From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753739AbcAGWcy (ORCPT <rfc822;w@1wt.eu>);
	Thu, 7 Jan 2016 17:32:54 -0500
Received: from terminus.zytor.com ([198.137.202.10]:44756 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753650AbcAGWcw (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 7 Jan 2016 17:32:52 -0500
Subject: Re: [PATCH] x86: Add an explicit barrier() to clflushopt()
To: Chris Wilson <chris@chris-wilson.co.uk>,
        Andy Lutomirski <luto@amacapital.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
        "H . Peter Anvin" <hpa@linux.intel.com>,
        Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Imre Deak <imre.deak@intel.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        DRI <dri-devel@lists.freedesktop.org>
References: <1445248735-11915-1-git-send-email-chris@chris-wilson.co.uk>
 <20160107101652.GF652@nuc-i3427.alporthouse.com>
 <CALCETrU8otVfBe0+N-E0sc=j2L79qh7gqte7QSVb_YzGbJYNCA@mail.gmail.com>
 <20160107194413.GA25144@nuc-i3427.alporthouse.com>
 <568ED31F.1090004@zytor.com>
 <20160107215401.GB25144@nuc-i3427.alporthouse.com>
 <568EE6E6.4000904@zytor.com>
From: "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <568EE777.80700@zytor.com>
Date: Thu, 7 Jan 2016 14:32:23 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.4.0
MIME-Version: 1.0
In-Reply-To: <568EE6E6.4000904@zytor.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 01/07/16 14:29, H. Peter Anvin wrote:
> 
> I would be very interested in knowing if replacing the final clflushopt
> with a clflush would resolve your problems (in which case the last mb()
> shouldn't be necessary either.)
> 

Nevermind.  CLFLUSH is not ordered with regards to CLFLUSHOPT to the
same cache line.

Could you add a sync_cpu(); call to the end (can replace the final mb())
and see if that helps your case?

	-hpa