2 FreeRTOS.org V4.3.0 - Copyright (C) 2003-2007 Richard Barry.
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4 This file is part of the FreeRTOS.org distribution.
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6 FreeRTOS.org is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2 of the License, or
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9 (at your option) any later version.
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11 FreeRTOS.org is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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16 You should have received a copy of the GNU General Public License
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17 along with FreeRTOS.org; if not, write to the Free Software
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18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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20 A special exception to the GPL can be applied should you wish to distribute
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21 a combined work that includes FreeRTOS.org, without being obliged to provide
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22 the source code for any proprietary components. See the licensing section
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23 of http://www.FreeRTOS.org for full details of how and when the exception
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26 ***************************************************************************
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27 See http://www.FreeRTOS.org for documentation, latest information, license
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28 and contact details. Please ensure to read the configuration and relevant
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29 port sections of the online documentation.
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31 Also see http://www.SafeRTOS.com for an IEC 61508 compliant version along
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32 with commercial development and support options.
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33 ***************************************************************************
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37 * This file exercises the event mechanism whereby more than one task is
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38 * blocked waiting for the same event.
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40 * The demo creates five tasks - four 'event' tasks, and a controlling task.
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41 * The event tasks have various different priorities and all block on reading
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42 * the same queue. The controlling task writes data to the queue, then checks
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43 * to see which of the event tasks read the data from the queue. The
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44 * controlling task has the lowest priority of all the tasks so is guaranteed
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45 * to always get preempted immediately upon writing to the queue.
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47 * By selectively suspending and resuming the event tasks the controlling task
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48 * can check that the highest priority task that is blocked on the queue is the
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49 * task that reads the posted data from the queue.
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51 * Two of the event tasks share the same priority. When neither of these tasks
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52 * are suspended they should alternate - one reading one message from the queue,
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53 * the other the next message, etc.
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56 /* Standard includes. */
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61 /* Scheduler include files. */
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62 #include "FreeRTOS.h"
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66 /* Demo program include files. */
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67 #include "mevents.h"
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70 /* Demo specific constants. */
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71 #define evtSTACK_SIZE ( ( unsigned portBASE_TYPE ) 128 )
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72 #define evtNUM_TASKS ( 4 )
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73 #define evtQUEUE_LENGTH ( ( unsigned portBASE_TYPE ) 3 )
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74 #define evtNO_DELAY 0
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76 /* Just indexes used to uniquely identify the tasks. Note that two tasks are
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77 'highest' priority. */
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78 #define evtHIGHEST_PRIORITY_INDEX_2 3
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79 #define evtHIGHEST_PRIORITY_INDEX_1 2
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80 #define evtMEDIUM_PRIORITY_INDEX 1
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81 #define evtLOWEST_PRIORITY_INDEX 0
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83 /* Each event task increments one of these counters each time it reads data
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85 static volatile portBASE_TYPE xTaskCounters[ evtNUM_TASKS ] = { 0, 0, 0, 0 };
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87 /* Each time the controlling task posts onto the queue it increments the
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88 expected count of the task that it expected to read the data from the queue
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89 (i.e. the task with the highest priority that should be blocked on the queue).
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91 xExpectedTaskCounters are incremented from the controlling task, and
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92 xTaskCounters are incremented from the individual event tasks - therefore
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93 comparing xTaskCounters to xExpectedTaskCounters shows whether or not the
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94 correct task was unblocked by the post. */
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95 static portBASE_TYPE xExpectedTaskCounters[ evtNUM_TASKS ] = { 0, 0, 0, 0 };
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97 /* Handles to the four event tasks. These are required to suspend and resume
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99 static xTaskHandle xCreatedTasks[ evtNUM_TASKS ];
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101 /* The single queue onto which the controlling task posts, and the four event
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103 static xQueueHandle xQueue;
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105 /* Flag used to indicate whether or not an error has occurred at any time.
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106 An error is either the queue being full when not expected, or an unexpected
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107 task reading data from the queue. */
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108 static portBASE_TYPE xHealthStatus = pdPASS;
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110 /*-----------------------------------------------------------*/
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112 /* Function that implements the event task. This is created four times. */
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113 static void prvMultiEventTask( void *pvParameters );
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115 /* Function that implements the controlling task. */
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116 static void prvEventControllerTask( void *pvParameters );
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118 /* This is a utility function that posts data to the queue, then compares
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119 xExpectedTaskCounters with xTaskCounters to ensure everything worked as
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122 The event tasks all have higher priorities the controlling task. Therefore
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123 the controlling task will always get preempted between writhing to the queue
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124 and checking the task counters.
