2 FreeRTOS V8.2.0rc1 - Copyright (C) 2014 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 This file is part of the FreeRTOS distribution.
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9 FreeRTOS is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License (version 2) as published by the
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11 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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13 >>! NOTE: The modification to the GPL is included to allow you to !<<
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14 >>! distribute a combined work that includes FreeRTOS without being !<<
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15 >>! obliged to provide the source code for proprietary components !<<
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16 >>! outside of the FreeRTOS kernel. !<<
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18 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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19 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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20 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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21 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * Having a problem? Start by reading the FAQ "My application does *
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28 * not run, what could be wrong?". Have you defined configASSERT()? *
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30 * http://www.FreeRTOS.org/FAQHelp.html *
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32 ***************************************************************************
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34 ***************************************************************************
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36 * FreeRTOS provides completely free yet professionally developed, *
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37 * robust, strictly quality controlled, supported, and cross *
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38 * platform software that is more than just the market leader, it *
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39 * is the industry's de facto standard. *
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41 * Help yourself get started quickly while simultaneously helping *
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42 * to support the FreeRTOS project by purchasing a FreeRTOS *
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43 * tutorial book, reference manual, or both: *
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44 * http://www.FreeRTOS.org/Documentation *
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46 ***************************************************************************
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48 ***************************************************************************
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50 * Investing in training allows your team to be as productive as *
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51 * possible as early as possible, lowering your overall development *
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52 * cost, and enabling you to bring a more robust product to market *
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53 * earlier than would otherwise be possible. Richard Barry is both *
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54 * the architect and key author of FreeRTOS, and so also the world's *
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55 * leading authority on what is the world's most popular real time *
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56 * kernel for deeply embedded MCU designs. Obtaining your training *
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57 * from Richard ensures your team will gain directly from his in-depth *
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58 * product knowledge and years of usage experience. Contact Real Time *
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59 * Engineers Ltd to enquire about the FreeRTOS Masterclass, presented *
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60 * by Richard Barry: http://www.FreeRTOS.org/contact
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62 ***************************************************************************
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64 ***************************************************************************
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66 * You are receiving this top quality software for free. Please play *
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67 * fair and reciprocate by reporting any suspected issues and *
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68 * participating in the community forum: *
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69 * http://www.FreeRTOS.org/support *
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73 ***************************************************************************
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75 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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76 license and Real Time Engineers Ltd. contact details.
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78 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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79 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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80 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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82 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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83 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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85 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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86 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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87 licenses offer ticketed support, indemnification and commercial middleware.
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89 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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90 engineered and independently SIL3 certified version for use in safety and
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91 mission critical applications that require provable dependability.
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97 The tasks defined on this page demonstrate the use of recursive mutexes.
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99 For recursive mutex functionality the created mutex should be created using
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100 xSemaphoreCreateRecursiveMutex(), then be manipulated
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101 using the xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() API
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104 This demo creates three tasks all of which access the same recursive mutex:
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106 prvRecursiveMutexControllingTask() has the highest priority so executes
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107 first and grabs the mutex. It then performs some recursive accesses -
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108 between each of which it sleeps for a short period to let the lower
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109 priority tasks execute. When it has completed its demo functionality
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110 it gives the mutex back before suspending itself.
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112 prvRecursiveMutexBlockingTask() attempts to access the mutex by performing
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113 a blocking 'take'. The blocking task has a lower priority than the
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114 controlling task so by the time it executes the mutex has already been
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115 taken by the controlling task, causing the blocking task to block. It
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116 does not unblock until the controlling task has given the mutex back,
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117 and it does not actually run until the controlling task has suspended
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118 itself (due to the relative priorities). When it eventually does obtain
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119 the mutex all it does is give the mutex back prior to also suspending
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120 itself. At this point both the controlling task and the blocking task are
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123 prvRecursiveMutexPollingTask() runs at the idle priority. It spins round
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124 a tight loop attempting to obtain the mutex with a non-blocking call. As
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125 the lowest priority task it will not successfully obtain the mutex until
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126 both the controlling and blocking tasks are suspended. Once it eventually
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127 does obtain the mutex it first unsuspends both the controlling task and
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128 blocking task prior to giving the mutex back - resulting in the polling
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129 task temporarily inheriting the controlling tasks priority.
