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52 * Simple demonstration of the usage of counting semaphore.
55 /* Scheduler include files. */
60 /* Demo program include files. */
63 /* The maximum count value that the semaphore used for the demo can hold. */
64 #define countMAX_COUNT_VALUE ( 200 )
66 /* Constants used to indicate whether or not the semaphore should have been
67 created with its maximum count value, or its minimum count value. These
68 numbers are used to ensure that the pointers passed in as the task parameters
70 #define countSTART_AT_MAX_COUNT ( 0xaa )
71 #define countSTART_AT_ZERO ( 0x55 )
73 /* Two tasks are created for the test. One uses a semaphore created with its
74 count value set to the maximum, and one with the count value set to zero. */
75 #define countNUM_TEST_TASKS ( 2 )
76 #define countDONT_BLOCK ( 0 )
78 /*-----------------------------------------------------------*/
80 /* Flag that will be latched to pdTRUE should any unexpected behaviour be
81 detected in any of the tasks. */
82 static volatile portBASE_TYPE xErrorDetected = pdFALSE;
84 /*-----------------------------------------------------------*/
87 * The demo task. This simply counts the semaphore up to its maximum value,
88 * the counts it back down again. The result of each semaphore 'give' and
89 * 'take' is inspected, with an error being flagged if it is found not to be
90 * the expected result.
92 static void prvCountingSemaphoreTask( void *pvParameters );
95 * Utility function to increment the semaphore count value up from zero to
96 * countMAX_COUNT_VALUE.
98 static void prvIncrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter );
101 * Utility function to decrement the semaphore count value up from
102 * countMAX_COUNT_VALUE to zero.
104 static void prvDecrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter );
106 /*-----------------------------------------------------------*/
108 /* The structure that is passed into the task as the task parameter. */
109 typedef struct COUNT_SEM_STRUCT
111 /* The semaphore to be used for the demo. */
112 xSemaphoreHandle xSemaphore;
114 /* Set to countSTART_AT_MAX_COUNT if the semaphore should be created with
115 its count value set to its max count value, or countSTART_AT_ZERO if it
116 should have been created with its count value set to 0. */
117 unsigned portBASE_TYPE uxExpectedStartCount;
119 /* Incremented on each cycle of the demo task. Used to detect a stalled
121 unsigned portBASE_TYPE uxLoopCounter;
124 /* Two structures are defined, one is passed to each test task. */
125 static volatile xCountSemStruct xParameters[ countNUM_TEST_TASKS ];
127 /*-----------------------------------------------------------*/
129 void vStartCountingSemaphoreTasks( void )
131 /* Create the semaphores that we are going to use for the test/demo. The
132 first should be created such that it starts at its maximum count value,
133 the second should be created such that it starts with a count value of zero. */
134 xParameters[ 0 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, countMAX_COUNT_VALUE );
135 xParameters[ 0 ].uxExpectedStartCount = countSTART_AT_MAX_COUNT;
136 xParameters[ 0 ].uxLoopCounter = 0;
138 xParameters[ 1 ].xSemaphore = xSemaphoreCreateCounting( countMAX_COUNT_VALUE, 0 );
139 xParameters[ 1 ].uxExpectedStartCount = 0;
140 xParameters[ 1 ].uxLoopCounter = 0;
142 /* Were the semaphores created? */
143 if( ( xParameters[ 0 ].xSemaphore != NULL ) || ( xParameters[ 1 ].xSemaphore != NULL ) )
145 /* Create the demo tasks, passing in the semaphore to use as the parameter. */
146 xTaskCreate( prvCountingSemaphoreTask, ( signed portCHAR * ) "CNT1", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 0 ] ), tskIDLE_PRIORITY, NULL );
