[PATCH] Avoid small irq preemption recursion window

This will get rid of the stack recursion possibility that can occur if
an IRQ happens to hit the IRQ return path right after we've reset
preempt_count() to 0 and are about to disable interrupts again.
Trivially fixed by just moving the preempt count update to inside the
interrupt disable.

This makes the current PREEMPT_ACTIVE method fully work for IRQ
recursions.

arch/i386/kernel/entry.S

@@ -187,8 +187,8 @@ need_resched:
 	movl $PREEMPT_ACTIVE,TI_preempt_count(%ebp)
 	sti
 	call schedule
-	movl $0,TI_preempt_count(%ebp)
 	cli
+	movl $0,TI_preempt_count(%ebp)
 	jmp need_resched
 #endif