Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758753AbZGCSa3 (ORCPT ); Fri, 3 Jul 2009 14:30:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756472AbZGCSaX (ORCPT ); Fri, 3 Jul 2009 14:30:23 -0400 Received: from casper.infradead.org ([85.118.1.10]:50598 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756067AbZGCSaW (ORCPT ); Fri, 3 Jul 2009 14:30:22 -0400 Date: Fri, 3 Jul 2009 11:30:02 -0700 From: Arjan van de Ven To: Ingo Molnar Cc: Eric Dumazet , Linus Torvalds , mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH -tip] x86: atomic64: inline atomic64_read() Message-ID: <20090703113002.6c2c103b@infradead.org> In-Reply-To: <20090703181815.GC3405@elte.hu> References: <4A4E1AA2.30002@gmail.com> <20090703180450.GB3405@elte.hu> <20090703111033.6e9627de@infradead.org> <20090703181815.GC3405@elte.hu> Organization: Intel X-Mailer: Claws Mail 3.7.1 (GTK+ 2.14.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1255 Lines: 43 On Fri, 3 Jul 2009 20:18:15 +0200 Ingo Molnar wrote: > > * Arjan van de Ven wrote: > > > On Fri, 3 Jul 2009 20:04:50 +0200 > > Ingo Molnar wrote: > > > > > > +static inline u64 atomic64_read(atomic64_t *ptr) > > > > +{ > > > > + u64 res; > > > > + > > > > + asm volatile( > > > > + "mov %%ebx, %%eax\n\t" > > > > + "mov %%ecx, %%edx\n\t" > > > > + LOCK_PREFIX "cmpxchg8b %1\n" > > > > also afaik cmpxchg implies the lock prefix, so no need to make an > > explicit one... it just adds code size and alternatives-work > > good point! > > Is the same true of XADD as well? If yes then we can remove the lock > prefix from those as well - there's a few uses of that on 32-bit and > 64-bit as well. > ok never mind I was wrong, it seems cmpxchg does NOT imply a lock prefix, nor does xadd. > Ingo -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/