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132 /* Scheduler include files. */
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133 #include "FreeRTOS.h"
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135 #include "semphr.h"
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137 /* Demo app include files. */
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138 #include "recmutex.h"
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140 /* Priorities assigned to the three tasks. recmuCONTROLLING_TASK_PRIORITY can
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141 be overridden by a definition in FreeRTOSConfig.h. */
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142 #ifndef recmuCONTROLLING_TASK_PRIORITY
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143 #define recmuCONTROLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 2 )
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145 #define recmuBLOCKING_TASK_PRIORITY ( tskIDLE_PRIORITY + 1 )
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146 #define recmuPOLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 0 )
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148 /* The recursive call depth. */
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149 #define recmuMAX_COUNT ( 10 )
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152 #define recmuSHORT_DELAY ( 20 / portTICK_PERIOD_MS )
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153 #define recmuNO_DELAY ( ( TickType_t ) 0 )
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154 #define recmuEIGHT_TICK_DELAY ( ( TickType_t ) 8 )
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156 /* The three tasks as described at the top of this file. */
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157 static void prvRecursiveMutexControllingTask( void *pvParameters );
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158 static void prvRecursiveMutexBlockingTask( void *pvParameters );
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159 static void prvRecursiveMutexPollingTask( void *pvParameters );
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161 /* The mutex used by the demo. */
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162 static SemaphoreHandle_t xMutex;
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164 /* Variables used to detect and latch errors. */
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165 static volatile BaseType_t xErrorOccurred = pdFALSE, xControllingIsSuspended = pdFALSE, xBlockingIsSuspended = pdFALSE;
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166 static volatile UBaseType_t uxControllingCycles = 0, uxBlockingCycles = 0, uxPollingCycles = 0;
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168 /* Handles of the two higher priority tasks, required so they can be resumed
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170 static TaskHandle_t xControllingTaskHandle, xBlockingTaskHandle;
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172 /*-----------------------------------------------------------*/
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174 void vStartRecursiveMutexTasks( void )
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176 /* Just creates the mutex and the three tasks. */
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178 xMutex = xSemaphoreCreateRecursiveMutex();
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180 /* vQueueAddToRegistry() adds the mutex to the registry, if one is
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181 in use. The registry is provided as a means for kernel aware
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182 debuggers to locate mutex and has no purpose if a kernel aware debugger
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183 is not being used. The call to vQueueAddToRegistry() will be removed
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184 by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
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185 defined to be less than 1. */
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186 vQueueAddToRegistry( ( QueueHandle_t ) xMutex, "Recursive_Mutex" );
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189 if( xMutex != NULL )
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191 xTaskCreate( prvRecursiveMutexControllingTask, "Rec1", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle );
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192 xTaskCreate( prvRecursiveMutexBlockingTask, "Rec2", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle );
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193 xTaskCreate( prvRecursiveMutexPollingTask, "Rec3", configMINIMAL_STACK_SIZE, NULL, recmuPOLLING_TASK_PRIORITY, NULL );
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196 /*-----------------------------------------------------------*/
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198 static void prvRecursiveMutexControllingTask( void *pvParameters )
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202 /* Just to remove compiler warning. */
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203 ( void ) pvParameters;
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207 /* Should not be able to 'give' the mutex, as we have not yet 'taken'
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208 it. The first time through, the mutex will not have been used yet,
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209 subsequent times through, at this point the mutex will be held by the
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211 if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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213 xErrorOccurred = pdTRUE;
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216 for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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218 /* We should now be able to take the mutex as many times as
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221 The first time through the mutex will be immediately available, on
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222 subsequent times through the mutex will be held by the polling task
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223 at this point and this Take will cause the polling task to inherit
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224 the priority of this task. In this case the block time must be
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225 long enough to ensure the polling task will execute again before the
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226 block time expires. If the block time does expire then the error
