vTaskDelete() for task removal in FreeRTOS - Step-by-Step Execution

Concept Flow - vTaskDelete() for task removal

Create Task

↓

Task Running

↓

Call vTaskDelete(task_handle)

↓

Task Removed from Scheduler

↓

Task Resources Freed

↓

Task No Longer Runs

This flow shows how a task is created, runs, then is deleted using vTaskDelete(), which removes it from the scheduler and frees its resources.

Execution Sample

FreeRTOS

void Task1(void *pvParameters) {
  while(1) {
    // do work
    vTaskDelete(NULL); // delete self
  }
}

This code shows a task that deletes itself by calling vTaskDelete(NULL) inside its loop.

Execution Table

Step	Action	Task State	Scheduler Status	Output/Effect
1	Task1 created and started	Ready	Task1 scheduled to run	Task1 will run when scheduled
2	Task1 starts running	Running	Task1 running	Task1 executes code inside loop
3	vTaskDelete(NULL) called inside Task1	Deleting	Task1 removed from scheduler	Task1 will stop running
4	Task1 resources freed	Deleted	No longer scheduled	Task1 no longer exists
5	Scheduler runs other tasks	Other tasks running	Task1 gone	System continues without Task1

💡 Task1 calls vTaskDelete(NULL), so it is removed and deleted, stopping its execution.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
Task1 State	Not created	Running	Deleting	Deleted
Scheduler	No tasks	Task1 scheduled	Task1 removed	Task1 gone

Key Moments - 3 Insights

Why do we pass NULL to vTaskDelete() to delete the current task?

Passing NULL tells vTaskDelete() to delete the task that calls it, as shown in execution_table step 3 where Task1 deletes itself.

What happens if we delete a task that is currently running?

The task is marked for deletion and removed from the scheduler immediately, stopping its execution as shown in step 3 and 4.

Does vTaskDelete() free the task's memory automatically?

Yes, after removal from the scheduler, the task's resources are freed as shown in step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the task state immediately after calling vTaskDelete(NULL)?

A Running

B Ready

C Deleting

D Deleted

💡 Hint

Check execution_table row 3 under 'Task State' column.

At which step does the task stop being scheduled by the FreeRTOS scheduler?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at 'Scheduler Status' column in execution_table rows 2 and 3.

If we replace vTaskDelete(NULL) with vTaskDelete(task_handle) for another task, what changes in the execution flow?

A The specified task is deleted instead of the current task

B The current task deletes itself as before

C No task is deleted

D The scheduler stops all tasks

💡 Hint

vTaskDelete deletes the task given by the handle, not necessarily the caller; see concept_flow.

Concept Snapshot

vTaskDelete(task_handle) removes a task from FreeRTOS scheduler.
Pass NULL to delete the current task.
Task is removed immediately and resources freed.
Deleted tasks stop running and cannot be resumed.
Use carefully to avoid deleting wrong tasks.

Full Transcript

This visual execution shows how vTaskDelete() removes a task in FreeRTOS. First, a task is created and scheduled. When the task calls vTaskDelete(NULL), it deletes itself by removing from the scheduler and freeing resources. The task state changes from running to deleting, then deleted. The scheduler no longer runs the deleted task. Passing NULL deletes the current task; passing a task handle deletes that specific task. This stops the task from running and frees memory. The execution table and variable tracker show these state changes step-by-step.