From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753901Ab1G0NWq (ORCPT ); Wed, 27 Jul 2011 09:22:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751555Ab1G0NWo (ORCPT ); Wed, 27 Jul 2011 09:22:44 -0400 Subject: list sort From: Steven Whitehouse To: Artem Bityutskiy , Don Mullis , Dave Chinner Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Organization: Red Hat UK Ltd Date: Wed, 27 Jul 2011 14:23:34 +0100 Message-ID: <1311773014.2801.23.camel@menhir> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, There seems to be an issue with list_sort trying to compare an object to itself. I spotted it first in a list for which I knew that I had unique keys, so had put a BUG() in the cmp function if the keys being compared were equal. While investigating I discovered that the objects themselves were equal (and hence the keys, also). The following addition to the list_sort test also triggers twice during the self test: diff --git a/lib/list_sort.c b/lib/list_sort.c index d7325c6..afa4a97 100644 --- a/lib/list_sort.c +++ b/lib/list_sort.c @@ -198,6 +198,8 @@ static int __init cmp(void *priv, struct list_head *a, struct list_head *b) { struct debug_el *ela, *elb; + WARN_ON(a == b); + ela = container_of(a, struct debug_el, list); elb = container_of(b, struct debug_el, list); While it appears generally harmless, since the list does appear to be correctly sorted, it is doing extra work needlessly. I couldn't find a listing in the maintainers' file for list_sort, so I used git to find those who'd worked on it recently, Steve.