Why runtime monitoring catches RTOS bugs in FreeRTOS - See It in Action

Why runtime monitoring catches RTOS bugs

📖 Scenario: You are working with a FreeRTOS-based embedded system. Sometimes, tasks behave unexpectedly or the system crashes. You want to understand how runtime monitoring helps catch these bugs early.

🎯 Goal: Build a simple FreeRTOS task setup and add runtime monitoring variables to detect task overruns and unexpected states.

📋 What You'll Learn

Create a FreeRTOS task list with exact task names and priorities

Add a runtime monitoring variable to track task execution time

Implement a check to detect if a task exceeds its allowed runtime

Print a warning message when a task overrun is detected

💡 Why This Matters

🌍 Real World

Embedded systems often run multiple tasks with strict timing requirements. Runtime monitoring helps detect when tasks take too long, preventing system crashes or unexpected behavior.

💼 Career

Understanding runtime monitoring in RTOS is essential for embedded developers and DevOps engineers working on real-time systems to ensure reliability and quick bug detection.

1

Create FreeRTOS tasks

Create two FreeRTOS tasks named TaskA and TaskB with priorities 2 and 1 respectively. Use xTaskCreate to create them.

FreeRTOS

int main(void) {
    // Create TaskA and TaskB with priorities 2 and 1
    // Your code here
    vTaskStartScheduler();
}

Need a hint?

Use xTaskCreate with the exact task names and priorities given.

2

Add runtime monitoring variable

Add a global variable TaskA_RunTime initialized to 0 to track the execution time of TaskA.

FreeRTOS

// Add TaskA_RunTime variable here (global)
// Your code here

int main(void) {
    xTaskCreate(TaskA, "TaskA", 1000, NULL, 2, NULL);
    xTaskCreate(TaskB, "TaskB", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
}

Need a hint?

Declare TaskA_RunTime as an unsigned int and initialize it to zero.

3

Check for task runtime overrun

Inside TaskA function, add code to increment TaskA_RunTime by 1 each cycle. Then add an if statement to check if TaskA_RunTime exceeds 100 and set a flag TaskA_Overrun to 1 if true.

FreeRTOS

unsigned int TaskA_RunTime = 0;
unsigned int TaskA_Overrun = 0;

void TaskA(void *pvParameters) {
    while(1) {
        // Increment runtime and check overrun
        // Your code here
    }
}

int main(void) {
    xTaskCreate(TaskA, "TaskA", 1000, NULL, 2, NULL);
    xTaskCreate(TaskB, "TaskB", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
}

Need a hint?

Increment TaskA_RunTime inside the loop and check if it is greater than 100 to set TaskA_Overrun.

4

Print warning on overrun

In the TaskB function, add code to check if TaskA_Overrun is 1. If yes, print "Warning: TaskA overrun detected!" using printf and reset the flag to 0.

FreeRTOS

unsigned int TaskA_RunTime = 0;
unsigned int TaskA_Overrun = 0;

void TaskA(void *pvParameters) {
    while(1) {
        TaskA_RunTime++;
        if (TaskA_RunTime > 100) {
            TaskA_Overrun = 1;
        }
        vTaskDelay(1);
    }
}

void TaskB(void *pvParameters) {
    while(1) {
        // Check if TaskA_Overrun is 1 and print warning
        // Your code here
    }
}

int main(void) {
    xTaskCreate(TaskA, "TaskA", 1000, NULL, 2, NULL);
    xTaskCreate(TaskB, "TaskB", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
}

Need a hint?

Use if (TaskA_Overrun == 1) inside TaskB to check and printf to print the warning message. Reset the flag after printing.