2 FreeRTOS V8.2.2 - Copyright (C) 2015 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 This file is part of the FreeRTOS distribution.
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9 FreeRTOS is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License (version 2) as published by the
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11 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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13 ***************************************************************************
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14 >>! NOTE: The modification to the GPL is included to allow you to !<<
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15 >>! distribute a combined work that includes FreeRTOS without being !<<
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16 >>! obliged to provide the source code for proprietary components !<<
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17 >>! outside of the FreeRTOS kernel. !<<
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18 ***************************************************************************
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20 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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21 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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22 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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23 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * FreeRTOS provides completely free yet professionally developed, *
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28 * robust, strictly quality controlled, supported, and cross *
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29 * platform software that is more than just the market leader, it *
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30 * is the industry's de facto standard. *
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32 * Help yourself get started quickly while simultaneously helping *
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33 * to support the FreeRTOS project by purchasing a FreeRTOS *
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34 * tutorial book, reference manual, or both: *
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35 * http://www.FreeRTOS.org/Documentation *
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37 ***************************************************************************
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39 http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
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40 the FAQ page "My application does not run, what could be wrong?". Have you
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41 defined configASSERT()?
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43 http://www.FreeRTOS.org/support - In return for receiving this top quality
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44 embedded software for free we request you assist our global community by
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45 participating in the support forum.
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47 http://www.FreeRTOS.org/training - Investing in training allows your team to
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48 be as productive as possible as early as possible. Now you can receive
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49 FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
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50 Ltd, and the world's leading authority on the world's leading RTOS.
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52 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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53 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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54 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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56 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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57 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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59 http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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60 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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61 licenses offer ticketed support, indemnification and commercial middleware.
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63 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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64 engineered and independently SIL3 certified version for use in safety and
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65 mission critical applications that require provable dependability.
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71 * Creates two sets of two tasks. The tasks within a set share a variable, access
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72 * to which is guarded by a semaphore.
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74 * Each task starts by attempting to obtain the semaphore. On obtaining a
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75 * semaphore a task checks to ensure that the guarded variable has an expected
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76 * value. It then clears the variable to zero before counting it back up to the
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77 * expected value in increments of 1. After each increment the variable is checked
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78 * to ensure it contains the value to which it was just set. When the starting
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79 * value is again reached the task releases the semaphore giving the other task in
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80 * the set a chance to do exactly the same thing. The starting value is high
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81 * enough to ensure that a tick is likely to occur during the incrementing loop.
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83 * An error is flagged if at any time during the process a shared variable is
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84 * found to have a value other than that expected. Such an occurrence would
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85 * suggest an error in the mutual exclusion mechanism by which access to the
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86 * variable is restricted.
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88 * The first set of two tasks poll their semaphore. The second set use blocking
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91 * \page SemTestC semtest.c
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92 * \ingroup DemoFiles
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97 Changes from V1.2.0:
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99 + The tasks that operate at the idle priority now use a lower expected
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100 count than those running at a higher priority. This prevents the low
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101 priority tasks from signaling an error because they have not been
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102 scheduled enough time for each of them to count the shared variable to
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105 Changes from V2.0.0
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107 + Delay periods are now specified using variables and constants of
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108 TickType_t rather than unsigned long.
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110 Changes from V2.1.1
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112 + The stack size now uses configMINIMAL_STACK_SIZE.
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113 + String constants made file scope to decrease stack depth on 8051 port.
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116 #include <stdlib.h>
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118 /* Scheduler include files. */
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119 #include "FreeRTOS.h"
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121 #include "semphr.h"
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123 /* Demo app include files. */
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124 #include "semtest.h"
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127 /* The value to which the shared variables are counted. */
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128 #define semtstBLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xfff )
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129 #define semtstNON_BLOCKING_EXPECTED_VALUE ( ( unsigned long ) 0xff )
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131 #define semtstSTACK_SIZE configMINIMAL_STACK_SIZE
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133 #define semtstNUM_TASKS ( 4 )
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135 #define semtstDELAY_FACTOR ( ( TickType_t ) 10 )
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137 /* The task function as described at the top of the file. */
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138 static void prvSemaphoreTest( void *pvParameters );
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140 /* Structure used to pass parameters to each task. */
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141 typedef struct SEMAPHORE_PARAMETERS
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143 SemaphoreHandle_t xSemaphore;
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144 volatile unsigned long *pulSharedVariable;
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145 TickType_t xBlockTime;
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146 } xSemaphoreParameters;
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148 /* Variables used to check that all the tasks are still running without errors. */
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149 static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 };
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150 static volatile short sNextCheckVariable = 0;
