[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: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/entry.S

@@ -554,6 +554,7 @@ iret_label:
 	/* running with kernel gs */
 bad_iret:
 	movq $-9999,%rdi	/* better code? */
+	sti
 	jmp do_exit			
 	.previous