begriffs open source - cmsis-freertos/blob - Demo/Common/Full/semtest.c

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67 1 tab == 4 spaces!

68 */

69

70 /**

71 * Creates two sets of two tasks. The tasks within a set share a variable, access

72 * to which is guarded by a semaphore.

73 *

74 * Each task starts by attempting to obtain the semaphore. On obtaining a

75 * semaphore a task checks to ensure that the guarded variable has an expected

76 * value. It then clears the variable to zero before counting it back up to the

77 * expected value in increments of 1. After each increment the variable is checked

78 * to ensure it contains the value to which it was just set. When the starting

79 * value is again reached the task releases the semaphore giving the other task in

80 * the set a chance to do exactly the same thing. The starting value is high

81 * enough to ensure that a tick is likely to occur during the incrementing loop.

82 *

83 * An error is flagged if at any time during the process a shared variable is

84 * found to have a value other than that expected. Such an occurrence would

85 * suggest an error in the mutual exclusion mechanism by which access to the

86 * variable is restricted.

87 *

88 * The first set of two tasks poll their semaphore. The second set use blocking

89 * calls.

90 *

91 * \page SemTestC semtest.c

92 * \ingroup DemoFiles

93 * <HR>

94 */

95

96 /*

97 Changes from V1.2.0:

98

99 + The tasks that operate at the idle priority now use a lower expected

100 count than those running at a higher priority. This prevents the low

101 priority tasks from signaling an error because they have not been

102 scheduled enough time for each of them to count the shared variable to

103 the high value.

104

105 Changes from V2.0.0

106

107 + Delay periods are now specified using variables and constants of

108 TickType_t rather than unsigned long.

109

110 Changes from V2.1.1

111

112 + The stack size now uses configMINIMAL_STACK_SIZE.

113 + String constants made file scope to decrease stack depth on 8051 port.

114 */

115

116 #include <stdlib.h>

117

118 /* Scheduler include files. */

119 #include "FreeRTOS.h"

120 #include "task.h"

121 #include "semphr.h"

122

123 /* Demo app include files. */

124 #include "semtest.h"

125 #include "print.h"

126

127 /* The value to which the shared variables are counted. */

128 #define semtstBLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xfff )

129 #define semtstNON_BLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xff )

130

131 #define semtstSTACK_SIZE configMINIMAL_STACK_SIZE

132

133 #define semtstNUM_TASKS ( 4 )

134

135 #define semtstDELAY_FACTOR ( ( TickType_t ) 10 )

136

137 /* The task function as described at the top of the file. */

138 static void prvSemaphoreTest( void *pvParameters );

139

140 /* Structure used to pass parameters to each task. */

141 typedef struct SEMAPHORE_PARAMETERS

142 {

143 SemaphoreHandle_t xSemaphore;

144 volatile unsigned long *pulSharedVariable;

145 TickType_t xBlockTime;

146 } xSemaphoreParameters;

147

148 /* Variables used to check that all the tasks are still running without errors. */

149 static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 };

150 static volatile short sNextCheckVariable = 0;

151

152 /* Strings to print if USE_STDIO is defined. */

153 const char * const pcPollingSemaphoreTaskError = "Guarded shared variable in unexpected state.\r\n";

154 const char * const pcSemaphoreTaskStart = "Guarded shared variable task started.\r\n";

155

156 /*-----------------------------------------------------------*/

157

158 void vStartSemaphoreTasks( unsigned portBASE_TYPE uxPriority )

159 {

160 xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;

161 const TickType_t xBlockTime = ( TickType_t ) 100;

162

163 /* Create the structure used to pass parameters to the first two tasks. */

164 pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );

165

166 if( pxFirstSemaphoreParameters != NULL )

167 {

168 /* Create the semaphore used by the first two tasks. */

169 vSemaphoreCreateBinary( pxFirstSemaphoreParameters->xSemaphore );

170

171 if( pxFirstSemaphoreParameters->xSemaphore != NULL )

172 {

173 /* Create the variable which is to be shared by the first two tasks. */

174 pxFirstSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );

175

176 /* Initialise the share variable to the value the tasks expect. */

177 *( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;

178

179 /* The first two tasks do not block on semaphore calls. */

180 pxFirstSemaphoreParameters->xBlockTime = ( TickType_t ) 0;

181

182 /* Spawn the first two tasks. As they poll they operate at the idle priority. */

