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366 lines
12 KiB
C
366 lines
12 KiB
C
/*
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FreeRTOS.org V5.0.4 - Copyright (C) 2003-2008 Richard Barry.
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This file is part of the FreeRTOS.org distribution.
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FreeRTOS.org is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FreeRTOS.org is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FreeRTOS.org; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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A special exception to the GPL can be applied should you wish to distribute
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a combined work that includes FreeRTOS.org, without being obliged to provide
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the source code for any proprietary components. See the licensing section
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of http://www.FreeRTOS.org for full details of how and when the exception
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can be applied.
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***************************************************************************
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***************************************************************************
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* *
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* SAVE TIME AND MONEY! We can port FreeRTOS.org to your own hardware, *
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* and even write all or part of your application on your behalf. *
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* See http://www.OpenRTOS.com for details of the services we provide to *
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* expedite your project. *
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* *
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***************************************************************************
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***************************************************************************
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Please ensure to read the configuration and relevant port sections of the
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online documentation.
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http://www.FreeRTOS.org - Documentation, latest information, license and
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contact details.
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http://www.SafeRTOS.com - A version that is certified for use in safety
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critical systems.
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http://www.OpenRTOS.com - Commercial support, development, porting,
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licensing and training services.
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*/
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/*
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The tasks defined on this page demonstrate the use of recursive mutexes.
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For recursive mutex functionality the created mutex should be created using
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xSemaphoreCreateRecursiveMutex(), then be manipulated
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using the xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() API
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functions.
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This demo creates three tasks all of which access the same recursive mutex:
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prvRecursiveMutexControllingTask() has the highest priority so executes
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first and grabs the mutex. It then performs some recursive accesses -
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between each of which it sleeps for a short period to let the lower
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priority tasks execute. When it has completed its demo functionality
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it gives the mutex back before suspending itself.
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prvRecursiveMutexBlockingTask() attempts to access the mutex by performing
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a blocking 'take'. The blocking task has a lower priority than the
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controlling task so by the time it executes the mutex has already been
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taken by the controlling task, causing the blocking task to block. It
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does not unblock until the controlling task has given the mutex back,
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and it does not actually run until the controlling task has suspended
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itself (due to the relative priorities). When it eventually does obtain
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the mutex all it does is give the mutex back prior to also suspending
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itself. At this point both the controlling task and the blocking task are
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suspended.
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prvRecursiveMutexPollingTask() runs at the idle priority. It spins round
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a tight loop attempting to obtain the mutex with a non-blocking call. As
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the lowest priority task it will not successfully obtain the mutex until
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both the controlling and blocking tasks are suspended. Once it eventually
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does obtain the mutex it first unsuspends both the controlling task and
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blocking task prior to giving the mutex back - resulting in the polling
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task temporarily inheriting the controlling tasks priority.
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*/
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/* Scheduler include files. */
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#include "FreeRTOS.h"
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#include "task.h"
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#include "semphr.h"
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/* Demo app include files. */
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#include "recmutex.h"
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/* Priorities assigned to the three tasks. */
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#define recmuCONTROLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 2 )
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#define recmuBLOCKING_TASK_PRIORITY ( tskIDLE_PRIORITY + 1 )
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#define recmuPOLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 0 )
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/* The recursive call depth. */
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#define recmuMAX_COUNT ( 10 )
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/* Misc. */
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#define recmuSHORT_DELAY ( 20 / portTICK_RATE_MS )
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#define recmuNO_DELAY ( ( portTickType ) 0 )
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#define recmuTWO_TICK_DELAY ( ( portTickType ) 2 )
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/* The three tasks as described at the top of this file. */
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static void prvRecursiveMutexControllingTask( void *pvParameters );
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static void prvRecursiveMutexBlockingTask( void *pvParameters );
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static void prvRecursiveMutexPollingTask( void *pvParameters );
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/* The mutex used by the demo. */
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static xSemaphoreHandle xMutex;
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/* Variables used to detect and latch errors. */
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static volatile portBASE_TYPE xErrorOccurred = pdFALSE, xControllingIsSuspended = pdFALSE, xBlockingIsSuspended = pdFALSE;
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static volatile unsigned portBASE_TYPE uxControllingCycles = 0, uxBlockingCycles, uxPollingCycles = 0;
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/* Handles of the two higher priority tasks, required so they can be resumed
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(unsuspended). */
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static xTaskHandle xControllingTaskHandle, xBlockingTaskHandle;
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/*-----------------------------------------------------------*/
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void vStartRecursiveMutexTasks( void )
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{
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/* Just creates the mutex and the three tasks. */
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xMutex = xSemaphoreCreateRecursiveMutex();
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/* vQueueAddToRegistry() adds the mutex to the registry, if one is
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in use. The registry is provided as a means for kernel aware
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debuggers to locate mutex and has no purpose if a kernel aware debugger
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is not being used. The call to vQueueAddToRegistry() will be removed
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by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
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defined to be less than 1. */
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vQueueAddToRegistry( ( xQueueHandle ) xMutex, ( signed portCHAR * ) "Recursive_Mutex" );
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if( xMutex != NULL )
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{
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xTaskCreate( prvRecursiveMutexControllingTask, ( signed portCHAR * ) "Rec1", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle );
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xTaskCreate( prvRecursiveMutexBlockingTask, ( signed portCHAR * ) "Rec2", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle );
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xTaskCreate( prvRecursiveMutexPollingTask, ( signed portCHAR * ) "Rec3", configMINIMAL_STACK_SIZE, NULL, recmuPOLLING_TASK_PRIORITY, NULL );
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}
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}
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/*-----------------------------------------------------------*/
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static void prvRecursiveMutexControllingTask( void *pvParameters )
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{
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unsigned portBASE_TYPE ux;
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/* Just to remove compiler warning. */
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( void ) pvParameters;
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for( ;; )
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{
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/* Should not be able to 'give' the mutex, as we have not yet 'taken'
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it. */
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if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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{
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/* We should now be able to take the mutex as many times as
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we like. A one tick delay is used so the polling task will
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inherit our priority on all but the first cycle of this task.
