[PATCH] x86_64: Don't call do_exit with interrupts disabled after IRET exception

This caused a sigreturn with bad argument on a preemptible kernel
to complain with

Debug: sleeping function called from invalid context at /home/lsrc/quilt/linux/include/linux/rwsem.h:43
in_atomic():0, irqs_disabled():1

Call Trace: {__might_sleep+190} {profile_task_exit+21}
       {__do_exit+34} {do_wait+0}

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>