tasks.c

freemodbus-v019.zip 是v0.19版本的代码

#endif

/*
 * When a task is created, the stack of the task is filled with a known value.
 * This function determines the 'high water mark' of the task stack by
 * determining how much of the stack remains at the original preset value.
 */
#if ( configUSE_TRACE_FACILITY == 1 )

	unsigned portSHORT usTaskCheckFreeStackSpace( const unsigned portCHAR *pucStackByte );

#endif

/*lint +e956 */





/*-----------------------------------------------------------
 * TASK CREATION API documented in task.h
 *----------------------------------------------------------*/

signed portBASE_TYPE xTaskCreate( pdTASK_CODE pvTaskCode, const signed portCHAR * const pcName, unsigned portSHORT usStackDepth, void *pvParameters, unsigned portBASE_TYPE uxPriority, xTaskHandle *pxCreatedTask )
{
signed portBASE_TYPE xReturn;
tskTCB * pxNewTCB;
static unsigned portBASE_TYPE uxTaskNumber = 0; /*lint !e956 Static is deliberate - this is guarded before use. */

	/* Allocate the memory required by the TCB and stack for the new task.
	checking that the allocation was successful. */
	pxNewTCB = prvAllocateTCBAndStack( usStackDepth );

	if( pxNewTCB != NULL )
	{		
		portSTACK_TYPE *pxTopOfStack;

		/* Setup the newly allocated TCB with the initial state of the task. */
		prvInitialiseTCBVariables( pxNewTCB, usStackDepth, pcName, uxPriority );

		/* Calculate the top of stack address.  This depends on whether the
		stack grows from high memory to low (as per the 80x86) or visa versa.
		portSTACK_GROWTH is used to make the result positive or negative as
		required by the port. */
		#if portSTACK_GROWTH < 0
		{
			pxTopOfStack = pxNewTCB->pxStack + ( pxNewTCB->usStackDepth - 1 );
		}
		#else
		{
			pxTopOfStack = pxNewTCB->pxStack;	
		}
		#endif

		/* Initialize the TCB stack to look as if the task was already running,
		but had been interrupted by the scheduler.  The return address is set
		to the start of the task function. Once the stack has been initialised
		the	top of stack variable is updated. */
		pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pvTaskCode, pvParameters );

		/* We are going to manipulate the task queues to add this task to a
		ready list, so must make sure no interrupts occur. */
		portENTER_CRITICAL();
		{
			uxCurrentNumberOfTasks++;
			if( uxCurrentNumberOfTasks == ( unsigned portBASE_TYPE ) 1 )
			{
				/* As this is the first task it must also be the current task. */
				pxCurrentTCB = ( volatile tskTCB * volatile ) pxNewTCB;

				/* This is the first task to be created so do the preliminary
				initialisation required.  We will not recover if this call
				fails, but we will report the failure. */
				prvInitialiseTaskLists();
			}
			else
			{	
				/* If the scheduler is not already running, make this task the
				current task if it is the highest priority task to be created
				so far. */
				if( xSchedulerRunning == pdFALSE )
				{
					if( pxCurrentTCB->uxPriority <= uxPriority )
					{
						pxCurrentTCB = ( volatile tskTCB * volatile ) pxNewTCB;	
					}
				}
			}				

			/* Remember the top priority to make context switching faster.  Use
			the priority in pxNewTCB as this has been capped to a valid value. */
			if( pxNewTCB->uxPriority > uxTopUsedPriority )
			{
				uxTopUsedPriority = pxNewTCB->uxPriority;
			}

			/* Add a counter into the TCB for tracing only. */
			pxNewTCB->uxTCBNumber = uxTaskNumber;
			uxTaskNumber++;

			prvAddTaskToReadyQueue( pxNewTCB );

			xReturn = pdPASS;
		}
		portEXIT_CRITICAL();
	}
	else
	{
		xReturn = errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY;
	}

	if( xReturn == pdPASS )
	{
		if( ( void * ) pxCreatedTask != NULL )
		{
			/* Pass the TCB out - in an anonymous way.  The calling function/
			task can use this as a handle to delete the task later if
			required.*/
			*pxCreatedTask = ( xTaskHandle ) pxNewTCB;
		}

		if( xSchedulerRunning != pdFALSE )
		{
			/* If the created task is of a higher priority than the current task
			then it should run now. */
			if( pxCurrentTCB->uxPriority < uxPriority )
			{
				taskYIELD();
			}
		}
	}

