| /* |
| FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd. |
| |
| *************************************************************************** |
| * * |
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| * "Using the FreeRTOS Real Time Kernel - a Practical Guide" * |
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| * A pdf reference manual is also available. Both are usually delivered * |
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| *************************************************************************** |
| |
| 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 exception 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. See the GNU General Public License for |
| more details. You should have received a copy of the GNU General Public |
| License and the FreeRTOS license exception along with FreeRTOS; if not it |
| can be viewed here: http://www.freertos.org/a00114.html and also obtained |
| by writing to Richard Barry, contact details for whom are available on the |
| FreeRTOS WEB site. |
| |
| 1 tab == 4 spaces! |
| |
| http://www.FreeRTOS.org - Documentation, latest information, license and |
| contact details. |
| |
| http://www.SafeRTOS.com - A version that is certified for use in safety |
| critical systems. |
| |
| http://www.OpenRTOS.com - Commercial support, development, porting, |
| licensing and training services. |
| */ |
| |
| /* |
| 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. */ |
| #define recmuCONTROLLING_TASK_PRIORITY ( tskIDLE_PRIORITY + 2 ) |
| #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_RATE_MS ) |
| #define recmuNO_DELAY ( ( portTickType ) 0 ) |
| #define recmuTWO_TICK_DELAY ( ( portTickType ) 2 ) |
| |
| /* 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 xSemaphoreHandle xMutex; |
| |
| /* Variables used to detect and latch errors. */ |
| static volatile portBASE_TYPE xErrorOccurred = pdFALSE, xControllingIsSuspended = pdFALSE, xBlockingIsSuspended = pdFALSE; |
| static volatile unsigned portBASE_TYPE uxControllingCycles = 0, uxBlockingCycles, uxPollingCycles = 0; |
| |
| /* Handles of the two higher priority tasks, required so they can be resumed |
| (unsuspended). */ |
| static xTaskHandle 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((xQueueHandle) xMutex, (signed portCHAR *) "Recursive_Mutex"); |
| |
| |
| if (xMutex != NULL) { |
| xTaskCreate(prvRecursiveMutexControllingTask, (signed portCHAR *) "Rec1", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle); |
| xTaskCreate(prvRecursiveMutexBlockingTask, (signed portCHAR *) "Rec2", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle); |
| xTaskCreate(prvRecursiveMutexPollingTask, (signed portCHAR *) "Rec3", configMINIMAL_STACK_SIZE, NULL, recmuPOLLING_TASK_PRIORITY, NULL); |
| } |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvRecursiveMutexControllingTask(void *pvParameters) |
| { |
| unsigned portBASE_TYPE ux; |
| |
| /* Just to remove compiler warning. */ |
| (void) pvParameters; |
| |
| for (;;) { |
| /* Should not be able to 'give' the mutex, as we have not yet 'taken' |
| it. */ |
| 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. A one tick delay is used so the polling task will |
| inherit our priority on all but the first cycle of this task. |
| If we did not block attempting to receive the mutex then no |
| priority inheritance would occur. */ |
| if (xSemaphoreTakeRecursive(xMutex, recmuTWO_TICK_DELAY) != pdPASS) { |
| xErrorOccurred = pdTRUE; |
| } |
| |
| /* Ensure the other task attempting to access the mutex (and the |
| other demo tasks) are able to execute. */ |
| 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. */ |
| 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 sh ould 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 to the blocking task can execute. */ |
| xControllingIsSuspended = pdTRUE; |
| vTaskSuspend(NULL); |
| xControllingIsSuspended = pdFALSE; |
| } |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvRecursiveMutexBlockingTask(void *pvParameters) |
| { |
| /* Just to remove compiler warning. */ |
| (void) pvParameters; |
| |
| for (;;) { |
| /* Attempt to obtain the mutex. We should block until the |
| controlling task has given up the mutex, and not actually execute |
| past this call until the controlling task is suspended. */ |
| if (xSemaphoreTakeRecursive(xMutex, portMAX_DELAY) == 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. */ |
| if (xSemaphoreTakeRecursive(xMutex, recmuNO_DELAY) == pdPASS) { |
| /* Is the blocking task suspended? */ |
| if (xBlockingIsSuspended != 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. */ |
| vTaskResume(xBlockingTaskHandle); |
| vTaskResume(xControllingTaskHandle); |
| |
| /* Release the mutex, disinheriting the higher priority again. */ |
| if (xSemaphoreGiveRecursive(xMutex) != pdPASS) { |
| xErrorOccurred = pdTRUE; |
| } |
| } |
| } |
| |
| #if configUSE_PREEMPTION == 0 |
| { |
| taskYIELD(); |
| } |
| #endif |
| } |
| } |
| /*-----------------------------------------------------------*/ |
| |
| /* This is called to check that all the created tasks are still running. */ |
| portBASE_TYPE xAreRecursiveMutexTasksStillRunning(void) |
| { |
| portBASE_TYPE xReturn; |
| static unsigned portBASE_TYPE 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; |
| } |
| |
| |
| |
| |