From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH] x86: Add an explicit barrier() to clflushopt() Date: Thu, 7 Jan 2016 14:32:23 -0800 Message-ID: <568EE777.80700@zytor.com> References: <1445248735-11915-1-git-send-email-chris@chris-wilson.co.uk> <20160107101652.GF652@nuc-i3427.alporthouse.com> <20160107194413.GA25144@nuc-i3427.alporthouse.com> <568ED31F.1090004@zytor.com> <20160107215401.GB25144@nuc-i3427.alporthouse.com> <568EE6E6.4000904@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from mail.zytor.com (terminus.zytor.com [198.137.202.10]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0DE746E6E3 for ; Thu, 7 Jan 2016 14:32:51 -0800 (PST) In-Reply-To: <568EE6E6.4000904@zytor.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Chris Wilson , Andy Lutomirski , "linux-kernel@vger.kernel.org" , Ross Zwisler , "H . Peter Anvin" , Borislav Petkov , Brian Gerst , Denys Vlasenko , Linus Torvalds , Thomas Gleixner , Imre Deak , Daniel Vetter , DRI List-Id: dri-devel@lists.freedesktop.org T24gMDEvMDcvMTYgMTQ6MjksIEguIFBldGVyIEFudmluIHdyb3RlOgo+IAo+IEkgd291bGQgYmUg dmVyeSBpbnRlcmVzdGVkIGluIGtub3dpbmcgaWYgcmVwbGFjaW5nIHRoZSBmaW5hbCBjbGZsdXNo b3B0Cj4gd2l0aCBhIGNsZmx1c2ggd291bGQgcmVzb2x2ZSB5b3VyIHByb2JsZW1zIChpbiB3aGlj aCBjYXNlIHRoZSBsYXN0IG1iKCkKPiBzaG91bGRuJ3QgYmUgbmVjZXNzYXJ5IGVpdGhlci4pCj4g CgpOZXZlcm1pbmQuICBDTEZMVVNIIGlzIG5vdCBvcmRlcmVkIHdpdGggcmVnYXJkcyB0byBDTEZM VVNIT1BUIHRvIHRoZQpzYW1lIGNhY2hlIGxpbmUuCgpDb3VsZCB5b3UgYWRkIGEgc3luY19jcHUo KTsgY2FsbCB0byB0aGUgZW5kIChjYW4gcmVwbGFjZSB0aGUgZmluYWwgbWIoKSkKYW5kIHNlZSBp ZiB0aGF0IGhlbHBzIHlvdXIgY2FzZT8KCgktaHBhCgoKX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxA bGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHA6Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1h bi9saXN0aW5mby9kcmktZGV2ZWwK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753739AbcAGWcy (ORCPT ); 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 ); Thu, 7 Jan 2016 17:32:52 -0500 Subject: Re: [PATCH] x86: Add an explicit barrier() to clflushopt() To: Chris Wilson , Andy Lutomirski , "linux-kernel@vger.kernel.org" , Ross Zwisler , "H . Peter Anvin" , Borislav Petkov , Brian Gerst , Denys Vlasenko , Linus Torvalds , Thomas Gleixner , Imre Deak , Daniel Vetter , DRI References: <1445248735-11915-1-git-send-email-chris@chris-wilson.co.uk> <20160107101652.GF652@nuc-i3427.alporthouse.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" 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: 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