path: root/FreeRTOS/Demo/Common/Minimal/countsem.c

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/*
 * Simple demonstration of the usage of counting semaphore.
 */

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

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

/* The maximum count value that the semaphore used for the demo can hold. */
#define countMAX_COUNT_VALUE       ( 200 )

/* Constants used to indicate whether or not the semaphore should have been
 * created with its maximum count value, or its minimum count value.  These
 * numbers are used to ensure that the pointers passed in as the task parameters
 * are valid. */
#define countSTART_AT_MAX_COUNT    ( 0xaa )
#define countSTART_AT_ZERO         ( 0x55 )

/* Two tasks are created for the test.  One uses a semaphore created with its
 * count value set to the maximum, and one with the count value set to zero. */
#define countNUM_TEST_TASKS        ( 2 )
#define countDONT_BLOCK            ( 0 )

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

/* Flag that will be latched to pdTRUE should any unexpected behaviour be
 * detected in any of the tasks. */
static volatile BaseType_t xErrorDetected = pdFALSE;

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

/*
 * The demo task.  This simply counts the semaphore up to its maximum value,
 * the counts it back down again.  The result of each semaphore 'give' and
 * 'take' is inspected, with an error being flagged if it is found not to be
 * the expected result.
 */
static void prvCountingSemaphoreTask( void * pvParameters );

/*
 * Utility function to increment the semaphore count value up from zero to
 * countMAX_COUNT_VALUE.
 */
static void prvIncrementSemaphoreCount( SemaphoreHandle_t xSemaphore,
                                        volatile UBaseType_t * puxLoopCounter );

/*
 * Utility function to decrement the semaphore count value up from
 * countMAX_COUNT_VALUE to zero.
 */
static void prvDecrementSemaphoreCount( SemaphoreHandle_t xSemaphore,
                                        volatile UBaseType_t * puxLoopCounter );

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

/* The structure that is passed into the task as the task parameter. */
typedef struct COUNT_SEM_STRUCT
{
    /* The semaphore to be used for the demo. */
    SemaphoreHandle_t xSemaphore;

    /* Set to countSTART_AT_MAX_COUNT if the semaphore should be created with
     * its count value set to its max count value, or countSTART_AT_ZERO if it
     * should have been created with its count value set to 0. */
    UBaseType_t uxExpectedStartCount;

    /* Incremented on each cycle of the demo task.  Used to detect a stalled
     * task. */
    volatile UBaseType_t uxLoopCounter;
} xCountSemStruct;

/* Two structures are defined, one is passed to each test task. */
static xCountSemStruct xParameters[ countNUM_TEST_TASKS ];

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

void vStartCountingSemaphoreTasks( void )
{
    /* Create the semaphores that we are going to use for the test/demo.  The
     * first should be created such that it starts at its maximum count value,
     * the second should be created such that it starts with a count value of zero. */
    xParameters[ 0 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, countMAX_COUNT_VALUE );
    xParameters[ 0 ].uxExpectedStartCount = countSTART_AT_MAX_COUNT;
    xParameters[ 0 ].uxLoopCounter = 0;

    xParameters[ 1 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, 0 );
    xParameters[ 1 ].uxExpectedStartCount = 0;
    xParameters[ 1 ].uxLoopCounter = 0;

    /* Were the semaphores created? */
    if( ( xParameters[ 0 ].xSemaphore != NULL ) || ( xParameters[ 1 ].xSemaphore != 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( ( QueueHandle_t ) xParameters[ 0 ].xSemaphore, "Counting_Sem_1" );
        vQueueAddToRegistry( ( QueueHandle_t ) xParameters[ 1 ].xSemaphore, "Counting_Sem_2" );

        /* Create the demo tasks, passing in the semaphore to use as the parameter. */
        xTaskCreate( prvCountingSemaphoreTask, "CNT1", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 0 ] ), tskIDLE_PRIORITY, NULL );
        xTaskCreate( prvCountingSemaphoreTask, "CNT2", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 1 ] ), tskIDLE_PRIORITY, NULL );
    }
}
/*-----------------------------------------------------------*/

static void prvDecrementSemaphoreCount( SemaphoreHandle_t xSemaphore,
                                        volatile UBaseType_t * puxLoopCounter )
{
    UBaseType_t ux;

