2 FreeRTOS V6.0.0 - Copyright (C) 2009 Real Time Engineers Ltd.
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4 This file is part of the FreeRTOS distribution.
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6 FreeRTOS is free software; you can redistribute it and/or modify it under
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7 the terms of the GNU General Public License (version 2) as published by the
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8 Free Software Foundation and modified by the FreeRTOS exception.
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9 **NOTE** The exception to the GPL is included to allow you to distribute a
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10 combined work that includes FreeRTOS without being obliged to provide the
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11 source code for proprietary components outside of the FreeRTOS kernel.
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12 Alternative commercial license and support terms are also available upon
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13 request. See the licensing section of http://www.FreeRTOS.org for full
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16 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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21 You should have received a copy of the GNU General Public License along
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22 with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
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23 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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26 ***************************************************************************
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28 * The FreeRTOS eBook and reference manual are available to purchase for a *
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29 * small fee. Help yourself get started quickly while also helping the *
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30 * FreeRTOS project! See http://www.FreeRTOS.org/Documentation for details *
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32 ***************************************************************************
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36 Please ensure to read the configuration and relevant port sections of the
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37 online documentation.
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39 http://www.FreeRTOS.org - Documentation, latest information, license and
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42 http://www.SafeRTOS.com - A version that is certified for use in safety
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45 http://www.OpenRTOS.com - Commercial support, development, porting,
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46 licensing and training services.
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50 * The first test creates three tasks - two counter tasks (one continuous count
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51 * and one limited count) and one controller. A "count" variable is shared
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52 * between all three tasks. The two counter tasks should never be in a "ready"
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53 * state at the same time. The controller task runs at the same priority as
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54 * the continuous count task, and at a lower priority than the limited count
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57 * One counter task loops indefinitely, incrementing the shared count variable
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58 * on each iteration. To ensure it has exclusive access to the variable it
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59 * raises it's priority above that of the controller task before each
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60 * increment, lowering it again to it's original priority before starting the
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63 * The other counter task increments the shared count variable on each
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64 * iteration of it's loop until the count has reached a limit of 0xff - at
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65 * which point it suspends itself. It will not start a new loop until the
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66 * controller task has made it "ready" again by calling vTaskResume ().
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67 * This second counter task operates at a higher priority than controller
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68 * task so does not need to worry about mutual exclusion of the counter
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71 * The controller task is in two sections. The first section controls and
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72 * monitors the continuous count task. When this section is operational the
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73 * limited count task is suspended. Likewise, the second section controls
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74 * and monitors the limited count task. When this section is operational the
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75 * continuous count task is suspended.
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77 * In the first section the controller task first takes a copy of the shared
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78 * count variable. To ensure mutual exclusion on the count variable it
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79 * suspends the continuous count task, resuming it again when the copy has been
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80 * taken. The controller task then sleeps for a fixed period - during which
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81 * the continuous count task will execute and increment the shared variable.
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82 * When the controller task wakes it checks that the continuous count task
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83 * has executed by comparing the copy of the shared variable with its current
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84 * value. This time, to ensure mutual exclusion, the scheduler itself is
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85 * suspended with a call to vTaskSuspendAll (). This is for demonstration
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86 * purposes only and is not a recommended technique due to its inefficiency.
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88 * After a fixed number of iterations the controller task suspends the
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89 * continuous count task, and moves on to its second section.
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91 * At the start of the second section the shared variable is cleared to zero.
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92 * The limited count task is then woken from it's suspension by a call to
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93 * vTaskResume (). As this counter task operates at a higher priority than
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94 * the controller task the controller task should not run again until the
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95 * shared variable has been counted up to the limited value causing the counter
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96 * task to suspend itself. The next line after vTaskResume () is therefore
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97 * a check on the shared variable to ensure everything is as expected.
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100 * The second test consists of a couple of very simple tasks that post onto a
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101 * queue while the scheduler is suspended. This test was added to test parts
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102 * of the scheduler not exercised by the first test.
