From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757581AbYD2W6f (ORCPT ); Tue, 29 Apr 2008 18:58:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752729AbYD2W60 (ORCPT ); Tue, 29 Apr 2008 18:58:26 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:34215 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751068AbYD2W6Z (ORCPT ); Tue, 29 Apr 2008 18:58:25 -0400 Date: Tue, 29 Apr 2008 15:58:24 -0700 (PDT) Message-Id: <20080429.155824.183713623.davem@davemloft.net> To: tglx@linutronix.de Cc: torvalds@linux-foundation.org, harvey.harrison@gmail.com, mingo@elte.hu, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] bitops: remove "optimizations" From: David Miller In-Reply-To: References: <20080429.030332.88897602.davem@davemloft.net> <20080429.053412.15412725.davem@davemloft.net> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner Date: Tue, 29 Apr 2008 18:51:51 +0200 (CEST) > The question is, whether it broke things or just unearthed some bug > hidden elsewhere. So I did a quick test, just #if 0'ing out the optimization inline portions of the find_first_bit() code in linux/bitops.h, and forcing it to always unconditionally call __find_first_bit() fixes the regression. Given that others who tested could not find one case where the optimization cases actually applied, and it's breaking things for me, my theory is that it's triggering for some obscure case on sparc64 and thus showing a bug in these optimizations since in practice I'm the only person to actually test this new code.