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 * The first test creates three tasks - two counter tasks (one continuous count
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69 * and one limited count) and one controller. A "count" variable is shared
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70 * between all three tasks. The two counter tasks should never be in a "ready"
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71 * state at the same time. The controller task runs at the same priority as
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72 * the continuous count task, and at a lower priority than the limited count
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75 * One counter task loops indefinitely, incrementing the shared count variable
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76 * on each iteration. To ensure it has exclusive access to the variable it
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77 * raises it's priority above that of the controller task before each
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78 * increment, lowering it again to it's original priority before starting the
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81 * The other counter task increments the shared count variable on each
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82 * iteration of it's loop until the count has reached a limit of 0xff - at
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83 * which point it suspends itself. It will not start a new loop until the
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84 * controller task has made it "ready" again by calling vTaskResume ().
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85 * This second counter task operates at a higher priority than controller
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86 * task so does not need to worry about mutual exclusion of the counter
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89 * The controller task is in two sections. The first section controls and
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90 * monitors the continuous count task. When this section is operational the
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91 * limited count task is suspended. Likewise, the second section controls
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92 * and monitors the limited count task. When this section is operational the
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93 * continuous count task is suspended.
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95 * In the first section the controller task first takes a copy of the shared
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96 * count variable. To ensure mutual exclusion on the count variable it
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97 * suspends the continuous count task, resuming it again when the copy has been
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98 * taken. The controller task then sleeps for a fixed period - during which
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99 * the continuous count task will execute and increment the shared variable.
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100 * When the controller task wakes it checks that the continuous count task
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101 * has executed by comparing the copy of the shared variable with its current
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102 * value. This time, to ensure mutual exclusion, the scheduler itself is
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103 * suspended with a call to vTaskSuspendAll (). This is for demonstration
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104 * purposes only and is not a recommended technique due to its inefficiency.
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106 * After a fixed number of iterations the controller task suspends the
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107 * continuous count task, and moves on to its second section.
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109 * At the start of the second section the shared variable is cleared to zero.
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110 * The limited count task is then woken from it's suspension by a call to
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111 * vTaskResume (). As this counter task operates at a higher priority than
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112 * the controller task the controller task should not run again until the
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113 * shared variable has been counted up to the limited value causing the counter
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114 * task to suspend itself. The next line after vTaskResume () is therefore
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115 * a check on the shared variable to ensure everything is as expected.
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118 * The second test consists of a couple of very simple tasks that post onto a
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119 * queue while the scheduler is suspended. This test was added to test parts
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120 * of the scheduler not exercised by the first test.
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123 * The final set of two tasks implements a third test. This simply raises the
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124 * priority of a task while the scheduler is suspended. Again this test was
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125 * added to exercise parts of the code not covered by the first test.
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127 * \page Priorities dynamic.c
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128 * \ingroup DemoFiles
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133 Changes from V2.0.0
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135 + Delay periods are now specified using variables and constants of
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136 portTickType rather than unsigned long.
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137 + Added a second, simple test that uses the functions
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138 vQueueReceiveWhenSuspendedTask() and vQueueSendWhenSuspendedTask().
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140 Changes from V3.1.1
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142 + Added a third simple test that uses the vTaskPrioritySet() function
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143 while the scheduler is suspended.
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144 + Modified the controller task slightly to test the calling of
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145 vTaskResumeAll() while the scheduler is suspended.
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148 #include <stdlib.h>
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150 /* Scheduler include files. */
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151 #include "FreeRTOS.h"
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153 #include "semphr.h"
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155 /* Demo app include files. */
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156 #include "dynamic.h"
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159 /* Function that implements the "limited count" task as described above. */
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160 static void vLimitedIncrementTask( void * pvParameters );
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162 /* Function that implements the "continuous count" task as described above. */
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163 static void vContinuousIncrementTask( void * pvParameters );
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165 /* Function that implements the controller task as described above. */
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166 static void vCounterControlTask( void * pvParameters );
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168 /* The simple test functions that check sending and receiving while the
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169 scheduler is suspended. */
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170 static void vQueueReceiveWhenSuspendedTask( void *pvParameters );
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171 static void vQueueSendWhenSuspendedTask( void *pvParameters );
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173 /* The simple test functions that check raising and lowering of task priorities
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174 while the scheduler is suspended. */
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175 static void prvChangePriorityWhenSuspendedTask( void *pvParameters );
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176 static void prvChangePriorityHelperTask( void *pvParameters );
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179 /* Demo task specific constants. */
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180 #define priSTACK_SIZE ( ( unsigned short ) configMINIMAL_STACK_SIZE )
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181 #define priSLEEP_TIME ( ( portTickType ) 50 )
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182 #define priLOOPS ( 5 )
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183 #define priMAX_COUNT ( ( unsigned long ) 0xff )
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184 #define priNO_BLOCK ( ( portTickType ) 0 )
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185 #define priSUSPENDED_QUEUE_LENGTH ( 1 )
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187 /*-----------------------------------------------------------*/
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189 /* Handles to the two counter tasks. These could be passed in as parameters
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190 to the controller task to prevent them having to be file scope. */
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191 static xTaskHandle xContinuousIncrementHandle, xLimitedIncrementHandle, xChangePriorityWhenSuspendedHandle;
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193 /* The shared counter variable. This is passed in as a parameter to the two
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194 counter variables for demonstration purposes. */
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195 static unsigned long ulCounter;
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197 /* Variable used in a similar way by the test that checks the raising and
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198 lowering of task priorities while the scheduler is suspended. */
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199 static unsigned long ulPrioritySetCounter;
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201 /* Variables used to check that the tasks are still operating without error.
