Demo/Common/Minimal/integer.c

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/*
 * This version of integer. c is for use on systems that have limited stack
 * space and no display facilities.  The complete version can be found in
 * the Demo/Common/Full directory.
 *
 * As with the full version, the tasks created in this file are a good test 
 * of the scheduler context switch mechanism.  The processor has to access 
 * 32bit variables in two or four chunks (depending on the processor).  The low 
 * priority of these tasks means there is a high probability that a context 
 * switch will occur mid calculation.  See flop. c documentation for 
 * more information.
 *
 */

/*
Changes from V1.2.1

	+ The constants used in the calculations are larger to ensure the
	  optimiser does not truncate them to 16 bits.

Changes from V1.2.3

	+ uxTaskCheck is now just used as a boolean.  Instead of incrementing
	  the variable each cycle of the task, the variable is simply set to
	  true.  sAreIntegerMathsTaskStillRunning() sets it back to false and
	  expects it to have been set back to true by the time it is called
	  again.
	+ A division has been included in the calculation.
*/

#include <stdlib.h>

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"

/* Demo program include files. */
#include "integer.h"

/* The constants used in the calculation. */
#define intgCONST1				( ( portLONG ) 123 )
#define intgCONST2				( ( portLONG ) 234567 )
#define intgCONST3				( ( portLONG ) -3 )
#define intgCONST4				( ( portLONG ) 7 )
#define intgEXPECTED_ANSWER		( ( ( intgCONST1 + intgCONST2 ) * intgCONST3 ) / intgCONST4 )

#define intgSTACK_SIZE			configMINIMAL_STACK_SIZE

/* As this is the minimal version, we will only create one task. */
#define intgNUMBER_OF_TASKS		( 1 )

/* The task function.  Repeatedly performs a 32 bit calculation, checking the
result against the expected result.  If the result is incorrect then the
context switch must have caused some corruption. */
static portTASK_FUNCTION_PROTO( vCompeteingIntMathTask, pvParameters );

/* Variables that are set to true within the calculation task to indicate
that the task is still executing.  The check task sets the variable back to
false, flagging an error if the variable is still false the next time it
is called. */
static volatile signed portBASE_TYPE xTaskCheck[ intgNUMBER_OF_TASKS ] = { ( signed portBASE_TYPE ) pdFALSE };

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

void vStartIntegerMathTasks( unsigned portBASE_TYPE uxPriority )
{
portSHORT sTask;

	for( sTask = 0; sTask < intgNUMBER_OF_TASKS; sTask++ )
	{
		xTaskCreate( vCompeteingIntMathTask, ( signed portCHAR * ) "IntMath", intgSTACK_SIZE, ( void * ) &( xTaskCheck[ sTask ] ), uxPriority, ( xTaskHandle * ) NULL );
	}
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vCompeteingIntMathTask, pvParameters )
{
/* These variables are all effectively set to constants so they are volatile to
ensure the compiler does not just get rid of them. */
volatile portLONG lValue;
portSHORT sError = pdFALSE;
volatile signed portBASE_TYPE *pxTaskHasExecuted;

	/* Set a pointer to the variable we are going to set to true each
	iteration.  This is also a good test of the parameter passing mechanism
	within each port. */
	pxTaskHasExecuted = ( volatile signed portBASE_TYPE * ) pvParameters;

	/* Keep performing a calculation and checking the result against a constant. */
	for( ;; )
	{
		/* Perform the calculation.  This will store partial value in
		registers, resulting in a good test of the context switch mechanism. */
		lValue = intgCONST1;
		lValue += intgCONST2;

		/* Yield in case cooperative scheduling is being used. */
		#if configUSE_PREEMPTION == 0
		{
			taskYIELD();
		}
		#endif

		/* Finish off the calculation. */
		lValue *= intgCONST3;
		lValue /= intgCONST4;

		/* If the calculation is found to be incorrect we stop setting the 
		TaskHasExecuted variable so the check task can see an error has 
		occurred. */
		if( lValue != intgEXPECTED_ANSWER ) /*lint !e774 volatile used to prevent this being optimised out. */
		{
			sError = pdTRUE;
		}

		if( sError == pdFALSE )
		{
			/* We have not encountered any errors, so set the flag that show
			we are still executing.  This will be periodically cleared by
			the check task. */
			portENTER_CRITICAL();
				*pxTaskHasExecuted = pdTRUE;
			portEXIT_CRITICAL();
		}

		/* Yield in case cooperative scheduling is being used. */
		#if configUSE_PREEMPTION == 0
		{
			taskYIELD();
		}
		#endif
	}
}
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running. */
portBASE_TYPE xAreIntegerMathsTaskStillRunning( void )
{
portBASE_TYPE xReturn = pdTRUE;
portSHORT sTask;

	/* Check the maths tasks are still running by ensuring their check variables 
	are still being set to true. */
	for( sTask = 0; sTask < intgNUMBER_OF_TASKS; sTask++ )
	{
		if( xTaskCheck[ sTask ] == pdFALSE )
		{
			/* The check has not incremented so an error exists. */
			xReturn = pdFALSE;
		}

		/* Reset the check variable so we can tell if it has been set by
		the next time around. */
		xTaskCheck[ sTask ] = pdFALSE;
	}

	return xReturn;
}