[Solved] Examine the following FreeRTOS ISR code snippet for nested interrupt handling:void ISR_MediumPriority(void) { BaseType_t xHigherPriorityTaskWoken =... } }What is the main issue with this code? | FreeRTOS

FreeRTOS - Interrupt Management

Examine the following FreeRTOS ISR code snippet for nested interrupt handling:

void ISR_MediumPriority(void) {
  BaseType_t xHigherPriorityTaskWoken = pdFALSE;
  xSemaphoreGiveFromISR(xSemaphore, &xHigherPriorityTaskWoken);
  if(xHigherPriorityTaskWoken) {
    taskYIELD();
  }
}

What is the main issue with this code?

AUsing xSemaphoreGiveFromISR() instead of xSemaphoreGive() in ISR

BNot initializing xHigherPriorityTaskWoken to pdTRUE before use

CCalling taskYIELD() inside an ISR instead of using portYIELD_FROM_ISR()

DFailing to check if the semaphore handle is NULL before giving

Step-by-Step Solution

Solution:

Step 1: Identify the ISR context
Inside an ISR, FreeRTOS requires special yield functions to safely switch tasks.
Step 2: Check the yield function used
The code calls taskYIELD(), which is intended for task context, not ISR context.
Step 3: Correct function usage
In ISR, portYIELD_FROM_ISR(xHigherPriorityTaskWoken) must be used to request a context switch.
Final Answer:
Calling taskYIELD() inside an ISR instead of using portYIELD_FROM_ISR() -> Option C
Quick Check:
ISR yield must use portYIELD_FROM_ISR() [OK]

Quick Trick: Use portYIELD_FROM_ISR() to yield inside ISRs [OK]

Common Mistakes:

Using taskYIELD() inside an ISR
Not using portYIELD_FROM_ISR() after ISR API calls
Assuming xHigherPriorityTaskWoken must be true initially

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More FreeRTOS Quizzes

Examine the following FreeRTOS ISR code snippet for nested interrupt handling:

Step 1: Identify the ISR context

Step 2: Check the yield function used

Step 3: Correct function usage

Final Answer:

Quick Check:

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