Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751160Ab1BNRpa (ORCPT ); Mon, 14 Feb 2011 12:45:30 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:35362 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751209Ab1BNRp1 (ORCPT ); Mon, 14 Feb 2011 12:45:27 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type; b=nAKsAq7eQus6xMJ0x5G/nF33+73BQJ3CN31iOZziftWorfs5+d/fUjD2m2PQio625h N6TwB6bP+Uhi/0GXSPff+q1IWkOM/yGxwS6qkuyYncus3DPk95tAEWru/Cv2I4HoUBkm RyCF8Xg4GxPEPrfyJOxxL848T3LEVxdJHZXyQ= MIME-Version: 1.0 In-Reply-To: <1297705095.5226.136.camel@laptop> 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> <1297705095.5226.136.camel@laptop> From: Mike Frysinger Date: Mon, 14 Feb 2011 12:45:06 -0500 X-Google-Sender-Auth: 76Op97PUNLdRpv-_KAAaiBXK_YM Message-ID: Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates To: Peter Zijlstra 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" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1446 Lines: 31 On Mon, Feb 14, 2011 at 12:38, Peter Zijlstra wrote: > 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 words you use seem to form a line of reasoning that makes sense to me. we'll have to play first though to double check. > The only problem would be when you could get cache aliasing and read > something totally unrelated. being a nommu arch, there shouldnt be any cache aliasing issues. we're just trying to make sure that what another core has pushed out isnt stale in another core's cache when the other core does the read. -mike -- 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/