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105 * The final set of two tasks implements a third test. This simply raises the
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106 * priority of a task while the scheduler is suspended. Again this test was
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107 * added to exercise parts of the code not covered by the first test.
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109 * \page Priorities dynamic.c
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110 * \ingroup DemoFiles
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115 Changes from V2.0.0
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117 + Delay periods are now specified using variables and constants of
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118 portTickType rather than unsigned long.
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119 + Added a second, simple test that uses the functions
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120 vQueueReceiveWhenSuspendedTask() and vQueueSendWhenSuspendedTask().
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122 Changes from V3.1.1
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124 + Added a third simple test that uses the vTaskPrioritySet() function
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125 while the scheduler is suspended.
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126 + Modified the controller task slightly to test the calling of
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127 vTaskResumeAll() while the scheduler is suspended.
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130 #include <stdlib.h>
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132 /* Scheduler include files. */
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133 #include "FreeRTOS.h"
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135 #include "semphr.h"
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137 /* Demo app include files. */
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138 #include "dynamic.h"
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141 /* Function that implements the "limited count" task as described above. */
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142 static void vLimitedIncrementTask( void * pvParameters );
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144 /* Function that implements the "continuous count" task as described above. */
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145 static void vContinuousIncrementTask( void * pvParameters );
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147 /* Function that implements the controller task as described above. */
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148 static void vCounterControlTask( void * pvParameters );
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150 /* The simple test functions that check sending and receiving while the
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151 scheduler is suspended. */
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152 static void vQueueReceiveWhenSuspendedTask( void *pvParameters );
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153 static void vQueueSendWhenSuspendedTask( void *pvParameters );
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155 /* The simple test functions that check raising and lowering of task priorities
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156 while the scheduler is suspended. */
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157 static void prvChangePriorityWhenSuspendedTask( void *pvParameters );
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158 static void prvChangePriorityHelperTask( void *pvParameters );
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161 /* Demo task specific constants. */
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162 #define priSTACK_SIZE ( ( unsigned short ) configMINIMAL_STACK_SIZE )
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163 #define priSLEEP_TIME ( ( portTickType ) 50 )
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164 #define priLOOPS ( 5 )
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165 #define priMAX_COUNT ( ( unsigned long ) 0xff )
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166 #define priNO_BLOCK ( ( portTickType ) 0 )
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167 #define priSUSPENDED_QUEUE_LENGTH ( 1 )
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169 /*-----------------------------------------------------------*/
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171 /* Handles to the two counter tasks. These could be passed in as parameters
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172 to the controller task to prevent them having to be file scope. */
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173 static xTaskHandle xContinuousIncrementHandle, xLimitedIncrementHandle, xChangePriorityWhenSuspendedHandle;
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175 /* The shared counter variable. This is passed in as a parameter to the two
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176 counter variables for demonstration purposes. */
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177 static unsigned long ulCounter;
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179 /* Variable used in a similar way by the test that checks the raising and
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180 lowering of task priorities while the scheduler is suspended. */
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181 static unsigned long ulPrioritySetCounter;
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183 /* Variables used to check that the tasks are still operating without error.
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184 Each complete iteration of the controller task increments this variable
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185 provided no errors have been found. The variable maintaining the same value
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186 is therefore indication of an error. */
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187 static unsigned short usCheckVariable = ( unsigned short ) 0;
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188 static portBASE_TYPE xSuspendedQueueSendError = pdFALSE;
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189 static portBASE_TYPE xSuspendedQueueReceiveError = pdFALSE;
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190 static portBASE_TYPE xPriorityRaiseWhenSuspendedError = pdFALSE;
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192 /* Queue used by the second test. */
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193 xQueueHandle xSuspendedTestQueue;
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195 /*-----------------------------------------------------------*/
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197 * Start the seven tasks as described at the top of the file.
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198 * Note that the limited count task is given a higher priority.