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202 Each complete iteration of the controller task increments this variable
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203 provided no errors have been found. The variable maintaining the same value
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204 is therefore indication of an error. */
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205 static unsigned short usCheckVariable = ( unsigned short ) 0;
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206 static portBASE_TYPE xSuspendedQueueSendError = pdFALSE;
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207 static portBASE_TYPE xSuspendedQueueReceiveError = pdFALSE;
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208 static portBASE_TYPE xPriorityRaiseWhenSuspendedError = pdFALSE;
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210 /* Queue used by the second test. */
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211 xQueueHandle xSuspendedTestQueue;
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213 /*-----------------------------------------------------------*/
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215 * Start the seven tasks as described at the top of the file.
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216 * Note that the limited count task is given a higher priority.
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218 void vStartDynamicPriorityTasks( void )
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220 xSuspendedTestQueue = xQueueCreate( priSUSPENDED_QUEUE_LENGTH, sizeof( unsigned long ) );
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221 xTaskCreate( vContinuousIncrementTask, "CONT_INC", priSTACK_SIZE, ( void * ) &ulCounter, tskIDLE_PRIORITY, &xContinuousIncrementHandle );
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222 xTaskCreate( vLimitedIncrementTask, "LIM_INC", priSTACK_SIZE, ( void * ) &ulCounter, tskIDLE_PRIORITY + 1, &xLimitedIncrementHandle );
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223 xTaskCreate( vCounterControlTask, "C_CTRL", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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224 xTaskCreate( vQueueSendWhenSuspendedTask, "SUSP_SEND", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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225 xTaskCreate( vQueueReceiveWhenSuspendedTask, "SUSP_RECV", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
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226 xTaskCreate( prvChangePriorityWhenSuspendedTask, "1st_P_CHANGE", priSTACK_SIZE, NULL, tskIDLE_PRIORITY + 1, NULL );
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227 xTaskCreate( prvChangePriorityHelperTask, "2nd_P_CHANGE", priSTACK_SIZE, NULL, tskIDLE_PRIORITY, &xChangePriorityWhenSuspendedHandle );
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229 /*-----------------------------------------------------------*/
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232 * Just loops around incrementing the shared variable until the limit has been
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233 * reached. Once the limit has been reached it suspends itself.
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235 static void vLimitedIncrementTask( void * pvParameters )
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237 unsigned long *pulCounter;
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239 /* Take a pointer to the shared variable from the parameters passed into
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241 pulCounter = ( unsigned long * ) pvParameters;
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243 /* This will run before the control task, so the first thing it does is
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244 suspend - the control task will resume it when ready. */
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245 vTaskSuspend( NULL );
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249 /* Just count up to a value then suspend. */
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250 ( *pulCounter )++;
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252 if( *pulCounter >= priMAX_COUNT )
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254 vTaskSuspend( NULL );
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258 /*-----------------------------------------------------------*/
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261 * Just keep counting the shared variable up. The control task will suspend
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262 * this task when it wants.
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264 static void vContinuousIncrementTask( void * pvParameters )
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266 unsigned long *pulCounter;
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267 unsigned portBASE_TYPE uxOurPriority;
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269 /* Take a pointer to the shared variable from the parameters passed into
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271 pulCounter = ( unsigned long * ) pvParameters;
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273 /* Query our priority so we can raise it when exclusive access to the
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274 shared variable is required. */
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275 uxOurPriority = uxTaskPriorityGet( NULL );
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279 /* Raise our priority above the controller task to ensure a context
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280 switch does not occur while we are accessing this variable. */
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281 vTaskPrioritySet( NULL, uxOurPriority + 1 );
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282 ( *pulCounter )++;
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283 vTaskPrioritySet( NULL, uxOurPriority );
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285 #if configUSE_PREEMPTION == 0
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290 /*-----------------------------------------------------------*/
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293 * Controller task as described above.
