2 FreeRTOS V8.2.0 - Copyright (C) 2015 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 ***************************************************************************
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14 >>! NOTE: The modification to the GPL is included to allow you to !<<
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15 >>! distribute a combined work that includes FreeRTOS without being !<<
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16 >>! obliged to provide the source code for proprietary components !<<
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17 >>! outside of the FreeRTOS kernel. !<<
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18 ***************************************************************************
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20 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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21 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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22 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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23 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * FreeRTOS provides completely free yet professionally developed, *
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28 * robust, strictly quality controlled, supported, and cross *
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29 * platform software that is more than just the market leader, it *
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30 * is the industry's de facto standard. *
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32 * Help yourself get started quickly while simultaneously helping *
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33 * to support the FreeRTOS project by purchasing a FreeRTOS *
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34 * tutorial book, reference manual, or both: *
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35 * http://www.FreeRTOS.org/Documentation *
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37 ***************************************************************************
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39 http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
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40 the FAQ page "My application does not run, what could be wrong?". Have you
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41 defined configASSERT()?
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43 http://www.FreeRTOS.org/support - In return for receiving this top quality
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44 embedded software for free we request you assist our global community by
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45 participating in the support forum.
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47 http://www.FreeRTOS.org/training - Investing in training allows your team to
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48 be as productive as possible as early as possible. Now you can receive
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49 FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
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50 Ltd, and the world's leading authority on the world's leading RTOS.
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52 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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53 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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54 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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56 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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57 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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59 http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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60 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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61 licenses offer ticketed support, indemnification and commercial middleware.
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63 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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64 engineered and independently SIL3 certified version for use in safety and
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65 mission critical applications that require provable dependability.
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71 The tasks defined on this page demonstrate the use of recursive mutexes.
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73 For recursive mutex functionality the created mutex should be created using
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74 xSemaphoreCreateRecursiveMutex(), then be manipulated
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75 using the xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() API
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78 This demo creates three tasks all of which access the same recursive mutex:
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80 prvRecursiveMutexControllingTask() has the highest priority so executes
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81 first and grabs the mutex. It then performs some recursive accesses -
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82 between each of which it sleeps for a short period to let the lower
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83 priority tasks execute. When it has completed its demo functionality
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84 it gives the mutex back before suspending itself.
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86 prvRecursiveMutexBlockingTask() attempts to access the mutex by performing
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87 a blocking 'take'. The blocking task has a lower priority than the
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88 controlling task so by the time it executes the mutex has already been
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89 taken by the controlling task, causing the blocking task to block. It
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90 does not unblock until the controlling task has given the mutex back,
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91 and it does not actually run until the controlling task has suspended
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92 itself (due to the relative priorities). When it eventually does obtain
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93 the mutex all it does is give the mutex back prior to also suspending
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94 itself. At this point both the controlling task and the blocking task are
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97 prvRecursiveMutexPollingTask() runs at the idle priority. It spins round
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98 a tight loop attempting to obtain the mutex with a non-blocking call. As
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99 the lowest priority task it will not successfully obtain the mutex until
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100 both the controlling and blocking tasks are suspended. Once it eventually
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101 does obtain the mutex it first unsuspends both the controlling task and
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102 blocking task prior to giving the mutex back - resulting in the polling
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103 task temporarily inheriting the controlling tasks priority.
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106 /* Scheduler include files. */
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107 #include "FreeRTOS.h"
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109 #include "semphr.h"
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111 /* Demo app include files. */
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112 #include "recmutex.h"
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114 /* Priorities assigned to the three tasks. recmuCONTROLLING_TASK_PRIORITY can
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115 be overridden by a definition in FreeRTOSConfig.h. */
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116 #ifndef recmuCONTROLLING_TASK_PRIORITY
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117 #define recmuCONTROLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 2 )
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119 #define recmuBLOCKING_TASK_PRIORITY ( tskIDLE_PRIORITY + 1 )
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120 #define recmuPOLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 0 )
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122 /* The recursive call depth. */
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123 #define recmuMAX_COUNT ( 10 )
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126 #define recmuSHORT_DELAY ( 20 / portTICK_PERIOD_MS )
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127 #define recmuNO_DELAY ( ( TickType_t ) 0 )
