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[108.28.192.105]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c07c5f3a4dsm94830685a.2.2025.02.13.06.26.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Feb 2025 06:26:16 -0800 (PST) Message-ID: <2dc054c7-c596-b283-b26a-86c52e48efe0@gmail.com> Date: Thu, 13 Feb 2025 09:26:14 -0500 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH net-next v19 00/26] Introducing OpenVPN Data Channel Offload Content-Language: en-US To: Antonio Quartulli , netdev@vger.kernel.org, Eric Dumazet , Jakub Kicinski , Paolo Abeni , Donald Hunter , Shuah Khan , sd@queasysnail.net, ryazanov.s.a@gmail.com, Andrew Lunn Cc: Simon Horman , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Xiao Liang , steffen.klassert@secunet.com, antony.antony@secunet.com, willemdebruijn.kernel@gmail.com, David Ahern , Andrew Lunn , Shuah Khan , Andrew Morton References: <20250211-b4-ovpn-v19-0-86d5daf2a47a@openvpn.net> From: Sean Anderson In-Reply-To: <20250211-b4-ovpn-v19-0-86d5daf2a47a@openvpn.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Antonio, On 2/10/25 19:39, Antonio Quartulli wrote: > NOTE: TCP tests are still showing the following warning while running > iperf. > I have analysed the report several times, but it definitely looks like > a false positive to me, so nothing to worry about. > > Basically the lockdep engine gets confused thinking that we are > acquiring the lock twice on the same sock, but actually: > 1) the kernel is first locking the 'iperf' (user) TCP socket; > 2) ovpn is later locking the underlying TCP trasport socket. > > So there is NO risk of deadlock (and indeed nothing hangs), but I > couldn't find a way to make the warning go away. I think you can use a "nested" lock to avoid this. See e.g. commit 86a41ea9fd79 ("l2tp: fix lockdep splat") for an example. --Sean [1] https://www.kernel.org/doc/html/latest/locking/lockdep-design.html#exception-nested-data-dependencies-leading-to-nested-locking