Task states (Ready, Running, Blocked, Suspended) in FreeRTOS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this FreeRTOS task state check?

Consider a FreeRTOS task that is created and immediately started. The task then calls vTaskDelay() for 100 ticks. What will be the task state right after vTaskDelay() is called?

FreeRTOS

TaskHandle_t xTask;

void vTaskFunction(void *pvParameters) {
    // Task runs
    vTaskDelay(100);
    // Task resumes here
    for(;;) {}
}

int main() {
    xTaskCreate(vTaskFunction, "Task", 1000, NULL, 1, &xTask);
    vTaskStartScheduler();
    // After scheduler starts, what is the state of xTask immediately after vTaskDelay call?
}

A Running

B Ready

C Blocked

D Suspended

💡 Hint

Think about what vTaskDelay() does to the task state.

When a task calls vTaskDelay(), it enters the Blocked state for the specified number of ticks. It is not Running or Ready during this delay period.

🧠 Conceptual

intermediate

Which task state allows a task to be selected by the scheduler to run?

In FreeRTOS, which task state means the task is ready and waiting for CPU time?

A Ready

B Suspended

C Blocked

D Deleted

💡 Hint

Think about which state means the task can run but is waiting for the CPU.

The Ready state means the task is prepared to run and is waiting for the scheduler to assign CPU time.

❓ Predict Output

advanced

What happens if a task is suspended and then resumed?

Given a task that is suspended using vTaskSuspend() and later resumed with vTaskResume(), what is the task state immediately after resuming?

FreeRTOS

TaskHandle_t xTask;

void vTaskFunction(void *pvParameters) {
    for(;;) {
        // Task code
    }
}

int main() {
    xTaskCreate(vTaskFunction, "Task", 1000, NULL, 1, &xTask);
    vTaskStartScheduler();
    vTaskSuspend(xTask);
    // Task is suspended here
    vTaskResume(xTask);
    // What is the state now?
}

A Running

B Ready

C Suspended

D Blocked

💡 Hint

Resuming a suspended task makes it available to run again.

When a suspended task is resumed, it moves to the Ready state, waiting for the scheduler to run it.

🔧 Debug

advanced

Why does this task never run after creation?

Examine the code below. The task is created but never runs. What is the reason?

FreeRTOS

TaskHandle_t xTask;

void vTaskFunction(void *pvParameters) {
    for(;;) {
        // Task code
    }
}

int main() {
    xTaskCreate(vTaskFunction, "Task", 1000, NULL, 1, &xTask);
    // Missing vTaskStartScheduler();
    // What is the task state?
}

A The task is in Ready state but scheduler is not started, so it never runs.

B The task is Suspended because it was not started properly.

C The task is Blocked because it waits for an event.

D The task is Deleted immediately after creation.

💡 Hint

Think about what starts the FreeRTOS scheduler.

Without calling vTaskStartScheduler(), the scheduler never runs, so tasks remain Ready but never execute.

🧠 Conceptual

expert

How does FreeRTOS handle a task that is both blocked and suspended?

If a task is in the Blocked state waiting for a delay to expire, and then vTaskSuspend() is called on it, what is the task state?

A The task remains Blocked until the delay expires, then moves to Suspended.

B The task is Deleted automatically.

C The task moves to Ready state immediately.

D The task immediately moves to Suspended, ignoring the delay.

💡 Hint

Suspending a task overrides other states.

Calling vTaskSuspend() forces the task into the Suspended state immediately, regardless of whether it was Blocked.