docs: private FileDetails getOldestInactive() {
  		for (FileDetails curFd : fileList) {
  			if (curFd.pid == null)
  				return curFd ;
  			synchronized(activeFilesMap) {
  				FileDetails cur4Pid = activeFilesMap.get(curFd.pid) ;
  				if ( cur4Pid == null || cur4Pid != curFd) {
  					return curFd ;
  				}
  			}
  		}
  		return null ;
  	}