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

#if ( INCLUDE_vTaskDelete == 1 )

	void vTaskDelete( xTaskHandle pxTaskToDelete )
	{
	tskTCB *pxTCB;

		taskENTER_CRITICAL();
		{
			/* If null is passed in here then we are deleting ourselves. */
			pxTCB = prvGetTCBFromHandle( pxTaskToDelete );

			/* Remove task from the ready list and place in the	termination list.
			This will stop the task from be scheduled.  The idle task will check
			the termination list and free up any memory allocated by the
			scheduler for the TCB and stack. */
			vListRemove( &( pxTCB->xGenericListItem ) );

			/* Is the task waiting on an event also? */												
			if( pxTCB->xEventListItem.pvContainer )
			{
				vListRemove( &( pxTCB->xEventListItem ) );
			}

			vListInsertEnd( ( xList * ) &xTasksWaitingTermination, &( pxTCB->xGenericListItem ) );

			/* Increment the ucTasksDeleted variable so the idle task knows
			there is a task that has been deleted and that it should therefore
			check the xTasksWaitingTermination list. */
			++uxTasksDeleted;
		}
		taskEXIT_CRITICAL();

		/* Force a reschedule if we have just deleted the current task. */
		if( ( void * ) pxTaskToDelete == NULL )
		{
			taskYIELD();
		}
	}

#endif






/*-----------------------------------------------------------
 * TASK CONTROL API documented in task.h
 *----------------------------------------------------------*/

#if ( INCLUDE_vTaskDelayUntil == 1 )
	void vTaskDelayUntil( portTickType *pxPreviousWakeTime, portTickType xTimeIncrement )
	{
	portTickType xTimeToWake;
	portBASE_TYPE xAlreadyYielded, xShouldDelay = pdFALSE;

		vTaskSuspendAll();
		{
			/* Generate the tick time at which the task wants to wake. */
			xTimeToWake = *pxPreviousWakeTime + xTimeIncrement;

			if( xTickCount < *pxPreviousWakeTime )
			{
				/* The tick count has overflowed since this function was
				lasted called.  In this case the only time we should ever
				actually delay is if the wake time has also	overflowed,
				and the wake time is greater than the tick time.  When this
				is the case it is as if neither time had overflowed. */
				if( ( xTimeToWake < *pxPreviousWakeTime ) && ( xTimeToWake > xTickCount ) )
				{
					xShouldDelay = pdTRUE;
				}
			}
			else
			{
				/* The tick time has not overflowed.  In this case we will
				delay if either the wake time has overflowed, and/or the
				tick time is less than the wake time. */
				if( ( xTimeToWake < *pxPreviousWakeTime ) || ( xTimeToWake > xTickCount ) )
				{
					xShouldDelay = pdTRUE;
				}
			}

			/* Update the wake time ready for the next call. */
			*pxPreviousWakeTime = xTimeToWake;

			if( xShouldDelay )
			{
				/* 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. */
				vListRemove( ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );

				/* The list item will be inserted in wake time order. */
				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 ) );
				}
			}
		}
		xAlreadyYielded = xTaskResumeAll();

		/* Force a reschedule if xTaskResumeAll has not already done so, we may
		have put ourselves to sleep. */
		if( !xAlreadyYielded )
		{
			taskYIELD();
		}
	}
#endif
/*-----------------------------------------------------------*/

#if ( INCLUDE_vTaskDelay == 1 )
	void vTaskDelay( portTickType xTicksToDelay )
	{
	portTickType xTimeToWake;
	signed portBASE_TYPE xAlreadyYielded = pdFALSE;

		/* A delay time of zero just forces a reschedule. */
		if( xTicksToDelay > ( portTickType ) 0 )
		{
			vTaskSuspendAll();
			{
				/* A task that is removed from the event list while the
				scheduler is suspended will not get placed in the ready
				list or removed from the blocked list until the scheduler
				is resumed.
				
