gyro_board/src/usb/CommonDemoTasks/semtest.c

/*
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/*
 * Creates two sets of two tasks.  The tasks within a set share a variable, access
 * to which is guarded by a semaphore.
 *
 * Each task starts by attempting to obtain the semaphore.  On obtaining a
 * semaphore a task checks to ensure that the guarded variable has an expected
 * value.  It then clears the variable to zero before counting it back up to the
 * expected value in increments of 1.  After each increment the variable is checked
 * to ensure it contains the value to which it was just set. When the starting
 * value is again reached the task releases the semaphore giving the other task in
 * the set a chance to do exactly the same thing.  The starting value is high
 * enough to ensure that a tick is likely to occur during the incrementing loop.
 *
 * An error is flagged if at any time during the process a shared variable is
 * found to have a value other than that expected.  Such an occurrence would
 * suggest an error in the mutual exclusion mechanism by which access to the
 * variable is restricted.
 *
 * The first set of two tasks poll their semaphore.  The second set use blocking
 * calls.
 *
 */


#include <stdlib.h>

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

/* Demo app include files. */
#include "semtest.h"

/* The value to which the shared variables are counted. */
#define semtstBLOCKING_EXPECTED_VALUE		( ( unsigned long ) 0xfff )
#define semtstNON_BLOCKING_EXPECTED_VALUE	( ( unsigned long ) 0xff  )

#define semtstSTACK_SIZE			configMINIMAL_STACK_SIZE

#define semtstNUM_TASKS				( 4 )

#define semtstDELAY_FACTOR			( ( portTickType ) 10 )

/* The task function as described at the top of the file. */
static portTASK_FUNCTION_PROTO(prvSemaphoreTest, pvParameters);

/* Structure used to pass parameters to each task. */
typedef struct SEMAPHORE_PARAMETERS {
	xSemaphoreHandle xSemaphore;
	volatile unsigned long *pulSharedVariable;
	portTickType xBlockTime;
} xSemaphoreParameters;

/* Variables used to check that all the tasks are still running without errors. */
static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 };
static volatile short sNextCheckVariable = 0;

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

void vStartSemaphoreTasks(unsigned portBASE_TYPE uxPriority)
{
	xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
	const portTickType xBlockTime = (portTickType) 100;

	/* Create the structure used to pass parameters to the first two tasks. */
	pxFirstSemaphoreParameters = (xSemaphoreParameters *) pvPortMalloc(sizeof(xSemaphoreParameters));

	if (pxFirstSemaphoreParameters != NULL) {
		/* Create the semaphore used by the first two tasks. */
		vSemaphoreCreateBinary(pxFirstSemaphoreParameters->xSemaphore);

		if (pxFirstSemaphoreParameters->xSemaphore != NULL) {
			/* Create the variable which is to be shared by the first two tasks. */
			pxFirstSemaphoreParameters->pulSharedVariable = (unsigned long *) pvPortMalloc(sizeof(unsigned long));

			/* Initialise the share variable to the value the tasks expect. */
			*(pxFirstSemaphoreParameters->pulSharedVariable) = semtstNON_BLOCKING_EXPECTED_VALUE;

			/* The first two tasks do not block on semaphore calls. */
			pxFirstSemaphoreParameters->xBlockTime = (portTickType) 0;

			/* Spawn the first two tasks.  As they poll they operate at the idle priority. */
			xTaskCreate(prvSemaphoreTest, (signed char *) "PolSEM1", semtstSTACK_SIZE, (void *) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, (xTaskHandle *) NULL);
			xTaskCreate(prvSemaphoreTest, (signed char *) "PolSEM2", semtstSTACK_SIZE, (void *) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, (xTaskHandle *) NULL);
		}
	}

