Subversion Repositories openrisc_2011-10-31

/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************

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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.

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*/

/*

        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 )

/* In this version the tick period is very long, so the short delay cannot be

for too many ticks, or the check task will execute and find that the recmutex

tasks have not completed their functionality and then signal an error.  The

delay does however have to be long enough to allow the lower priority tasks

a chance of executing - this is basically achieved by reducing the number

of times the loop that takes/gives the recursive mutex executes. */

#define recmuMAX_COUNT                                  ( 2 )

#define recmuSHORT_DELAY                                ( 20 )

#define recmuNO_DELAY                                   ( ( portTickType ) 0 )

#define recmuFIVE_TICK_DELAY                    ( ( portTickType ) 5 )

/* 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 = 0, 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 * ) "Rec1Ctrl", configMINIMAL_STACK_SIZE, NULL, recmuCONTROLLING_TASK_PRIORITY, &xControllingTaskHandle );

        xTaskCreate( prvRecursiveMutexBlockingTask, ( signed portCHAR * ) "Rec2Blck", configMINIMAL_STACK_SIZE, NULL, recmuBLOCKING_TASK_PRIORITY, &xBlockingTaskHandle );

        xTaskCreate( prvRecursiveMutexPollingTask, ( signed portCHAR * ) "Rec3Poll", 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.   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, recmuFIVE_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. */

                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, which in turn should only

                happen when the controlling task is also suspended. */

                if( xSemaphoreTakeRecursive( xMutex, recmuNO_DELAY ) == pdPASS )

                {

                        /* 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;

                                }

                                /* 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;

}