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128 #define recmuEIGHT_TICK_DELAY ( ( TickType_t ) 8 )
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130 /* The three tasks as described at the top of this file. */
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131 static void prvRecursiveMutexControllingTask( void *pvParameters );
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132 static void prvRecursiveMutexBlockingTask( void *pvParameters );
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133 static void prvRecursiveMutexPollingTask( void *pvParameters );
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135 /* The mutex used by the demo. */
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136 static SemaphoreHandle_t xMutex;
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138 /* Variables used to detect and latch errors. */
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139 static volatile BaseType_t xErrorOccurred = pdFALSE, xControllingIsSuspended = pdFALSE, xBlockingIsSuspended = pdFALSE;
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140 static volatile UBaseType_t uxControllingCycles = 0, uxBlockingCycles = 0, uxPollingCycles = 0;
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142 /* Handles of the two higher priority tasks, required so they can be resumed
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144 static TaskHandle_t xControllingTaskHandle, xBlockingTaskHandle;
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146 /*-----------------------------------------------------------*/
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148 void vStartRecursiveMutexTasks( void )
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150 /* Just creates the mutex and the three tasks. */
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152 xMutex = xSemaphoreCreateRecursiveMutex();
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154 /* vQueueAddToRegistry() adds the mutex to the registry, if one is
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155 in use. The registry is provided as a means for kernel aware
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156 debuggers to locate mutex and has no purpose if a kernel aware debugger
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157 is not being used. The call to vQueueAddToRegistry() will be removed
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158 by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
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159 defined to be less than 1. */
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160 vQueueAddToRegistry( ( QueueHandle_t ) xMutex, "Recursive_Mutex" );
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163 if( xMutex != NULL )
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165 xTaskCreate( prvRecursiveMutexControllingTask, "Rec1", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle );
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166 xTaskCreate( prvRecursiveMutexBlockingTask, "Rec2", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle );
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167 xTaskCreate( prvRecursiveMutexPollingTask, "Rec3", configMINIMAL_STACK_SIZE, NULL, recmuPOLLING_TASK_PRIORITY, NULL );
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170 /*-----------------------------------------------------------*/
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172 static void prvRecursiveMutexControllingTask( void *pvParameters )
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176 /* Just to remove compiler warning. */
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177 ( void ) pvParameters;
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181 /* Should not be able to 'give' the mutex, as we have not yet 'taken'
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182 it. The first time through, the mutex will not have been used yet,
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183 subsequent times through, at this point the mutex will be held by the
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185 if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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187 xErrorOccurred = pdTRUE;
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190 for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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192 /* We should now be able to take the mutex as many times as
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195 The first time through the mutex will be immediately available, on
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196 subsequent times through the mutex will be held by the polling task
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197 at this point and this Take will cause the polling task to inherit
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198 the priority of this task. In this case the block time must be
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199 long enough to ensure the polling task will execute again before the
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200 block time expires. If the block time does expire then the error
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201 flag will be set here. */
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202 if( xSemaphoreTakeRecursive( xMutex, recmuEIGHT_TICK_DELAY ) != pdPASS )
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204 xErrorOccurred = pdTRUE;
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207 /* Ensure the other task attempting to access the mutex (and the
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208 other demo tasks) are able to execute to ensure they either block
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209 (where a block time is specified) or return an error (where no
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210 block time is specified) as the mutex is held by this task. */
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211 vTaskDelay( recmuSHORT_DELAY );
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214 /* For each time we took the mutex, give it back. */
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215 for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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217 /* Ensure the other task attempting to access the mutex (and the
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218 other demo tasks) are able to execute. */
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219 vTaskDelay( recmuSHORT_DELAY );
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221 /* We should now be able to give the mutex as many times as we
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222 took it. When the mutex is available again the Blocking task
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223 should be unblocked but not run because it has a lower priority
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224 than this task. The polling task should also not run at this point
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225 as it too has a lower priority than this task. */
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226 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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228 xErrorOccurred = pdTRUE;
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232 /* Having given it back the same number of times as it was taken, we
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233 should no longer be the mutex owner, so the next give should fail. */
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234 if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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236 xErrorOccurred = pdTRUE;
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239 /* Keep count of the number of cycles this task has performed so a
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240 stall can be detected. */
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241 uxControllingCycles++;
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243 /* Suspend ourselves so the blocking task can execute. */
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244 xControllingIsSuspended = pdTRUE;
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245 vTaskSuspend( NULL );
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246 xControllingIsSuspended = pdFALSE;
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249 /*-----------------------------------------------------------*/
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251 static void prvRecursiveMutexBlockingTask( void *pvParameters )
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253 /* Just to remove compiler warning. */
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254 ( void ) pvParameters;
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258 /* This task will run while the controlling task is blocked, and the
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259 controlling task will block only once it has the mutex - therefore
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260 this call should block until the controlling task has given up the
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261 mutex, and not actually execute past this call until the controlling
