/* FreeRTOS V8.1.2 - Copyright (C) 2014 Real Time Engineers Ltd. All rights reserved VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION. *************************************************************************** * * * FreeRTOS provides completely free yet professionally developed, * * robust, strictly quality controlled, supported, and cross * * platform software that has become a de facto standard. * * * * Help yourself get started quickly and support the FreeRTOS * * project by purchasing a FreeRTOS tutorial book, reference * * manual, or both from: http://www.FreeRTOS.org/Documentation * * * * Thank you! * * * *************************************************************************** This file is part of the FreeRTOS distribution. FreeRTOS is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (version 2) as published by the Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception. >>! NOTE: The modification to the GPL is included to allow you to !<< >>! distribute a combined work that includes FreeRTOS without being !<< >>! obliged to provide the source code for proprietary components !<< >>! outside of the FreeRTOS kernel. !<< FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Full license text is available from the following link: http://www.freertos.org/a00114.html 1 tab == 4 spaces! *************************************************************************** * * * Having a problem? Start by reading the FAQ "My application does * * not run, what could be wrong?" * * * * http://www.FreeRTOS.org/FAQHelp.html * * * *************************************************************************** http://www.FreeRTOS.org - Documentation, books, training, latest versions, license and Real Time Engineers Ltd. contact details. http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products, including FreeRTOS+Trace - an indispensable productivity tool, a DOS compatible FAT file system, and our tiny thread aware UDP/IP stack. http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS licenses offer ticketed support, indemnification and middleware. http://www.SafeRTOS.com - High Integrity Systems also provide a safety engineered and independently SIL3 certified version for use in safety and mission critical applications that require provable dependability. 1 tab == 4 spaces! */ /* The tasks defined on this page demonstrate the use of recursive mutexes. For recursive mutex functionality the created mutex should be created using xSemaphoreCreateRecursiveMutex(), then be manipulated using the xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() API functions. This demo creates three tasks all of which access the same recursive mutex: prvRecursiveMutexControllingTask() has the highest priority so executes first and grabs the mutex. It then performs some recursive accesses - between each of which it sleeps for a short period to let the lower priority tasks execute. When it has completed its demo functionality it gives the mutex back before suspending itself. prvRecursiveMutexBlockingTask() attempts to access the mutex by performing a blocking 'take'. The blocking task has a lower priority than the controlling task so by the time it executes the mutex has already been taken by the controlling task, causing the blocking task to block. It does not unblock until the controlling task has given the mutex back, and it does not actually run until the controlling task has suspended itself (due to the relative priorities). When it eventually does obtain the mutex all it does is give the mutex back prior to also suspending itself. At this point both the controlling task and the blocking task are suspended. prvRecursiveMutexPollingTask() runs at the idle priority. It spins round a tight loop attempting to obtain the mutex with a non-blocking call. As the lowest priority task it will not successfully obtain the mutex until both the controlling and blocking tasks are suspended. Once it eventually does obtain the mutex it first unsuspends both the controlling task and blocking task prior to giving the mutex back - resulting in the polling task temporarily inheriting the controlling tasks priority. */ /* Scheduler include files. */ #include "FreeRTOS.h" #include "task.h" #include "semphr.h" /* Demo app include files. */ #include "recmutex.h" /* Priorities assigned to the three tasks. recmuCONTROLLING_TASK_PRIORITY can be overridden by a definition in FreeRTOSConfig.h. */ #ifndef recmuCONTROLLING_TASK_PRIORITY #define recmuCONTROLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 2 ) #endif #define recmuBLOCKING_TASK_PRIORITY ( tskIDLE_PRIORITY + 1 ) #define recmuPOLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 0 ) /* The recursive call depth. */ #define recmuMAX_COUNT ( 10 ) /* Misc. */ #define recmuSHORT_DELAY ( 20 / portTICK_PERIOD_MS ) #define recmuNO_DELAY ( ( TickType_t ) 0 ) #define recmuEIGHT_TICK_DELAY ( ( TickType_t ) 8 ) /* The three tasks as described at the top of this file. */ static void prvRecursiveMutexControllingTask( void *pvParameters ); static void prvRecursiveMutexBlockingTask( void *pvParameters ); static void prvRecursiveMutexPollingTask( void *pvParameters ); /* The mutex used by the demo. */ static SemaphoreHandle_t xMutex; /* Variables used to detect and latch errors. */ static volatile BaseType_t xErrorOccurred = pdFALSE, xControllingIsSuspended = pdFALSE, xBlockingIsSuspended = pdFALSE; static volatile UBaseType_t uxControllingCycles = 0, uxBlockingCycles = 0, uxPollingCycles = 0; /* Handles of the two higher priority tasks, required so they can be resumed (unsuspended). */ static TaskHandle_t xControllingTaskHandle, xBlockingTaskHandle; /*-----------------------------------------------------------*/ void vStartRecursiveMutexTasks( void ) { /* Just creates the mutex and the three tasks. */ xMutex = xSemaphoreCreateRecursiveMutex(); /* vQueueAddToRegistry() adds the mutex to the registry, if one is in use. The registry is provided as a means for kernel aware debuggers to locate mutex and has no purpose if a kernel aware debugger is not being used. The call to vQueueAddToRegistry() will be removed by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is defined to be less than 1. */ vQueueAddToRegistry( ( QueueHandle_t ) xMutex, "Recursive_Mutex" ); if( xMutex != NULL ) { xTaskCreate( prvRecursiveMutexControllingTask, "Rec1", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle ); xTaskCreate( prvRecursiveMutexBlockingTask, "Rec2", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle ); xTaskCreate( prvRecursiveMutexPollingTask, "Rec3", configMINIMAL_STACK_SIZE, NULL, recmuPOLLING_TASK_PRIORITY, NULL ); } } /*-----------------------------------------------------------*/ static void prvRecursiveMutexControllingTask( void *pvParameters ) { UBaseType_t ux; /* Just to remove compiler warning. */ ( void ) pvParameters; for( ;; ) { /* Should not be able to 'give' the mutex, as we have not yet 'taken' it. The first time through, the mutex will not have been used yet, subsequent times through, at this point the mutex will be held by the polling task. */ if( xSemaphoreGiveRecursive( xMutex ) == pdPASS ) { xErrorOccurred = pdTRUE; } for( ux = 0; ux < recmuMAX_COUNT; ux++ ) { /* We should now be able to take the mutex as many times as we like. The first time through the mutex will be immediately available, on subsequent times through the mutex will be held by the polling task at this point and this Take will cause the polling task to inherit the priority of this task. In this case the block time must be long enough to ensure the polling task will execute again before the block time expires. If the block time does expire then the error flag will be set here. */ if( xSemaphoreTakeRecursive( xMutex, recmuEIGHT_TICK_DELAY ) != pdPASS ) { xErrorOccurred = pdTRUE; } /* Ensure the other task attempting to access the mutex (and the other demo tasks) are able to execute to ensure they either block (where a block time is specified) or return an error (where no block time is specified) as the mutex is held by this task. */ vTaskDelay( recmuSHORT_DELAY ); } /* For each time we took the mutex, give it back. */ for( ux = 0; ux < recmuMAX_COUNT; ux++ ) { /* Ensure the other task attempting to access the mutex (and the other demo tasks) are able to execute. */ vTaskDelay( recmuSHORT_DELAY ); /* We should now be able to give the mutex as many times as we took it. When the mutex is available again the Blocking task should be unblocked but not run because it has a lower priority than this task. The polling task should also not run at this point as it too has a lower priority than this task. */ if( xSemaphoreGiveRecursive( xMutex ) != pdPASS ) { xErrorOccurred = pdTRUE; } } /* Having given it back the same number of times as it was taken, we should no longer be the mutex owner, so the next give should fail. */ if( xSemaphoreGiveRecursive( xMutex ) == pdPASS ) { xErrorOccurred = pdTRUE; } /* Keep count of the number of cycles this task has performed so a stall can be detected. */ uxControllingCycles++; /* Suspend ourselves so the blocking task can execute. */ xControllingIsSuspended = pdTRUE; vTaskSuspend( NULL ); xControllingIsSuspended = pdFALSE; } } /*-----------------------------------------------------------*/ static void prvRecursiveMutexBlockingTask( void *pvParameters ) { /* Just to remove compiler warning. */ ( void ) pvParameters; for( ;; ) { /* This task will run while the controlling task is blocked, and the controlling