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152 /* Strings to print if USE_STDIO is defined. */
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153 const char * const pcPollingSemaphoreTaskError = "Guarded shared variable in unexpected state.\r\n";
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154 const char * const pcSemaphoreTaskStart = "Guarded shared variable task started.\r\n";
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156 /*-----------------------------------------------------------*/
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158 void vStartSemaphoreTasks( unsigned portBASE_TYPE uxPriority )
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160 xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
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161 const TickType_t xBlockTime = ( TickType_t ) 100;
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163 /* Create the structure used to pass parameters to the first two tasks. */
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164 pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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166 if( pxFirstSemaphoreParameters != NULL )
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168 /* Create the semaphore used by the first two tasks. */
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169 vSemaphoreCreateBinary( pxFirstSemaphoreParameters->xSemaphore );
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171 if( pxFirstSemaphoreParameters->xSemaphore != NULL )
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173 /* Create the variable which is to be shared by the first two tasks. */
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174 pxFirstSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );
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176 /* Initialise the share variable to the value the tasks expect. */
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177 *( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;
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179 /* The first two tasks do not block on semaphore calls. */
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180 pxFirstSemaphoreParameters->xBlockTime = ( TickType_t ) 0;
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182 /* Spawn the first two tasks. As they poll they operate at the idle priority. */
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183 xTaskCreate( prvSemaphoreTest, "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );
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184 xTaskCreate( prvSemaphoreTest, "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );
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188 /* Do exactly the same to create the second set of tasks, only this time
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189 provide a block time for the semaphore calls. */
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190 pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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191 if( pxSecondSemaphoreParameters != NULL )
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193 vSemaphoreCreateBinary( pxSecondSemaphoreParameters->xSemaphore );
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195 if( pxSecondSemaphoreParameters->xSemaphore != NULL )
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197 pxSecondSemaphoreParameters->pulSharedVariable = ( unsigned long * ) pvPortMalloc( sizeof( unsigned long ) );
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198 *( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;
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199 pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_PERIOD_MS;
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201 xTaskCreate( prvSemaphoreTest, "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );
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202 xTaskCreate( prvSemaphoreTest, "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );
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206 /*-----------------------------------------------------------*/
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208 static void prvSemaphoreTest( void *pvParameters )
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210 xSemaphoreParameters *pxParameters;
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211 volatile unsigned long *pulSharedVariable, ulExpectedValue;
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212 unsigned long ulCounter;
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213 short sError = pdFALSE, sCheckVariableToUse;
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215 /* See which check variable to use. sNextCheckVariable is not semaphore
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217 portENTER_CRITICAL();
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218 sCheckVariableToUse = sNextCheckVariable;
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219 sNextCheckVariable++;
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220 portEXIT_CRITICAL();
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222 /* Queue a message for printing to say the task has started. */
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223 vPrintDisplayMessage( &pcSemaphoreTaskStart );
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225 /* A structure is passed in as the parameter. This contains the shared
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226 variable being guarded. */
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227 pxParameters = ( xSemaphoreParameters * ) pvParameters;
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228 pulSharedVariable = pxParameters->pulSharedVariable;
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230 /* If we are blocking we use a much higher count to ensure loads of context
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231 switches occur during the count. */
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232 if( pxParameters->xBlockTime > ( TickType_t ) 0 )
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234 ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
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238 ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
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243 /* Try to obtain the semaphore. */
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244 if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )
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246 /* We have the semaphore and so expect any other tasks using the
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247 shared variable to have left it in the state we expect to find
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249 if( *pulSharedVariable != ulExpectedValue )
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251 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );
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255 /* Clear the variable, then count it back up to the expected value
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256 before releasing the semaphore. Would expect a context switch or
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257 two during this time. */
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258 for( ulCounter = ( unsigned long ) 0; ulCounter <= ulExpectedValue; ulCounter++ )
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260 *pulSharedVariable = ulCounter;
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261 if( *pulSharedVariable != ulCounter )
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263 if( sError == pdFALSE )
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265 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );
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271 /* Release the semaphore, and if no errors have occurred increment the check
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273 if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )
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275 vPrintDisplayMessage( &pcPollingSemaphoreTaskError );
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279 if( sError == pdFALSE )
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281 if( sCheckVariableToUse < semtstNUM_TASKS )
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283 ( sCheckVariables[ sCheckVariableToUse ] )++;
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287 /* If we have a block time then we are running at a priority higher
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288 than the idle priority. This task takes a long time to complete
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289 a cycle (deliberately so to test the guarding) so will be starving
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290 out lower priority tasks. Block for some time to allow give lower
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291 priority tasks some processor time. */
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292 vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );
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296 if( pxParameters->xBlockTime == ( TickType_t ) 0 )
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298 /* We have not got the semaphore yet, so no point using the
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299 processor. We are not blocking when attempting to obtain the
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306 /*-----------------------------------------------------------*/
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308 /* This is called to check that all the created tasks are still running. */
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309 portBASE_TYPE xAreSemaphoreTasksStillRunning( void )
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311 static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
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312 portBASE_TYPE xTask, xReturn = pdTRUE;
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314 for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )
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316 if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )
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321 sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
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