the busy prune id uid does not clear  it merely removes one entry if it needs to  i figured the is very clearly not a ulong max  it is real purpose it to check if it is still busy after the sleep  if it is still busy  then we want to tell all the readers to  go away we kill them  then do yet another run to clear all the entries ulong max  if it is not busy  then we preserve the readers and let one more run go unhindered the one line comment on line describes what we are doing  it is obviously not enough comment 