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([2001:ee0:4f4c:210:2998:e0cd:90d5:9648]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29dae49ca50sm128075925ad.20.2025.12.08.07.48.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Dec 2025 07:48:33 -0800 (PST) Message-ID: <39958cd6-3ab1-433a-8eed-129304bc059e@gmail.com> Date: Mon, 8 Dec 2025 22:48:26 +0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] virtio-net: enable all napis before scheduling refill work To: netdev@vger.kernel.org Cc: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, bpf@vger.kernel.org References: <20251208153419.18196-1-minhquangbui99@gmail.com> Content-Language: en-US From: Bui Quang Minh In-Reply-To: <20251208153419.18196-1-minhquangbui99@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/8/25 22:34, Bui Quang Minh wrote: > Calling napi_disable() on an already disabled napi can cause the > deadlock. In commit 4bc12818b363 ("virtio-net: disable delayed refill > when pausing rx"), to avoid the deadlock, when pausing the RX in > virtnet_rx_pause[_all](), we disable and cancel the delayed refill work. > However, in the virtnet_rx_resume_all(), we enable the delayed refill > work too early before enabling all the receive queue napis. > > The deadlock can be reproduced by running > selftests/drivers/net/hw/xsk_reconfig.py with multiqueue virtio-net > device and inserting a cond_resched() inside the for loop in > virtnet_rx_resume_all() to increase the success rate. Because the worker > processing the delayed refilled work runs on the same CPU as > virtnet_rx_resume_all(), a reschedule is needed to cause the deadlock. > In real scenario, the contention on netdev_lock can cause the > reschedule. > > This fixes the deadlock by ensuring all receive queue's napis are > enabled before we enable the delayed refill work in > virtnet_rx_resume_all() and virtnet_open(). > > Fixes: 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx") > Reported-by: Paolo Abeni > Closes: https://netdev-ctrl.bots.linux.dev/logs/vmksft/drv-hw-dbg/results/400961/3-xdp-py/stderr > Signed-off-by: Bui Quang Minh I forgot to add Cc:stable@vger.kernel.org. I will add in next version. Thanks, Quang Minh. > --- > drivers/net/virtio_net.c | 59 +++++++++++++++++++--------------------- > 1 file changed, 28 insertions(+), 31 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 8e04adb57f52..f2b1ea65767d 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2858,6 +2858,20 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq, > return err != -ENOMEM; > } > > +static void virtnet_rx_refill_all(struct virtnet_info *vi) > +{ > + bool schedule_refill = false; > + int i; > + > + enable_delayed_refill(vi); > + for (i = 0; i < vi->curr_queue_pairs; i++) > + if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) > + schedule_refill = true; > + > + if (schedule_refill) > + schedule_delayed_work(&vi->refill, 0); > +} > + > static void skb_recv_done(struct virtqueue *rvq) > { > struct virtnet_info *vi = rvq->vdev->priv; > @@ -3216,19 +3230,14 @@ static int virtnet_open(struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int i, err; > > - enable_delayed_refill(vi); > - > for (i = 0; i < vi->max_queue_pairs; i++) { > - if (i < vi->curr_queue_pairs) > - /* Make sure we have some buffers: if oom use wq. */ > - if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) > - schedule_delayed_work(&vi->refill, 0); > - > err = virtnet_enable_queue_pair(vi, i); > if (err < 0) > goto err_enable_qp; > } > > + virtnet_rx_refill_all(vi); > + > if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) { > if (vi->status & VIRTIO_NET_S_LINK_UP) > netif_carrier_on(vi->dev); > @@ -3463,39 +3472,27 @@ static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq) > __virtnet_rx_pause(vi, rq); > } > > -static void __virtnet_rx_resume(struct virtnet_info *vi, > - struct receive_queue *rq, > - bool refill) > -{ > - bool running = netif_running(vi->dev); > - bool schedule_refill = false; > - > - if (refill && !try_fill_recv(vi, rq, GFP_KERNEL)) > - schedule_refill = true; > - if (running) > - virtnet_napi_enable(rq); > - > - if (schedule_refill) > - schedule_delayed_work(&vi->refill, 0); > -} > - > static void virtnet_rx_resume_all(struct virtnet_info *vi) > { > int i; > > - enable_delayed_refill(vi); > - for (i = 0; i < vi->max_queue_pairs; i++) { > - if (i < vi->curr_queue_pairs) > - __virtnet_rx_resume(vi, &vi->rq[i], true); > - else > - __virtnet_rx_resume(vi, &vi->rq[i], false); > + if (netif_running(vi->dev)) { > + for (i = 0; i < vi->max_queue_pairs; i++) > + virtnet_napi_enable(&vi->rq[i]); > + > + virtnet_rx_refill_all(vi); > } > } > > static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue *rq) > { > - enable_delayed_refill(vi); > - __virtnet_rx_resume(vi, rq, true); > + if (netif_running(vi->dev)) { > + virtnet_napi_enable(rq); > + > + enable_delayed_refill(vi); > + if (!try_fill_recv(vi, rq, GFP_KERNEL)) > + schedule_delayed_work(&vi->refill, 0); > + } > } > > static int virtnet_rx_resize(struct virtnet_info *vi,