问FreeRTOS:为什么要在isrHandler中调用taskYIELD_FROM_ISR()方法

EN

/* A stream buffer that has already been created. */
StreamBufferHandle_t xStreamBuffer;

void vAnInterruptServiceRoutine( void ) {
  size_t xBytesSent;
  char *pcStringToSend = "String to send";
  BaseType_t xHigherPriorityTaskWoken = pdFALSE;

  /* Attempt to send the string to the stream buffer. */
  xBytesSent = xStreamBufferSendFromISR(xStreamBuffer,(void *) pcStringToSend,strlen( pcStringToSend),&xHigherPriorityTaskWoken);

  if(xBytesSent != strlen(pcStringToSend)){
    /* There was not enough free space in the stream buffer for the entire string to be written, ut xBytesSent bytes were written. */
  }

  /* 
    If xHigherPriorityTaskWoken was set to pdTRUE inside xStreamBufferSendFromISR() then a    
    task that has a priority above the priority of the currently executing task was unblocked 
    and a context switch should be performed to ensure the ISR returns to the unblocked task. 
    In most FreeRTOS ports this is done by simply passing xHigherPriorityTaskWoken into 
    taskYIELD_FROM_ISR(), which will test the variables value, and perform the context switch 
    if necessary. Check the documentation for the port in use for port specific instructions. 
  */

  taskYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}