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([2001:ee0:4f0e:fb30:cbc1:cad1:513d:e384]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3058494aa8csm7608800a91.16.2025.04.06.19.27.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 06 Apr 2025 19:27:48 -0700 (PDT) Message-ID: <30419bd6-13b1-4426-9f93-b38b66ef7c3a@gmail.com> Date: Mon, 7 Apr 2025 09:27:41 +0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] virtio-net: disable delayed refill when pausing rx To: Xuan Zhuo Cc: "Michael S . Tsirkin" , Jason Wang , Andrew Lunn , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , "David S . Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, virtualization@lists.linux.dev References: <20250404093903.37416-1-minhquangbui99@gmail.com> <1743987836.9938157-1-xuanzhuo@linux.alibaba.com> Content-Language: en-US From: Bui Quang Minh In-Reply-To: <1743987836.9938157-1-xuanzhuo@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/7/25 08:03, Xuan Zhuo wrote: > On Fri, 4 Apr 2025 16:39:03 +0700, Bui Quang Minh wrote: >> When pausing rx (e.g. set up xdp, xsk pool, rx resize), we call >> napi_disable() on the receive queue's napi. In delayed refill_work, it >> also calls napi_disable() on the receive queue's napi. This can leads to >> deadlock when napi_disable() is called on an already disabled napi. This >> scenario can be reproducible by binding a XDP socket to virtio-net >> interface without setting up the fill ring. As a result, try_fill_recv >> will fail until the fill ring is set up and refill_work is scheduled. > > So, what is the problem? The refill_work is waiting? As I know, that thread > will sleep some time, so the cpu can do other work. When napi_disable is called on an already disabled napi, it will sleep in napi_disable_locked while still holding the netdev_lock. As a result, later napi_enable gets stuck too as it cannot acquire the netdev_lock. This leads to refill_work and the pause-then-resume tx are stuck altogether. Thanks, Quang Minh.