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126 @param xExpectedTask The index to the task that the controlling task thinks
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127 should be the highest priority task waiting for data, and
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128 therefore the task that will unblock.
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130 @param xIncrement The number of items that should be written to the queue.
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132 static void prvCheckTaskCounters( portBASE_TYPE xExpectedTask, portBASE_TYPE xIncrement );
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134 /* This is just incremented each cycle of the controlling tasks function so
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135 the main application can ensure the test is still running. */
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136 static portBASE_TYPE xCheckVariable = 0;
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138 /*-----------------------------------------------------------*/
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140 void vStartMultiEventTasks( void )
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142 /* Create the queue to be used for all the communications. */
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143 xQueue = xQueueCreate( evtQUEUE_LENGTH, ( unsigned portBASE_TYPE ) sizeof( unsigned portBASE_TYPE ) );
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145 /* Start the controlling task. This has the idle priority to ensure it is
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146 always preempted by the event tasks. */
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147 xTaskCreate( prvEventControllerTask, "EvntCTRL", evtSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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149 /* Start the four event tasks. Note that two have priority 3, one
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150 priority 2 and the other priority 1. */
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151 xTaskCreate( prvMultiEventTask, "Event0", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 0 ] ), 1, &( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] ) );
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152 xTaskCreate( prvMultiEventTask, "Event1", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 1 ] ), 2, &( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] ) );
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153 xTaskCreate( prvMultiEventTask, "Event2", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 2 ] ), 3, &( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] ) );
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154 xTaskCreate( prvMultiEventTask, "Event3", evtSTACK_SIZE, ( void * ) &( xTaskCounters[ 3 ] ), 3, &( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] ) );
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156 /*-----------------------------------------------------------*/
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158 static void prvMultiEventTask( void *pvParameters )
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160 portBASE_TYPE *pxCounter;
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161 unsigned portBASE_TYPE uxDummy;
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162 const portCHAR * const pcTaskStartMsg = "Multi event task started.\r\n";
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164 /* The variable this task will increment is passed in as a parameter. */
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165 pxCounter = ( portBASE_TYPE * ) pvParameters;
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167 vPrintDisplayMessage( &pcTaskStartMsg );
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171 /* Block on the queue. */
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172 if( xQueueReceive( xQueue, &uxDummy, portMAX_DELAY ) )
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174 /* We unblocked by reading the queue - so simply increment
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175 the counter specific to this task instance. */
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180 xHealthStatus = pdFAIL;
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184 /*-----------------------------------------------------------*/
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186 static void prvEventControllerTask( void *pvParameters )
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188 const portCHAR * const pcTaskStartMsg = "Multi event controller task started.\r\n";
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189 portBASE_TYPE xDummy = 0;
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191 /* Just to stop warnings. */
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192 ( void ) pvParameters;
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194 vPrintDisplayMessage( &pcTaskStartMsg );
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198 /* All tasks are blocked on the queue. When a message is posted one of
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199 the two tasks that share the highest priority should unblock to read
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200 the queue. The next message written should unblock the other task with
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201 the same high priority, and so on in order. No other task should
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202 unblock to read data as they have lower priorities. */
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204 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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205 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_2, 1 );
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206 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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207 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_2, 1 );
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208 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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210 /* For the rest of these tests we don't need the second 'highest'
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211 priority task - so it is suspended. */
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212 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] );
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216 /* Now suspend the other highest priority task. The medium priority
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217 task will then be the task with the highest priority that remains
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218 blocked on the queue. */
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219 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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221 /* This time, when we post onto the queue we will expect the medium
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222 priority task to unblock and preempt us. */
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223 prvCheckTaskCounters( evtMEDIUM_PRIORITY_INDEX, 1 );
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225 /* Now try resuming the highest priority task while the scheduler is
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226 suspended. The task should start executing as soon as the scheduler
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227 is resumed - therefore when we post to the queue again, the highest
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228 priority task should again preempt us. */
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230 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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232 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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234 /* Now we are going to suspend the high and medium priority tasks. The
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235 low priority task should then preempt us. Again the task suspension is
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236 done with the whole scheduler suspended just for test purposes. */
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238 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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239 vTaskSuspend( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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241 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, 1 );