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If we did not block attempting to receive the mutex then no
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priority inheritance would occur. */
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if( xSemaphoreTakeRecursive( xMutex, recmuTWO_TICK_DELAY ) != pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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/* Ensure the other task attempting to access the mutex (and the
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other demo tasks) are able to execute. */
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vTaskDelay( recmuSHORT_DELAY );
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}
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/* For each time we took the mutex, give it back. */
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for( ux = 0; ux < recmuMAX_COUNT; ux++ )
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{
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/* Ensure the other task attempting to access the mutex (and the
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other demo tasks) are able to execute. */
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vTaskDelay( recmuSHORT_DELAY );
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/* We should now be able to give the mutex as many times as we
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took it. */
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if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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}
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/* Having given it back the same number of times as it was taken, we
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should no longer be the mutex owner, so the next give sh ould fail. */
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if( xSemaphoreGiveRecursive( xMutex ) == pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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/* Keep count of the number of cycles this task has performed so a
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stall can be detected. */
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uxControllingCycles++;
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/* Suspend ourselves to the blocking task can execute. */
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xControllingIsSuspended = pdTRUE;
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vTaskSuspend( NULL );
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xControllingIsSuspended = pdFALSE;
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}
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}
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/*-----------------------------------------------------------*/
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static void prvRecursiveMutexBlockingTask( void *pvParameters )
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{
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/* Just to remove compiler warning. */
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( void ) pvParameters;
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for( ;; )
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{
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/* Attempt to obtain the mutex. We should block until the
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controlling task has given up the mutex, and not actually execute
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past this call until the controlling task is suspended. */
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if( xSemaphoreTakeRecursive( xMutex, portMAX_DELAY ) == pdPASS )
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{
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if( xControllingIsSuspended != pdTRUE )
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{
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/* Did not expect to execute until the controlling task was
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suspended. */
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xErrorOccurred = pdTRUE;
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}
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else
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{
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/* Give the mutex back before suspending ourselves to allow
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the polling task to obtain the mutex. */
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if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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xBlockingIsSuspended = pdTRUE;
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vTaskSuspend( NULL );
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xBlockingIsSuspended = pdFALSE;
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}
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}
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else
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{
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/* We should not leave the xSemaphoreTakeRecursive() function
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until the mutex was obtained. */
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xErrorOccurred = pdTRUE;
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}
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/* The controlling and blocking tasks should be in lock step. */
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if( uxControllingCycles != ( uxBlockingCycles + 1 ) )
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{
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xErrorOccurred = pdTRUE;
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}
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/* Keep count of the number of cycles this task has performed so a
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stall can be detected. */
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uxBlockingCycles++;
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}
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}
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/*-----------------------------------------------------------*/
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static void prvRecursiveMutexPollingTask( void *pvParameters )
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{
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/* Just to remove compiler warning. */
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( void ) pvParameters;
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for( ;; )
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{
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/* Keep attempting to obtain the mutex. We should only obtain it when
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the blocking task has suspended itself. */
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if( xSemaphoreTakeRecursive( xMutex, recmuNO_DELAY ) == pdPASS )
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{
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/* Is the blocking task suspended? */
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if( xBlockingIsSuspended != pdTRUE )
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{
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xErrorOccurred = pdTRUE;
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}
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else
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{
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/* Keep count of the number of cycles this task has performed so
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a stall can be detected. */
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uxPollingCycles++;
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/* We can resume the other tasks here even though they have a
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higher priority than the polling task. When they execute they
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will attempt to obtain the mutex but fail because the polling
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task is still the mutex holder. The polling task (this task)
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will then inherit the higher priority. */
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vTaskResume( xBlockingTaskHandle );
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vTaskResume( xControllingTaskHandle );
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/* Release the mutex, disinheriting the higher priority again. */
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if( xSemaphoreGiveRecursive( xMutex ) != pdPASS )
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{
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xErrorOccurred = pdTRUE;
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}
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}
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}
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#if configUSE_PREEMPTION == 0
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{
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taskYIELD();
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}
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#endif
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}
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}
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/*-----------------------------------------------------------*/
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/* This is called to check that all the created tasks are still running. */
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portBASE_TYPE xAreRecursiveMutexTasksStillRunning( void )
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{
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portBASE_TYPE xReturn;
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static unsigned portBASE_TYPE uxLastControllingCycles = 0, uxLastBlockingCycles = 0, uxLastPollingCycles = 0;
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/* Is the controlling task still cycling? */
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if( uxLastControllingCycles == uxControllingCycles )
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{
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xErrorOccurred = pdTRUE;
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}
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else
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{
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uxLastControllingCycles = uxControllingCycles;
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}
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/* Is the blocking task still cycling? */
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if( uxLastBlockingCycles == uxBlockingCycles )
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{
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xErrorOccurred = pdTRUE;
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}
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else
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{
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uxLastBlockingCycles = uxBlockingCycles;
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}
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/* Is the polling task still cycling? */
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if( uxLastPollingCycles == uxPollingCycles )
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{
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xErrorOccurred = pdTRUE;
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}
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else
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{
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uxLastPollingCycles = uxPollingCycles;
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}
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if( xErrorOccurred == pdTRUE )
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{
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xReturn = pdFAIL;
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}
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else
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{
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xReturn = pdTRUE;
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}
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return xReturn;
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}
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