uxTaskPriorityGet() for reading priority in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the priority of a FreeRTOS task.

FreeRTOS

UBaseType_t priority = uxTaskPriorityGet([1]);

Drag options to blanks, or click blank then click option'

AxTask

BxTaskHandle

CtaskHandle

Dhandle

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not the task handle.

Passing the task name as a string instead of the handle.

The function uxTaskPriorityGet() requires the task handle as argument. Here, taskHandle is the correct variable name representing the task.

2fill in blank

medium

Complete the code to print the priority of a task using printf.

FreeRTOS

printf("Priority: %u\n", [1]);

Drag options to blanks, or click blank then click option'

AuxTaskPriorityGet(taskHandle)

BtaskPriority

Cpriority

DgetPriority(taskHandle)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable that is not initialized with the priority.

Calling a non-existent function like getPriority().

The function uxTaskPriorityGet(taskHandle) returns the priority, which can be printed directly.

3fill in blank

hard

Fix the error in the code to correctly get and store the task priority.

FreeRTOS

UBaseType_t [1] = uxTaskPriorityGet(taskHandle);

Drag options to blanks, or click blank then click option'

Apriority

Bprio

CtaskPriority

DpriorityLevel

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that are not descriptive or confusing.

Not declaring the variable with the correct type UBaseType_t.

The variable priority is a common and clear name to store the priority value returned by uxTaskPriorityGet().

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps task names to their priorities for tasks with priority greater than 2.

FreeRTOS

{ [1]: uxTaskPriorityGet([2]) for [3] in tasks if uxTaskPriorityGet([3]) > 2 }

Drag options to blanks, or click blank then click option'

Atask.name

Btask

Ct

DtaskHandle

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name in the loop.

Not calling uxTaskPriorityGet() with the correct argument.

The dictionary comprehension maps each task's name (task.name) to its priority by calling uxTaskPriorityGet(task). The loop variable is task.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase task names to their priorities for tasks with priority greater than 3.

FreeRTOS

{ [1]: [2] for [3] in task_list if uxTaskPriorityGet([3]) > 3 }

Drag options to blanks, or click blank then click option'

Atask.name.upper()

BuxTaskPriorityGet(task)

Ctask

DtaskHandle

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable for the loop.

Not converting the task name to uppercase.

The dictionary comprehension uses task.name.upper() as the key, and the priority from uxTaskPriorityGet(task) as the value. The loop variable is task.

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