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: <ffffffff8012942d>{__might_sleep+190} <ffffffff80132768>{profile_task_exit+21}
       <ffffffff80133daf>{__do_exit+34} <ffffffff8013483d>{do_wait+0}


Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/x86_64/kernel/entry.S |    1 +
 1 files changed, 1 insertion(+)

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/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