title: C++ threading: first come mutex
body: <p>I am trying to solve the following architecture, but having some trouble. </p>
  
  <p>Basically there are multiple threads accessing the same the same object in parallel. The first thread is meant to execute <code>Object.A()</code> and all the other threads are supposed to wait until that process is finished and then proceed to execute <code>Object.B()</code> simultaneously without any blocking.</p>
  
  <p>Can't find any resources online that explain anything would produce this functionality and any "solution" that jumps to mind with 2 custom boolean mutexes doesn't seem to work.</p>