From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932397AbdJZM2d (ORCPT ); Thu, 26 Oct 2017 08:28:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33926 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932234AbdJZM2b (ORCPT ); Thu, 26 Oct 2017 08:28:31 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D6E2F356C7 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jasowang@redhat.com Subject: Re: [PATCH] virtio/ringtest: fix up need_event math To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org References: <1508982452-27245-1-git-send-email-mst@redhat.com> From: Jason Wang Message-ID: Date: Thu, 26 Oct 2017 20:28:21 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1508982452-27245-1-git-send-email-mst@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 26 Oct 2017 12:28:31 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017年10月26日 09:48, Michael S. Tsirkin wrote: > last kicked event index must be updated unconditionally: > even if we don't need to kick, we do not want to re-check > the same entry for events. > > Signed-off-by: Michael S. Tsirkin > --- > tools/virtio/ringtest/ring.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c > index 6b70c4e..d044a88 100644 > --- a/tools/virtio/ringtest/ring.c > +++ b/tools/virtio/ringtest/ring.c > @@ -196,16 +196,18 @@ bool enable_call() > > void kick_available(void) > { > + bool need; > + > /* Flush in previous flags write */ > /* Barrier C (for pairing) */ > smp_mb(); > - if (!need_event(event->kick_index, > - guest.avail_idx, > - guest.kicked_avail_idx)) > - return; > + need = need_event(event->kick_index, > + guest.avail_idx, > + guest.kicked_avail_idx); > > guest.kicked_avail_idx = guest.avail_idx; > - kick(); > + if (need) > + kick(); > } > > /* host side */ > @@ -265,14 +267,18 @@ bool use_buf(unsigned *lenp, void **bufp) > > void call_used(void) > { > + bool need; > + > /* Flush in previous flags write */ > /* Barrier D (for pairing) */ > smp_mb(); > - if (!need_event(event->call_index, > + > + need = !need_event(event->call_index, > host.used_idx, > - host.called_used_idx)) > - return; > + host.called_used_idx); > > host.called_used_idx = host.used_idx; > - call(); > + > + if (need) > + call(); > } Acked-by: Jason Wang