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/*
FreeRTOS.org V5.1.0 - Copyright (C) 2003-2008 Richard Barry.
This file is part of the FreeRTOS.org distribution.
FreeRTOS.org is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FreeRTOS.org 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
along with FreeRTOS.org; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
A special exception to the GPL can be applied should you wish to distribute
a combined work that includes FreeRTOS.org, without being obliged to provide
the source code for any proprietary components. See the licensing section
of http://www.FreeRTOS.org for full details of how and when the exception
can be applied.
***************************************************************************
***************************************************************************
* *
* SAVE TIME AND MONEY! We can port FreeRTOS.org to your own hardware, *
* and even write all or part of your application on your behalf. *
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* *
***************************************************************************
***************************************************************************
Please ensure to read the configuration and relevant port sections of the
online documentation.
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contact details.
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*/
/*
* Creates two sets of two tasks. The tasks within a set share a variable, access
* to which is guarded by a semaphore.
*
* Each task starts by attempting to obtain the semaphore. On obtaining a
* semaphore a task checks to ensure that the guarded variable has an expected
* value. It then clears the variable to zero before counting it back up to the
* expected value in increments of 1. After each increment the variable is checked
* to ensure it contains the value to which it was just set. When the starting
* value is again reached the task releases the semaphore giving the other task in
* the set a chance to do exactly the same thing. The starting value is high
* enough to ensure that a tick is likely to occur during the incrementing loop.
*
* An error is flagged if at any time during the process a shared variable is
* found to have a value other than that expected. Such an occurrence would
* suggest an error in the mutual exclusion mechanism by which access to the
* variable is restricted.
*
* The first set of two tasks poll their semaphore. The second set use blocking
* calls.
*
*/
#include <stdlib.h>
/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"
#include "semphr.h"
/* Demo app include files. */
#include "semtest.h"
/* The value to which the shared variables are counted. */
#define semtstBLOCKING_EXPECTED_VALUE ( ( unsigned portLONG ) 0xfff )
#define semtstNON_BLOCKING_EXPECTED_VALUE ( ( unsigned portLONG ) 0xff )
#define semtstSTACK_SIZE configMINIMAL_STACK_SIZE
#define semtstNUM_TASKS ( 4 )
#define semtstDELAY_FACTOR ( ( portTickType ) 10 )
/* The task function as described at the top of the file. */
static portTASK_FUNCTION_PROTO( prvSemaphoreTest, pvParameters );
/* Structure used to pass parameters to each task. */
typedef struct SEMAPHORE_PARAMETERS
{
xSemaphoreHandle xSemaphore;
volatile unsigned portLONG *pulSharedVariable;
portTickType xBlockTime;
} xSemaphoreParameters;
/* Variables used to check that all the tasks are still running without errors. */
static volatile portSHORT sCheckVariables[ semtstNUM_TASKS ] = { 0 };
static volatile portSHORT sNextCheckVariable = 0;
/*-----------------------------------------------------------*/
void vStartSemaphoreTasks( unsigned portBASE_TYPE uxPriority )
{
xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
const portTickType xBlockTime = ( portTickType ) 100;
/* Create the structure used to pass parameters to the first two tasks. */
pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
if( pxFirstSemaphoreParameters != NULL )
{
/* Create the semaphore used by the first two tasks. */
vSemaphoreCreateBinary( pxFirstSemaphoreParameters->xSemaphore );
if( pxFirstSemaphoreParameters->xSemaphore != NULL )
{
/* Create the variable which is to be shared by the first two tasks. */
pxFirstSemaphoreParameters->pulSharedVariable = ( unsigned portLONG * ) pvPortMalloc( sizeof( unsigned portLONG ) );
/* Initialise the share variable to the value the tasks expect. */
*( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;
/* The first two tasks do not block on semaphore calls. */
pxFirstSemaphoreParameters->xBlockTime = ( portTickType ) 0;
/* Spawn the first two tasks. As they poll they operate at the idle priority. */
xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
}
}
/* Do exactly the same to create the second set of tasks, only this time
provide a block time for the semaphore calls. */
pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
if( pxSecondSemaphoreParameters != NULL )
{
vSemaphoreCreateBinary( pxSecondSemaphoreParameters->xSemaphore );
if( pxSecondSemaphoreParameters->xSemaphore != NULL )
{
pxSecondSemaphoreParameters->pulSharedVariable = ( unsigned portLONG * ) pvPortMalloc( sizeof( unsigned portLONG ) );
*( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;
pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_RATE_MS;
xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
}
}
/* vQueueAddToRegistry() adds the semaphore to the registry, if one is
in use. The registry is provided as a means for kernel aware
debuggers to locate semaphores 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 ) pxFirstSemaphoreParameters->xSemaphore, ( signed portCHAR * ) "Counting_Sem_1" );
vQueueAddToRegistry( ( xQueueHandle ) pxSecondSemaphoreParameters->xSemaphore, ( signed portCHAR * ) "Counting_Sem_2" );
}
/*-----------------------------------------------------------*/
static portTASK_FUNCTION( prvSemaphoreTest, pvParameters )
{
xSemaphoreParameters *pxParameters;
volatile unsigned portLONG *pulSharedVariable, ulExpectedValue;
unsigned portLONG ulCounter;
portSHORT sError = pdFALSE, sCheckVariableToUse;
/* See which check variable to use. sNextCheckVariable is not semaphore
protected! */
portENTER_CRITICAL();
sCheckVariableToUse = sNextCheckVariable;
sNextCheckVariable++;
portEXIT_CRITICAL();
/* A structure is passed in as the parameter. This contains the shared
variable being guarded. */
pxParameters = ( xSemaphoreParameters * ) pvParameters;
pulSharedVariable = pxParameters->pulSharedVariable;
/* If we are blocking we use a much higher count to ensure loads of context
switches occur during the count. */
if( pxParameters->xBlockTime > ( portTickType ) 0 )
{
ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
}
else
{
ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
}
for( ;; )
{
/* Try to obtain the semaphore. */
if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )
{
/* We have the semaphore and so expect any other tasks using the
shared variable to have left it in the state we expect to find
it. */
if( *pulSharedVariable != ulExpectedValue )
{
sError = pdTRUE;
}
/* Clear the variable, then count it back up to the expected value
before releasing the semaphore. Would expect a context switch or
two during this time. */
for( ulCounter = ( unsigned portLONG ) 0; ulCounter <= ulExpectedValue; ulCounter++ )
{
*pulSharedVariable = ulCounter;
if( *pulSharedVariable != ulCounter )
{
sError = pdTRUE;
}
}
/* Release the semaphore, and if no errors have occurred increment the check
variable. */
if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )
{
sError = pdTRUE;
}
if( sError == pdFALSE )
{
if( sCheckVariableToUse < semtstNUM_TASKS )
{
( sCheckVariables[ sCheckVariableToUse ] )++;
}
}
/* If we have a block time then we are running at a priority higher
than the idle priority. This task takes a long time to complete
a cycle (deliberately so to test the guarding) so will be starving
out lower priority tasks. Block for some time to allow give lower
priority tasks some processor time. */
vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );
}
else
{
if( pxParameters->xBlockTime == ( portTickType ) 0 )
{
/* We have not got the semaphore yet, so no point using the
processor. We are not blocking when attempting to obtain the
semaphore. */
taskYIELD();
}
}
}
}
/*-----------------------------------------------------------*/
/* This is called to check that all the created tasks are still running. */
portBASE_TYPE xAreSemaphoreTasksStillRunning( void )
{
static portSHORT sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
portBASE_TYPE xTask, xReturn = pdTRUE;
for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )
{
if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )
{
xReturn = pdFALSE;
}
sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
}
return xReturn;
}