278 lines
10 KiB
C
278 lines
10 KiB
C
/*
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* FreeRTOS Kernel V10.3.0
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* Copyright (C) 2020 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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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,
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*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(
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sizeof(xSemaphoreParameters));
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if (pxFirstSemaphoreParameters != NULL) {
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/* Create the semaphore used by the first two tasks. */
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pxFirstSemaphoreParameters->xSemaphore =
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xSemaphoreCreateBinary();
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if (pxFirstSemaphoreParameters->xSemaphore != NULL) {
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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 =
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(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) =
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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",
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semtstSTACK_SIZE,
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(void *)pxFirstSemaphoreParameters,
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tskIDLE_PRIORITY, (TaskHandle_t *)NULL);
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xTaskCreate(prvSemaphoreTest, "PolSEM2",
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semtstSTACK_SIZE,
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(void *)pxFirstSemaphoreParameters,
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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(
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(QueueHandle_t)
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pxFirstSemaphoreParameters->xSemaphore,
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"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(
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sizeof(xSemaphoreParameters));
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if (pxSecondSemaphoreParameters != NULL) {
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pxSecondSemaphoreParameters->xSemaphore =
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xSemaphoreCreateBinary();
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if (pxSecondSemaphoreParameters->xSemaphore != NULL) {
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xSemaphoreGive(pxSecondSemaphoreParameters->xSemaphore);
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pxSecondSemaphoreParameters->pulSharedVariable =
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(uint32_t *)pvPortMalloc(sizeof(uint32_t));
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*(pxSecondSemaphoreParameters->pulSharedVariable) =
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semtstBLOCKING_EXPECTED_VALUE;
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pxSecondSemaphoreParameters->xBlockTime =
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xBlockTime / portTICK_PERIOD_MS;
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xTaskCreate(prvSemaphoreTest, "BlkSEM1",
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semtstSTACK_SIZE,
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(void *)pxSecondSemaphoreParameters,
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uxPriority, (TaskHandle_t *)NULL);
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xTaskCreate(prvSemaphoreTest, "BlkSEM2",
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semtstSTACK_SIZE,
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(void *)pxSecondSemaphoreParameters,
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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(
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(QueueHandle_t)
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pxSecondSemaphoreParameters->xSemaphore,
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"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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ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
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} else {
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ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
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}
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for (;;) {
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/* Try to obtain the semaphore. */
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if (xSemaphoreTake(pxParameters->xSemaphore,
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pxParameters->xBlockTime) == pdPASS) {
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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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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;
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ulCounter <= ulExpectedValue; ulCounter++) {
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*pulSharedVariable = ulCounter;
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if (*pulSharedVariable != ulCounter) {
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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) ==
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pdFALSE) {
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sError = pdTRUE;
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}
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if (sError == pdFALSE) {
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if (sCheckVariableToUse < semtstNUM_TASKS) {
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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 *
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semtstDELAY_FACTOR);
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} else {
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if (pxParameters->xBlockTime == (TickType_t)0) {
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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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if (sLastCheckVariables[xTask] == sCheckVariables[xTask]) {
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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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