From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753827AbaJ1KtY (ORCPT ); Tue, 28 Oct 2014 06:49:24 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:39908 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105AbaJ1KtW (ORCPT ); Tue, 28 Oct 2014 06:49:22 -0400 Date: Tue, 28 Oct 2014 10:49:18 +0000 From: Steve Capper To: David Miller Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [GIT] Sparc Message-ID: <20141028104917.GC4187@linaro.org> References: <20141024.133249.71272218161411159.davem@davemloft.net> <20141027140938.142f83a4c3bc6512dd73b54c@linux-foundation.org> <20141027.184327.1734954193920971940.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141027.184327.1734954193920971940.davem@davemloft.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 27, 2014 at 06:43:27PM -0400, David Miller wrote: > From: Andrew Morton > Date: Mon, 27 Oct 2014 14:09:38 -0700 > > > Perhaps sparc should be defining CONFIG_HAVE_GENERIC_RCU_GUP. > > > > We really should switch x86 to the generic version - from a quick read > > it looks like it will work without needing any changes. > > > > Steve, thoughts? > > We need to add the necessary hooks to the generic code so that x86 > doesn't so specualtive gets and instead do direct increments, > otherwise it's a performance regression, and then sparc can make use > of that as well. Agreed, I think x86 may require a helper to read 64-bit ptes (as it can't do that atomically). Also I think there's some subtlety in the way access_ok works that should be checked. The overall structure of the code looks the same to me, and I think it would be beneficial to extend then use the generic version for x86. Cheers, -- Steve