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295 static void vCounterControlTask( void * pvParameters )
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297 unsigned long ulLastCounter;
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299 short sError = pdFALSE;
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300 const char * const pcTaskStartMsg = "Priority manipulation tasks started.\r\n";
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301 const char * const pcTaskFailMsg = "Priority manipulation Task Failed\r\n";
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303 /* Just to stop warning messages. */
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304 ( void ) pvParameters;
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306 /* Queue a message for printing to say the task has started. */
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307 vPrintDisplayMessage( &pcTaskStartMsg );
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311 /* Start with the counter at zero. */
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312 ulCounter = ( unsigned long ) 0;
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314 /* First section : */
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316 /* Check the continuous count task is running. */
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317 for( sLoops = 0; sLoops < priLOOPS; sLoops++ )
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319 /* Suspend the continuous count task so we can take a mirror of the
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320 shared variable without risk of corruption. */
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321 vTaskSuspend( xContinuousIncrementHandle );
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322 ulLastCounter = ulCounter;
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323 vTaskResume( xContinuousIncrementHandle );
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325 /* Now delay to ensure the other task has processor time. */
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326 vTaskDelay( priSLEEP_TIME );
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328 /* Check the shared variable again. This time to ensure mutual
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329 exclusion the whole scheduler will be locked. This is just for
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333 if( ulLastCounter == ulCounter )
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335 /* The shared variable has not changed. There is a problem
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336 with the continuous count task so flag an error. */
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339 vPrintDisplayMessage( &pcTaskFailMsg );
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347 /* Second section: */
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349 /* Suspend the continuous counter task so it stops accessing the shared variable. */
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350 vTaskSuspend( xContinuousIncrementHandle );
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352 /* Reset the variable. */
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353 ulCounter = ( unsigned long ) 0;
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355 /* Resume the limited count task which has a higher priority than us.
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356 We should therefore not return from this call until the limited count
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357 task has suspended itself with a known value in the counter variable.
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358 The scheduler suspension is not necessary but is included for test
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361 vTaskResume( xLimitedIncrementHandle );
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364 /* Does the counter variable have the expected value? */
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365 if( ulCounter != priMAX_COUNT )
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368 vPrintDisplayMessage( &pcTaskFailMsg );
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371 if( sError == pdFALSE )
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373 /* If no errors have occurred then increment the check variable. */
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374 portENTER_CRITICAL();
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376 portEXIT_CRITICAL();
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379 #if configUSE_PREEMPTION == 0
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383 /* Resume the continuous count task and do it all again. */
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384 vTaskResume( xContinuousIncrementHandle );
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387 /*-----------------------------------------------------------*/
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389 static void vQueueSendWhenSuspendedTask( void *pvParameters )
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391 static unsigned long ulValueToSend = ( unsigned long ) 0;
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392 const char * const pcTaskStartMsg = "Queue send while suspended task started.\r\n";
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393 const char * const pcTaskFailMsg = "Queue send while suspended failed.\r\n";
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395 /* Just to stop warning messages. */
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396 ( void ) pvParameters;
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398 /* Queue a message for printing to say the task has started. */
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399 vPrintDisplayMessage( &pcTaskStartMsg );
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405 /* We must not block while the scheduler is suspended! */
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406 if( xQueueSend( xSuspendedTestQueue, ( void * ) &ulValueToSend, priNO_BLOCK ) != pdTRUE )
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408 if( xSuspendedQueueSendError == pdFALSE )
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411 vPrintDisplayMessage( &pcTaskFailMsg );
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415 xSuspendedQueueSendError = pdTRUE;
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420 vTaskDelay( priSLEEP_TIME );
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425 /*-----------------------------------------------------------*/
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427 static void vQueueReceiveWhenSuspendedTask( void *pvParameters )
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429 static unsigned long ulExpectedValue = ( unsigned long ) 0, ulReceivedValue;
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430 const char * const pcTaskStartMsg = "Queue receive while suspended task started.\r\n";
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431 const char * const pcTaskFailMsg = "Queue receive while suspended failed.\r\n";
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432 portBASE_TYPE xGotValue;
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434 /* Just to stop warning messages. */
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435 ( void ) pvParameters;
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437 /* Queue a message for printing to say the task has started. */
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438 vPrintDisplayMessage( &pcTaskStartMsg );
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444 /* Suspending the scheduler here is fairly pointless and
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445 undesirable for a normal application. It is done here purely
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446 to test the scheduler. The inner xTaskResumeAll() should
