From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755234AbbAFMm5 (ORCPT ); Tue, 6 Jan 2015 07:42:57 -0500 Received: from mail-pd0-f169.google.com ([209.85.192.169]:42613 "EHLO mail-pd0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753236AbbAFMmz (ORCPT ); Tue, 6 Jan 2015 07:42:55 -0500 Date: Tue, 6 Jan 2015 04:45:28 -0800 From: Kent Overstreet To: Peter Zijlstra Cc: Sedat Dilek , Dave Jones , Linus Torvalds , LKML , Chris Mason Subject: Re: Linux 3.19-rc3 Message-ID: <20150106124528.GE26845@kmo-pixel> References: <20150106100621.GL29390@twins.programming.kicks-ass.net> <20150106110112.GQ29390@twins.programming.kicks-ass.net> <20150106110730.GA25846@kmo-pixel> <20150106114215.GS29390@twins.programming.kicks-ass.net> <20150106114842.GP10476@twins.programming.kicks-ass.net> <20150106120121.GB26845@kmo-pixel> <20150106122006.GW29390@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150106122006.GW29390@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 06, 2015 at 01:20:06PM +0100, Peter Zijlstra wrote: > We (probably me) should probably audit all the atomic_xchg() > implementations and documentation and fix that. I was very much under > the impression it should imply a full barrier (and it certainly does on > x86), the documentation should state the rule that any atomic_ function > that returns a result is fully serializing, therefore, because > atomic_xchg() has a return value, it should too. I think that the documentation was changed awhile ago - I'd have to check and I should sleep, though. It was probably 4-5 years ago that I saw that old weird "atomic_xchg() doesn't imply barriers" thing.