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227 flag will be set here. */
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228 if( xSemaphoreTakeRecursive( xMutex, recmuEIGHT_TICK_DELAY ) != pdPASS )
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230 xErrorOccurred = pdTRUE;
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233 /* Ensure the other task attempting to access the mutex (and the
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234 other demo tasks) are able to execute to ensure they either block
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235 (where a block time is specified) or return an error (where no
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236 block time is specified) as the mutex is held by this task. */
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237 vTaskDelay( recmuSHORT_DELAY );
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240 /* For each time we took the mutex, give it back. */
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241 for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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243 /* Ensure the other task attempting to access the mutex (and the
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244 other demo tasks) are able to execute. */
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245 vTaskDelay( recmuSHORT_DELAY );
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247 /* We should now be able to give the mutex as many times as we
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248 took it. When the mutex is available again the Blocking task
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249 should be unblocked but not run because it has a lower priority
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250 than this task. The polling task should also not run at this point
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251 as it too has a lower priority than this task. */
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252 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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254 xErrorOccurred = pdTRUE;
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258 /* Having given it back the same number of times as it was taken, we
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259 should no longer be the mutex owner, so the next give should fail. */
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260 if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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262 xErrorOccurred = pdTRUE;
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265 /* Keep count of the number of cycles this task has performed so a
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266 stall can be detected. */
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267 uxControllingCycles++;
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269 /* Suspend ourselves so the blocking task can execute. */
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270 xControllingIsSuspended = pdTRUE;
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271 vTaskSuspend( NULL );
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272 xControllingIsSuspended = pdFALSE;
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275 /*-----------------------------------------------------------*/
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277 static void prvRecursiveMutexBlockingTask( void *pvParameters )
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279 /* Just to remove compiler warning. */
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280 ( void ) pvParameters;
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284 /* This task will run while the controlling task is blocked, and the
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285 controlling task will block only once it has the mutex - therefore
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286 this call should block until the controlling task has given up the
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287 mutex, and not actually execute past this call until the controlling
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288 task is suspended. portMAX_DELAY - 1 is used instead of portMAX_DELAY
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289 to ensure the task's state is reported as Blocked and not Suspended in
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290 a later call to configASSERT() (within the polling task). */
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291 if( xSemaphoreTakeRecursive( xMutex, ( portMAX_DELAY - 1 ) ) == pdPASS )
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293 if( xControllingIsSuspended != pdTRUE )
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295 /* Did not expect to execute until the controlling task was
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297 xErrorOccurred = pdTRUE;
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301 /* Give the mutex back before suspending ourselves to allow
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302 the polling task to obtain the mutex. */
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303 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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305 xErrorOccurred = pdTRUE;
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308 xBlockingIsSuspended = pdTRUE;
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309 vTaskSuspend( NULL );
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310 xBlockingIsSuspended = pdFALSE;
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315 /* We should not leave the xSemaphoreTakeRecursive() function
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316 until the mutex was obtained. */
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317 xErrorOccurred = pdTRUE;
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320 /* The controlling and blocking tasks should be in lock step. */
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321 if( uxControllingCycles != ( uxBlockingCycles + 1 ) )
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323 xErrorOccurred = pdTRUE;
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326 /* Keep count of the number of cycles this task has performed so a
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327 stall can be detected. */
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328 uxBlockingCycles++;
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331 /*-----------------------------------------------------------*/
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333 static void prvRecursiveMutexPollingTask( void *pvParameters )
