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([2001:ee0:4f4c:210:6eab:bb4c:4cd9:ccec]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a2f3c828e6sm410760635ad.24.2026.01.03.20.33.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 03 Jan 2026 20:33:27 -0800 (PST) Message-ID: <54e15e32-ee0d-4677-a85d-eb54ffe60a77@gmail.com> Date: Sun, 4 Jan 2026 11:33:20 +0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2 1/3] virtio-net: don't schedule delayed refill worker To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, 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, stable@vger.kernel.org References: <20260102152023.10773-1-minhquangbui99@gmail.com> <20260102152023.10773-2-minhquangbui99@gmail.com> <20260103115424-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Bui Quang Minh In-Reply-To: <20260103115424-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/3/26 23:57, Michael S. Tsirkin wrote: > On Fri, Jan 02, 2026 at 10:20:21PM +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 >> such as races and deadlocks. 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 | 55 ++++++++++++++++++++++------------------ >> 1 file changed, 30 insertions(+), 25 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 1bb3aeca66c6..ac514c9383ae 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -3035,7 +3035,7 @@ static int virtnet_receive_packets(struct virtnet_info *vi, >> } >> >> static int virtnet_receive(struct receive_queue *rq, int budget, >> - unsigned int *xdp_xmit) >> + unsigned int *xdp_xmit, bool *retry_refill) >> { >> struct virtnet_info *vi = rq->vq->vdev->priv; >> struct virtnet_rq_stats stats = {}; >> @@ -3047,12 +3047,8 @@ static int virtnet_receive(struct receive_queue *rq, int budget, >> packets = virtnet_receive_packets(vi, rq, budget, xdp_xmit, &stats); >> >> 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)) >> + *retry_refill = true; >> } >> >> u64_stats_set(&stats.packets, packets); >> @@ -3129,18 +3125,18 @@ static int virtnet_poll(struct napi_struct *napi, int budget) >> struct send_queue *sq; >> unsigned int received; >> unsigned int xdp_xmit = 0; >> - bool napi_complete; >> + bool napi_complete, retry_refill = false; >> >> virtnet_poll_cleantx(rq, budget); >> >> - received = virtnet_receive(rq, budget, &xdp_xmit); >> + received = virtnet_receive(rq, budget, &xdp_xmit, &retry_refill); >> rq->packets_in_napi += received; >> >> if (xdp_xmit & VIRTIO_XDP_REDIR) >> xdp_do_flush(); >> >> /* Out of packets? */ >> - if (received < budget) { >> + if (received < budget && !retry_refill) { >> napi_complete = virtqueue_napi_complete(napi, rq->vq, received); >> /* Intentionally not taking dim_lock here. This may result in a >> * spurious net_dim call. But if that happens virtnet_rx_dim_work >> @@ -3160,7 +3156,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget) >> virtnet_xdp_put_sq(vi, sq); >> } >> >> - return received; >> + return retry_refill ? budget : received; >> } >> >> static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index) >> @@ -3230,9 +3226,11 @@ 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); >> + /* If this fails, we will retry later in >> + * NAPI poll, which is scheduled in the below >> + * virtnet_enable_queue_pair > hmm do we even need this, then? > >> + */ >> + try_fill_recv(vi, &vi->rq[i], GFP_KERNEL); >> >> err = virtnet_enable_queue_pair(vi, i); >> if (err < 0) >> @@ -3473,15 +3471,15 @@ static void __virtnet_rx_resume(struct virtnet_info *vi, >> 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 (refill) >> + /* If this fails, we will retry later in NAPI poll, which is >> + * scheduled in the below virtnet_napi_enable >> + */ >> + try_fill_recv(vi, rq, GFP_KERNEL); > > hmm do we even need this, then? > >> + >> 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) >> @@ -3777,6 +3775,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) >> struct virtio_net_rss_config_trailer old_rss_trailer; >> struct net_device *dev = vi->dev; >> struct scatterlist sg; >> + int i; >> >> if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ)) >> return 0; >> @@ -3829,11 +3828,17 @@ 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) { >> + /* Let the NAPI poll refill the receive buffer for us. We can't >> + * safely call try_fill_recv() here because the NAPI might be >> + * enabled already. >> + */ > I'd drop this comment, it does not clarify much. Here I want to note on why we can't use try_fill_recv like in other places. > >> + local_bh_disable(); >> + for (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