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245 /* Do the same basic test another few times - selectively suspending
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246 and resuming tasks and each time calling prvCheckTaskCounters() passing
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247 to the function the number of the task we expected to be unblocked by
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250 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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251 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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253 vTaskSuspendAll(); /* Just for test. */
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254 vTaskSuspendAll(); /* Just for test. */
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255 vTaskSuspendAll(); /* Just for even more test. */
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256 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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260 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, 1 );
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262 vTaskResume( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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263 prvCheckTaskCounters( evtMEDIUM_PRIORITY_INDEX, 1 );
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265 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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266 prvCheckTaskCounters( evtHIGHEST_PRIORITY_INDEX_1, 1 );
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272 /* Now a slight change, first suspend all tasks. */
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273 vTaskSuspend( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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274 vTaskSuspend( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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275 vTaskSuspend( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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277 /* Now when we resume the low priority task and write to the queue 3
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278 times. We expect the low priority task to service the queue three
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280 vTaskResume( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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281 prvCheckTaskCounters( evtLOWEST_PRIORITY_INDEX, evtQUEUE_LENGTH );
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283 /* Again suspend all tasks (only the low priority task is not suspended
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285 vTaskSuspend( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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287 /* This time we are going to suspend the scheduler, resume the low
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288 priority task, then resume the high priority task. In this state we
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289 will write to the queue three times. When the scheduler is resumed
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290 we expect the high priority task to service all three messages. */
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293 vTaskResume( xCreatedTasks[ evtLOWEST_PRIORITY_INDEX ] );
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294 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_1 ] );
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296 for( xDummy = 0; xDummy < evtQUEUE_LENGTH; xDummy++ )
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298 if( xQueueSend( xQueue, &xDummy, evtNO_DELAY ) != pdTRUE )
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300 xHealthStatus = pdFAIL;
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304 /* The queue should not have been serviced yet!. The scheduler
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305 is still suspended. */
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306 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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308 xHealthStatus = pdFAIL;
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313 /* We should have been preempted by resuming the scheduler - so by the
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314 time we are running again we expect the high priority task to have
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315 removed three items from the queue. */
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316 xExpectedTaskCounters[ evtHIGHEST_PRIORITY_INDEX_1 ] += evtQUEUE_LENGTH;
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317 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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319 xHealthStatus = pdFAIL;
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322 /* The medium priority and second high priority tasks are still
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323 suspended. Make sure to resume them before starting again. */
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324 vTaskResume( xCreatedTasks[ evtMEDIUM_PRIORITY_INDEX ] );
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325 vTaskResume( xCreatedTasks[ evtHIGHEST_PRIORITY_INDEX_2 ] );
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327 /* Just keep incrementing to show the task is still executing. */
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331 /*-----------------------------------------------------------*/
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333 static void prvCheckTaskCounters( portBASE_TYPE xExpectedTask, portBASE_TYPE xIncrement )
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335 portBASE_TYPE xDummy = 0;
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337 /* Write to the queue the requested number of times. The data written is
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339 for( xDummy = 0; xDummy < xIncrement; xDummy++ )
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341 if( xQueueSend( xQueue, &xDummy, evtNO_DELAY ) != pdTRUE )
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343 /* Did not expect to ever find the queue full. */
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344 xHealthStatus = pdFAIL;
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348 /* All the tasks blocked on the queue have a priority higher than the
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349 controlling task. Writing to the queue will therefore have caused this
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350 task to be preempted. By the time this line executes the event task will
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351 have executed and incremented its counter. Increment the expected counter
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352 to the same value. */
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353 ( xExpectedTaskCounters[ xExpectedTask ] ) += xIncrement;
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355 /* Check the actual counts and expected counts really are the same. */
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356 if( memcmp( ( void * ) xExpectedTaskCounters, ( void * ) xTaskCounters, sizeof( xExpectedTaskCounters ) ) )
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358 /* The counters were not the same. This means a task we did not expect
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359 to unblock actually did unblock. */
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360 xHealthStatus = pdFAIL;
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363 /*-----------------------------------------------------------*/
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365 portBASE_TYPE xAreMultiEventTasksStillRunning( void )
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367 static portBASE_TYPE xPreviousCheckVariable = 0;
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369 /* Called externally to periodically check that this test is still
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372 if( xPreviousCheckVariable == xCheckVariable )
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374 xHealthStatus = pdFAIL;
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377 xPreviousCheckVariable = xCheckVariable;
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379 return xHealthStatus;
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