From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965122AbbKCXyr (ORCPT ); Tue, 3 Nov 2015 18:54:47 -0500 Received: from mail-io0-f176.google.com ([209.85.223.176]:34591 "EHLO mail-io0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756071AbbKCXyp (ORCPT ); Tue, 3 Nov 2015 18:54:45 -0500 MIME-Version: 1.0 In-Reply-To: <20151103091636.GA23350@gmail.com> References: <20151103091636.GA23350@gmail.com> Date: Tue, 3 Nov 2015 15:54:45 -0800 X-Google-Sender-Auth: TIGb5UZ6F6gKXbfTAnOIoUQEcHQ Message-ID: Subject: Re: [GIT PULL] locking changes for v4.4 From: Linus Torvalds To: Ingo Molnar Cc: Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , "Paul E. McKenney" , Andrew Morton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 3, 2015 at 1:16 AM, Ingo Molnar wrote: > > - More gradual enhancements to atomic ops: new atomic*_read_ctrl() ops, > synchronize atomic_{read,set}() ordering requirements between architectures, > add atomic_long_t bitops. (Peter Zijlstra) >>From another thread: those new "atomic*_read_ctrl()" operations are complete voodoo programming, and should never ever be used. Those helpers seem to be based entirely on a mis-reading of alpha memory ordering that is actually not possible in a universe where causality exists. It's not a new disease - we already have READ_ONCE_CTRL(), but it is currently only actually used in one single place (but mentioned many times in documentation that is looking less and less like reality). But this pull request seems to make that thing be institutional, and spreads this mis-understanding out, and tries to "document" it as some kind of actual truth. Linus