    /* If the semaphore count is at its maximum then we should not be able to
     * 'give' the semaphore. */
    if( xSemaphoreGive( xSemaphore ) == pdPASS )
    {
        xErrorDetected = pdTRUE;
    }

    /* We should be able to 'take' the semaphore countMAX_COUNT_VALUE times. */
    for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
    {
        configASSERT( uxSemaphoreGetCount( xSemaphore ) == ( countMAX_COUNT_VALUE - ux ) );

        if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) != pdPASS )
        {
            /* We expected to be able to take the semaphore. */
            xErrorDetected = pdTRUE;
        }

        ( *puxLoopCounter )++;
    }

    #if configUSE_PREEMPTION == 0
        taskYIELD();
    #endif

    /* If the semaphore count is zero then we should not be able to	'take'
     * the semaphore. */
    configASSERT( uxSemaphoreGetCount( xSemaphore ) == 0 );

    if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
    {
        xErrorDetected = pdTRUE;
    }
}
/*-----------------------------------------------------------*/

static void prvIncrementSemaphoreCount( SemaphoreHandle_t xSemaphore,
                                        volatile UBaseType_t * puxLoopCounter )
{
    UBaseType_t ux;

    /* If the semaphore count is zero then we should not be able to	'take'
     * the semaphore. */
    if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
    {
        xErrorDetected = pdTRUE;
    }

    /* We should be able to 'give' the semaphore countMAX_COUNT_VALUE times. */
    for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
    {
        configASSERT( uxSemaphoreGetCount( xSemaphore ) == ux );

        if( xSemaphoreGive( xSemaphore ) != pdPASS )
        {
            /* We expected to be able to take the semaphore. */
            xErrorDetected = pdTRUE;
        }

        ( *puxLoopCounter )++;
    }

    #if configUSE_PREEMPTION == 0
        taskYIELD();
    #endif

    /* If the semaphore count is at its maximum then we should not be able to
     * 'give' the semaphore. */
    if( xSemaphoreGive( xSemaphore ) == pdPASS )
    {
        xErrorDetected = pdTRUE;
    }
}
/*-----------------------------------------------------------*/

static void prvCountingSemaphoreTask( void * pvParameters )
{
    xCountSemStruct * pxParameter;

    #ifdef USE_STDIO
        void vPrintDisplayMessage( const char * const * ppcMessageToSend );

        const char * const pcTaskStartMsg = "Counting semaphore demo started.\r\n";

        /* Queue a message for printing to say the task has started. */
        vPrintDisplayMessage( &pcTaskStartMsg );
    #endif

    /* The semaphore to be used was passed as the parameter. */
    pxParameter = ( xCountSemStruct * ) pvParameters;

    /* Did we expect to find the semaphore already at its max count value, or
     * at zero? */
    if( pxParameter->uxExpectedStartCount == countSTART_AT_MAX_COUNT )
    {
        prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
    }

    /* Now we expect the semaphore count to be 0, so this time there is an
     * error if we can take the semaphore. */
    if( xSemaphoreTake( pxParameter->xSemaphore, 0 ) == pdPASS )
    {
        xErrorDetected = pdTRUE;
    }

    for( ; ; )
    {
        prvIncrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
        prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
    }
}
/*-----------------------------------------------------------*/

BaseType_t xAreCountingSemaphoreTasksStillRunning( void )
{
    static UBaseType_t uxLastCount0 = 0, uxLastCount1 = 0;
    BaseType_t xReturn = pdPASS;

    /* Return fail if any 'give' or 'take' did not result in the expected
     * behaviour. */
    if( xErrorDetected != pdFALSE )
    {
        xReturn = pdFAIL;
    }

    /* Return fail if either task is not still incrementing its loop counter. */
    if( uxLastCount0 == xParameters[ 0 ].uxLoopCounter )
    {
        xReturn = pdFAIL;
    }
    else
    {
        uxLastCount0 = xParameters[ 0 ].uxLoopCounter;
    }

    if( uxLastCount1 == xParameters[ 1 ].uxLoopCounter )
    {
        xReturn = pdFAIL;
    }
    else
    {
        uxLastCount1 = xParameters[ 1 ].uxLoopCounter;
    }

    return xReturn;
}