147 xTaskCreate( prvCountingSemaphoreTask, ( signed portCHAR * ) "CNT2", configMINIMAL_STACK_SIZE, ( void * ) &( xParameters[ 1 ] ), tskIDLE_PRIORITY, NULL );
150 /*-----------------------------------------------------------*/
152 static void prvDecrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter )
154 unsigned portBASE_TYPE ux;
156 /* If the semaphore count is at its maximum then we should not be able to
157 'give' the semaphore. */
158 if( xSemaphoreGive( xSemaphore ) == pdPASS )
160 xErrorDetected = pdTRUE;
163 /* We should be able to 'take' the semaphore countMAX_COUNT_VALUE times. */
164 for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
166 if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) != pdPASS )
168 /* We expected to be able to take the semaphore. */
169 xErrorDetected = pdTRUE;
172 ( *puxLoopCounter )++;
175 #if configUSE_PREEMPTION == 0
179 /* If the semaphore count is zero then we should not be able to 'take'
181 if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
183 xErrorDetected = pdTRUE;
186 /*-----------------------------------------------------------*/
188 static void prvIncrementSemaphoreCount( xSemaphoreHandle xSemaphore, unsigned portBASE_TYPE *puxLoopCounter )
190 unsigned portBASE_TYPE ux;
192 /* If the semaphore count is zero then we should not be able to 'take'
194 if( xSemaphoreTake( xSemaphore, countDONT_BLOCK ) == pdPASS )
196 xErrorDetected = pdTRUE;
199 /* We should be able to 'give' the semaphore countMAX_COUNT_VALUE times. */
200 for( ux = 0; ux < countMAX_COUNT_VALUE; ux++ )
202 if( xSemaphoreGive( xSemaphore ) != pdPASS )
204 /* We expected to be able to take the semaphore. */
205 xErrorDetected = pdTRUE;
208 ( *puxLoopCounter )++;
211 #if configUSE_PREEMPTION == 0
215 /* If the semaphore count is at its maximum then we should not be able to
216 'give' the semaphore. */
217 if( xSemaphoreGive( xSemaphore ) == pdPASS )
219 xErrorDetected = pdTRUE;
222 /*-----------------------------------------------------------*/
224 static void prvCountingSemaphoreTask( void *pvParameters )
226 xCountSemStruct *pxParameter;
229 void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
231 const portCHAR * const pcTaskStartMsg = "Counting semaphore demo started.\r\n";
233 /* Queue a message for printing to say the task has started. */
234 vPrintDisplayMessage( &pcTaskStartMsg );
237 /* The semaphore to be used was passed as the parameter. */
238 pxParameter = ( xCountSemStruct * ) pvParameters;
240 /* Did we expect to find the semaphore already at its max count value, or
242 if( pxParameter->uxExpectedStartCount == countSTART_AT_MAX_COUNT )
244 prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
247 /* Now we expect the semaphore count to be 0, so this time there is an
248 error if we can take the semaphore. */
249 if( xSemaphoreTake( pxParameter->xSemaphore, 0 ) == pdPASS )
251 xErrorDetected = pdTRUE;
256 prvIncrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
257 prvDecrementSemaphoreCount( pxParameter->xSemaphore, &( pxParameter->uxLoopCounter ) );
260 /*-----------------------------------------------------------*/
262 portBASE_TYPE xAreCountingSemaphoreTasksStillRunning( void )
264 static unsigned portBASE_TYPE uxLastCount0 = 0, uxLastCount1 = 0;
265 portBASE_TYPE xReturn = pdPASS;
267 /* Return fail if any 'give' or 'take' did not result in the expected
269 if( xErrorDetected != pdFALSE )
274 /* Return fail if either task is not still incrementing its loop counter. */
275 if( uxLastCount0 == xParameters[ 0 ].uxLoopCounter )
281 uxLastCount0 = xParameters[ 0 ].uxLoopCounter;
284 if( uxLastCount1 == xParameters[ 1 ].uxLoopCounter )
290 uxLastCount1 = xParameters[ 1 ].uxLoopCounter;