270 lines
10 KiB
C
270 lines
10 KiB
C
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/*
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* FreeRTOS Kernel V10.2.1
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* Copyright (C) 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* http://www.FreeRTOS.org
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* http://aws.amazon.com/freertos
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*
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* 1 tab == 4 spaces!
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*/
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/*
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* Creates two sets of two tasks. The tasks within a set share a variable, access
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* to which is guarded by a semaphore.
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*
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* Each task starts by attempting to obtain the semaphore. On obtaining a
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* semaphore a task checks to ensure that the guarded variable has an expected
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* value. It then clears the variable to zero before counting it back up to the
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* expected value in increments of 1. After each increment the variable is checked
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* to ensure it contains the value to which it was just set. When the starting
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* value is again reached the task releases the semaphore giving the other task in
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* the set a chance to do exactly the same thing. The starting value is high
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* enough to ensure that a tick is likely to occur during the incrementing loop.
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*
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* An error is flagged if at any time during the process a shared variable is
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* found to have a value other than that expected. Such an occurrence would
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* suggest an error in the mutual exclusion mechanism by which access to the
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* variable is restricted.
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*
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* The first set of two tasks poll their semaphore. The second set use blocking
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* calls.
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*
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*/
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#include <stdlib.h>
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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 "semtest.h"
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/* The value to which the shared variables are counted. */
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#define semtstBLOCKING_EXPECTED_VALUE ( ( uint32_t ) 0xfff )
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#define semtstNON_BLOCKING_EXPECTED_VALUE ( ( uint32_t ) 0xff )
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#define semtstSTACK_SIZE configMINIMAL_STACK_SIZE
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#define semtstNUM_TASKS ( 4 )
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#define semtstDELAY_FACTOR ( ( TickType_t ) 10 )
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/* The task function as described at the top of the file. */
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static portTASK_FUNCTION_PROTO( prvSemaphoreTest, pvParameters );
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/* Structure used to pass parameters to each task. */
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typedef struct SEMAPHORE_PARAMETERS
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{
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SemaphoreHandle_t xSemaphore;
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volatile uint32_t *pulSharedVariable;
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TickType_t xBlockTime;
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} xSemaphoreParameters;
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/* Variables used to check that all the tasks are still running without errors. */
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static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 };
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static volatile short sNextCheckVariable = 0;
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/*-----------------------------------------------------------*/
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void vStartSemaphoreTasks( UBaseType_t uxPriority )
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{
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xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
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const TickType_t xBlockTime = ( TickType_t ) 100;
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/* Create the structure used to pass parameters to the first two tasks. */
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pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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if( pxFirstSemaphoreParameters != NULL )
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{
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/* Create the semaphore used by the first two tasks. */
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pxFirstSemaphoreParameters->xSemaphore = xSemaphoreCreateBinary();
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if( pxFirstSemaphoreParameters->xSemaphore != NULL )
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{
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xSemaphoreGive( pxFirstSemaphoreParameters->xSemaphore );
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/* Create the variable which is to be shared by the first two tasks. */
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pxFirstSemaphoreParameters->pulSharedVariable = ( uint32_t * ) pvPortMalloc( sizeof( uint32_t ) );
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/* Initialise the share variable to the value the tasks expect. */
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*( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;
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/* The first two tasks do not block on semaphore calls. */
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pxFirstSemaphoreParameters->xBlockTime = ( TickType_t ) 0;
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/* Spawn the first two tasks. As they poll they operate at the idle priority. */
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xTaskCreate( prvSemaphoreTest, "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );
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xTaskCreate( prvSemaphoreTest, "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL );
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/* vQueueAddToRegistry() adds the semaphore to the registry, if one
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is in use. The registry is provided as a means for kernel aware
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debuggers to locate semaphores and has no purpose if a kernel aware
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debugger is not being used. The call to vQueueAddToRegistry() will
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be removed by the pre-processor if configQUEUE_REGISTRY_SIZE is not
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defined or is defined to be less than 1. */
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vQueueAddToRegistry( ( QueueHandle_t ) pxFirstSemaphoreParameters->xSemaphore, "Counting_Sem_1" );
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}
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}
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/* Do exactly the same to create the second set of tasks, only this time
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provide a block time for the semaphore calls. */
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pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
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if( pxSecondSemaphoreParameters != NULL )
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{
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pxSecondSemaphoreParameters->xSemaphore = xSemaphoreCreateBinary();
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if( pxSecondSemaphoreParameters->xSemaphore != NULL )
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{
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xSemaphoreGive( pxSecondSemaphoreParameters->xSemaphore );
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pxSecondSemaphoreParameters->pulSharedVariable = ( uint32_t * ) pvPortMalloc( sizeof( uint32_t ) );
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*( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;
