Stack overflow detection (method 1 and 2) in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable stack overflow checking method 1 in FreeRTOSConfig.h.

FreeRTOS

#define configCHECK_FOR_STACK_OVERFLOW [1]

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

A0

B3

C2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the value to 0 disables checking.

Using 2 enables method 2, not method 1.

Setting configCHECK_FOR_STACK_OVERFLOW to 1 enables method 1 stack overflow checking in FreeRTOS.

2fill in blank

medium

Complete the function prototype for the stack overflow hook used with method 1 or 2.

FreeRTOS

void vApplicationStackOverflowHook([1]);

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Avoid

BTaskHandle_t xTask, char *pcTaskName

CTaskHandle_t xTask

Dint xTask

Attempts:

3 left

💡 Hint

Common Mistakes

Using only one parameter.

Using incorrect parameter types.

The hook function receives the task handle and the task name as parameters.

3fill in blank

hard

Fix the error in the stack overflow hook implementation to correctly handle method 2 detection.

FreeRTOS

void vApplicationStackOverflowHook(TaskHandle_t xTask, char *pcTaskName) {
    [1];
    for( ;; );
}

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AtaskDISABLE_INTERRUPTS()

BvTaskSuspendAll()

CvTaskDelete(xTask)

DportYIELD()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling vTaskDelete inside the hook.

Not disabling interrupts before infinite loop.

Disabling interrupts immediately prevents further damage after detecting stack overflow.

4fill in blank

hard

Fill both blanks to configure FreeRTOS for stack overflow detection method 2 and enable the hook.

FreeRTOS

#define configCHECK_FOR_STACK_OVERFLOW [1]
#define configUSE_STACK_OVERFLOW_HOOK [2]

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A2

B1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the hook macro to 0 disables the hook.

Using method 1 value instead of 2.

Method 2 is enabled by setting configCHECK_FOR_STACK_OVERFLOW to 2 and enabling the hook with configUSE_STACK_OVERFLOW_HOOK set to 1.

5fill in blank

hard

Fill all three blanks to implement a stack overflow hook that disables interrupts, logs the task name, and halts the system.

FreeRTOS

void vApplicationStackOverflowHook(TaskHandle_t xTask, char *pcTaskName) {
    [1];
    printf("Stack overflow in task: %s\n", [2]);
    for( [3] );
}

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

AtaskDISABLE_INTERRUPTS()

BpcTaskName

C;;

DvTaskSuspendAll()

Attempts:

3 left

💡 Hint

Common Mistakes

Not disabling interrupts before printing.

Using incorrect loop syntax.

The hook disables interrupts, prints the task name, and enters an infinite loop to halt the system.

Practice

1. What is the main purpose of stack overflow detection in FreeRTOS?

easy

A. To reduce RAM usage by tasks

B. To prevent tasks from using more stack memory than allocated

C. To increase CPU clock speed

D. To speed up task switching

Solution

1. Step 1: Understand stack overflow concept

   Stack overflow happens when a task uses more stack memory than allocated, causing memory corruption.

2. Step 2: Identify purpose of detection

   Stack overflow detection helps catch this problem early to prevent crashes or unpredictable behavior.

3. Final Answer:

   To prevent tasks from using more stack memory than allocated -> Option B

4. Quick Check:

   Stack overflow detection = prevent excess stack use [OK]

Hint: Stack overflow detection stops tasks using too much stack [OK]

Common Mistakes:

• Confusing stack overflow with CPU speed
• Thinking it reduces RAM usage
• Assuming it speeds up task switching

2. Which FreeRTOS configuration enables Method 1 stack overflow detection?

easy

A. configMAX_PRIORITIES set to 5

B. configUSE_PREEMPTION set to 0

C. configUSE_IDLE_HOOK set to 1

D. configCHECK_FOR_STACK_OVERFLOW set to 1 or 2

Solution

1. Step 1: Identify config for stack overflow detection

   FreeRTOS uses configCHECK_FOR_STACK_OVERFLOW to enable Method 1 detection.

2. Step 2: Understand valid values

   Setting configCHECK_FOR_STACK_OVERFLOW to 1 or 2 activates automatic detection on context switches.

3. Final Answer:

   configCHECK_FOR_STACK_OVERFLOW set to 1 or 2 -> Option D

4. Quick Check:

   configCHECK_FOR_STACK_OVERFLOW = 1 or 2 [OK]

Hint: Method 1 uses configCHECK_FOR_STACK_OVERFLOW = 1 or 2 [OK]

Common Mistakes:

• Confusing unrelated config options
• Using configUSE_PREEMPTION for stack checks
• Setting configMAX_PRIORITIES thinking it affects stack

3. Given this FreeRTOS hook function for Method 1:

void vApplicationStackOverflowHook(TaskHandle_t xTask, char *pcTaskName) {
    printf("Stack overflow detected in task: %s\n", pcTaskName);
    while(1); // Halt
}

What will happen if a stack overflow is detected?

medium

A. Prints task name and halts the system

B. Resets the task automatically

C. Ignores the overflow and continues

D. Logs overflow but continues running

Solution

1. Step 1: Analyze the hook function code

   The function prints the task name where overflow occurred and then enters an infinite loop.

2. Step 2: Understand effect of infinite loop

   The infinite loop halts the system to prevent further damage after overflow detection.

3. Final Answer:

   Prints task name and halts the system -> Option A

4. Quick Check:

   Stack overflow hook prints and halts [OK]

Hint: Stack overflow hook prints and stops system [OK]

Common Mistakes:

• Thinking system resets automatically
• Assuming overflow is ignored
• Believing task restarts without halt

4. In Method 2 stack overflow detection, which mistake will cause incorrect detection?

medium

A. Using vApplicationStackOverflowHook function

B. Enabling configCHECK_FOR_STACK_OVERFLOW to 2

C. Not initializing the stack pointer check value properly

D. Setting configUSE_PREEMPTION to 1

Solution

1. Step 1: Understand Method 2 detection

   Method 2 manually checks stack pointer against a known value to detect overflow.

2. Step 2: Identify common error

   If the initial stack pointer check value is not set correctly, the comparison will be invalid, causing false negatives or positives.

3. Final Answer:

   Not initializing the stack pointer check value properly -> Option C

4. Quick Check:

   Method 2 needs correct stack pointer init [OK]

Hint: Method 2 needs proper stack pointer initialization [OK]

Common Mistakes:

• Confusing Method 1 config with Method 2
• Ignoring stack pointer initialization
• Assuming hook function is used in Method 2

5. You want to implement stack overflow detection in your FreeRTOS project using Method 1. Which steps should you follow to ensure it works correctly?

hard

A. Set configCHECK_FOR_STACK_OVERFLOW to 1 or 2 and implement vApplicationStackOverflowHook

B. Manually compare stack pointers in each task without config changes

C. Disable preemption and use configUSE_IDLE_HOOK for detection

D. Increase task stack size to avoid overflow without detection

Solution

1. Step 1: Enable Method 1 detection in config

   Set configCHECK_FOR_STACK_OVERFLOW to 1 or 2 to activate automatic detection during context switches.

2. Step 2: Implement the hook function

   Define vApplicationStackOverflowHook to handle overflow events, e.g., log and halt.

3. Final Answer:

   Set configCHECK_FOR_STACK_OVERFLOW to 1 or 2 and implement vApplicationStackOverflowHook -> Option A

4. Quick Check:

   Method 1 = config + hook function [OK]

Hint: Method 1 needs config and hook function implemented [OK]

Common Mistakes:

• Trying manual pointer checks for Method 1
• Disabling preemption thinking it helps detection
• Ignoring hook function implementation