From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH V2 5/6] vhost_net: poll vhost queue after marking DMA is done Date: Mon, 02 Sep 2013 11:06:54 +0800 Message-ID: <522400CE.3020102@redhat.com> References: <1377836962-49780-1-git-send-email-jasowang@redhat.com> <1377836962-49780-6-git-send-email-jasowang@redhat.com> <1377881073.2065.10.camel@bwh-desktop.uk.level5networks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1377881073.2065.10.camel@bwh-desktop.uk.level5networks.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 To: Ben Hutchings Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, mst@redhat.com List-Id: virtualization@lists.linuxfoundation.org On 08/31/2013 12:44 AM, Ben Hutchings wrote: > On Fri, 2013-08-30 at 12:29 +0800, Jason Wang wrote: >> We used to poll vhost queue before making DMA is done, this is racy if vhost >> thread were waked up before marking DMA is done which can result the signal to >> be missed. Fix this by always poll the vhost thread before DMA is done. > Does this bug only exist in net-next or is it older? Should the fix go > to net and stable branches? This should go for the stable branches too (3.4 above). Thanks for the checking. > > Ben. > >> Signed-off-by: Jason Wang >> --- >> drivers/vhost/net.c | 9 +++++---- >> 1 files changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c >> index ff60c2a..d09c17c 100644 >> --- a/drivers/vhost/net.c >> +++ b/drivers/vhost/net.c >> @@ -308,6 +308,11 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) >> struct vhost_virtqueue *vq = ubufs->vq; >> int cnt = atomic_read(&ubufs->kref.refcount); >> >> + /* set len to mark this desc buffers done DMA */ >> + vq->heads[ubuf->desc].len = success ? >> + VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN; >> + vhost_net_ubuf_put(ubufs); >> + >> /* >> * Trigger polling thread if guest stopped submitting new buffers: >> * in this case, the refcount after decrement will eventually reach 1 >> @@ -318,10 +323,6 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) >> */ >> if (cnt <= 2 || !(cnt % 16)) >> vhost_poll_queue(&vq->poll); >> - /* set len to mark this desc buffers done DMA */ >> - vq->heads[ubuf->desc].len = success ? >> - VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN; >> - vhost_net_ubuf_put(ubufs); >> } >> >> /* Expects to be always run from workqueue - which acts as