From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AFD54400 for ; Sun, 4 Jan 2026 08:35:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767515715; cv=none; b=fNkmFNVYC5VTC9pwXd3tYCPxBM92AGsc9u09BY0b/4qTXedWBHAtXG0K9uQali600GpcBYoEowyfi0otAb6B6/PjYDecz+/EtstJSqsshzz9t/heENENkEj1Zu4Vo35bFob3YTNW/P5ARs/yaphlXOwnEOxeCxJpRMmOxvrqeno= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767515715; c=relaxed/simple; bh=eh/G7NXvMlnitQDBYTjGmYbYR7qvOpK6QBEB1BtFFZk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IljDLVWD9gfCf2fJzafr53pVSCqTdG35jSS5gbVd1a0WkrTwD3PKpxHORDpP/T5cP6m0WPDsDOLnebm3yYV/zj+4HmWJZYXJbhRU9PM4OsLAJNQkPiSj0/mUc9EYoDOSTLJqbgcMjGEw7s5e+mkSLo2lthq00rjFixEibSTBb2M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=NH5FqNkS; arc=none smtp.client-ip=209.85.214.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="NH5FqNkS" Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-2a0bb2f093aso132410185ad.3 for ; Sun, 04 Jan 2026 00:35:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1767515713; x=1768120513; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=zYcNf5ruViQ0Bt7O6W4MTNR6Ck20+B4qnwscXLHJrJ4=; b=NH5FqNkSopY9ZyBmxALYz0wr7Y3pa6gCLfdjCgzhB6la3xEK25CYec2gwf+7J50/j5 Zc+AsXEsyfFcfqcVH7Iz3zvWZTfyiFhS2imYdtO1b51cvwujJDEcDnqxBcmRmNrhKAXF 404D2Y2lgCuEu2xfIyxEgAJ2j2biARUa3IXWjAiENAl/138FAEqLNGDlbvvRhwn+H28N u/UqB3UENBjjWVayxqfPITYUcIBeQYFhUHQ6tUfoWp7pGjx8mL6gj5L4x7/s26jRUTjn Eo64/vDsETVqzOxK2zAT62kk/EZFpuxZDMZNKoL3LXJ8RW7kIkld+OOjYqKQVhpRSfkY +yPQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767515713; x=1768120513; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=zYcNf5ruViQ0Bt7O6W4MTNR6Ck20+B4qnwscXLHJrJ4=; b=toyHsEwtQmuOP8+G4GErJNKXfkQ7HJhRMuboHnv8D9eugKvd3TbmiXjglAPXycWZ63 oT+9Xj4oc6hARABMZofPWEYKiSANsLjhRQV2Wlj40K1ElSMiDD2sh/fD5UaCGwIg/DkH 25MH+yuqY30dhbeYpDDvzP5YXtT3SCV+2f2PIqaqhYkEjSi+cYOeqXZj+GEuwZrssyDO vcGUA/RvTrGPR0ki2cr8IIXrrMpnFQJ2Reo8lBnG7SkaE+9fD2YKNHA7HCDkb97SA9Am bitgXcUv7RpTeH9vAWW/gOfd0TnHFqVpvOB4GC0gexyUzw8WPrPHzHFwtJBNLpe9Hr1i f/BA== X-Gm-Message-State: AOJu0Yx/3eHgGPT0wxvqoYIJL7tozkp1f4WfLK1uzl+8jKHvpcJss6sk 0TDOF7qHoIoEfPVy6fe92AHDvvIfahfP++K8uh2t3e3XeIfnzv4rgTw9 X-Gm-Gg: AY/fxX4UI9EwpvRyyHeZmGHprVFvwmYZZ9ZZgcLF/kvVQc3ZYMeCKxZ0hZIZZwJsUU9 DfajYpgj+uuYr+WBc7FFSqkxVHtY3117CA3qK/TYLLgSPvxuZA1HBMjTGAX1UK7dM7QjBDE+bso 7p/xD04hgxBr1J8jPpmXKhQvH8N+BqZbmiSNTDCqYoYat3sWZMEg7oWe3EzAdbhQs2/jaIWCqh9 m/HRBGtdgQhg4+DPLPvlMvXE4PWcP+BPaIKLnn8gm0jHNc4oU5KZYfTyxCZNGTe6EZ70z3MYuXs WIUnOLRN8BICJuoQiP7xdNTyyAe+bj7OrrfL6XMX4LymUKW6iTpP572F6PcKysBJPoyvTdvdHAU K3W083v4YR9CSuIOpUVQgBxZTOmxCbu43cuzpzbjDsCmgAieZQaouWrfoVImJp1VdMOCFfEecOJ UMohvQeIKVXi+B+TUhESHI X-Google-Smtp-Source: AGHT+IGONnUzqL7+hHcisSojq0N9wRnZKkoN8MPifLQrP1FZZCuWqkigoPO5dJvLiXoTCd9y6sg47Q== X-Received: by 2002:a05:6a20:394a:b0:35c:dfd6:6acb with SMTP id adf61e73a8af0-376a7af5089mr41512918637.30.1767515712648; Sun, 04 Jan 2026 00:35:12 -0800 (PST) Received: from [172.16.98.252] ([14.161.45.246]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34f44ea585fsm2120401a91.0.2026.01.04.00.34.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 04 Jan 2026 00:35:12 -0800 (PST) Message-ID: <6bac1895-d4a3-4e98-8f39-358fa14102db@gmail.com> Date: Sun, 4 Jan 2026 15:34:52 +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: Jason Wang Cc: netdev@vger.kernel.org, "Michael S. Tsirkin" , 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> Content-Language: en-US From: Bui Quang Minh In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 1/4/26 13:09, Jason Wang wrote: > On Fri, Jan 2, 2026 at 11:20 PM 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); > I think we can simply let virtnet_receive() to return the budget when > reill fails. That makes sense, I'll change it. > >> 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 >> + */ >> + try_fill_recv(vi, &vi->rq[i], GFP_KERNEL); > Consider NAPI will be eventually scheduled, I wonder if it's still > worth to refill here. With GFP_KERNEL here, I think it's more likely to succeed than GFP_ATOMIC in NAPI poll. Another small benefit is that the actual packet can happen earlier. In case the receive buffer is empty and we don't refill here, the #1 NAPI poll refill the buffer and the #2 NAPI poll can receive packets. The #2 NAPI poll is scheduled in the interrupt handler because the #1 NAPI poll will deschedule the NAPI and enable the device interrupt. In case we successfully refill here, the #1 NAPI poll can receive packets right away. > >> 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); > and here. > >> + >> 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. >> + */ >> + 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 >> > Thanks > Thanks, Quang Minh.