commit 15e8f348db372dec21229fda5d52ae6ee7e64666
author Roland McGrath <roland@redhat.com> Mon Jun 23 20:41:12 2008 -0700
committer Roland McGrath <roland@redhat.com> Wed Jul 23 17:43:36 2008 -0700
tree 73afc044ef5b4e29a893e98afee2fe794938aeb3
parent 20b7997e8abdf338dcc27fb4f1333c4973a7f113

x86_64: remove bogus optimization in sysret_signal

This short-circuit path in sysret_signal looks wrong to me.
AFAICT, in practice the branch is never taken--and if it were,
it would go wrong.  To wit, try loading a module whose init
function does set_thread_flag(TIF_IRET), and see insmod crash
(presumably with a wrong user stack pointer).

This is because the FIXUP_TOP_OF_STACK work hasn't been done yet
when we jump around the call to ptregscall_common and get to
int_with_check--where it expects the user RSP,SS,CS and EFLAGS to
have been stored by FIXUP_TOP_OF_STACK.

I don't think it's normally possible to get to sysret_signal with no
_TIF_DO_NOTIFY_MASK bits set anyway, so these two instructions are
already superfluous.  If it ever did happen, it is harmless to call
do_notify_resume with nothing for it to do.

Signed-off-by: Roland McGrath <roland@redhat.com>