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200 void vStartDynamicPriorityTasks( void )
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202 xSuspendedTestQueue = xQueueCreate( priSUSPENDED_QUEUE_LENGTH, sizeof( unsigned long ) );
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203 xTaskCreate( vContinuousIncrementTask, "CONT_INC", priSTACK_SIZE, ( void * ) &ulCounter, tskIDLE_PRIORITY, &xContinuousIncrementHandle );
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204 xTaskCreate( vLimitedIncrementTask, "LIM_INC", priSTACK_SIZE, ( void * ) &ulCounter, tskIDLE_PRIORITY + 1, &xLimitedIncrementHandle );
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205 xTaskCreate( vCounterControlTask, "C_CTRL", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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206 xTaskCreate( vQueueSendWhenSuspendedTask, "SUSP_SEND", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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207 xTaskCreate( vQueueReceiveWhenSuspendedTask, "SUSP_RECV", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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208 xTaskCreate( prvChangePriorityWhenSuspendedTask, "1st_P_CHANGE", priSTACK_SIZE, NULL, tskIDLE_PRIORITY + 1, NULL );
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209 xTaskCreate( prvChangePriorityHelperTask, "2nd_P_CHANGE", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, &xChangePriorityWhenSuspendedHandle );
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211 /*-----------------------------------------------------------*/
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214 * Just loops around incrementing the shared variable until the limit has been
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215 * reached. Once the limit has been reached it suspends itself.
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217 static void vLimitedIncrementTask( void * pvParameters )
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219 unsigned long *pulCounter;
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221 /* Take a pointer to the shared variable from the parameters passed into
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223 pulCounter = ( unsigned long * ) pvParameters;
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225 /* This will run before the control task, so the first thing it does is
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226 suspend - the control task will resume it when ready. */
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227 vTaskSuspend( NULL );
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231 /* Just count up to a value then suspend. */
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232 ( *pulCounter )++;
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234 if( *pulCounter >= priMAX_COUNT )
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236 vTaskSuspend( NULL );
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240 /*-----------------------------------------------------------*/
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243 * Just keep counting the shared variable up. The control task will suspend
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244 * this task when it wants.
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246 static void vContinuousIncrementTask( void * pvParameters )
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248 unsigned long *pulCounter;
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249 unsigned portBASE_TYPE uxOurPriority;
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251 /* Take a pointer to the shared variable from the parameters passed into
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253 pulCounter = ( unsigned long * ) pvParameters;
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255 /* Query our priority so we can raise it when exclusive access to the
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256 shared variable is required. */
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257 uxOurPriority = uxTaskPriorityGet( NULL );
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261 /* Raise our priority above the controller task to ensure a context
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262 switch does not occur while we are accessing this variable. */
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263 vTaskPrioritySet( NULL, uxOurPriority + 1 );
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264 ( *pulCounter )++;
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265 vTaskPrioritySet( NULL, uxOurPriority );
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267 #if configUSE_PREEMPTION == 0
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272 /*-----------------------------------------------------------*/
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275 * Controller task as described above.
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277 static void vCounterControlTask( void * pvParameters )
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279 unsigned long ulLastCounter;
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281 short sError = pdFALSE;
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282 const char * const pcTaskStartMsg = "Priority manipulation tasks started.\r\n";
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283 const char * const pcTaskFailMsg = "Priority manipulation Task Failed\r\n";
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285 /* Just to stop warning messages. */
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286 ( void ) pvParameters;
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288 /* Queue a message for printing to say the task has started. */
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289 vPrintDisplayMessage( &pcTaskStartMsg );
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293 /* Start with the counter at zero. */
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294 ulCounter = ( unsigned long ) 0;
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296 /* First section : */
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298 /* Check the continuous count task is running. */
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299 for( sLoops = 0; sLoops < priLOOPS; sLoops++ )
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301 /* Suspend the continuous count task so we can take a mirror of the
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302 shared variable without risk of corruption. */
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303 vTaskSuspend( xContinuousIncrementHandle );
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304 ulLastCounter = ulCounter;
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305 vTaskResume( xContinuousIncrementHandle );
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307 /* Now delay to ensure the other task has processor time. */
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308 vTaskDelay( priSLEEP_TIME );
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310 /* Check the shared variable again. This time to ensure mutual
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311 exclusion the whole scheduler will be locked. This is just for
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315 if( ulLastCounter == ulCounter )
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317 /* The shared variable has not changed. There is a problem
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318 with the continuous count task so flag an error. */
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321 vPrintDisplayMessage( &pcTaskFailMsg );
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329 /* Second section: */
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331 /* Suspend the continuous counter task so it stops accessing the shared variable. */
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332 vTaskSuspend( xContinuousIncrementHandle );
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334 /* Reset the variable. */
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335 ulCounter = ( unsigned long ) 0;
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337 /* Resume the limited count task which has a higher priority than us.
