ] ) ) )
				{
					prvListTaskWithinSingleList( pcWriteBuffer, ( xList * ) &( pxReadyTasksLists[ uxQueue ] ), tskREADY_CHAR );			
				}
			}while( uxQueue > ( unsigned portSHORT ) tskIDLE_PRIORITY );

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

			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 = ( volatile signed portCHAR * volatile )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
 *----------------------------------------------------------*/


inline 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
}
/*-----------------------------------------------------------*/

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

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

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

void vTaskPlaceOnEventList( xList *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 *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 );
	}