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262 task is suspended. portMAX_DELAY - 1 is used instead of portMAX_DELAY
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263 to ensure the task's state is reported as Blocked and not Suspended in
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264 a later call to configASSERT() (within the polling task). */
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265 if( xSemaphoreTakeRecursive( xMutex, ( portMAX_DELAY - 1 ) ) == pdPASS )
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267 if( xControllingIsSuspended != pdTRUE )
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269 /* Did not expect to execute until the controlling task was
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271 xErrorOccurred = pdTRUE;
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275 /* Give the mutex back before suspending ourselves to allow
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276 the polling task to obtain the mutex. */
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277 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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279 xErrorOccurred = pdTRUE;
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282 xBlockingIsSuspended = pdTRUE;
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283 vTaskSuspend( NULL );
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284 xBlockingIsSuspended = pdFALSE;
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289 /* We should not leave the xSemaphoreTakeRecursive() function
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290 until the mutex was obtained. */
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291 xErrorOccurred = pdTRUE;
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294 /* The controlling and blocking tasks should be in lock step. */
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295 if( uxControllingCycles != ( uxBlockingCycles + 1 ) )
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297 xErrorOccurred = pdTRUE;
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300 /* Keep count of the number of cycles this task has performed so a
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301 stall can be detected. */
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302 uxBlockingCycles++;
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305 /*-----------------------------------------------------------*/
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307 static void prvRecursiveMutexPollingTask( void *pvParameters )
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309 /* Just to remove compiler warning. */
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310 ( void ) pvParameters;
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314 /* Keep attempting to obtain the mutex. We should only obtain it when
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315 the blocking task has suspended itself, which in turn should only
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316 happen when the controlling task is also suspended. */
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317 if( xSemaphoreTakeRecursive( xMutex, recmuNO_DELAY ) == pdPASS )
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319 #if( INCLUDE_eTaskGetState == 1 )
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321 configASSERT( eTaskGetState( xControllingTaskHandle ) == eSuspended );
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322 configASSERT( eTaskGetState( xBlockingTaskHandle ) == eSuspended );
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324 #endif /* INCLUDE_eTaskGetState */
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326 /* Is the blocking task suspended? */
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327 if( ( xBlockingIsSuspended != pdTRUE ) || ( xControllingIsSuspended != pdTRUE ) )
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329 xErrorOccurred = pdTRUE;
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333 /* Keep count of the number of cycles this task has performed
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334 so a stall can be detected. */
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337 /* We can resume the other tasks here even though they have a
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338 higher priority than the polling task. When they execute they
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339 will attempt to obtain the mutex but fail because the polling
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340 task is still the mutex holder. The polling task (this task)
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341 will then inherit the higher priority. The Blocking task will
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342 block indefinitely when it attempts to obtain the mutex, the
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343 Controlling task will only block for a fixed period and an
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344 error will be latched if the polling task has not returned the
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345 mutex by the time this fixed period has expired. */
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346 vTaskResume( xBlockingTaskHandle );
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347 vTaskResume( xControllingTaskHandle );
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349 /* The other two tasks should now have executed and no longer
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351 if( ( xBlockingIsSuspended == pdTRUE ) || ( xControllingIsSuspended == pdTRUE ) )
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353 xErrorOccurred = pdTRUE;
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356 #if( INCLUDE_uxTaskPriorityGet == 1 )
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358 /* Check priority inherited. */
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359 configASSERT( uxTaskPriorityGet( NULL ) == recmuCONTROLLING_TASK_PRIORITY );
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361 #endif /* INCLUDE_uxTaskPriorityGet */
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363 #if( INCLUDE_eTaskGetState == 1 )
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365 configASSERT( eTaskGetState( xControllingTaskHandle ) == eBlocked );
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366 configASSERT( eTaskGetState( xBlockingTaskHandle ) == eBlocked );
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368 #endif /* INCLUDE_eTaskGetState */
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370 /* Release the mutex, disinheriting the higher priority again. */
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371 if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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373 xErrorOccurred = pdTRUE;
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376 #if( INCLUDE_uxTaskPriorityGet == 1 )
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378 /* Check priority disinherited. */
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379 configASSERT( uxTaskPriorityGet( NULL ) == recmuPOLLING_TASK_PRIORITY );
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381 #endif /* INCLUDE_uxTaskPriorityGet */
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385 #if configUSE_PREEMPTION == 0
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392 /*-----------------------------------------------------------*/
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394 /* This is called to check that all the created tasks are still running. */
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395 BaseType_t xAreRecursiveMutexTasksStillRunning( void )
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397 BaseType_t xReturn;
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398 static UBaseType_t uxLastControllingCycles = 0, uxLastBlockingCycles = 0, uxLastPollingCycles = 0;
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400 /* Is the controlling task still cycling? */
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401 if( uxLastControllingCycles == uxControllingCycles )
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403 xErrorOccurred = pdTRUE;
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407 uxLastControllingCycles = uxControllingCycles;
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410 /* Is the blocking task still cycling? */
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411 if( uxLastBlockingCycles == uxBlockingCycles )
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413 xErrorOccurred = pdTRUE;
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417 uxLastBlockingCycles = uxBlockingCycles;
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420 /* Is the polling task still cycling? */
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421 if( uxLastPollingCycles == uxPollingCycles )
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423 xErrorOccurred = pdTRUE;
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427 uxLastPollingCycles = uxPollingCycles;
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430 if( xErrorOccurred == pdTRUE )
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