Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751362Ab1BNRml (ORCPT ); Mon, 14 Feb 2011 12:42:41 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:54327 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751088Ab1BNRmk (ORCPT ); Mon, 14 Feb 2011 12:42:40 -0500 Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates From: Peter Zijlstra To: Will Newton Cc: Steven Rostedt , Jason Baron , Mathieu Desnoyers , hpa@zytor.com, mingo@elte.hu, tglx@linutronix.de, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com, avi@redhat.com, davem@davemloft.net, sam@ravnborg.org, ddaney@caviumnetworks.com, michael@ellerman.id.au, linux-kernel@vger.kernel.org, Mike Frysinger , Chris Metcalf , dhowells , Martin Schwidefsky , "heiko.carstens" , benh In-Reply-To: References: <1297452328.5226.89.camel@laptop> <1297460297.5226.99.camel@laptop> <1297536465.5226.108.camel@laptop> <20110214155113.GA2840@redhat.com> <1297699024.2401.12.camel@twins> <20110214160437.GB2840@redhat.com> <1297700754.5226.110.camel@laptop> <20110214162947.GA3449@redhat.com> <1297701438.5226.113.camel@laptop> <1297702013.23343.51.camel@gandalf.stny.rr.com> <1297703892.23343.71.camel@gandalf.stny.rr.com> <1297704447.5226.127.camel@laptop> Content-Type: text/plain; charset="UTF-8" Date: Mon, 14 Feb 2011 18:43:48 +0100 Message-ID: <1297705428.5226.142.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 972 Lines: 24 On Mon, 2011-02-14 at 17:38 +0000, Will Newton wrote: > On Mon, Feb 14, 2011 at 5:27 PM, Peter Zijlstra wrote: > > >> So all but a few have basically (as you said on IRC) > >> #define atomic_read(v) ACCESS_ONCE(v) > > > > ACCESS_ONCE(v->counter), but yeah :-) > > I maintain an out-of-tree architecture where that isn't the case > unfortunately [1]. Not expecting any special favours for being > out-of-tree of course, but just thought I would add that data point. > > [1] Our atomic operations go around the cache rather than through it, > so the value of an atomic cannot be read with a normal load > instruction. Cannot how? It would observe a stale value? That is acceptable for atomic_read(). -- 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/