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447 never return pdTRUE as the scheduler is still locked by the
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453 xGotValue = xQueueReceive( xSuspendedTestQueue, ( void * ) &ulReceivedValue, priNO_BLOCK );
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455 if( xTaskResumeAll() )
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457 xSuspendedQueueReceiveError = pdTRUE;
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462 #if configUSE_PREEMPTION == 0
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466 } while( xGotValue == pdFALSE );
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468 if( ulReceivedValue != ulExpectedValue )
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470 if( xSuspendedQueueReceiveError == pdFALSE )
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472 vPrintDisplayMessage( &pcTaskFailMsg );
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474 xSuspendedQueueReceiveError = pdTRUE;
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480 /*-----------------------------------------------------------*/
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482 static void prvChangePriorityWhenSuspendedTask( void *pvParameters )
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484 const char * const pcTaskStartMsg = "Priority change when suspended task started.\r\n";
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485 const char * const pcTaskFailMsg = "Priority change when suspended task failed.\r\n";
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487 /* Just to stop warning messages. */
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488 ( void ) pvParameters;
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490 /* Queue a message for printing to say the task has started. */
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491 vPrintDisplayMessage( &pcTaskStartMsg );
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495 /* Start with the counter at 0 so we know what the counter should be
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496 when we check it next. */
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497 ulPrioritySetCounter = ( unsigned long ) 0;
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499 /* Resume the helper task. At this time it has a priority lower than
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500 ours so no context switch should occur. */
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501 vTaskResume( xChangePriorityWhenSuspendedHandle );
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503 /* Check to ensure the task just resumed has not executed. */
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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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514 /* Now try raising the priority while the scheduler is suspended. */
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517 vTaskPrioritySet( xChangePriorityWhenSuspendedHandle, ( configMAX_PRIORITIES - 1 ) );
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519 /* Again, even though the helper task has a priority greater than
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520 ours, it should not have executed yet because the scheduler is
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522 portENTER_CRITICAL();
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524 if( ulPrioritySetCounter != ( unsigned long ) 0 )
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526 xPriorityRaiseWhenSuspendedError = pdTRUE;
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527 vPrintDisplayMessage( &pcTaskFailMsg );
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530 portEXIT_CRITICAL();
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534 /* Now the scheduler has been resumed the helper task should
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535 immediately preempt us and execute. When it executes it will increment
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536 the ulPrioritySetCounter exactly once before suspending itself.
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538 We should now always find the counter set to 1. */
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539 portENTER_CRITICAL();
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541 if( ulPrioritySetCounter != ( unsigned long ) 1 )
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543 xPriorityRaiseWhenSuspendedError = pdTRUE;
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544 vPrintDisplayMessage( &pcTaskFailMsg );
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547 portEXIT_CRITICAL();
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549 /* Delay until we try this again. */
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550 vTaskDelay( priSLEEP_TIME * 2 );
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552 /* Set the priority of the helper task back ready for the next
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553 execution of this task. */
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555 vTaskPrioritySet( xChangePriorityWhenSuspendedHandle, tskIDLE_PRIORITY );
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559 /*-----------------------------------------------------------*/
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561 static void prvChangePriorityHelperTask( void *pvParameters )
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563 /* Just to stop warning messages. */
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564 ( void ) pvParameters;
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568 /* This is the helper task for prvChangePriorityWhenSuspendedTask().
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569 It has it's priority raised and lowered. When it runs it simply
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570 increments the counter then suspends itself again. This allows
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571 prvChangePriorityWhenSuspendedTask() to know how many times it has
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573 ulPrioritySetCounter++;
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574 vTaskSuspend( NULL );
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577 /*-----------------------------------------------------------*/
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579 /* Called to check that all the created tasks are still running without error. */
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580 portBASE_TYPE xAreDynamicPriorityTasksStillRunning( void )
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582 /* Keep a history of the check variables so we know if it has been incremented
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583 since the last call. */
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584 static unsigned short usLastTaskCheck = ( unsigned short ) 0;
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585 portBASE_TYPE xReturn = pdTRUE;
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587 /* Check the tasks are still running by ensuring the check variable
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588 is still incrementing. */
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590 if( usCheckVariable == usLastTaskCheck )
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592 /* The check has not incremented so an error exists. */
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596 if( xSuspendedQueueSendError == pdTRUE )
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601 if( xSuspendedQueueReceiveError == pdTRUE )
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606 if( xPriorityRaiseWhenSuspendedError == pdTRUE )
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611 usLastTaskCheck = usCheckVariable;
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