This is indeed a new bug, and it is not architecture-specific.  In my
recent changes to close some race conditions, I overlooked the case of a
process using PTRACE_ATTACH on its own children.  The new PT_ATTACHED flag
does not really mean "PTRACE_ATTACH was used", it means "PTRACE_ATTACH is
changing the ->parent link".

This fixes the problem that Stephane Eranian program demonstrates.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>