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338 We should therefore not return from this call until the limited count
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339 task has suspended itself with a known value in the counter variable.
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340 The scheduler suspension is not necessary but is included for test
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343 vTaskResume( xLimitedIncrementHandle );
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346 /* Does the counter variable have the expected value? */
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347 if( ulCounter != priMAX_COUNT )
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350 vPrintDisplayMessage( &pcTaskFailMsg );
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353 if( sError == pdFALSE )
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355 /* If no errors have occurred then increment the check variable. */
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356 portENTER_CRITICAL();
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358 portEXIT_CRITICAL();
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361 #if configUSE_PREEMPTION == 0
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365 /* Resume the continuous count task and do it all again. */
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366 vTaskResume( xContinuousIncrementHandle );
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369 /*-----------------------------------------------------------*/
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371 static void vQueueSendWhenSuspendedTask( void *pvParameters )
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373 static unsigned long ulValueToSend = ( unsigned long ) 0;
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374 const char * const pcTaskStartMsg = "Queue send while suspended task started.\r\n";
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375 const char * const pcTaskFailMsg = "Queue send while suspended failed.\r\n";
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377 /* Just to stop warning messages. */
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378 ( void ) pvParameters;
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380 /* Queue a message for printing to say the task has started. */
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381 vPrintDisplayMessage( &pcTaskStartMsg );
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387 /* We must not block while the scheduler is suspended! */
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388 if( xQueueSend( xSuspendedTestQueue, ( void * ) &ulValueToSend, priNO_BLOCK ) != pdTRUE )
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390 if( xSuspendedQueueSendError == pdFALSE )
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393 vPrintDisplayMessage( &pcTaskFailMsg );
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397 xSuspendedQueueSendError = pdTRUE;
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402 vTaskDelay( priSLEEP_TIME );
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407 /*-----------------------------------------------------------*/
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409 static void vQueueReceiveWhenSuspendedTask( void *pvParameters )
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411 static unsigned long ulExpectedValue = ( unsigned long ) 0, ulReceivedValue;
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412 const char * const pcTaskStartMsg = "Queue receive while suspended task started.\r\n";
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413 const char * const pcTaskFailMsg = "Queue receive while suspended failed.\r\n";
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414 portBASE_TYPE xGotValue;
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416 /* Just to stop warning messages. */
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417 ( void ) pvParameters;
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419 /* Queue a message for printing to say the task has started. */
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420 vPrintDisplayMessage( &pcTaskStartMsg );
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426 /* Suspending the scheduler here is fairly pointless and
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427 undesirable for a normal application. It is done here purely
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428 to test the scheduler. The inner xTaskResumeAll() should
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429 never return pdTRUE as the scheduler is still locked by the
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435 xGotValue = xQueueReceive( xSuspendedTestQueue, ( void * ) &ulReceivedValue, priNO_BLOCK );
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437 if( xTaskResumeAll() )
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439 xSuspendedQueueReceiveError = pdTRUE;
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444 #if configUSE_PREEMPTION == 0
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448 } while( xGotValue == pdFALSE );
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450 if( ulReceivedValue != ulExpectedValue )
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452 if( xSuspendedQueueReceiveError == pdFALSE )
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454 vPrintDisplayMessage( &pcTaskFailMsg );
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456 xSuspendedQueueReceiveError = pdTRUE;
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462 /*-----------------------------------------------------------*/
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464 static void prvChangePriorityWhenSuspendedTask( void *pvParameters )
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466 const char * const pcTaskStartMsg = "Priority change when suspended task started.\r\n";
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467 const char * const pcTaskFailMsg = "Priority change when suspended task failed.\r\n";
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469 /* Just to stop warning messages. */
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470 ( void ) pvParameters;
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472 /* Queue a message for printing to say the task has started. */