	/* Do exactly the same to create the second set of tasks, only this time
	provide a block time for the semaphore calls. */
	pxSecondSemaphoreParameters = (xSemaphoreParameters *) pvPortMalloc(sizeof(xSemaphoreParameters));
	if (pxSecondSemaphoreParameters != NULL) {
		vSemaphoreCreateBinary(pxSecondSemaphoreParameters->xSemaphore);

		if (pxSecondSemaphoreParameters->xSemaphore != NULL) {
			pxSecondSemaphoreParameters->pulSharedVariable = (unsigned long *) pvPortMalloc(sizeof(unsigned long));
			*(pxSecondSemaphoreParameters->pulSharedVariable) = semtstBLOCKING_EXPECTED_VALUE;
			pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_RATE_MS;

			xTaskCreate(prvSemaphoreTest, (signed char *) "BlkSEM1", semtstSTACK_SIZE, (void *) pxSecondSemaphoreParameters, uxPriority, (xTaskHandle *) NULL);
			xTaskCreate(prvSemaphoreTest, (signed char *) "BlkSEM2", semtstSTACK_SIZE, (void *) pxSecondSemaphoreParameters, uxPriority, (xTaskHandle *) NULL);
		}
	}

	/* vQueueAddToRegistry() adds the semaphore to the registry, if one is
	in use.  The registry is provided as a means for kernel aware
	debuggers to locate semaphores and has no purpose if a kernel aware debugger
	is not being used.  The call to vQueueAddToRegistry() will be removed
	by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
	defined to be less than 1. */
	vQueueAddToRegistry((xQueueHandle) pxFirstSemaphoreParameters->xSemaphore, (signed char *) "Counting_Sem_1");
	vQueueAddToRegistry((xQueueHandle) pxSecondSemaphoreParameters->xSemaphore, (signed char *) "Counting_Sem_2");
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION(prvSemaphoreTest, pvParameters)
{
	xSemaphoreParameters *pxParameters;
	volatile unsigned long *pulSharedVariable, ulExpectedValue;
	unsigned long ulCounter;
	short sError = pdFALSE, sCheckVariableToUse;

	/* See which check variable to use.  sNextCheckVariable is not semaphore
	protected! */
	portENTER_CRITICAL();
	sCheckVariableToUse = sNextCheckVariable;
	sNextCheckVariable++;
	portEXIT_CRITICAL();

	/* A structure is passed in as the parameter.  This contains the shared
	variable being guarded. */
	pxParameters = (xSemaphoreParameters *) pvParameters;
	pulSharedVariable = pxParameters->pulSharedVariable;

	/* If we are blocking we use a much higher count to ensure loads of context
	switches occur during the count. */
	if (pxParameters->xBlockTime > (portTickType) 0) {
		ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
	} else {
		ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
	}

	for (;;) {
		/* Try to obtain the semaphore. */
		if (xSemaphoreTake(pxParameters->xSemaphore, pxParameters->xBlockTime) == pdPASS) {
			/* We have the semaphore and so expect any other tasks using the
			shared variable to have left it in the state we expect to find
			it. */
			if (*pulSharedVariable != ulExpectedValue) {
				sError = pdTRUE;
			}

			/* Clear the variable, then count it back up to the expected value
			before releasing the semaphore.  Would expect a context switch or
			two during this time. */
			for (ulCounter = (unsigned long) 0; ulCounter <= ulExpectedValue; ulCounter++) {
				*pulSharedVariable = ulCounter;
				if (*pulSharedVariable != ulCounter) {
					sError = pdTRUE;
				}
			}

			/* Release the semaphore, and if no errors have occurred increment the check
			variable. */
			if (xSemaphoreGive(pxParameters->xSemaphore) == pdFALSE) {
				sError = pdTRUE;
			}

			if (sError == pdFALSE) {
				if (sCheckVariableToUse < semtstNUM_TASKS) {
					(sCheckVariables[ sCheckVariableToUse ])++;
				}
			}

			/* If we have a block time then we are running at a priority higher
			than the idle priority.  This task takes a long time to complete
			a cycle	(deliberately so to test the guarding) so will be starving
			out lower priority tasks.  Block for some time to allow give lower
			priority tasks some processor time. */
			vTaskDelay(pxParameters->xBlockTime * semtstDELAY_FACTOR);
		} else {
			if (pxParameters->xBlockTime == (portTickType) 0) {
				/* We have not got the semaphore yet, so no point using the
				processor.  We are not blocking when attempting to obtain the
				semaphore. */
				taskYIELD();
			}
		}
	}
}
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running. */
portBASE_TYPE xAreSemaphoreTasksStillRunning(void)
{
	static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
	portBASE_TYPE xTask, xReturn = pdTRUE;

	for (xTask = 0; xTask < semtstNUM_TASKS; xTask++) {
		if (sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ]) {
			xReturn = pdFALSE;
		}

		sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
	}

	return xReturn;
}