Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755863Ab1BNRhL (ORCPT ); Mon, 14 Feb 2011 12:37:11 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:37422 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754792Ab1BNRhI (ORCPT ); Mon, 14 Feb 2011 12:37:08 -0500 Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates From: Peter Zijlstra To: Mike Frysinger 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, Chris Metcalf , dhowells , Martin Schwidefsky , "heiko.carstens" , benh , "Paul E. McKenney" 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 18:38:15 +0100 Message-ID: <1297705095.5226.136.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: 1037 Lines: 23 On Mon, 2011-02-14 at 12:29 -0500, Mike Frysinger wrote: > On Mon, Feb 14, 2011 at 12:27, Peter Zijlstra wrote: > > On Mon, 2011-02-14 at 12:18 -0500, Steven Rostedt wrote: > >> blackfin, seems to be doing quite a lot. Not sure if it is required, but > >> that may need a bit of investigating to understand why it does the > >> raw_uncached thing. > > > > From what I can tell its flushing its write cache, invalidating its > > d-cache and then issue the read, something which is _way_ overboard. > > not when the cores in a SMP system lack cache coherency But atomic_read() is completely unordered, so even on a non-coherent system a regular read should suffice, any old value is correct. The only problem would be when you could get cache aliasing and read something totally unrelated. -- 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/