From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH RFC] virtio_net: enable tx interrupt Date: Wed, 15 Oct 2014 12:40:43 +0800 Message-ID: <543DFACB.5030905@redhat.com> References: <1413323524-23380-1-git-send-email-mst@redhat.com> <20141014231154.GA23806@redhat.com> <543DF92C.6060209@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Return-path: In-Reply-To: <543DF92C.6060209@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On 10/15/2014 12:33 PM, Jason Wang wrote: > On 10/15/2014 07:11 AM, Michael S. Tsirkin wrote: >> > On Wed, Oct 15, 2014 at 12:53:59AM +0300, Michael S. Tsirkin wrote: >>>> >> > static void skb_xmit_done(struct virtqueue *vq) >>>> >> > { >>>> >> > struct virtnet_info *vi = vq->vdev->priv; >>>> >> > + struct send_queue *sq = &vi->sq[vq2txq(vq)]; >>>> >> > >>>> >> > - /* Suppress further interrupts. */ >>>> >> > - virtqueue_disable_cb(vq); >>>> >> > - >> > One note here: current code seems racy because of doing >> > virtqueue_disable_cb from skb_xmit_done that I'm dropping here: there's >> > no guarantee we don't get an interrupt while tx ring is running, and if >> > that happens we can end up with interrupts disabled forever. >> > > Looks harmless since: > > - if event index is enabled, virtqueue_disable_cb() does nothing in fact. > - if event index is disabled, we don't depend on tx interrupt and when > num_free is low we will try to enable the tx interrupt again. Ok, I think I get you here. For 'current' you mean the rfc I post.