Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264305AbUFZSzu (ORCPT ); Sat, 26 Jun 2004 14:55:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266333AbUFZSzu (ORCPT ); Sat, 26 Jun 2004 14:55:50 -0400 Received: from fw.osdl.org ([65.172.181.6]:22506 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S264305AbUFZSzs (ORCPT ); Sat, 26 Jun 2004 14:55:48 -0400 Date: Sat, 26 Jun 2004 11:54:24 -0700 (PDT) From: Linus Torvalds To: Vojtech Pavlik cc: James Bottomley , Andrew Morton , Paul Jackson , PARISC list , Linux Kernel Subject: Re: [PATCH] Fix the cpumask rewrite In-Reply-To: <20040626182820.GA3723@ucw.cz> Message-ID: References: <1088266111.1943.15.camel@mulgrave> <1088268405.1942.25.camel@mulgrave> <1088270298.1942.40.camel@mulgrave> <20040626182820.GA3723@ucw.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 937 Lines: 26 On Sat, 26 Jun 2004, Vojtech Pavlik wrote: > > At least input pretty much relies on the fact that bitops don't need > locking and act as memory barriers. Well, plain test_bit() has always been more relaxed than the others, and has never implied a memory barrier. Only the "test_and_set/clear()" things imply memory barriers. What we _could_ do (without changing any existing rules) is to add a "__test_bit()" that is the relaxed version that doesn't do any of the volatile etc. That would match the "__" versions of the other bit operations. Then people who know that they use the bits without any volatility issues can use that one, and let the compiler optimize more. Hmm? Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/