From: David Mosberger <davidm@napali.hpl.hp.com>

At the moment, if you don't set CLONE_CHILD_SETTID/CLONE_CHILD_CLEARTID,
the {set,clear}_child_tid values get inherited from the parent task.  I may
be missing something, but I suspect that's not the intended behavior.  The
patch below instead clears the respective members.