Task starvation and priority inversion in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a task with the highest priority.

FreeRTOS

xTaskCreate(taskFunction, "Task1", 1000, NULL, [1], NULL);

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A0

B1

C5

DconfigMAX_PRIORITIES - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as highest priority (0 is the lowest).

Using a priority higher than configMAX_PRIORITIES - 1.

The highest priority in FreeRTOS is configMAX_PRIORITIES - 1 because priorities start at 0.

2fill in blank

medium

Complete the code to take a mutex to avoid priority inversion.

FreeRTOS

xSemaphoreTake([1], portMAX_DELAY);

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AxQueue

BxTaskHandle

CxMutex

DxTimer

Attempts:

3 left

💡 Hint

Common Mistakes

Using a queue handle instead of a mutex.

Using a timer handle instead of a mutex.

Mutexes are used to avoid priority inversion by controlling access to shared resources.

3fill in blank

hard

Fix the error in the code to prevent task starvation by yielding the processor.

FreeRTOS

void vTaskFunction(void *pvParameters) {
    for(;;) {
        // Task code
        [1]();
    }
}

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AtaskYIELD

BvTaskSuspend

CvTaskDelay

DxSemaphoreGive

Attempts:

3 left

💡 Hint

Common Mistakes

Using vTaskDelay without a delay time.

Suspending the task instead of yielding.

Calling taskYIELD() allows other tasks of the same priority to run, preventing starvation.

4fill in blank

hard

Fill both blanks to create a priority inheritance mutex and take it.

FreeRTOS

xMutex = xSemaphoreCreate[1]();
if(xSemaphoreTake(xMutex, [2]) == pdTRUE) {
    // Access resource
}

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AMutex

BBinary

CportMAX_DELAY

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using binary semaphore instead of mutex for priority inheritance.

Using 0 as wait time which causes immediate failure if mutex is not available.

Creating a mutex with xSemaphoreCreateMutex() enables priority inheritance. Using portMAX_DELAY waits indefinitely to take the mutex.

5fill in blank

hard

Fill all three blanks to create a task that avoids starvation by delaying and yielding.

FreeRTOS

void vTaskFunction(void *pvParameters) {
    for(;;) {
        // Do work
        vTaskDelay([1]);
        [2]();
        vTaskDelay([3]);
    }
}

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ApdMS_TO_TICKS(10)

BtaskYIELD

CpdMS_TO_TICKS(5)

DvTaskSuspend

Attempts:

3 left

💡 Hint

Common Mistakes

Using vTaskSuspend() which stops the task indefinitely.

Not yielding between delays.

Delaying the task with vTaskDelay() and yielding with taskYIELD() helps prevent starvation by allowing other tasks to run.