FreeRTOS/Common/Minimal/countsem.c

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  52 */
  53
  54
  55 /*
  56  * Simple demonstration of the usage of counting semaphore.
  57  */
  58
  59 /* Scheduler include files. */
  60 #include "FreeRTOS.h"
  61 #include "task.h"
  62 #include "semphr.h"
  63
  64 /* Demo program include files. */
  65 #include "countsem.h"
  66
  67 /* The maximum count value that the semaphore used for the demo can hold. */
  68 #define countMAX_COUNT_VALUE    ( 200 )
  69
  70 /* Constants used to indicate whether or not the semaphore should have been
  71 created with its maximum count value, or its minimum count value.  These
  72 numbers are used to ensure that the pointers passed in as the task parameters
  73 are valid. */
  74 #define countSTART_AT_MAX_COUNT ( 0xaa )
  75 #define countSTART_AT_ZERO              ( 0x55 )
  76
  77 /* Two tasks are created for the test.  One uses a semaphore created with its
  78 count value set to the maximum, and one with the count value set to zero. */
  79 #define countNUM_TEST_TASKS             ( 2 )
  80 #define countDONT_BLOCK                 ( 0 )
  81
  82 /*-----------------------------------------------------------*/
  83
  84 /* Flag that will be latched to pdTRUE should any unexpected behaviour be
  85 detected in any of the tasks. */
  86 static volatile portBASE_TYPE xErrorDetected = pdFALSE;
  87
  88 /*-----------------------------------------------------------*/
  89
  90 /*
  91  * The demo task.  This simply counts the semaphore up to its maximum value,
  92  * the counts it back down again.  The result of each semaphore 'give' and
  93  * 'take' is inspected, with an error being flagged if it is found not to be
  94  * the expected result.
  95  */
  96 static void prvCountingSemaphoreTask( void *pvParameters );
  97
  98 /*
  99  * Utility function to increment the semaphore count value up from zero to
 100  * countMAX_COUNT_VALUE.
 101  */
 102 static void prvIncrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter );
 103
 104 /*
 105  * Utility function to decrement the semaphore count value up from
 106  * countMAX_COUNT_VALUE to zero.
 107  */
 108 static void prvDecrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter );
 109
 110 /*-----------------------------------------------------------*/
 111
 112 /* The structure that is passed into the task as the task parameter. */
 113 typedef struct COUNT_SEM_STRUCT
 114 {
 115         /* The semaphore to be used for the demo. */
 116         xSemaphoreHandle xSemaphore;
 117
 118         /* Set to countSTART_AT_MAX_COUNT if the semaphore should be created with
 119         its count value set to its max count value, or countSTART_AT_ZERO if it
 120         should have been created with its count value set to 0. */
 121         unsigned portBASE_TYPE uxExpectedStartCount;
 122
 123         /* Incremented on each cycle of the demo task.  Used to detect a stalled
 124         task. */
 125         unsigned portBASE_TYPE uxLoopCounter;
 126 } xCountSemStruct;
 127
 128 /* Two structures are defined, one is passed to each test task. */
 129 static volatile xCountSemStruct xParameters[ countNUM_TEST_TASKS ];
 130
 131 /*-----------------------------------------------------------*/
 132
 133 void vStartCountingSemaphoreTasks( void )
 134 {
 135         /* Create the semaphores that we are going to use for the test/demo.  The
 136         first should be created such that it starts at its maximum count value,
 137         the second should be created such that it starts with a count value of zero. */
 138         xParameters[ 0 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, countMAX_COUNT_VALUE );
 139         xParameters[ 0 ].uxExpectedStartCount = countSTART_AT_MAX_COUNT;
 140         xParameters[ 0 ].uxLoopCounter = 0;
 141
 142         xParameters[ 1 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, 0 );
 143         xParameters[ 1 ].uxExpectedStartCount = 0;
 144         xParameters[ 1 ].uxLoopCounter = 0;
 145
 146         /* vQueueAddToRegistry() adds the semaphore to the registry, if one is
 147         in use.  The registry is provided as a means for kernel aware
 148         debuggers to locate semaphores and has no purpose if a kernel aware debugger
 149         is not being used.  The call to vQueueAddToRegistry() will be removed
 150         by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
 151         defined to be less than 1. */
 152         vQueueAddToRegistry( ( xQueueHandle ) xParameters[ 0 ].xSemaphore, ( signed portCHAR * ) "Counting_Sem_1" );
 153         vQueueAddToRegistry( ( xQueueHandle ) xParameters[ 1 ].xSemaphore, ( signed portCHAR * ) "Counting_Sem_2" );
 154
 155
 156         /* Were the semaphores created? */
 157         if( ( xParameters[ 0 ].xSemaphore != NULL ) || ( xParameters[ 1 ].xSemaphore != NULL ) )
 158         {
 159                 /* Create the demo tasks, passing in the semaphore to use as the parameter. */
 160                 xTaskCreate( prvCountingSemaphoreTask, ( signed portCHAR * ) "CNT1", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 0 ] ), tskIDLE_PRIORITY, NULL );
 161                 xTaskCreate( prvCountingSemaphoreTask, ( signed portCHAR * ) "CNT2", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 1 ] ), tskIDLE_PRIORITY, NULL );
