2 FreeRTOS V7.2.0 - Copyright (C) 2012 Real Time Engineers Ltd.
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5 ***************************************************************************
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7 * FreeRTOS tutorial books are available in pdf and paperback. *
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8 * Complete, revised, and edited pdf reference manuals are also *
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11 * Purchasing FreeRTOS documentation will not only help you, by *
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12 * ensuring you get running as quickly as possible and with an *
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13 * in-depth knowledge of how to use FreeRTOS, it will also help *
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14 * the FreeRTOS project to continue with its mission of providing *
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15 * professional grade, cross platform, de facto standard solutions *
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16 * for microcontrollers - completely free of charge! *
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18 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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20 * Thank you for using FreeRTOS, and thank you for your support! *
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22 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 >>>NOTE<<< The modification to the GPL is included to allow you to
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31 distribute a combined work that includes FreeRTOS without being obliged to
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32 provide the source code for proprietary components outside of the FreeRTOS
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33 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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34 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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35 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 ***************************************************************************
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46 * Having a problem? Start by reading the FAQ "My application does *
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47 * not run, what could be wrong? *
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49 * http://www.FreeRTOS.org/FAQHelp.html *
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51 ***************************************************************************
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54 http://www.FreeRTOS.org - Documentation, training, latest information,
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55 license and contact details.
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57 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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58 including FreeRTOS+Trace - an indispensable productivity tool.
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60 Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
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61 the code with commercial support, indemnification, and middleware, under
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62 the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
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63 provide a safety engineered and independently SIL3 certified version under
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64 the SafeRTOS brand: http://www.SafeRTOS.com.
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68 * This file exercises the event mechanism whereby more than one task is
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69 * blocked waiting for the same event.
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71 * The demo creates five tasks - four 'event' tasks, and a controlling task.
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72 * The event tasks have various different priorities and all block on reading
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73 * the same queue. The controlling task writes data to the queue, then checks
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74 * to see which of the event tasks read the data from the queue. The
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75 * controlling task has the lowest priority of all the tasks so is guaranteed
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76 * to always get preempted immediately upon writing to the queue.
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78 * By selectively suspending and resuming the event tasks the controlling task
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79 * can check that the highest priority task that is blocked on the queue is the
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80 * task that reads the posted data from the queue.
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82 * Two of the event tasks share the same priority. When neither of these tasks
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83 * are suspended they should alternate - one reading one message from the queue,
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84 * the other the next message, etc.
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87 /* Standard includes. */
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92 /* Scheduler include files. */
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93 #include "FreeRTOS.h"
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97 /* Demo program include files. */
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98 #include "mevents.h"
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101 /* Demo specific constants. */
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102 #define evtSTACK_SIZE ( ( unsigned portBASE_TYPE ) configMINIMAL_STACK_SIZE )
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103 #define evtNUM_TASKS ( 4 )
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104 #define evtQUEUE_LENGTH ( ( unsigned portBASE_TYPE ) 3 )
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105 #define evtNO_DELAY 0
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107 /* Just indexes used to uniquely identify the tasks. Note that two tasks are
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108 'highest' priority. */
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109 #define evtHIGHEST_PRIORITY_INDEX_2 3
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110 #define evtHIGHEST_PRIORITY_INDEX_1 2
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111 #define evtMEDIUM_PRIORITY_INDEX 1
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112 #define evtLOWEST_PRIORITY_INDEX 0
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114 /* Each event task increments one of these counters each time it reads data
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116 static volatile portBASE_TYPE xTaskCounters[ evtNUM_TASKS ] = { 0, 0, 0, 0 };
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118 /* Each time the controlling task posts onto the queue it increments the
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119 expected count of the task that it expected to read the data from the queue
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120 (i.e. the task with the highest priority that should be blocked on the queue).
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122 xExpectedTaskCounters are incremented from the controlling task, and
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123 xTaskCounters are incremented from the individual event tasks - therefore
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124 comparing xTaskCounters to xExpectedTaskCounters shows whether or not the
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125 correct task was unblocked by the post. */
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126 static portBASE_TYPE xExpectedTaskCounters[ evtNUM_TASKS ] = { 0, 0, 0, 0 };
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128 /* Handles to the four event tasks. These are required to suspend and resume
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130 static xTaskHandle xCreatedTasks[ evtNUM_TASKS ];
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132 /* The single queue onto which the controlling task posts, and the four event
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134 static xQueueHandle xQueue;
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136 /* Flag used to indicate whether or not an error has occurred at any time.
