From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3492221DB1 for ; Sat, 3 Jan 2026 17:35:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767461705; cv=none; b=ckVSAtb7Dv14IltRuOTE8yNwrrX8y6ee/DQriJGyXt7f/ddBjaBRpNgA2yNVmhQem8Ma2ncpTPgMRvqDSQ/iVmyPVQn+7JTF+1IHoMP7Q/2QKTs1MQ9QJLjcolHFe/CDO+NBv2Xb5RXoSiE0GtEzJ73CxQ6TUk9OMa70MAFQu6k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767461705; c=relaxed/simple; bh=Y13wLH4ceaDvl1ihvg/aw+w3hrnNabyh10rQhk12QDQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=No0p77ZD51zieWDBWtB2mKSj0VvqqWWkwcH79jPkESVDGMqcHk19LopTliKE8hgPOFaHyA/HAFAXk9Haryu+jtXeibg9lmBGzE/NjRdEg6rx+v85oC3IvJHrFMg9rjf7AvRUJTvf81Ntz2eIlfe0BwrpNfleb/e/+pKKdbUW8Fs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ZPGs9L6G; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=H+MwUs7C; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZPGs9L6G"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="H+MwUs7C" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1767461702; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EEdIP9jALOvvc8ZF0tY5F3t+W442S2Znt+VKHwRg1LI=; b=ZPGs9L6GLa9jJ1MMUti3AoBPzEoM94zVCqvuZkAO9FyPUYV3/Fdfg/0B82sxkSYMhNib5t 63Ux49vfm0tmfZAFPXvzt/O8g3ovP2W6aBuOOqXSUeNlotvPfVXQVcpnaBaZUCQs24ylz+ 5ulTTrA1Sm8WNH8AoSKhblF6n2f2Wbo= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-204-f3GjcvcXNP-NQj-iwRPc4A-1; Sat, 03 Jan 2026 12:35:01 -0500 X-MC-Unique: f3GjcvcXNP-NQj-iwRPc4A-1 X-Mimecast-MFC-AGG-ID: f3GjcvcXNP-NQj-iwRPc4A_1767461700 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-47d3ffa98fcso50298135e9.3 for ; Sat, 03 Jan 2026 09:35:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1767461700; x=1768066500; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=EEdIP9jALOvvc8ZF0tY5F3t+W442S2Znt+VKHwRg1LI=; b=H+MwUs7C/KZVQL/QwHAOOXdE/JbjGUeXL2s47lESWGBrX9/g6/3nqejdF+q2gTQLZB ooD+YdYH2Pd/3k45rsJpwk715B2n2fli1W7BQXvS6gJLvIsNyFK1VpMWpgbKKM54Q1L5 xEiB1Jzb07bRJFHZwh4Ka4jG6BhXFTeDvTWdytt71gmr1UEZohqyoOg4wgn9A1DC9r3K K+BBYpsdi6V8ChrcuacLKJTnrSDzx/oItNbWDlvAgYELugIhCLBPVMV5iNnCsBpihyHT LfTJBqDbaIW3PwynD6uQZZ7moN89MYeIi4ZIBFd2WWWOTLl2c8U+WYjETm/wTP4hK98z WGFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767461700; x=1768066500; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=EEdIP9jALOvvc8ZF0tY5F3t+W442S2Znt+VKHwRg1LI=; b=skXhfLeVK8erpnbWbj02+UbQX26hTQkwfnThkK5quhwqg6EG2ILwaFQmDyz5G8nHuS cE8iJcWCwweuOI95zSQUsuluwSdQROONwHh+yUgu19P5vygL0WPbpPZWfbf2BaRtI2Ji PpB39a0K0W9uYdPTaB5ZaeheZuI4vAm7NXX5syjgbmV7UhsX0N/HxLvAKV8ef3J7uUT5 p3Dnbd/WYDOpRgnKmYPOLj+f2pB0EpPaZIFseXNUulgrvuouHgQMN+2oqK0yeuobHZet dRoxblBZsoQnYsjtyf4liwXq62JRAIMeFIh6qAtz3Gtn6AHLgEoCMLvi9NEgNp5v/Ph4 5kCg== X-Forwarded-Encrypted: i=1; AJvYcCVqL9hiOf1XUTsc4AxTQd959UaynpLuS8EHLupuj5Kc7jm4tvdeEwTfxE1eWZ1WHNGMoPGBuoBwIThJtrY=@vger.kernel.org X-Gm-Message-State: AOJu0YxNKUU4KakCpTUyBA9k6cxRsIyOEmqUn13WBKmUf2GHEGjPIQ1T EimEb1bYe8K+Jt4aa1p9YqanJtM0FwcYyr/TWqCNMNMGWky1W7hlhzCvV7+yawfkXQ4AIrHFvf7 2jV2wiZBC0P3E4P1dLXD1bWdM5KlJnU+zGjMeqQ5g+muh6TpN+TEfo1lRJBtdKR9pvg== X-Gm-Gg: AY/fxX6ksNEmS86aBm3g6/FXlVbiY0ldPYdS1EQSVoJu87a6aYftTxThyY42S9Y1iY3 I3O6Tg1/0NKVZipRt6yA9HjrXTfGZSQh0+03syvQNbcdJem4lyR6XWIqIqOUd/tlRpw2SnjVF5g 7E/2tKugIliKrJo5YTkBhAyv7f9aPP0eG753jLSoXqRIupBOhpImSdw8Fkf8SMOxdxYZgWLTWoX IZfHoLF9b/3vQSfHfcmwA3Sh3gVvJQldchtC23hZzNp0fbVysfZY7BSpk1YpK975wIJ8vLagBIO pnMZjw72XM4XUqhwDlEP08kxYKYfhcJo9vtC0pmJrMWPYfxX1OA+G3XfSFVDxTW7UiXibQuagYw 00oU= X-Received: by 2002:a05:600c:1d1d:b0:47a:94fc:d057 with SMTP id 5b1f17b1804b1-47d19538d98mr456348945e9.2.1767461699739; Sat, 03 Jan 2026 09:34:59 -0800 (PST) X-Google-Smtp-Source: AGHT+IGsvgbzF9KuB+7M5SVS6+TnF2qNTINOjinMqCh3ayX5afcmIoMa8eQxNaipc5DNoNmcMJrY9A== X-Received: by 2002:a05:600c:1d1d:b0:47a:94fc:d057 with SMTP id 5b1f17b1804b1-47d19538d98mr456348655e9.2.1767461699245; Sat, 03 Jan 2026 09:34:59 -0800 (PST) Received: from redhat.com ([147.235.217.121]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d6d33eefesm46522085e9.12.2026.01.03.09.34.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 03 Jan 2026 09:34:58 -0800 (PST) Date: Sat, 3 Jan 2026 12:34:54 -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 v2 1/3] virtio-net: don't schedule delayed refill worker Message-ID: <20260103123411-mutt-send-email-mst@kernel.org> References: <20260102152023.10773-1-minhquangbui99@gmail.com> <20260102152023.10773-2-minhquangbui99@gmail.com> <20260103115424-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260103115424-mutt-send-email-mst@kernel.org> On Sat, Jan 03, 2026 at 11:57:43AM -0500, 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? Oh this one is GFP_KERNEL. So it makes it more likely the ring will be filled. > > + */ > > + 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. > > > + 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