From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763658AbXGWIvM (ORCPT ); Mon, 23 Jul 2007 04:51:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756024AbXGWIu6 (ORCPT ); Mon, 23 Jul 2007 04:50:58 -0400 Received: from an-out-0708.google.com ([209.85.132.245]:65436 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755363AbXGWIu5 (ORCPT ); Mon, 23 Jul 2007 04:50:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=eFFEDHJA8VDKftmjjOkTMovIMGLpcyl0LFDpp9eNUR0tKOnRL4aT/MJe96R5bU9pcnJNbZHVgAvNcMQUSIFcmU1RT6FTTU2C8ggJq0+LPwjMWq1KS+Xs9wBhEY9bLC0VJR0RUI/ePXgcU4v37cGvgRpVj/plYCmKbjfyia0OALo= Message-ID: Date: Mon, 23 Jul 2007 14:20:56 +0530 From: "Satyam Sharma" To: "Nick Piggin" Subject: Re: [PATCH] AFS: Fix file locking Cc: "Linus Torvalds" , "Andrew Morton" , linux-kernel@vger.kernel.org In-Reply-To: <46A4539D.9060100@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20070717124732.22619.34179.stgit@warthog.cambridge.redhat.com> <20070717175017.8b8a8976.akpm@linux-foundation.org> <469DABA5.9070706@yahoo.com.au> <20070719204102.7b82692d.akpm@linux-foundation.org> <46A04129.1020900@yahoo.com.au> <46A4539D.9060100@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 7/23/07, Nick Piggin wrote: > Linus Torvalds wrote: > > > > On Fri, 20 Jul 2007, Nick Piggin wrote: > > > >>So you did. Then to answer that, yes it could be faster because there are > >>stupid volatiles sprinkled all over the bitops code so you could easily > >>end up having to do more loads. Does it make a real difference? Unlikely, > >>but David loves counting cycles :) > > > > > > I thought we long long since removed the volatiles. They are buggy and > > horrible, and we really want to let the compiler combine multiple > > test-bits, and if they matter that implies locking is buggy or something > > worse.. > > > > Ie we'd *want* > > > > if (test_bit(x, y) || test_bit(z,y)) > > > > to be rewritten by the compiler as testing bits x/z at the same time. > > Yep. We'd also want __set_bit(x, y); __set_bit(z, y); and such to be > combined. > > > > But now I'm too scared to look. > > Not a chance :) Even the asm-generic "reference" implementation ratifies > the volatile crapiness. Would you take a patch? Coincidentally, I'm working on a cleanup of the bitops code just now -- I stumbled upon a lot of varied bogosity in there :-) Intend to send it out in a couple of hours, probably. Satyam