[Solved] What is wrong with this deferred interrupt processing approach? void ISR_Handler(void) { xSemaphoreGiveFromISR(&sem, NULL); } Assuming sem is a binary semaphore. | FreeRTOS

FreeRTOS - Interrupt Management

What is wrong with this deferred interrupt processing approach?

void ISR_Handler(void) {
  xSemaphoreGiveFromISR(&sem, NULL);
}

Assuming sem is a binary semaphore.

ASemaphore must be given before ISR starts

BxSemaphoreGiveFromISR cannot be called from ISR

CBinary semaphores cannot be used for deferred processing

DPassing NULL instead of BaseType_t* for xHigherPriorityTaskWoken is incorrect

Step-by-Step Solution

Solution:

Step 1: Check xSemaphoreGiveFromISR parameters
Second parameter must be a pointer to BaseType_t variable to detect if yield needed.
Step 2: Why NULL is wrong
Passing NULL disables context switch request, possibly delaying higher priority task.
Final Answer:
Passing NULL instead of BaseType_t* for xHigherPriorityTaskWoken is incorrect -> Option D
Quick Check:
Always pass BaseType_t* to FromISR APIs [OK]

Quick Trick: Always provide BaseType_t* to FromISR functions [OK]

Common Mistakes:

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What is wrong with this deferred interrupt processing approach?