vTaskDelete() for task removal in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to delete the current FreeRTOS task.

FreeRTOS

void TaskFunction(void *pvParameters) {
    // Task code here
    [1](NULL); // Delete this task
}

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

AvTaskDelete

BxTaskCreate

CvTaskStartScheduler

DvTaskSuspend

Attempts:

3 left

💡 Hint

Common Mistakes

Using xTaskCreate instead of vTaskDelete.

Trying to suspend the task instead of deleting it.

The function vTaskDelete(NULL) deletes the currently running task.

2fill in blank

medium

Complete the code to delete a task using its handle.

FreeRTOS

TaskHandle_t xHandle = NULL;

// Task creation code here

[1](xHandle); // Delete the task using its handle

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

AvTaskSuspend

BvTaskDelete

CxTaskCreate

DvTaskResume

Attempts:

3 left

💡 Hint

Common Mistakes

Using xTaskCreate instead of vTaskDelete.

Trying to suspend or resume the task instead of deleting.

Use vTaskDelete(xHandle) to delete a task by its handle.

3fill in blank

hard

Fix the error in the code to properly delete the task.

FreeRTOS

void TaskFunction(void *pvParameters) {
    // Task code
    [1](NULL); // Incorrect deletion
}

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

AxTaskResume

BxTaskDelete

CvTaskSuspend

DvTaskDelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'xTaskDelete' which does not exist.

Confusing suspend and delete functions.

The correct function to delete a task is vTaskDelete(), not xTaskDelete().

4fill in blank

hard

Fill both blanks to create and then delete a task properly.

FreeRTOS

TaskHandle_t xTaskHandle = NULL;

[1](TaskFunction, "Task", 1000, NULL, 1, &xTaskHandle);

[2](xTaskHandle);

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

AxTaskCreate

BvTaskSuspend

CvTaskDelete

DvTaskStartScheduler

Attempts:

3 left

💡 Hint

Common Mistakes

Using vTaskDelete before creating the task.

Using suspend instead of delete.

First, create the task with xTaskCreate(), then delete it with vTaskDelete().

5fill in blank

hard

Fill all three blanks to create a task, delete it, and then start the scheduler.

FreeRTOS

TaskHandle_t xHandle = NULL;

[1](TaskFunction, "Task", 512, NULL, 2, &xHandle);

[2](xHandle);

[3]();

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

AxTaskCreate

BvTaskDelete

CvTaskStartScheduler

DvTaskSuspend

Attempts:

3 left

💡 Hint

Common Mistakes

Starting scheduler before creating tasks.

Deleting task before creating it.

Using suspend instead of delete.

Create the task with xTaskCreate(), delete it with vTaskDelete(), then start the scheduler with vTaskStartScheduler().

Practice

1. What does the FreeRTOS function vTaskDelete() do?

easy

A. It removes a task from the scheduler and frees its resources.

B. It pauses a task temporarily without deleting it.

C. It creates a new task and adds it to the scheduler.

D. It suspends all tasks except the idle task.

Solution

1. Step 1: Understand the purpose of vTaskDelete()

   This function is designed to remove a task from FreeRTOS and free the memory and resources it used.

2. Step 2: Compare with other task functions

   Functions like suspending or pausing do not remove the task or free resources, only vTaskDelete() does that.

3. Final Answer:

   It removes a task from the scheduler and frees its resources. -> Option A

4. Quick Check:

   vTaskDelete() = Remove task and free resources [OK]

Hint: vTaskDelete() means task removal and resource freeing [OK]

Common Mistakes:

• Confusing deletion with suspension or pausing
• Thinking it creates or starts tasks
• Assuming it only stops task temporarily

2. Which of the following is the correct syntax to delete the currently running task in FreeRTOS?

easy

A. vTaskDelete(NULL);

B. vTaskDelete(xTaskHandle);

C. vTaskDelete();

D. vTaskDelete(currentTask);

Solution

1. Step 1: Recall how to delete the current task

   Passing NULL to vTaskDelete() tells FreeRTOS to delete the task that is currently running.

