FreeRTOS vTasDelete() 函數執行流程 （6）

前言

1. 本博文基於MDK5和FreeRTOS V9.0.0開發，相當於一個筆記；
2. 本博文假設函數的建立和刪除都在動態內存環境下進行（configSUPPORT_DYNAMIC_ALLOCATION == 1且 configSUPPORT_STATIC_ALLOCATION == 0）；
3. 如有不足之處，還請多多指教；

vTasDelete() 任務刪除函數

attention: 刪除與建立相對立，與掛起有區別；
刪除與掛起的區別： 刪除了，這個任務就消失了，所佔用的動態內存空間就被釋放了，就和這個世界拜拜了；而掛起就是將任務掛在Suspended List列表上嗑瓜子，看着其他任務執行，自己不被調度器調度執行；

函數流程圖：

源碼：

#if ( INCLUDE_vTaskDelete == 1 )

	void vTaskDelete( TaskHandle_t xTaskToDelete )
	{
	TCB_t *pxTCB;

		taskENTER_CRITICAL();
		{
			/* If null is passed in here then it is the calling task that is
			being deleted. */
			pxTCB = prvGetTCBFromHandle( xTaskToDelete );

			/* Remove task from the ready list. */
			if( uxListRemove( &( pxTCB->xStateListItem ) ) == ( UBaseType_t ) 0 )
			{
				taskRESET_READY_PRIORITY( pxTCB->uxPriority );
			}
			else
			{
				mtCOVERAGE_TEST_MARKER();
			}

			/* Is the task waiting on an event also? */
			if( listLIST_ITEM_CONTAINER( &( pxTCB->xEventListItem ) ) != NULL )
			{
				( void ) uxListRemove( &( pxTCB->xEventListItem ) );
			}
			else
			{
				mtCOVERAGE_TEST_MARKER();
			}

			/* Increment the uxTaskNumber also so kernel aware debuggers can
			detect that the task lists need re-generating.  This is done before
			portPRE_TASK_DELETE_HOOK() as in the Windows port that macro will
			not return. */
			uxTaskNumber++;

			if( pxTCB == pxCurrentTCB )
			{
				/* A task is deleting itself.  This cannot complete within the
				task itself, as a context switch to another task is required.
				Place the task in the termination list.  The idle task will
				check the termination list and free up any memory allocated by
				the scheduler for the TCB and stack of the deleted task. */
				vListInsertEnd( &xTasksWaitingTermination, &( pxTCB->xStateListItem ) );

				/* 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. */
				++uxDeletedTasksWaitingCleanUp;

				/* The pre-delete hook is primarily for the Windows simulator,
				in which Windows specific clean up operations are performed,
				after which it is not possible to yield away from this task -
				hence xYieldPending is used to latch that a context switch is
				required. */
				portPRE_TASK_DELETE_HOOK( pxTCB, &xYieldPending );
			}
			else
			{
				--uxCurrentNumberOfTasks;
				prvDeleteTCB( pxTCB );

				/* Reset the next expected unblock time in case it referred to
				the task that has just been deleted. */
				prvResetNextTaskUnblockTime();
			}

			traceTASK_DELETE( pxTCB );
		}
		taskEXIT_CRITICAL();

		/* Force a reschedule if it is the currently running task that has just
		been deleted. */
		if( xSchedulerRunning != pdFALSE )
		{
			if( pxTCB == pxCurrentTCB )
			{
				configASSERT( uxSchedulerSuspended == 0 );
				portYIELD_WITHIN_API();
			}
			else
			{
				mtCOVERAGE_TEST_MARKER();
			}
		}
	}

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