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473 vPrintDisplayMessage( &pcTaskStartMsg );
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477 /* Start with the counter at 0 so we know what the counter should be
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478 when we check it next. */
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479 ulPrioritySetCounter = ( unsigned long ) 0;
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481 /* Resume the helper task. At this time it has a priority lower than
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482 ours so no context switch should occur. */
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483 vTaskResume( xChangePriorityWhenSuspendedHandle );
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485 /* Check to ensure the task just resumed has not executed. */
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486 portENTER_CRITICAL();
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488 if( ulPrioritySetCounter != ( unsigned long ) 0 )
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490 xPriorityRaiseWhenSuspendedError = pdTRUE;
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491 vPrintDisplayMessage( &pcTaskFailMsg );
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494 portEXIT_CRITICAL();
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496 /* Now try raising the priority while the scheduler is suspended. */
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499 vTaskPrioritySet( xChangePriorityWhenSuspendedHandle, ( configMAX_PRIORITIES - 1 ) );
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501 /* Again, even though the helper task has a priority greater than
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502 ours, it should not have executed yet because the scheduler is
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504 portENTER_CRITICAL();
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506 if( ulPrioritySetCounter != ( unsigned long ) 0 )
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508 xPriorityRaiseWhenSuspendedError = pdTRUE;
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509 vPrintDisplayMessage( &pcTaskFailMsg );
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512 portEXIT_CRITICAL();
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516 /* Now the scheduler has been resumed the helper task should
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517 immediately preempt us and execute. When it executes it will increment
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518 the ulPrioritySetCounter exactly once before suspending itself.
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520 We should now always find the counter set to 1. */
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521 portENTER_CRITICAL();
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523 if( ulPrioritySetCounter != ( unsigned long ) 1 )
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525 xPriorityRaiseWhenSuspendedError = pdTRUE;
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526 vPrintDisplayMessage( &pcTaskFailMsg );
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529 portEXIT_CRITICAL();
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531 /* Delay until we try this again. */
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532 vTaskDelay( priSLEEP_TIME * 2 );
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534 /* Set the priority of the helper task back ready for the next
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535 execution of this task. */
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537 vTaskPrioritySet( xChangePriorityWhenSuspendedHandle, tskIDLE_PRIORITY );
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541 /*-----------------------------------------------------------*/
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543 static void prvChangePriorityHelperTask( void *pvParameters )
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545 /* Just to stop warning messages. */
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546 ( void ) pvParameters;
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550 /* This is the helper task for prvChangePriorityWhenSuspendedTask().
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551 It has it's priority raised and lowered. When it runs it simply
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552 increments the counter then suspends itself again. This allows
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553 prvChangePriorityWhenSuspendedTask() to know how many times it has
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555 ulPrioritySetCounter++;
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556 vTaskSuspend( NULL );
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559 /*-----------------------------------------------------------*/
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561 /* Called to check that all the created tasks are still running without error. */
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562 portBASE_TYPE xAreDynamicPriorityTasksStillRunning( void )
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564 /* Keep a history of the check variables so we know if it has been incremented
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565 since the last call. */
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566 static unsigned short usLastTaskCheck = ( unsigned short ) 0;
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567 portBASE_TYPE xReturn = pdTRUE;
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569 /* Check the tasks are still running by ensuring the check variable
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570 is still incrementing. */
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572 if( usCheckVariable == usLastTaskCheck )
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574 /* The check has not incremented so an error exists. */
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578 if( xSuspendedQueueSendError == pdTRUE )
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583 if( xSuspendedQueueReceiveError == pdTRUE )
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588 if( xPriorityRaiseWhenSuspendedError == pdTRUE )
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593 usLastTaskCheck = usCheckVariable;
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