2. Step 2: Check other options

   Options A and D use variables that may not be defined or correct. vTaskDelete(); misses the required parameter.

3. Final Answer:

   vTaskDelete(NULL); -> Option A

4. Quick Check:

   Delete current task = vTaskDelete(NULL) [OK]

Hint: Use NULL to delete the running task in vTaskDelete() [OK]

Common Mistakes:

• Omitting the parameter in vTaskDelete()
• Passing an undefined task handle
• Using variable names instead of NULL for current task

3. Consider the following FreeRTOS code snippet:

void Task1(void *pvParameters) {
    // Task code
    vTaskDelete(NULL);
}

void main() {
    xTaskCreate(Task1, "Task1", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
}

What happens when Task1 runs?

medium

A. Task1 causes a runtime error due to NULL parameter.

B. Task1 deletes another task passed as NULL.

C. Task1 deletes itself and frees its resources.

D. Task1 suspends itself but remains in the scheduler.

Solution

1. Step 1: Analyze vTaskDelete(NULL) inside Task1

   Passing NULL deletes the currently running task, which is Task1 itself.

2. Step 2: Understand the effect on Task1

   Task1 will remove itself from the scheduler and free its resources immediately after running.

3. Final Answer:

   Task1 deletes itself and frees its resources. -> Option C

4. Quick Check:

   vTaskDelete(NULL) inside task = self-delete [OK]

Hint: vTaskDelete(NULL) inside task deletes that task itself [OK]

Common Mistakes:

• Thinking NULL deletes a different task
• Assuming it causes an error with NULL
• Confusing deletion with suspension

4. Given this code snippet:

TaskHandle_t xHandle = NULL;
xTaskCreate(TaskFunction, "Task", 1000, NULL, 1, &xHandle);
vTaskDelete(xHandle);

What is the problem with this code?

medium

A. The task handle is NULL, so deletion fails.

B. The task is deleted but not removed from the scheduler.

C. vTaskDelete() requires NULL to delete the current task only.

D. Deleting a task immediately after creation may cause undefined behavior.

Solution

1. Step 1: Understand task creation and immediate deletion

   The task is created and its handle stored in xHandle. Immediately deleting it may cause issues if the task has not started or scheduler not running.

2. Step 2: Recognize timing and scheduler state

   Deleting a task before the scheduler runs or before the task starts can cause undefined or unexpected behavior.

3. Final Answer:

   Deleting a task immediately after creation may cause undefined behavior. -> Option D

4. Quick Check:

   Delete right after create = possible undefined behavior [OK]

Hint: Avoid deleting tasks immediately after creation before scheduler runs [OK]

Common Mistakes:

• Assuming NULL only deletes current task (it can delete any valid handle)
• Ignoring scheduler state before deleting tasks
• Thinking deletion does not remove task from scheduler

5. You have multiple tasks running and want to safely delete a task named TaskToDelete from another task. Which approach is correct?

hard

A. Call vTaskDelete(NULL); from the other task to delete TaskToDelete.

B. Call vTaskDelete(TaskToDeleteHandle); directly from the other task after ensuring TaskToDeleteHandle is valid.

C. Suspend TaskToDelete and then call vTaskDelete(NULL); from the other task.

D. Use vTaskDelete() without parameters to delete TaskToDelete.

Solution

1. Step 1: Identify how to delete a specific task from another task

   To delete a specific task, you must pass its task handle to vTaskDelete(). The handle must be valid and known.

2. Step 2: Check other options for correctness

   Passing NULL deletes the current running task, not another. Omitting parameters is invalid syntax.

3. Final Answer:

   Call vTaskDelete(TaskToDeleteHandle); directly from the other task after ensuring TaskToDeleteHandle is valid. -> Option B

4. Quick Check:

   Delete specific task = vTaskDelete(taskHandle) [OK]

Hint: Pass the task's handle to vTaskDelete() to remove it safely [OK]

Common Mistakes:

• Using NULL to delete a different task
• Calling vTaskDelete() without parameters
• Not verifying task handle validity before deletion