title: Wait notify pthreads unix C++
body: <p>I have n threads , each modifying an object O(k) where k can be 0 to n-1.</p>
  
  <p>Now there is a listener thread l, that needs to get an alert when any of the thread,k, has modified its object O(k)</p>
  
  <p>What is the fastest way to implement this situation ? </p>