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pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_PERIOD_MS;
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xTaskCreate( prvSemaphoreTest, "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );
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xTaskCreate( prvSemaphoreTest, "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL );
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/* vQueueAddToRegistry() adds the semaphore to the registry, if one
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is in use. The registry is provided as a means for kernel aware
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debuggers to locate semaphores and has no purpose if a kernel aware
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debugger is not being used. The call to vQueueAddToRegistry() will
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be removed by the pre-processor if configQUEUE_REGISTRY_SIZE is not
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defined or is defined to be less than 1. */
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vQueueAddToRegistry( ( QueueHandle_t ) pxSecondSemaphoreParameters->xSemaphore, "Counting_Sem_2" );
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}
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}
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}
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/*-----------------------------------------------------------*/
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static portTASK_FUNCTION( prvSemaphoreTest, pvParameters )
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{
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xSemaphoreParameters *pxParameters;
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volatile uint32_t *pulSharedVariable, ulExpectedValue;
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uint32_t ulCounter;
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short sError = pdFALSE, sCheckVariableToUse;
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/* See which check variable to use. sNextCheckVariable is not semaphore
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protected! */
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portENTER_CRITICAL();
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sCheckVariableToUse = sNextCheckVariable;
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sNextCheckVariable++;
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portEXIT_CRITICAL();
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/* A structure is passed in as the parameter. This contains the shared
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variable being guarded. */
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pxParameters = ( xSemaphoreParameters * ) pvParameters;
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pulSharedVariable = pxParameters->pulSharedVariable;
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/* If we are blocking we use a much higher count to ensure loads of context
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switches occur during the count. */
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if( pxParameters->xBlockTime > ( TickType_t ) 0 )
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{
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ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
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}
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else
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{
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ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
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}
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for( ;; )
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{
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/* Try to obtain the semaphore. */
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if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )
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{
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/* We have the semaphore and so expect any other tasks using the
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shared variable to have left it in the state we expect to find
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it. */
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if( *pulSharedVariable != ulExpectedValue )
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{
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sError = pdTRUE;
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}
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/* Clear the variable, then count it back up to the expected value
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before releasing the semaphore. Would expect a context switch or
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two during this time. */
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for( ulCounter = ( uint32_t ) 0; ulCounter <= ulExpectedValue; ulCounter++ )
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{
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*pulSharedVariable = ulCounter;
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if( *pulSharedVariable != ulCounter )
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{
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sError = pdTRUE;
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}
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}
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/* Release the semaphore, and if no errors have occurred increment the check
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variable. */
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if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )
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{
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sError = pdTRUE;
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}
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if( sError == pdFALSE )
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{
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if( sCheckVariableToUse < semtstNUM_TASKS )
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{
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( sCheckVariables[ sCheckVariableToUse ] )++;
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}
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}
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/* If we have a block time then we are running at a priority higher
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than the idle priority. This task takes a long time to complete
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a cycle (deliberately so to test the guarding) so will be starving
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out lower priority tasks. Block for some time to allow give lower
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priority tasks some processor time. */
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vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );
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}
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else
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{
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if( pxParameters->xBlockTime == ( TickType_t ) 0 )
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{
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/* We have not got the semaphore yet, so no point using the
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processor. We are not blocking when attempting to obtain the
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semaphore. */
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taskYIELD();
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}
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}
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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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BaseType_t xAreSemaphoreTasksStillRunning( void )
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{
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static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
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BaseType_t xTask, xReturn = pdTRUE;
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for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )
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{
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if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )
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{
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xReturn = pdFALSE;
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}
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sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
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}
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return xReturn;
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}
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