From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754022AbYEaC0J (ORCPT ); Fri, 30 May 2008 22:26:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750801AbYEaCZ4 (ORCPT ); Fri, 30 May 2008 22:25:56 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:41824 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750762AbYEaCZ4 (ORCPT ); Fri, 30 May 2008 22:25:56 -0400 Date: Fri, 30 May 2008 19:25:06 -0700 (PDT) From: Linus Torvalds To: Ulrich Drepper cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mtk.manpages@gmail.com Subject: Re: [PATCH 3/3] 64-bit futexes: x86 support In-Reply-To: <200805310127.m4V1RLdP013819@devserv.devel.redhat.com> Message-ID: References: <200805310127.m4V1RLdP013819@devserv.devel.redhat.com> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 30 May 2008, Ulrich Drepper wrote: > > +#ifdef CONFIG_X86_32 > + /* Not all 32-bit machines support 8-byte cmpxchg. We just > + unconditionally perform a runtime check for the feature. */ > + if ((op & FUTEX_FLAG_64) && !boot_cpu_has(X86_FEATURE_CX8)) > + return -ENOSYS; > +#endif Also, doesn't this mean that effectively you have given up on any CPU before the Pentium entirely? Not that I want to take the patches _anyway_, but it seems doubly stupid. Those things are going to be UP machines, so you could have just emulated it with no correctness issues by disabling preemption. Linus