 162         }
 163 }
 164 /*-----------------------------------------------------------*/
 165
 166 static void prvDecrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter )
 167 {
 168 unsigned portBASE_TYPE ux;
 169
 170         /* If the semaphore count is at its maximum then we should not be able to
 171         'give' the semaphore. */
 172         if( xSemaphoreGive( xSemaphore ) == pdPASS )
 173         {
 174                 xErrorDetected = pdTRUE;
 175         }
 176
 177         /* We should be able to 'take' the semaphore countMAX_COUNT_VALUE times. */
 178         for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
 179         {
 180                 if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) != pdPASS )
 181                 {
 182                         /* We expected to be able to take the semaphore. */
 183                         xErrorDetected = pdTRUE;
 184                 }
 185
 186                 ( *puxLoopCounter )++;
 187         }
 188
 189         #if configUSE_PREEMPTION == 0
 190                 taskYIELD();
 191         #endif
 192
 193         /* If the semaphore count is zero then we should not be able to 'take'
 194         the semaphore. */
 195         if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
 196         {
 197                 xErrorDetected = pdTRUE;
 198         }
 199 }
 200 /*-----------------------------------------------------------*/
 201
 202 static void prvIncrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter )
 203 {
 204 unsigned portBASE_TYPE ux;
 205
 206         /* If the semaphore count is zero then we should not be able to 'take'
 207         the semaphore. */
 208         if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
 209         {
 210                 xErrorDetected = pdTRUE;
 211         }
 212
 213         /* We should be able to 'give' the semaphore countMAX_COUNT_VALUE times. */
 214         for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
 215         {
 216                 if( xSemaphoreGive( xSemaphore ) != pdPASS )
 217                 {
 218                         /* We expected to be able to take the semaphore. */
 219                         xErrorDetected = pdTRUE;
 220                 }
 221
 222                 ( *puxLoopCounter )++;
 223         }
 224
 225         #if configUSE_PREEMPTION == 0
 226                 taskYIELD();
 227         #endif
 228
 229         /* If the semaphore count is at its maximum then we should not be able to
 230         'give' the semaphore. */
 231         if( xSemaphoreGive( xSemaphore ) == pdPASS )
 232         {
 233                 xErrorDetected = pdTRUE;
 234         }
 235 }
 236 /*-----------------------------------------------------------*/
 237
 238 static void prvCountingSemaphoreTask( void *pvParameters )
 239 {
 240 xCountSemStruct *pxParameter;
 241
 242         #ifdef USE_STDIO
 243         void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
 244
 245                 const portCHAR * const pcTaskStartMsg = "Counting semaphore demo started.\r\n";
 246
 247                 /* Queue a message for printing to say the task has started. */
 248                 vPrintDisplayMessage( &pcTaskStartMsg );
 249         #endif
 250
 251         /* The semaphore to be used was passed as the parameter. */
 252         pxParameter = ( xCountSemStruct * ) pvParameters;
 253
 254         /* Did we expect to find the semaphore already at its max count value, or
 255         at zero? */
 256         if( pxParameter->uxExpectedStartCount == countSTART_AT_MAX_COUNT )
 257         {
 258                 prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
 259         }
 260
 261         /* Now we expect the semaphore count to be 0, so this time there is an
 262         error if we can take the semaphore. */
 263         if( xSemaphoreTake( pxParameter->xSemaphore, 0 ) == pdPASS )
 264         {
 265                 xErrorDetected = pdTRUE;
 266         }
 267
 268         for( ;; )
 269         {
 270                 prvIncrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
 271                 prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
 272         }
 273 }
 274 /*-----------------------------------------------------------*/
 275
 276 portBASE_TYPE xAreCountingSemaphoreTasksStillRunning( void )
 277 {
 278 static unsigned portBASE_TYPE uxLastCount0 = 0, uxLastCount1 = 0;
 279 portBASE_TYPE xReturn = pdPASS;
 280
 281         /* Return fail if any 'give' or 'take' did not result in the expected
 282         behaviour. */
 283         if( xErrorDetected != pdFALSE )
 284         {
 285                 xReturn = pdFAIL;
 286         }
 287
 288         /* Return fail if either task is not still incrementing its loop counter. */
 289         if( uxLastCount0 == xParameters[ 0 ].uxLoopCounter )
 290         {
 291                 xReturn = pdFAIL;
 292         }
 293         else
 294         {
 295                 uxLastCount0 = xParameters[ 0 ].uxLoopCounter;
 296         }
 297
 298         if( uxLastCount1 == xParameters[ 1 ].uxLoopCounter )
 299         {
 300                 xReturn = pdFAIL;
 301         }
 302         else
 303         {
 304                 uxLastCount1 = xParameters[ 1 ].uxLoopCounter;
 305         }
 306
 307         return xReturn;
 308 }
 309
 310