[PATCH] s/preempt_count()/in_atomic() in do_exit()

This converts the debugging check in do_exit from a check on
preempt_count() to in_atomic().

The main benefit to this is we will stop warning over the BKL and now
use the standard mechanism for such checks.

kernel/exit.c

@@ -626,7 +626,7 @@ NORET_TYPE void do_exit(long code)
 	tsk->flags |= PF_EXITING;
 	del_timer_sync(&tsk->real_timer);
 
-	if (unlikely(preempt_count()))
+	if (unlikely(in_atomic()))
 		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
 				current->comm, current->pid,
 				preempt_count());