183 xTaskCreate( prvSemaphoreTest, "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );

184 xTaskCreate( prvSemaphoreTest, "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );

185 }

186 }

187

188 /* Do exactly the same to create the second set of tasks, only this time

189 provide a block time for the semaphore calls. */

190 pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );

191 if( pxSecondSemaphoreParameters != NULL )

192 {

193 vSemaphoreCreateBinary( pxSecondSemaphoreParameters->xSemaphore );

194

195 if( pxSecondSemaphoreParameters->xSemaphore != NULL )

196 {

197 pxSecondSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );

198 *( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;

199 pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_PERIOD_MS;

200

201 xTaskCreate( prvSemaphoreTest, "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );

202 xTaskCreate( prvSemaphoreTest, "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );

203 }

204 }

205 }

206 /*-----------------------------------------------------------*/

207

208 static void prvSemaphoreTest( void *pvParameters )

209 {

210 xSemaphoreParameters *pxParameters;

211 volatile unsigned long *pulSharedVariable, ulExpectedValue;

212 unsigned long ulCounter;

213 short sError = pdFALSE, sCheckVariableToUse;

214

215 /* See which check variable to use. sNextCheckVariable is not semaphore

216 protected! */

217 portENTER_CRITICAL();

218 sCheckVariableToUse = sNextCheckVariable;

219 sNextCheckVariable++;

220 portEXIT_CRITICAL();

221

222 /* Queue a message for printing to say the task has started. */

223 vPrintDisplayMessage( &pcSemaphoreTaskStart );

224

225 /* A structure is passed in as the parameter. This contains the shared

226 variable being guarded. */

227 pxParameters = ( xSemaphoreParameters * ) pvParameters;

228 pulSharedVariable = pxParameters->pulSharedVariable;

229

230 /* If we are blocking we use a much higher count to ensure loads of context

231 switches occur during the count. */

232 if( pxParameters->xBlockTime > ( TickType_t ) 0 )

233 {

234 ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;

235 }

236 else

237 {

238 ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;

239 }

240

241 for( ;; )

242 {

243 /* Try to obtain the semaphore. */

244 if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )

245 {

246 /* We have the semaphore and so expect any other tasks using the

247 shared variable to have left it in the state we expect to find

248 it. */

249 if( *pulSharedVariable != ulExpectedValue )

250 {

251 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );

252 sError = pdTRUE;

253 }

254

255 /* Clear the variable, then count it back up to the expected value

256 before releasing the semaphore. Would expect a context switch or

257 two during this time. */

258 for( ulCounter = ( unsigned long ) 0; ulCounter <= ulExpectedValue; ulCounter++ )

259 {

260 *pulSharedVariable = ulCounter;

261 if( *pulSharedVariable != ulCounter )

262 {

263 if( sError == pdFALSE )

264 {

265 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );

266 }

267 sError = pdTRUE;

268 }

269 }

270

271 /* Release the semaphore, and if no errors have occurred increment the check

272 variable. */

273 if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )

274 {

275 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );

276 sError = pdTRUE;

277 }

278

279 if( sError == pdFALSE )

280 {

281 if( sCheckVariableToUse < semtstNUM_TASKS )

282 {

283 ( sCheckVariables[ sCheckVariableToUse ] )++;

284 }

285 }

286

287 /* If we have a block time then we are running at a priority higher

288 than the idle priority. This task takes a long time to complete

289 a cycle (deliberately so to test the guarding) so will be starving

290 out lower priority tasks. Block for some time to allow give lower

291 priority tasks some processor time. */

292 vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );

293 }

294 else

295 {

296 if( pxParameters->xBlockTime == ( TickType_t ) 0 )

297 {

298 /* We have not got the semaphore yet, so no point using the

299 processor. We are not blocking when attempting to obtain the

300 semaphore. */

301 taskYIELD();

302 }

303 }

304 }

305 }

306 /*-----------------------------------------------------------*/

307

308 /* This is called to check that all the created tasks are still running. */

309 portBASE_TYPE xAreSemaphoreTasksStillRunning( void )

310 {

311 static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };

312 portBASE_TYPE xTask, xReturn = pdTRUE;

313

314 for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )

315 {

316 if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )

317 {

318 xReturn = pdFALSE;

319 }

320

321 sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];

322 }

323

324 return xReturn;

325 }

326

327