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137 An error is either the queue being full when not expected, or an unexpected
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138 task reading data from the queue. */
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139 static portBASE_TYPE xHealthStatus = pdPASS;
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141 /*-----------------------------------------------------------*/
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143 /* Function that implements the event task. This is created four times. */
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144 static void prvMultiEventTask( void *pvParameters );
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146 /* Function that implements the controlling task. */
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147 static void prvEventControllerTask( void *pvParameters );
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149 /* This is a utility function that posts data to the queue, then compares
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150 xExpectedTaskCounters with xTaskCounters to ensure everything worked as
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153 The event tasks all have higher priorities the controlling task. Therefore
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154 the controlling task will always get preempted between writhing to the queue
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155 and checking the task counters.
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157 @param xExpectedTask The index to the task that the controlling task thinks
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158 should be the highest priority task waiting for data, and
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159 therefore the task that will unblock.
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161 @param xIncrement The number of items that should be written to the queue.
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163 static void prvCheckTaskCounters( portBASE_TYPE xExpectedTask, portBASE_TYPE xIncrement );
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165 /* This is just incremented each cycle of the controlling tasks function so
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166 the main application can ensure the test is still running. */
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167 static portBASE_TYPE xCheckVariable = 0;
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169 /*-----------------------------------------------------------*/
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171 void vStartMultiEventTasks( void )
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173 /* Create the queue to be used for all the communications. */
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174 xQueue = xQueueCreate( evtQUEUE_LENGTH, ( unsigned portBASE_TYPE ) sizeof( unsigned portBASE_TYPE ) );
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176 /* Start the controlling task. This has the idle priority to ensure it is
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177 always preempted by the event tasks. */
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178 xTaskCreate( prvEventControllerTask, "EvntCTRL", evtSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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180 /* Start the four event tasks. Note that two have priority 3, one
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181 priority 2 and the other priority 1. */
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182 xTaskCreate( prvMultiEventTask, "Event0", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 0 ] ), 1, &( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] ) );
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183 xTaskCreate( prvMultiEventTask, "Event1", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 1 ] ), 2, &( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] ) );
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184 xTaskCreate( prvMultiEventTask, "Event2", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 2 ] ), 3, &( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] ) );
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185 xTaskCreate( prvMultiEventTask, "Event3", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 3 ] ), 3, &( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] ) );
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187 /*-----------------------------------------------------------*/
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189 static void prvMultiEventTask( void *pvParameters )
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191 portBASE_TYPE *pxCounter;
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192 unsigned portBASE_TYPE uxDummy;
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193 const char * const pcTaskStartMsg = "Multi event task started.\r\n";
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195 /* The variable this task will increment is passed in as a parameter. */
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196 pxCounter = ( portBASE_TYPE * ) pvParameters;
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198 vPrintDisplayMessage( &pcTaskStartMsg );
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202 /* Block on the queue. */
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203 if( xQueueReceive( xQueue, &uxDummy, portMAX_DELAY ) )
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205 /* We unblocked by reading the queue - so simply increment
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206 the counter specific to this task instance. */
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211 xHealthStatus = pdFAIL;
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215 /*-----------------------------------------------------------*/
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217 static void prvEventControllerTask( void *pvParameters )
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219 const char * const pcTaskStartMsg = "Multi event controller task started.\r\n";
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220 portBASE_TYPE xDummy = 0;
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222 /* Just to stop warnings. */
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223 ( void ) pvParameters;
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225 vPrintDisplayMessage( &pcTaskStartMsg );
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229 /* All tasks are blocked on the queue. When a message is posted one of
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230 the two tasks that share the highest priority should unblock to read
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231 the queue. The next message written should unblock the other task with
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232 the same high priority, and so on in order. No other task should
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233 unblock to read data as they have lower priorities. */
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235 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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236 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_2, 1 );
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237 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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238 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_2, 1 );
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239 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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241 /* For the rest of these tests we don't need the second 'highest'
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242 priority task - so it is suspended. */
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243 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] );
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247 /* Now suspend the other highest priority task. The medium priority
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248 task will then be the task with the highest priority that remains
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249 blocked on the queue. */
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250 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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252 /* This time, when we post onto the queue we will expect the medium
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253 priority task to unblock and preempt us. */
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254 prvCheckTaskCounters( evtMEDIUM_PRIORITY_INDEX, 1 );
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256 /* Now try resuming the highest priority task while the scheduler is
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257 suspended. The task should start executing as soon as the scheduler
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258 is resumed - therefore when we post to the queue again, the highest
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259 priority task should again preempt us. */
