[Solved] Consider this FreeRTOS ISR snippet: void ISR_Handler() { BaseType_t xHigherPriorityTaskWoken = pdFALSE;... } What is the main effect of calling portYIELD_FROM_ISR(xHigherPriorityTaskWoken);? | FreeRTOS

FreeRTOS - Interrupt Management

Consider this FreeRTOS ISR snippet:

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

What is the main effect of calling portYIELD_FROM_ISR(xHigherPriorityTaskWoken);?

AIt disables all interrupts until the next tick.

BIt forces a context switch if a higher priority task was woken.

CIt delays the ISR execution by one tick.

DIt resets the semaphore to zero.

Step-by-Step Solution

Solution:

Step 1: Understand portYIELD_FROM_ISR usage
This macro requests a context switch if a higher priority task was woken by the ISR.
Step 2: Analyze the effect on task scheduling
If xHigherPriorityTaskWoken is true, the scheduler switches to that task immediately after ISR.
Final Answer:
It forces a context switch if a higher priority task was woken. -> Option B
Quick Check:
portYIELD_FROM_ISR triggers context switch [OK]

Quick Trick: portYIELD_FROM_ISR triggers immediate switch if needed [OK]

Common Mistakes:

Thinking it disables interrupts
Assuming it delays ISR
Believing it resets semaphores

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More FreeRTOS Quizzes

Consider this FreeRTOS ISR snippet:

Step 1: Understand portYIELD_FROM_ISR usage

Step 2: Analyze the effect on task scheduling

Final Answer:

Quick Check:

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