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Tsirkin" , 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> <30419bd6-13b1-4426-9f93-b38b66ef7c3a@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 4/8/25 14:34, Jason Wang wrote: > On Mon, Apr 7, 2025 at 10:27 AM Bui Quang Minh wrote: >> 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. > This needs to be added to the chagelog. And it looks like this is a fix for > > commit 413f0271f3966e0c73d4937963f19335af19e628 > Author: Jakub Kicinski > Date: Tue Jan 14 19:53:14 2025 -0800 > > net: protect NAPI enablement with netdev_lock() > > ? I'm not aware of this, will update the fix tags in the next patch. > I wonder if it's simpler to just hold the netdev lock in resize or xsk > binding instead of this. That looks cleaner, let me try that approach. Thanks, Quang Minh