title: what is RT_PREEMPT? how is it different from preempt rt ?does these mean same real time patch to linux?
body: <p>I presently working on hardrealtime linux.
  when i search regarding documentation of topic RT_PREEMPT .
  different sites turn up with different names like preempt-rt,rt-preempt.</p>
  
  <p>can someone say me the exact link or any resources which could help me look on RT_PREEMPT?</p>