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Sat, 03 Jan 2026 01:13:13 -0800 (PST) Received: from redhat.com ([2a06:c701:73d7:4800:ba30:1c4a:380d:b509]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4325b6bfe88sm80644627f8f.19.2026.01.03.01.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 03 Jan 2026 01:13:12 -0800 (PST) Date: Sat, 3 Jan 2026 04:13:09 -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 Subject: Re: [PATCH net v2 0/3] virtio-net: fix the deadlock when disabling rx NAPI Message-ID: <20260103041213-mutt-send-email-mst@kernel.org> References: <20260102152023.10773-1-minhquangbui99@gmail.com> Precedence: bulk X-Mailing-List: bpf@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: <20260102152023.10773-1-minhquangbui99@gmail.com> On Fri, Jan 02, 2026 at 10:20:20PM +0700, Bui Quang Minh wrote: > Calling napi_disable() on an already disabled napi can cause the > deadlock. In commit 4bc12818b363 ("virtio-net: disable delayed refill > when pausing rx"), to avoid the deadlock, when pausing the RX in > virtnet_rx_pause[_all](), we disable and cancel the delayed refill work. > However, in the virtnet_rx_resume_all(), we enable the delayed refill > work too early before enabling all the receive queue napis. > > The deadlock can be reproduced by running > selftests/drivers/net/hw/xsk_reconfig.py with multiqueue virtio-net > device and inserting a cond_resched() inside the for loop in > virtnet_rx_resume_all() to increase the success rate. Because the worker > processing the delayed refilled work runs on the same CPU as > virtnet_rx_resume_all(), a reschedule is needed to cause the deadlock. > In real scenario, the contention on netdev_lock can cause the > reschedule. > > Due to the complexity of delayed refill worker, in this series, we remove > it. When we fail to refill the receive buffer, we will retry in the next > NAPI poll instead. > - Patch 1: removes delayed refill worker schedule and retry refill in next > NAPI > - Patch 2, 3: removes and clean up unused delayed refill worker code > > For testing, I've run the following tests with no issue so far > - selftests/drivers/net/hw/xsk_reconfig.py which sets up the XDP zerocopy > without providing any descriptors to the fill ring. As a result, > try_fill_recv will always fail. > - Send TCP packets from host to guest while guest is nearly OOM and some > try_fill_recv calls fail. Thanks, the patches look good to me. Sent some nitpicking comments, with these addressed: Acked-by: Michael S. Tsirkin > Changes in v2: > - Remove the delayed refill worker to simplify the logic instead of trying > to fix it > - Link to v1: > https://lore.kernel.org/netdev/20251223152533.24364-1-minhquangbui99@gmail.com/ > > Link to the previous approach and discussion: > https://lore.kernel.org/netdev/20251212152741.11656-1-minhquangbui99@gmail.com/ > > Thanks, > Quang Minh. > > Bui Quang Minh (3): > virtio-net: don't schedule delayed refill worker > virtio-net: remove unused delayed refill worker > virtio-net: clean up __virtnet_rx_pause/resume > > drivers/net/virtio_net.c | 171 +++++++++------------------------------ > 1 file changed, 40 insertions(+), 131 deletions(-) > > -- > 2.43.0