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335 /* Just to remove compiler warning. */
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336 ( void ) pvParameters;
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340 /* Keep attempting to obtain the mutex. We should only obtain it when
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341 the blocking task has suspended itself, which in turn should only
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342 happen when the controlling task is also suspended. */
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343 if( xSemaphoreTakeRecursive( xMutex, recmuNO_DELAY ) == pdPASS )
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345 #if( INCLUDE_eTaskGetState == 1 )
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347 configASSERT( eTaskGetState( xControllingTaskHandle ) == eSuspended );
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348 configASSERT( eTaskGetState( xBlockingTaskHandle ) == eSuspended );
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350 #endif /* INCLUDE_eTaskGetState */
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352 /* Is the blocking task suspended? */
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353 if( ( xBlockingIsSuspended != pdTRUE ) || ( xControllingIsSuspended != pdTRUE ) )
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355 xErrorOccurred = pdTRUE;
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359 /* Keep count of the number of cycles this task has performed
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360 so a stall can be detected. */
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363 /* We can resume the other tasks here even though they have a
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364 higher priority than the polling task. When they execute they
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365 will attempt to obtain the mutex but fail because the polling
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366 task is still the mutex holder. The polling task (this task)
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367 will then inherit the higher priority. The Blocking task will
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368 block indefinitely when it attempts to obtain the mutex, the
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369 Controlling task will only block for a fixed period and an
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370 error will be latched if the polling task has not returned the
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371 mutex by the time this fixed period has expired. */
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372 vTaskResume( xBlockingTaskHandle );
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373 vTaskResume( xControllingTaskHandle );
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375 /* The other two tasks should now have executed and no longer
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377 if( ( xBlockingIsSuspended == pdTRUE ) || ( xControllingIsSuspended == pdTRUE ) )
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379 xErrorOccurred = pdTRUE;
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382 #if( INCLUDE_uxTaskPriorityGet == 1 )
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384 /* Check priority inherited. */
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385 configASSERT( uxTaskPriorityGet( NULL ) == recmuCONTROLLING_TASK_PRIORITY );
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387 #endif /* INCLUDE_uxTaskPriorityGet */
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389 #if( INCLUDE_eTaskGetState == 1 )
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391 configASSERT( eTaskGetState( xControllingTaskHandle ) == eBlocked );
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392 configASSERT( eTaskGetState( xBlockingTaskHandle ) == eBlocked );
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394 #endif /* INCLUDE_eTaskGetState */
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396 /* Release the mutex, disinheriting the higher priority again. */
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397 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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399 xErrorOccurred = pdTRUE;
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402 #if( INCLUDE_uxTaskPriorityGet == 1 )
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404 /* Check priority disinherited. */
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405 configASSERT( uxTaskPriorityGet( NULL ) == recmuPOLLING_TASK_PRIORITY );
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407 #endif /* INCLUDE_uxTaskPriorityGet */
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411 #if configUSE_PREEMPTION == 0
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418 /*-----------------------------------------------------------*/
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420 /* This is called to check that all the created tasks are still running. */
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421 BaseType_t xAreRecursiveMutexTasksStillRunning( void )
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423 BaseType_t xReturn;
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424 static UBaseType_t uxLastControllingCycles = 0, uxLastBlockingCycles = 0, uxLastPollingCycles = 0;
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426 /* Is the controlling task still cycling? */
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427 if( uxLastControllingCycles == uxControllingCycles )
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429 xErrorOccurred = pdTRUE;
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433 uxLastControllingCycles = uxControllingCycles;
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436 /* Is the blocking task still cycling? */
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437 if( uxLastBlockingCycles == uxBlockingCycles )
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439 xErrorOccurred = pdTRUE;
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443 uxLastBlockingCycles = uxBlockingCycles;
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446 /* Is the polling task still cycling? */
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447 if( uxLastPollingCycles == uxPollingCycles )
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449 xErrorOccurred = pdTRUE;
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453 uxLastPollingCycles = uxPollingCycles;
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456 if( xErrorOccurred == pdTRUE )
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