				This task cannot be in an event list as it is the currently
				executing task. */

				/* Calculate the time to wake - this may overflow but this is
				not a problem. */
				xTimeToWake = xTickCount + xTicksToDelay;

				/* 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. */
				vListRemove( ( xListItem * ) &( pxCurrentTCB->xGenericListItem ) );

				/* The list item will be inserted in wake time order. */
				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 ) );
				}
			}
			xAlreadyYielded = xTaskResumeAll();
		}
		
		/* Force a reschedule if xTaskResumeAll has not already done so, we may
		have put ourselves to sleep. */
		if( !xAlreadyYielded )
		{
			taskYIELD();
		}
	}
#endif
/*-----------------------------------------------------------*/

#if ( INCLUDE_uxTaskPriorityGet == 1 )

	unsigned portBASE_TYPE uxTaskPriorityGet( xTaskHandle pxTask )
	{
	tskTCB *pxTCB;
	unsigned portBASE_TYPE uxReturn;

		taskENTER_CRITICAL();
		{
			/* If null is passed in here then we are changing the
			priority of the calling function. */
			pxTCB = prvGetTCBFromHandle( pxTask );
			uxReturn = pxTCB->uxPriority;
		}
		taskEXIT_CRITICAL();

		return uxReturn;
	}

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

#if ( INCLUDE_vTaskPrioritySet == 1 )

	void vTaskPrioritySet( xTaskHandle pxTask, unsigned portBASE_TYPE uxNewPriority )
	{
	tskTCB *pxTCB;
	unsigned portBASE_TYPE uxCurrentPriority;

		/* Ensure the new priority is valid. */
		if( uxNewPriority >= configMAX_PRIORITIES )
		{
			uxNewPriority = configMAX_PRIORITIES - 1;
		}

		taskENTER_CRITICAL();
		{
			/* If null is passed in here then we are changing the
			priority of the calling function. */
			pxTCB = prvGetTCBFromHandle( pxTask );
			uxCurrentPriority = pxTCB->uxPriority;

			if( uxCurrentPriority != uxNewPriority )
			{
				pxTCB->uxPriority = uxNewPriority;

				/* If the task is in the blocked or suspended list we need do
				nothing more than change it's priority variable. However, if
				the task is in a ready list it needs to be removed and placed
				in the queue appropriate to its new priority. */
				if( listIS_CONTAINED_WITHIN( &( pxReadyTasksLists[ uxCurrentPriority ] ), &( pxTCB->xGenericListItem ) ) )
				{
					if( uxSchedulerSuspended == ( unsigned portBASE_TYPE ) pdFALSE )
					{
						/* The task is currently in its ready list - remove before adding
						it to it's new ready list. */
						vListRemove( &( pxTCB->xGenericListItem ) );
						prvAddTaskToReadyQueue( pxTCB );
					}
					else
					{
						/* We cannot access the delayed or ready lists, so will hold this
						task pending until the scheduler is resumed. */
						vListInsertEnd( ( xList * ) &( xPendingReadyList ), &( pxTCB->xEventListItem ) );
					}
				}			
			}
		}
		taskEXIT_CRITICAL();

		/* The priority change may have readied a task of higher
		priority than the calling task. */
		taskYIELD();
	}

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

#if ( INCLUDE_vTaskSuspend == 1 )

	void vTaskSuspend( xTaskHandle pxTaskToSuspend )
	{
	tskTCB *pxTCB;

		taskENTER_CRITICAL();
		{
			/* If null is passed in here then we are suspending ourselves. */
			pxTCB = prvGetTCBFromHandle( pxTaskToSuspend );

			/* Remove task from the ready/delayed list and place in the	suspended list. */
			vListRemove( &( pxTCB->xGenericListItem ) );

			/* Is the task waiting on an event also? */