task will block only once it has the mutex - therefore this call should block until the controlling task has given up the mutex, and not actually execute past this call until the controlling task is suspended. portMAX_DELAY - 1 is used instead of portMAX_DELAY to ensure the task's state is reported as Blocked and not Suspended in a later call to configASSERT() (within the polling task). */ if( xSemaphoreTakeRecursive( xMutex, ( portMAX_DELAY - 1 ) ) == pdPASS ) { if( xControllingIsSuspended != pdTRUE ) { /* Did not expect to execute until the controlling task was suspended. */ xErrorOccurred = pdTRUE; } else { /* Give the mutex back before suspending ourselves to allow the polling task to obtain the mutex. */ if( xSemaphoreGiveRecursive( xMutex ) != pdPASS ) { xErrorOccurred = pdTRUE; } xBlockingIsSuspended = pdTRUE; vTaskSuspend( NULL ); xBlockingIsSuspended = pdFALSE; } } else { /* We should not leave the xSemaphoreTakeRecursive() function until the mutex was obtained. */ xErrorOccurred = pdTRUE; } /* The controlling and blocking tasks should be in lock step. */ if( uxControllingCycles != ( uxBlockingCycles + 1 ) ) { xErrorOccurred = pdTRUE; } /* Keep count of the number of cycles this task has performed so a stall can be detected. */ uxBlockingCycles++; } } /*-----------------------------------------------------------*/ static void prvRecursiveMutexPollingTask( void *pvParameters ) { /* Just to remove compiler warning. */ ( void ) pvParameters; for( ;; ) { /* Keep attempting to obtain the mutex. We should only obtain it when the blocking task has suspended itself, which in turn should only happen when the controlling task is also suspended. */ if( xSemaphoreTakeRecursive( xMutex, recmuNO_DELAY ) == pdPASS ) { #if( INCLUDE_eTaskGetState == 1 ) { configASSERT( eTaskGetState( xControllingTaskHandle ) == eSuspended ); configASSERT( eTaskGetState( xBlockingTaskHandle ) == eSuspended ); } #endif /* INCLUDE_eTaskGetState */ /* Is the blocking task suspended? */ if( ( xBlockingIsSuspended != pdTRUE ) || ( xControllingIsSuspended != pdTRUE ) ) { xErrorOccurred = pdTRUE; } else { /* Keep count of the number of cycles this task has performed so a stall can be detected. */ uxPollingCycles++; /* We can resume the other tasks here even though they have a higher priority than the polling task. When they execute they will attempt to obtain the mutex but fail because the polling task is still the mutex holder. The polling task (this task) will then inherit the higher priority. The Blocking task will block indefinitely when it attempts to obtain the mutex, the Controlling task will only block for a fixed period and an error will be latched if the polling task has not returned the mutex by the time this fixed period has expired. */ vTaskResume( xBlockingTaskHandle ); vTaskResume( xControllingTaskHandle ); /* The other two tasks should now have executed and no longer be suspended. */ if( ( xBlockingIsSuspended == pdTRUE ) || ( xControllingIsSuspended == pdTRUE ) ) { xErrorOccurred = pdTRUE; } #if( INCLUDE_uxTaskPriorityGet == 1 ) { /* Check priority inherited. */ configASSERT( uxTaskPriorityGet( NULL ) == recmuCONTROLLING_TASK_PRIORITY ); } #endif /* INCLUDE_uxTaskPriorityGet */ #if( INCLUDE_eTaskGetState == 1 ) { configASSERT( eTaskGetState( xControllingTaskHandle ) == eBlocked ); configASSERT( eTaskGetState( xBlockingTaskHandle ) == eBlocked ); } #endif /* INCLUDE_eTaskGetState */ /* Release the mutex, disinheriting the higher priority again. */ if( xSemaphoreGiveRecursive( xMutex ) != pdPASS ) { xErrorOccurred = pdTRUE; } #if( INCLUDE_uxTaskPriorityGet == 1 ) { /* Check priority disinherited. */ configASSERT( uxTaskPriorityGet( NULL ) == recmuPOLLING_TASK_PRIORITY ); } #endif /* INCLUDE_uxTaskPriorityGet */ } } #if configUSE_PREEMPTION == 0 { taskYIELD(); } #endif } } /*-----------------------------------------------------------*/ /* This is called to check that all the created tasks are still running. */ BaseType_t xAreRecursiveMutexTasksStillRunning( void ) { BaseType_t xReturn; static UBaseType_t uxLastControllingCycles = 0, uxLastBlockingCycles = 0, uxLastPollingCycles = 0; /* Is the controlling task still cycling? */ if( uxLastControllingCycles == uxControllingCycles ) { xErrorOccurred = pdTRUE; } else { uxLastControllingCycles = uxControllingCycles; } /* Is the blocking task still cycling? */ if( uxLastBlockingCycles == uxBlockingCycles ) { xErrorOccurred = pdTRUE; } else { uxLastBlockingCycles = uxBlockingCycles; } /* Is the polling task still cycling? */ if( uxLastPollingCycles == uxPollingCycles ) { xErrorOccurred = pdTRUE; } else { uxLastPollingCycles = uxPollingCycles; } if( xErrorOccurred == pdTRUE ) { xReturn = pdFAIL; } else { xReturn = pdTRUE; } return xReturn; }