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([14.187.47.150]) by smtp.googlemail.com with ESMTPSA id 41be03b00d2f7-c4cbfc2f481sm2674231a12.10.2026.01.06.07.04.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 07:05:00 -0800 (PST) From: Bui Quang Minh To: netdev@vger.kernel.org Cc: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=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, Bui Quang Minh , stable@vger.kernel.org Subject: [PATCH net v3 1/3] virtio-net: don't schedule delayed refill worker Date: Tue, 6 Jan 2026 22:04:36 +0700 Message-ID: <20260106150438.7425-2-minhquangbui99@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260106150438.7425-1-minhquangbui99@gmail.com> References: <20260106150438.7425-1-minhquangbui99@gmail.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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