/* * FreeRTOS V202212.00 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy of * this software and associated documentation files (the "Software"), to deal in * the Software without restriction, including without limitation the rights to * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of * the Software, and to permit persons to whom the Software is furnished to do so, * subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * * https://www.FreeRTOS.org * https://github.com/FreeRTOS * */ /* * 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 /* 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 ( ( uint32_t ) 0xfff ) #define semtstNON_BLOCKING_EXPECTED_VALUE ( ( uint32_t ) 0xff ) #define semtstSTACK_SIZE configMINIMAL_STACK_SIZE #define semtstNUM_TASKS ( 4 ) #define semtstDELAY_FACTOR ( ( TickType_t ) 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 { SemaphoreHandle_t xSemaphore; volatile uint32_t * pulSharedVariable; TickType_t xBlockTime; } xSemaphoreParameters; /* Variables used to check that all the tasks are still running without errors. */ static volatile short sCheckVariables[ semtstNUM_TASKS ] = { 0 }; static volatile short sNextCheckVariable = 0; /*-----------------------------------------------------------*/ void vStartSemaphoreTasks( UBaseType_t uxPriority ) { xSemaphoreParameters * pxFirstSemaphoreParameters, * pxSecondSemaphoreParameters; const TickType_t xBlockTime = ( TickType_t ) 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. */ pxFirstSemaphoreParameters->xSemaphore = xSemaphoreCreateBinary(); if( pxFirstSemaphoreParameters->xSemaphore != NULL ) { xSemaphoreGive( pxFirstSemaphoreParameters->xSemaphore ); /* Create the variable which is to be shared by the first two tasks. */ pxFirstSemaphoreParameters->pulSharedVariable = ( uint32_t * ) pvPortMalloc( sizeof( uint32_t ) ); /* 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 = ( TickType_t ) 0; /* Spawn the first two tasks. As they poll they operate at the idle priority. */ xTaskCreate( prvSemaphoreTest, "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) NULL ); xTaskCreate( prvSemaphoreTest, "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( TaskHandle_t * ) 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( ( QueueHandle_t ) pxFirstSemaphoreParameters->xSemaphore, "Counting_Sem_1" ); } } /* 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 ) { pxSecondSemaphoreParameters->xSemaphore = xSemaphoreCreateBinary(); if( pxSecondSemaphoreParameters->xSemaphore != NULL ) { xSemaphoreGive( pxSecondSemaphoreParameters->xSemaphore ); pxSecondSemaphoreParameters->pulSharedVariable = ( uint32_t * ) pvPortMalloc( sizeof( uint32_t ) ); *( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE; pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_PERIOD_MS; xTaskCreate( prvSemaphoreTest, "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) NULL ); xTaskCreate( prvSemaphoreTest, "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( TaskHandle_t * ) 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( ( QueueHandle_t ) pxSecondSemaphoreParameters->xSemaphore, "Counting_Sem_2" ); } } } /*-----------------------------------------------------------*/ static portTASK_FUNCTION( prvSemaphoreTest, pvParameters ) { xSemaphoreParameters * pxParameters; volatile uint32_t * pulSharedVariable, ulExpectedValue; uint32_t ulCounter; short 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 > ( TickType_t ) 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 = ( uint32_t ) 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. */ if( pxParameters->xBlockTime != ( TickType_t ) 0 ) { vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR ); } } else { if( pxParameters->xBlockTime == ( TickType_t ) 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. */ BaseType_t xAreSemaphoreTasksStillRunning( void ) { static short sLastCheckVariables[ semtstNUM_TASKS ] = { 0 }; BaseType_t xTask, xReturn = pdTRUE; for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ ) { if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] ) { xReturn = pdFALSE; } sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ]; } return xReturn; }