From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965407AbXDBNYE (ORCPT ); Mon, 2 Apr 2007 09:24:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965425AbXDBNYE (ORCPT ); Mon, 2 Apr 2007 09:24:04 -0400 Received: from mx1.suse.de ([195.135.220.2]:57300 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965419AbXDBNYD (ORCPT ); Mon, 2 Apr 2007 09:24:03 -0400 From: Oliver Neukum Organization: Novell To: Greg KH , linux-kernel@vger.kernel.org Subject: CPU ordering with respect to krefs Date: Mon, 2 Apr 2007 14:47:59 +0200 User-Agent: KMail/1.9.1 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704021447.59476.oneukum@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, some atomic operations are only atomic, not ordered. Thus a CPU is allowed to reorder memory references to an object to before the reference is obtained. This fixes it. Regards Oliver Signed-off-by: Oliver Neukum ------ --- a/lib/kref.c 2007-04-02 14:40:40.000000000 +0200 +++ b/lib/kref.c 2007-04-02 14:40:50.000000000 +0200 @@ -21,6 +21,7 @@ void kref_init(struct kref *kref) { atomic_set(&kref->refcount,1); + smp_mb(); } /** @@ -31,6 +32,7 @@ { WARN_ON(!atomic_read(&kref->refcount)); atomic_inc(&kref->refcount); + smp_mb__after_atomic_inc(); } /**