title: In Python, what are the cons of calling os.waitpid in a program with multiple threads?
body: <p>I've heard there are problems when calling os.waitpid from within a thread. I have not experienced such problems yet (especially using os.WNOHANG option). However I have not paid much attention to the performance implications of such use.</p>
  
  <p>Are there any performance penalties or any other issues one should be aware of?
  Does this have to do with os.waitpid (potentially) using signals?</p>
  
  <p>I don't see how signals could be related, though, since otherwise (I suppose) I wouldn't be able to get os.waitpid to return when calling it from a non-main thread.</p>