2 FreeRTOS V7.5.1 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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6 ***************************************************************************
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8 * FreeRTOS provides completely free yet professionally developed, *
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9 * robust, strictly quality controlled, supported, and cross *
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10 * platform software that has become a de facto standard. *
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12 * Help yourself get started quickly and support the FreeRTOS *
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13 * project by purchasing a FreeRTOS tutorial book, reference *
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14 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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18 ***************************************************************************
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20 This file is part of the FreeRTOS distribution.
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22 FreeRTOS is free software; you can redistribute it and/or modify it under
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23 the terms of the GNU General Public License (version 2) as published by the
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24 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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26 >>! NOTE: The modification to the GPL is included to allow you to distribute
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27 >>! a combined work that includes FreeRTOS without being obliged to provide
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28 >>! the source code for proprietary components outside of the FreeRTOS
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31 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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32 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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33 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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34 link: http://www.freertos.org/a00114.html
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38 ***************************************************************************
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40 * Having a problem? Start by reading the FAQ "My application does *
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41 * not run, what could be wrong?" *
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43 * http://www.FreeRTOS.org/FAQHelp.html *
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45 ***************************************************************************
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47 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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48 license and Real Time Engineers Ltd. contact details.
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50 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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51 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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52 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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54 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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55 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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56 licenses offer ticketed support, indemnification and middleware.
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58 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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59 engineered and independently SIL3 certified version for use in safety and
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60 mission critical applications that require provable dependability.
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66 * Creates two sets of two tasks. The tasks within a set share a variable, access
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67 * to which is guarded by a semaphore.
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69 * Each task starts by attempting to obtain the semaphore. On obtaining a
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70 * semaphore a task checks to ensure that the guarded variable has an expected
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71 * value. It then clears the variable to zero before counting it back up to the
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72 * expected value in increments of 1. After each increment the variable is checked
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73 * to ensure it contains the value to which it was just set. When the starting
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74 * value is again reached the task releases the semaphore giving the other task in
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75 * the set a chance to do exactly the same thing. The starting value is high
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76 * enough to ensure that a tick is likely to occur during the incrementing loop.
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78 * An error is flagged if at any time during the process a shared variable is
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79 * found to have a value other than that expected. Such an occurrence would
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80 * suggest an error in the mutual exclusion mechanism by which access to the
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81 * variable is restricted.
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83 * The first set of two tasks poll their semaphore. The second set use blocking
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91 /* Scheduler include files. */
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92 #include "FreeRTOS.h"
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96 /* Demo app include files. */
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97 #include "semtest.h"
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99 /* The value to which the shared variables are counted. */
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100 #define semtstBLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xfff )
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101 #define semtstNON_BLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xff )
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103 #define semtstSTACK_SIZE configMINIMAL_STACK_SIZE
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105 #define semtstNUM_TASKS ( 4 )
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107 #define semtstDELAY_FACTOR ( ( portTickType ) 10 )
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109 /* The task function as described at the top of the file. */
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110 static portTASK_FUNCTION_PROTO( prvSemaphoreTest, pvParameters );
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112 /* Structure used to pass parameters to each task. */
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113 typedef struct SEMAPHORE_PARAMETERS
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115 xSemaphoreHandle xSemaphore;
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116 volatile unsigned long *pulSharedVariable;
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117 portTickType xBlockTime;
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118 } xSemaphoreParameters;
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120 /* Variables used to check that all the tasks are still running without errors. */
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121 static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 };
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122 static volatile short sNextCheckVariable = 0;
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124 /*-----------------------------------------------------------*/
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126 void vStartSemaphoreTasks( unsigned portBASE_TYPE uxPriority )
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128 xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
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129 const portTickType xBlockTime = ( portTickType ) 100;
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131 /* Create the structure used to pass parameters to the first two tasks. */
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132 pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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134 if( pxFirstSemaphoreParameters != NULL )
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136 /* Create the semaphore used by the first two tasks. */
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137 vSemaphoreCreateBinary( pxFirstSemaphoreParameters->xSemaphore );
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139 if( pxFirstSemaphoreParameters->xSemaphore != NULL )
