Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752463AbaFBRjj (ORCPT ); Mon, 2 Jun 2014 13:39:39 -0400 Received: from terminus.zytor.com ([198.137.202.10]:53740 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751805AbaFBRji (ORCPT ); Mon, 2 Jun 2014 13:39:38 -0400 Message-ID: <538CB68A.6030408@zytor.com> Date: Mon, 02 Jun 2014 10:38:18 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Waiman Long , Jason Low CC: Mikulas Patocka , Linus Torvalds , Peter Zijlstra , jejb@parisc-linux.org, deller@gmx.de, John David Anglin , linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, chegu_vinod@hp.com, tglx@linutronix.de, riel@redhat.com, akpm@linux-foundation.org, davidlohr@hp.com, andi@firstfloor.org, aswin@hp.com, scott.norton@hp.com Subject: Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks References: <1401727810.7440.34.camel@j-VirtualBox> <538CB389.5080108@hp.com> In-Reply-To: <538CB389.5080108@hp.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/02/2014 10:25 AM, Waiman Long wrote: > > Doing an xchg is a very expensive operation compared with ACCESS_ONCE. I > will not suggest doing that to make it right for PA-RISC at the expense > of performance in other architectures. > And of course, this gets into the toxic question: what are reasonable minimum requirements for Linux? How far do we need to stretch to support niche architectures which have very small (Linux) userbases? -hpa -- 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/