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261 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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263 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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265 /* Now we are going to suspend the high and medium priority tasks. The
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266 low priority task should then preempt us. Again the task suspension is
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267 done with the whole scheduler suspended just for test purposes. */
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269 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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270 vTaskSuspend( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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272 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, 1 );
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274 /* Do the same basic test another few times - selectively suspending
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275 and resuming tasks and each time calling prvCheckTaskCounters() passing
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276 to the function the number of the task we expected to be unblocked by
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279 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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280 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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282 vTaskSuspendAll(); /* Just for test. */
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283 vTaskSuspendAll(); /* Just for test. */
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284 vTaskSuspendAll(); /* Just for even more test. */
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285 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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289 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, 1 );
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291 vTaskResume( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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292 prvCheckTaskCounters( evtMEDIUM_PRIORITY_INDEX, 1 );
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294 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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295 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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297 /* Now a slight change, first suspend all tasks. */
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298 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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299 vTaskSuspend( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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300 vTaskSuspend( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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302 /* Now when we resume the low priority task and write to the queue 3
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303 times. We expect the low priority task to service the queue three
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305 vTaskResume( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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306 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, evtQUEUE_LENGTH );
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308 /* Again suspend all tasks (only the low priority task is not suspended
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310 vTaskSuspend( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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312 /* This time we are going to suspend the scheduler, resume the low
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313 priority task, then resume the high priority task. In this state we
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314 will write to the queue three times. When the scheduler is resumed
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315 we expect the high priority task to service all three messages. */
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318 vTaskResume( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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319 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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321 for( xDummy = 0; xDummy < evtQUEUE_LENGTH; xDummy++ )
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323 if( xQueueSend( xQueue, &xDummy, evtNO_DELAY ) != pdTRUE )
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325 xHealthStatus = pdFAIL;
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329 /* The queue should not have been serviced yet!. The scheduler
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330 is still suspended. */
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331 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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333 xHealthStatus = pdFAIL;
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338 /* We should have been preempted by resuming the scheduler - so by the
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339 time we are running again we expect the high priority task to have
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340 removed three items from the queue. */
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341 xExpectedTaskCounters[ evtHIGHEST_PRIORITY_INDEX_1 ] += evtQUEUE_LENGTH;
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342 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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344 xHealthStatus = pdFAIL;
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347 /* The medium priority and second high priority tasks are still
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348 suspended. Make sure to resume them before starting again. */
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349 vTaskResume( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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350 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] );
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352 /* Just keep incrementing to show the task is still executing. */
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356 /*-----------------------------------------------------------*/
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358 static void prvCheckTaskCounters( portBASE_TYPE xExpectedTask, portBASE_TYPE xIncrement )
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360 portBASE_TYPE xDummy = 0;
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362 /* Write to the queue the requested number of times. The data written is
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364 for( xDummy = 0; xDummy < xIncrement; xDummy++ )
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366 if( xQueueSend( xQueue, &xDummy, evtNO_DELAY ) != pdTRUE )
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368 /* Did not expect to ever find the queue full. */
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369 xHealthStatus = pdFAIL;
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373 /* All the tasks blocked on the queue have a priority higher than the
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374 controlling task. Writing to the queue will therefore have caused this
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375 task to be preempted. By the time this line executes the event task will
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376 have executed and incremented its counter. Increment the expected counter
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377 to the same value. */
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378 ( xExpectedTaskCounters[ xExpectedTask ] ) += xIncrement;
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380 /* Check the actual counts and expected counts really are the same. */
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381 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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383 /* The counters were not the same. This means a task we did not expect
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384 to unblock actually did unblock. */
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385 xHealthStatus = pdFAIL;
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388 /*-----------------------------------------------------------*/
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390 portBASE_TYPE xAreMultiEventTasksStillRunning( void )
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392 static portBASE_TYPE xPreviousCheckVariable = 0;
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394 /* Called externally to periodically check that this test is still
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397 if( xPreviousCheckVariable == xCheckVariable )
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399 xHealthStatus = pdFAIL;
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402 xPreviousCheckVariable = xCheckVariable;
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404 return xHealthStatus;
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