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141 /* Create the variable which is to be shared by the first two tasks. */
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142 pxFirstSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );
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144 /* Initialise the share variable to the value the tasks expect. */
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145 *( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;
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147 /* The first two tasks do not block on semaphore calls. */
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148 pxFirstSemaphoreParameters->xBlockTime = ( portTickType ) 0;
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150 /* Spawn the first two tasks. As they poll they operate at the idle priority. */
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151 xTaskCreate( prvSemaphoreTest, ( signed char * ) "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
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152 xTaskCreate( prvSemaphoreTest, ( signed char * ) "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
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156 /* Do exactly the same to create the second set of tasks, only this time
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157 provide a block time for the semaphore calls. */
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158 pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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159 if( pxSecondSemaphoreParameters != NULL )
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161 vSemaphoreCreateBinary( pxSecondSemaphoreParameters->xSemaphore );
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163 if( pxSecondSemaphoreParameters->xSemaphore != NULL )
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165 pxSecondSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );
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166 *( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;
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167 pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_RATE_MS;
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169 xTaskCreate( prvSemaphoreTest, ( signed char * ) "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
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170 xTaskCreate( prvSemaphoreTest, ( signed char * ) "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
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174 /* vQueueAddToRegistry() adds the semaphore to the registry, if one is
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175 in use. The registry is provided as a means for kernel aware
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176 debuggers to locate semaphores and has no purpose if a kernel aware debugger
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177 is not being used. The call to vQueueAddToRegistry() will be removed
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178 by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
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179 defined to be less than 1. */
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180 vQueueAddToRegistry( ( xQueueHandle ) pxFirstSemaphoreParameters->xSemaphore, ( signed char * ) "Counting_Sem_1" );
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181 vQueueAddToRegistry( ( xQueueHandle ) pxSecondSemaphoreParameters->xSemaphore, ( signed char * ) "Counting_Sem_2" );
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183 /*-----------------------------------------------------------*/
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185 static portTASK_FUNCTION( prvSemaphoreTest, pvParameters )
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187 xSemaphoreParameters *pxParameters;
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188 volatile unsigned long *pulSharedVariable, ulExpectedValue;
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189 unsigned long ulCounter;
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190 short sError = pdFALSE, sCheckVariableToUse;
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192 /* See which check variable to use. sNextCheckVariable is not semaphore
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194 portENTER_CRITICAL();
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195 sCheckVariableToUse = sNextCheckVariable;
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196 sNextCheckVariable++;
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197 portEXIT_CRITICAL();
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199 /* A structure is passed in as the parameter. This contains the shared
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200 variable being guarded. */
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201 pxParameters = ( xSemaphoreParameters * ) pvParameters;
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202 pulSharedVariable = pxParameters->pulSharedVariable;
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204 /* If we are blocking we use a much higher count to ensure loads of context
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205 switches occur during the count. */
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206 if( pxParameters->xBlockTime > ( portTickType ) 0 )
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208 ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
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212 ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
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217 /* Try to obtain the semaphore. */
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218 if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )
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220 /* We have the semaphore and so expect any other tasks using the
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221 shared variable to have left it in the state we expect to find
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223 if( *pulSharedVariable != ulExpectedValue )
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228 /* Clear the variable, then count it back up to the expected value
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229 before releasing the semaphore. Would expect a context switch or
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230 two during this time. */
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231 for( ulCounter = ( unsigned long ) 0; ulCounter <= ulExpectedValue; ulCounter++ )
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233 *pulSharedVariable = ulCounter;
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234 if( *pulSharedVariable != ulCounter )
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240 /* Release the semaphore, and if no errors have occurred increment the check
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242 if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )
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247 if( sError == pdFALSE )
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249 if( sCheckVariableToUse < semtstNUM_TASKS )
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251 ( sCheckVariables[ sCheckVariableToUse ] )++;
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255 /* If we have a block time then we are running at a priority higher
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256 than the idle priority. This task takes a long time to complete
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257 a cycle (deliberately so to test the guarding) so will be starving
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258 out lower priority tasks. Block for some time to allow give lower
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259 priority tasks some processor time. */
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260 vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );
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264 if( pxParameters->xBlockTime == ( portTickType ) 0 )
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266 /* We have not got the semaphore yet, so no point using the
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267 processor. We are not blocking when attempting to obtain the
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274 /*-----------------------------------------------------------*/
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276 /* This is called to check that all the created tasks are still running. */
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277 portBASE_TYPE xAreSemaphoreTasksStillRunning( void )
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279 static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
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280 portBASE_TYPE xTask, xReturn = pdTRUE;
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282 for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )
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284 if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )
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289 sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
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