Put the compiler barrier() on the right side of the preemption

enable on UP-PREEMPT.

Without this, the enable could "migrate" up into the critical
region (on SMP, the actual spinlock would act as an additional
barrier and PREEMPT was ok).

include/linux/preempt.h

@@ -32,8 +32,8 @@ do { \
 
 #define preempt_enable_no_resched() \
 do { \
-	dec_preempt_count(); \
 	barrier(); \
+	dec_preempt_count(); \
 } while (0)
 
 #define preempt_check_resched() \