uxTaskPriorityGet() for reading priority in FreeRTOS

Introduction

This function helps you find out the priority level of a task in FreeRTOS. Knowing a task's priority helps you understand which tasks run first.

When you want to check the priority of a task to debug scheduling issues.

When you need to adjust behavior based on the priority of a task.

When you want to log or display task priorities for monitoring.

When you are creating a task manager and need to show task priorities.

Syntax

FreeRTOS

UBaseType_t uxTaskPriorityGet( TaskHandle_t xTask );

TaskHandle_t xTask is the handle (ID) of the task you want to check. If you pass NULL, it returns the priority of the current task.

The function returns the priority as a number where higher means more important.

Examples

Get the priority of the current running task.

FreeRTOS

UBaseType_t priority = uxTaskPriorityGet( NULL );

Get the priority of a specific task using its handle.

FreeRTOS

UBaseType_t priority = uxTaskPriorityGet( myTaskHandle );

Sample Program

This program creates a task with priority 3. Inside the task, it reads its own priority using uxTaskPriorityGet(NULL) and prints it. Then the task deletes itself.

FreeRTOS

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

void vTaskFunction(void *pvParameters) {
    UBaseType_t priority = uxTaskPriorityGet(NULL); // Get current task priority
    printf("Current task priority: %u\n", (unsigned int)priority);
    vTaskDelete(NULL); // Delete this task after printing
}

int main(void) {
    TaskHandle_t taskHandle = NULL;
    xTaskCreate(vTaskFunction, "Task1", configMINIMAL_STACK_SIZE, NULL, 3, &taskHandle);
    vTaskStartScheduler();
    return 0;
}

Important Notes

Passing NULL to uxTaskPriorityGet() returns the priority of the task that calls the function.

Task priorities are numbers where a higher number means higher priority.

Make sure the task handle you pass is valid to avoid errors.

Summary

uxTaskPriorityGet() reads the priority of a task in FreeRTOS.

Pass NULL to get the current task's priority.

Useful for debugging and managing task scheduling.

Practice

1.

What does the FreeRTOS function uxTaskPriorityGet() do?

easy

A. It returns the priority of a specified task.

B. It sets the priority of a specified task.

C. It deletes a specified task.

D. It creates a new task.

Solution

1. Step 1: Understand the function purpose

   uxTaskPriorityGet() is designed to read the priority of a task, not to modify or manage tasks.

2. Step 2: Match function behavior to options

   Only "It returns the priority of a specified task." correctly states it returns the priority of a specified task.

3. Final Answer:

   It returns the priority of a specified task. -> Option A

4. Quick Check:

   uxTaskPriorityGet() reads priority = It returns the priority of a specified task. [OK]

Hint: Remember: 'Get' means read, not change [OK]

Common Mistakes:

• Confusing 'get' with 'set' functions
• Thinking it creates or deletes tasks
• Assuming it returns task handle

2.

Which of the following is the correct way to get the priority of the current task using uxTaskPriorityGet()?

TaskHandle_t xTaskHandle;
UBaseType_t uxPriority = ?;

easy

A. uxPriority = uxTaskPriorityGet(xTaskHandle);

B. uxPriority = uxTaskPriorityGet(NULL);

C. uxPriority = uxTaskPriorityGet(&xTaskHandle);

D. uxPriority = uxTaskPriorityGet(*xTaskHandle);

Solution

1. Step 1: Recall how to get current task priority

   Passing NULL to uxTaskPriorityGet() returns the priority of the current task.

2. Step 2: Check each option

   uxPriority = uxTaskPriorityGet(xTaskHandle); uses uninitialized xTaskHandle (undefined behavior). uxPriority = uxTaskPriorityGet(&xTaskHandle); passes address (wrong type). uxPriority = uxTaskPriorityGet(*xTaskHandle); dereferences uninitialized handle (crash). Only uxPriority = uxTaskPriorityGet(NULL); is correct.

3. Final Answer:

   uxPriority = uxTaskPriorityGet(NULL); -> Option B

4. Quick Check:

   Use NULL for current task priority [OK]

Hint: Pass NULL to get current task priority [OK]

Common Mistakes:

• Passing address of handle instead of handle
• Dereferencing handle incorrectly
• Using uninitialized task handle

3.

Given the following code snippet, what will be printed?

TaskHandle_t xHandle = xTaskGetHandle("Task1");
UBaseType_t uxPriority = uxTaskPriorityGet(xHandle);
printf("Priority: %u\n", uxPriority);

Assume "Task1" exists and has priority 3.

medium

A. Priority: 0

B. Compilation error

C. Priority: 3

D. Priority: 1

Solution

1. Step 1: Understand task handle retrieval

   xTaskGetHandle("Task1") returns the handle of the task named "Task1" which exists with priority 3.

2. Step 2: Use uxTaskPriorityGet() to read priority

   Calling uxTaskPriorityGet(xHandle) returns the priority of that task, which is 3.

3. Final Answer:

   Priority: 3 -> Option C

4. Quick Check:

   uxTaskPriorityGet returns task priority = 3 [OK]

Hint: Get handle then get priority returns actual task priority [OK]

Common Mistakes:

• Assuming default priority 0
• Confusing handle with task name
• Expecting syntax error

4.

Identify the error in this code snippet:

TaskHandle_t xHandle;
UBaseType_t uxPriority = uxTaskPriorityGet(xHandle);
printf("Priority: %u\n", uxPriority);

medium

A. xHandle is uninitialized before use.

B. uxTaskPriorityGet() cannot be called with a TaskHandle_t.

C. printf format specifier is incorrect.

D. uxPriority should be a pointer.

Solution

1. Step 1: Check variable initialization

   xHandle is declared but not assigned any value before use.

2. Step 2: Understand consequences of uninitialized handle

   Passing an uninitialized handle to uxTaskPriorityGet() leads to undefined behavior or incorrect priority reading.

3. Final Answer:

   xHandle is uninitialized before use. -> Option A

4. Quick Check:

   Always initialize task handles before use [OK]

Hint: Initialize task handle before getting priority [OK]

Common Mistakes:

• Ignoring uninitialized variables
• Misunderstanding function parameter types
• Assuming pointer needed for uxPriority

5.

You want to check if the current task has higher priority than another task named "WorkerTask". Which code snippet correctly compares their priorities?

TaskHandle_t xWorkerHandle = xTaskGetHandle("WorkerTask");
UBaseType_t uxCurrentPriority = uxTaskPriorityGet(NULL);
UBaseType_t uxWorkerPriority = uxTaskPriorityGet(xWorkerHandle);
// What next?

hard

A. if (uxCurrentPriority != uxWorkerPriority) { /* current task higher */ }

B. if (uxCurrentPriority < uxWorkerPriority) { /* current task higher */ }

C. if (uxCurrentPriority == uxWorkerPriority) { /* current task higher */ }

D. if (uxCurrentPriority > uxWorkerPriority) { /* current task higher */ }

Solution

1. Step 1: Understand priority comparison logic

   Higher numeric value means higher priority in FreeRTOS.

2. Step 2: Compare current and worker task priorities

   Use > operator to check if current task priority is higher than worker's.

3. Final Answer:

   if (uxCurrentPriority > uxWorkerPriority) { /* current task higher */ } -> Option D

4. Quick Check:

   Higher number = higher priority [OK]

Hint: Use '>' to check if current task priority is higher [OK]

Common Mistakes:

• Using '<' instead of '>' for priority comparison
• Confusing equality with higher priority
• Not retrieving correct task handles