title: Calling ioctl on same file descriptor from two different processes
body: <p>If I call ioctl (this is a custom kernel driver to read/write Altera registers), and another process calls ioctl on the same file descriptor while the first ioctl is still executing, does the first call finish before the second call starts? </p>
  
  <p>I am unsure if I should put some sort of locking mechanism in the driver, or if it's unnecessary.</p>