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[80.230.31.118]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b842a27c760sm261977866b.24.2026.01.06.07.29.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 07:29:08 -0800 (PST) Date: Tue, 6 Jan 2026 10:29:05 -0500 From: "Michael S. Tsirkin" To: Bui Quang Minh Cc: netdev@vger.kernel.org, Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , 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, stable@vger.kernel.org Subject: Re: [PATCH net v3 1/3] virtio-net: don't schedule delayed refill worker Message-ID: <20260106100959-mutt-send-email-mst@kernel.org> References: <20260106150438.7425-1-minhquangbui99@gmail.com> <20260106150438.7425-2-minhquangbui99@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260106150438.7425-2-minhquangbui99@gmail.com> On Tue, Jan 06, 2026 at 10:04:36PM +0700, Bui Quang Minh wrote: > When we fail to refill the receive buffers, we schedule a delayed worker > to retry later. However, this worker creates some concurrency issues. > For example, when the worker runs concurrently with virtnet_xdp_set, > both need to temporarily disable queue's NAPI before enabling again. > Without proper synchronization, a deadlock can happen when > napi_disable() is called on an already disabled NAPI. That > napi_disable() call will be stuck and so will the subsequent > napi_enable() call. > > To simplify the logic and avoid further problems, we will instead retry > refilling in the next NAPI poll. > > 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 > Cc: stable@vger.kernel.org > Suggested-by: Xuan Zhuo > Signed-off-by: Bui Quang Minh Acked-by: Michael S. Tsirkin and CC stable I think. Can you do that pls? > --- > drivers/net/virtio_net.c | 48 +++++++++++++++++++++------------------- > 1 file changed, 25 insertions(+), 23 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 1bb3aeca66c6..f986abf0c236 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3046,16 +3046,16 @@ static int virtnet_receive(struct receive_queue *rq, int budget, > else > packets = virtnet_receive_packets(vi, rq, budget, xdp_xmit, &stats); > > + u64_stats_set(&stats.packets, packets); > if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { > - if (!try_fill_recv(vi, rq, GFP_ATOMIC)) { > - spin_lock(&vi->refill_lock); > - if (vi->refill_enabled) > - schedule_delayed_work(&vi->refill, 0); > - spin_unlock(&vi->refill_lock); > - } > + if (!try_fill_recv(vi, rq, GFP_ATOMIC)) > + /* We need to retry refilling in the next NAPI poll so > + * we must return budget to make sure the NAPI is > + * repolled. > + */ > + packets = budget; > } > > - u64_stats_set(&stats.packets, packets); > u64_stats_update_begin(&rq->stats.syncp); > for (i = 0; i < ARRAY_SIZE(virtnet_rq_stats_desc); i++) { > size_t offset = virtnet_rq_stats_desc[i].offset; > @@ -3230,9 +3230,10 @@ static int virtnet_open(struct net_device *dev) > > 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); > + /* Pre-fill rq agressively, to make sure we are ready to > + * get packets immediately. > + */ > + try_fill_recv(vi, &vi->rq[i], GFP_KERNEL); > > err = virtnet_enable_queue_pair(vi, i); > if (err < 0) > @@ -3472,16 +3473,15 @@ 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 (netif_running(vi->dev)) { > + /* Pre-fill rq agressively, to make sure we are ready to get > + * packets immediately. > + */ > + if (refill) > + try_fill_recv(vi, rq, GFP_KERNEL); > > - 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) > @@ -3829,11 +3829,13 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) > } > succ: > vi->curr_queue_pairs = queue_pairs; > - /* virtnet_open() will refill when device is going to up. */ > - spin_lock_bh(&vi->refill_lock); > - if (dev->flags & IFF_UP && vi->refill_enabled) > - schedule_delayed_work(&vi->refill, 0); > - spin_unlock_bh(&vi->refill_lock); > + if (dev->flags & IFF_UP) { > + local_bh_disable(); > + for (int i = 0; i < vi->curr_queue_pairs; ++i) > + virtqueue_napi_schedule(&vi->rq[i].napi, vi->rq[i].vq); > + > + local_bh_enable(); > + } > > return 0; > } > -- > 2.43.0