From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752648AbcFIL2N (ORCPT ); Thu, 9 Jun 2016 07:28:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:46222 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbcFIL2M (ORCPT ); Thu, 9 Jun 2016 07:28:12 -0400 Date: Thu, 9 Jun 2016 13:28:07 +0200 From: Borislav Petkov To: Paolo Bonzini Cc: Minfei Huang , luto@kernel.org, hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in function pvclock_read_flags Message-ID: <20160609112807.GB12860@pd.tnic> References: <1464329832-4638-3-git-send-email-mnghuan@gmail.com> <1464438463-8485-1-git-send-email-mnghuan@gmail.com> <20160608081739.GD26187@pd.tnic> <1ade9d3e-2064-c811-f718-371d91c7874c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1ade9d3e-2064-c811-f718-371d91c7874c@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 09, 2016 at 01:21:18PM +0200, Paolo Bonzini wrote: > This is basically implementing a seqcount. It needs two barriers and, Why does it need the two barriers? More details please. > technically, they should be virt_rmb() -- it really doesn't matter of > course because reads are never reordered on x86. You mean version = src->version; flags = src->flags; are not reordered? I don't think so. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --