[Solved] Given the following FreeRTOS ISR code snippet, what will be the value of xHigherPriorityTaskWoken after execution?void ISR_Timer(void) { BaseType_t xHigherPriorityTaskWoken = pdFALSE;... | FreeRTOS

FreeRTOS - Interrupt Management

Given the following FreeRTOS ISR code snippet, what will be the value of xHigherPriorityTaskWoken after execution?

void ISR_Timer(void) {
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    xSemaphoreGiveFromISR(xSemaphore, &xHigherPriorityTaskWoken);
    portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

Assume the semaphore unblocks a higher priority task waiting.

AUndefined behavior

BpdFALSE

CpdTRUE

DSemaphore handle value

Step-by-Step Solution

Solution:

Step 1: Understand xSemaphoreGiveFromISR behavior
This function sets xHigherPriorityTaskWoken to pdTRUE if a higher priority task is unblocked.
Step 2: Given higher priority task is unblocked
Since the semaphore unblocks a higher priority task, xHigherPriorityTaskWoken becomes pdTRUE.
Final Answer:
pdTRUE -> Option C
Quick Check:
Higher priority task unblocked = xHigherPriorityTaskWoken pdTRUE [OK]

Quick Trick: xHigherPriorityTaskWoken is pdTRUE if higher priority task unblocked [OK]

Common Mistakes:

Assuming xHigherPriorityTaskWoken stays pdFALSE always
Confusing semaphore handle with boolean flag
Ignoring the effect of unblocking higher priority tasks

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More FreeRTOS Quizzes

Given the following FreeRTOS ISR code snippet, what will be the value of xHigherPriorityTaskWoken after execution?

Step 1: Understand xSemaphoreGiveFromISR behavior

Step 2: Given higher priority task is unblocked

Final Answer:

Quick Check:

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