uxTaskPriorityGet() for reading priority in FreeRTOS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of uxTaskPriorityGet() for a created task?

Consider the following FreeRTOS code snippet. What will be the output printed by printf?

FreeRTOS

#include "FreeRTOS.h"
#include "task.h"
#include <stdio.h>

void vTaskFunction(void *pvParameters) {
    // Task code here
    vTaskDelete(NULL);
}

int main() {
    TaskHandle_t xTaskHandle = NULL;
    BaseType_t xReturned;
    UBaseType_t uxPriority;

    xReturned = xTaskCreate(vTaskFunction, "Task1", configMINIMAL_STACK_SIZE, NULL, 3, &xTaskHandle);
    if(xReturned == pdPASS) {
        uxPriority = uxTaskPriorityGet(xTaskHandle);
        printf("Task priority: %u\n", (unsigned int)uxPriority);
    }
    return 0;
}

A Task priority: 3

B Task priority: 0

C Compilation error due to missing task handle

D Task priority: configMAX_PRIORITIES

💡 Hint

Remember that uxTaskPriorityGet() returns the priority assigned when the task was created.

The task was created with priority 3, so uxTaskPriorityGet() returns 3. Option A is wrong because 0 is the idle priority. Option A is wrong because configMAX_PRIORITIES is the max allowed, not assigned. Option A is wrong because the task handle is correctly passed.

🧠 Conceptual

intermediate

What does uxTaskPriorityGet() return if passed NULL?

In FreeRTOS, what is the return value of uxTaskPriorityGet(NULL) when called from within a task?

A The priority of the calling task

B Zero (lowest priority)

C configMAX_PRIORITIES

D Causes a runtime error

💡 Hint

Passing NULL means the function uses the current task handle internally.

When uxTaskPriorityGet() is called with NULL, it returns the priority of the task that called the function. It does not cause an error or return zero.

🔧 Debug

advanced

Why does uxTaskPriorityGet() return 0 unexpectedly?

A developer creates a task with priority 4 but uxTaskPriorityGet() returns 0 for that task's handle. What is the most likely cause?

A The FreeRTOS kernel is not started yet

B The task priority was set to 0 after creation

C The task handle passed to <code>uxTaskPriorityGet()</code> is invalid or uninitialized

D The task was deleted before calling <code>uxTaskPriorityGet()</code>

💡 Hint

Check if the task handle is properly assigned after task creation.

If the task handle is invalid or NULL, uxTaskPriorityGet() may return 0 because it cannot find the task's priority. Other options are less likely because priority 0 means idle, and kernel not started or deleted task would cause different behaviors.

📝 Syntax

advanced

Which code snippet correctly reads a task's priority?

Which of the following code snippets correctly uses uxTaskPriorityGet() to read the priority of a task?

A UBaseType_t prio = uxTaskPriorityGet(&xTaskHandle);

B UBaseType_t prio = uxTaskPriorityGet(xTaskHandle);

C int prio = uxTaskPriorityGet(xTaskHandle);

D UBaseType_t prio = uxTaskPriorityGet(NULL, xTaskHandle);

💡 Hint

Check the function signature and parameter types.

uxTaskPriorityGet() takes a TaskHandle_t (not a pointer to it) and returns UBaseType_t. Option B matches this. Option B uses wrong return type. Option B passes pointer incorrectly. Option B passes two parameters which is invalid.

🚀 Application

expert

How to check and print the priority of the current task safely?

Write the correct sequence of code lines to get and print the priority of the currently running task in FreeRTOS.

A 3,4,1,2,5

B 3,1,4,2,5

C 1,3,2,4,5

D 1,2,3,4,5

💡 Hint

Declare variables first, then get current task handle, then get priority, then print.

The correct order is to declare variables (1,2), get current task handle (3), get priority (4), then print (5). Options that get handle before declaring variables or mix order are invalid.